10. Urogenital Tract

Authors: Dahnert, Wolfgang

Title: Radiology Review Manual, 6th Edition

Copyright 2007 Lippincott Williams & Wilkins

> Table of Contents > Urogenital Tract

function show_scrollbar() {}

Urogenital Tract

Differential Diagnosis of Urogenital Disorders

Renal failure

• = reduction in renal function

• rise in serum creatinine >2.5 mg/dL

Acute Renal Failure

• = clinical condition associated with rapid steadily increasing azotemia oliguria (<500 mL urine per day) over days / weeks

• Etiology:

  • PRERENAL

    • = renal hypoperfusion secondary to systemic illness

    • 1. Fluid + electrolyte depletion

    • 2. Hemorrhage

    • 3. Hepatic failure + hepatorenal syndrome

      • abnormally elevated resistive index

    • 4. Cardiac failure

    • 5. Sepsis

      • resistive index <0.75 in 80% of kidneys

  • RENAL (most common)

    • Acute tubular necrosis:

      • ischemia, nephrotoxins, radiographic contrast, hemoglobulinuria, myoglobulinuria, myocardial infarction, burns

      • resistive index 0.75 in 91% of kidneys

    • Acute glomerulonephritis + small vessel disease:

      • acute poststrep glomerulonephritis, rapidly progressive glomerulonephritis, lupus, polyarteritis nodosa, Sch nlein-Henoch purpura, subacute bacterial endocarditis, serum sickness, Goodpasture syndrome, malignant hypertension, hemolytic uremic syndrome, drug-related vasculitis, abruptio placentae

      • normal resistive index <0.70

    • Acute tubulointerstitial nephritis:

      • drug reaction, pyelonephritis, papillary necrosis

      • abnormal resistive index

    • Intrarenal precipitation (hypercalcemia, urate, myeloma protein)

    • Arterial / venous obstruction

    • Acute cortical necrosis

  • POSTRENAL (5%)

    • = result of outflow obstruction (rare)

    • Prostatism

    • Tumors of bladder, retroperitoneum, pelvis

    • Calculus

    • hydronephrosis

  • CONGENITAL

    • bilateral renal agenesis / dysplasia / infantile polycystic kidney disease, congenital nephrotic syndrome, congenital nephritis, perinatal hypoxia

• Incidence:  ATN + prerenal disease account for 75% of acute renal failure

Chronic Renal Failure (CRF)

• = decrease in renal function over months / years

• Incidence:  end-stage renal disease in 0.01% of U.S. population; 85,000 patients/year undergo hemodialysis; 8,000 renal transplantations/year

• Etiology:

  • INFLAMMATION / INFECTION

    • Glomerulonephritis

    • Chronic pyelonephritis

    • Tuberculosis

    • Sarcoidosis

  • VASCULAR

    • Renal vascular disease

    • Bilateral renal vein thrombosis

  • DYSPROTEINEMIA

    • Myeloma

    • Amyloid

    • Cryoglobulinemia

    • Waldenstr m macroglobulinemia

  • METABOLIC

    • Diabetes

    • Gout

    • Hypercalcemia

    • Hyperoxaluria

    • Cystinosis

    • Fabry disease

  • CONGENITAL

    • Polycystic kidney disease

    • Multicystic dysplastic kidney

    • Medullary cystic disease

    • Alport syndrome

    • Infantile nephrotic syndrome

  • MISCELLANEOUS

    • Hepatorenal syndrome

    • Radiation

Musculoskeletal Manifestations of CRF

• Renal osteodystrophy = combination of 2 HPT, osteoporosis, osteosclerosis, osteomalacia, soft-tissue and vascular calcifications

• Aluminum toxicity (1 30%)

  • Cause:  ingestion of aluminum salts phosphate-binding antacids (to control hyperphosphatemia)

  • aluminum serum level >100 ng/mL

  • signs of osteomalacia (>3 insufficiency fractures with predominant involvement of ribs)

  • avascular necrosis

  • lack of osteosclerosis

  • less evidence of subperiosteal resorption

• Amyloid deposition

  • Path:  amyloid consists of ₂-microglobulin

  • Organs:  bone, tenosynovium (carpal tunnel syndrome), vertebral disk, articular cartilage + capsule, ligament, muscle

• Destructive spondyloarthropathy (15%)

  • diskovertebral junction erosion + sclerosis

  • vertebral body compression

  P.878

  
  

  • disk space narrowing

  • Schmorl node formation

  • lack of osteophytosis

  • facet involvement with subluxation

• Tendon rupture

• Crystal deposition disease

  • Type:  calcium hydroxyapatite, CPPD, calcium oxalate, monosodium urate

• Osteomyelitis + septic arthritis

• Avascular necrosis (in up to 40%)

Diabetes insipidus

• = characterized by daily production of very large volume of dilute urine (specific gravity <1.005, <200 mOsm/L)

Pituitary Diabetes Insipidus

• = Hypothalamic Diabetes Insipidus

• = vasopressin-sensitive diabetes insipidus

• = vasopressin (ADH) production is reduced to <10%

• Cause:

  • idiopathic (27%)

    • septooptic dysplasia / rare familial (autosomal dominant X-linked) / sporadic disorder

    • Histo: atrophic supraoptic nucleus

    • never associated with anterior pituitary dysfunction

  • pituitary destruction by tumor / infiltrative disorder (32%):

    in childhood:	hypothalamic glioma, tuber cinereum hamartoma, craniopharyngioma, Langerhans histiocytosis, germinoma, leukemia, complication of meningitis
    in adulthood:	sarcoidosis, TB, metastasis

    • in 60% associated with anterior pituitary dysfunction

  • pituitary destruction by surgery (20%)

    • always associated with anterior pituitary dysfunction

  • head injury (17%)

    • in 20% associated with anterior pituitary dysfunction

• A lesion in the posterior pituitary will NOT produce diabetes insipidus, because it is simply the storage space for vasopressin!

Psychogenic Water Intoxication

• = compulsive intake of large amounts of fluid, which leads to inhibition of normal vasopressin production

• water deprivation test

Nephrogenic Diabetes Insipidus

• = poor reabsorption of water in collecting ducts due to end-organ resistance to vasopressin

• Cause:

  • congenital

    • Rare X-linked recessive genetic disorder with unresponsiveness of tubules + collecting system to vasopressin (in infants + young males) with variable expression

    • Autosomal dominant form (rare)

  • acquired = nephrogenic DI syndrome

    • = disorders affecting the medulla / distal nephrons:

      • medullary + polycystic disease, sickle cell nephropathy, postobstructive uropathy, reflux nephropathy, chronic uremic nephropathy, unilateral renal artery stenosis, acute tubular necrosis, drug toxicity, analgesic nephropathy, hypokalemic + hypercalcemic nephropathy, amyloidosis, sarcoidosis

• symptoms in infancy:

  • vomiting secondary to hypernatremic dehydration

  • mental retardation

  • caloric growth failure (water favored over formula)

• symptoms after infancy:

  • increased fluid intake

  • avoiding urination

  • bilateral hydroureteronephrosis

• Rx:  thiazide diuretics, low-salt diet, encouragement of frequent micturition, indomethacin

Hypercalcemia

• mnemonic: SHAMPOO DIRT

  • Sarcoidosis

  • Hyperparathyroidism, Hyperthyroidism

  • Alkali-milk syndrome

  • Metastases, Myeloma

  • Paget disease

  • Osteogenesis imperfecta

  • Osteopetrosis

  • D vitamin intoxication

  • Immobility

  • Renal tubular acidosis

  • Thiazides

Polycythemia

• Cause:  increased level of erythropoietin (acting on erythroid stem cells) secondary to a decrease in pO₂; erythropoietin precursor is produced in juxtaglomerular epithelioid cells of kidney + converted in blood

• A. RENAL

  • intrarenal

    • Vascular impairment

    • Renal cell carcinoma (5%)

    • Wilms tumor

    • Benign fibroma

    • Simple cyst (14%)

    • Polycystic kidney disease

  • postrenal

    • Obstructive uropathy (14%)

• B. EXTRARENAL

  • liver disease

    • Hepatoma

    • Regenerating hepatic cells

  • adrenal disease

    • Pheochromocytoma

    • Aldosteronoma

    • Cushing disease

• C. CNS DISEASE

  • Cerebellar hemangioblastoma

• D. Large uterine myomas

• NOT in: renal vein thrombosis, multicystic dysplastic kidney, medullary sponge kidney

P.879

Arterial hypertension

• PRIMARY / ESSENTIAL HYPERTENSION (85 90%)

• SECONDARY HYPERTENSION

  • Renal parenchymal disease (5 10%)

  • Potentially curable secondary hypertension (1 2%)

vascular
1. Renovascular disease	0.18 4.4%
2. Coarctation	0.6%
hormonal
1. Pheochromocytoma	0.04 0.2%
2. Cushing syndrome	0.3%
3. Primary aldosteronism	0.01 0.4%
4. Hyperthyroidism
5. Myxedema
renal
1. Unilateral renal disease

Renovascular Hypertension

• = normalization of blood pressure following nephrectomy / reestablishment of normal renal blood flow (Dx made in retrospect)

• Incidence:  1 5% of general population; 2nd most common cause of potentially curable hypertension

• Pathophysiology:

  • usually >50% stenosis at any level in renovascular bed leads to mildly reduced pressure in glomerular afferent arteriole (pressure falls precipitously in >80% stenosis); reduced pressure stimulates release of renin followed by angiotensin-II, and aldosterone causing

    • constriction of efferent glomerular arterioles

    • increase in systemic hypertension

    • sodium retention

• Cause:

  • Atherosclerosis (60 90%) in individuals >50 years of age

  • Fibromuscular dysplasia (10 35%) in women <40 years of age

  • Neurofibromatosis

  • Pheochromocytoma

  • Fibrous bands (congenital stenosis, retroperitoneal fibrosis, postradiation artery stenosis)

  • Arteritis (Buerger disease, polyarteritis nodosa, Takayasu disease, thrombangitis obliterans, syphilitic arteritis)

  • Arteriovenous malformation / fistula

    • renin-mediated hypertension (due to renal ischemia distal to fistula)

  • Thromboembolic disease (eg, atrial fibrillation, prosthetic valve thrombi, cardiac myxoma, paradoxical emboli, atheromatous emboli)

  • Renal artery aneurysm

  • Extrinsic compression (eg, renal cyst, neoplasm, chronic subcapsular hematoma) = Page kidney

  • Middle aortic syndrome, aortic dissection, dissecting aortic aneurysm

  • Posttraumatic renovascular hypertension

    • occlusion of main renal artery

    • significant stenosis by intimal flap

    • severe renal contusion

    • segmental renal artery branch injury

• Renal artery stenosis is present in 77% of hypertensive patients!

• Renal artery stenosis is present in 32 49% of normotensive patients!

• 15 20% of patients remain hypertensive after restoration of normal renal blood flow!

Clinical findings that suggest renovascular disease:

• Onset of HTN <30 years and >50 years of age

• Hypertension refractory to therapy

• Accelerated / malignant hypertension

• Unexplained large increases in blood pressure above previously controlled / baseline values

• Symptomatic hypertension

Rx:

• Relieving renal artery stenosis

• Angiotensin-converting enzyme inhibitor

Hypertension in Children

Prevalence:   1 3%

• Coarse renal cortex scarring (36%)

• Glomerulonephritis (23%)

• Coarctation of aorta (10%)

• Renovascular disease (10%)

• Polycystic renal disease (6%)

• Hemolytic-uremic syndrome (4%)

• Catecholamine excess [pheochromocytoma, neuroblastoma] (3%)

• Renal tumor (2%)

• Essential hypertension (3%)

Arterial Hypotension

• Cause:  intrarenal hypovolemia, primary vasoconstriction, reduced glomerular filtration, depletion of intratubular urine volume

• May occur as a contrast reaction!

• Urogram reverts to normal after reversion of hypotension!

• bilateral small smooth kidneys (compared with size on preliminary films)

• increasingly dense nephrogram

• usually NO opacification of collecting system

• initially opacification of collecting system if hypotension occurs during contrast injection

Urinary Tract Infection

= pure growths of >100,000 organisms/mL urine

Prevalence:  3% of girls + 1% of boys during first 10 years of life

Underlying radiologic abnormality:

• Vesicoureteral reflux = VUR (30 40%)

• Obstructive uropathy (8%)

• Reflux nephropathy / scar formation (6%)

  • The prevalence of an underlying radiologic abnormality depends on age, sex, and frequency of previous infections!

Imaging objective:

• Identify patients at risk for reflux nephropathy

• Detect reflux nephropathy / scars

• Detect obstructive uropathy

• Minimize radiation, morbidity, and cost

  • VCUG:

    • for children <5 years of age with infection; normal results in 60 70%

  P.880

  
  

  • Renal cortical scintigraphy (DMSA / glucoheptonate):

    • to detect acute pyelonephritis (risk for scarring) / scar; with VUR there is twice the risk of cortical defects than without VUR

Gas in Urinary Tract

• Renal emphysema = renal / perirenal gas

  • Emphysematous pyelonephritis

  • Emphysematous pyelitis

  • Gas-forming perinephric abscess

  • Perinephric emphysema

• Bladder

  • Emphysematous cystitis

• Trauma

  • Penetrating trauma

  • Ureterosigmoidostomy, ileal conduit, catheterization with vesicoureteral reflux, percutaneous procedure

    • CAVE: anomalous posterior position of colon

  • Infarction of renal carcinoma (therapeutic / spontaneous)

• Fistula to urinary tract

  • Connection:  bronchus / cutis / GI tract (colon > duodenum > stomach > small bowel > appendix

  • Inflammation: chronic purulent renal infection, diverticulitis, Crohn disease

  • Neoplastic: colonic carcinoma

Retroperitoneum

Retroperitoneal Tumor by Tissue Component

• fat

  • Lipoma

  • Liposarcoma

  • Teratoma

• myxoid stroma

  • Neurogenic tumor: schwannoma, neurofibroma, ganglioneuroma, ganglioneuroblastoma, malignant peripheral nerve sheath tumor

  • Myxoid liposarcomas

  • Myxoid malignant fibrous histiocytoma

  • Desmoid tumor

  • Hemangiopericytomas

  • Leiomyomas, leiomyosarcomas

  • Malignant pericytomas

  • Rhabdomyosarcoma

  • Malignant mesenchymomas

• necrosis

  • Leiomyosarcoma

  • Paraganglioma

• cystic component

  • Lymphangioma

  • Mucinous cytsic tumor

  • Neurogenic tumor

• small round cells

  • Lymphoma

• hypervascularity

  • Paragangliomas

  • Hemangiopericytoma

  • Low-grade liposarcomas

  • Lymphoma

Primary Malignant Tumor of Retroperitoneum

• Liposarcoma

• Malignant fibrous histiocytoma

  • dystrophic calcifications in 25%

• Leiomyosarcoma

Low-density Retroperitoneal Mass

• Lipoma

  • sharply marginated, homogeneously fatty mass

• Lymphangioma

  • similar to lipoma if enough fat content

• Renal angiomyolipoma

  • intrarenal component

  • hypervascular with large feeding arteries, multiple aneurysms, laking without shunting, tortuous circum-ferential vessels, whorled parenchymal + venous phase

• Adrenal myelolipoma

  • density between fat + water

  • usually nonhomogeneous, occasionally with hemorrhage calcifications

• Xanthogranulomatous pyelonephritis

  • nonfunctioning kidney replaced by low-density material + central staghorn calculus

• Metastatic retroperitoneal tumors

• Renal cell carcinoma

• Fibrosarcoma, fibrous histiocytoma, mesenchymal sarcoma, malignant teratoma

  • density close to muscle

• Liposarcoma

Calcified Retroperitoneal Mass

• NONTUMORAL

  • Exuberant callus formation

  • Posttraumatic calcified hematoma

  • Myositis ossificans

  • Foreign body granuloma

  • Encapsulated textiloma / gossypiboma

    • (gossypium, Latin = cottton)

    • Cause: retained surgical sponge, gauze, towel

• BENIGN NEOPLASM

  • Ganglioneuroma

  • Schwannoma

  • Paraganglioma

  • Hemangiomna

  • Mature teratoma

• MALIGNANT NEOPLASM

  • Malignant fibrous histiocytoma

  • Dedifferentiated liposarcoma

  • Leiomyosarcoma

  • Malignant mesenchymoma

  • Malignant teratoma

  • Extraskeletal osteosarcoma

Adrenal Gland

Adrenal Medullary Disease

• Neuroblastoma

• Ganglioneuroblastoma

• Ganglioneuroma

• Pheochromocytoma

P.881

Adrenal Cortical Disease

• Adrenal hyperplasia

• Adrenocortical adenoma

• Adrenocortical carcinoma

• Cushing syndrome

• Conn syndrome

• Adrenogenital syndrome

Adrenocortical Hyperfunction

• Adrenogenital syndrome

• Conn syndrome = hyperaldosteronism

  • solitary unilateral adrenal adenoma + normal contralateral gland on CT may be due to:

    • aldosterone-producing adrenocortical adenoma

    • renin-responsive aldosterone-producing adenoma

    • idiopathic hyperaldosteronism with dominant hyperplastic / nonfunctional adenoma

• Cushing syndrome = hypercortisolism

  • DDx of Cushing syndrome

    • FOCAL UNILATERAL ADRENAL MASS

      • 2 4-cm focal mass in one adrenal gland + atrophy of contralateral gland = adrenal adenoma

      • >4-cm large focal mass with central necrosis in one adrenal gland + atrophy of contralateral gland = adrenal adenocarcinoma

    • BILATERAL ADRENAL ENLARGEMENT

      • diffuse uniform thickening = Cushing disease

    • MULTIPLE BILATERAL ADRENAL NODULES

      • macronodules = multinodular hyperplasia of long-standing Cushing disease

      • large nodules (autonomous ACTH-independent) = massive macronodular hyperplasia

      • small nodules = primary pigmented nodular adrenal disease

Bilateral Large Adrenals

• mnemonic:  4 H PM

  • Hodgkin disease

  • Hyperplasia

  • Hemorrhage

  • Histoplasmosis / TB

  • Pheochromocytoma

  • Metastasis

Unilateral Adrenal Mass

• Incidental discovery of adrenal mass in 1% of all CT

  • = incidentaloma!

• Risk for adrenocortical carcinoma:    0.06 4.7%

• Criteria to differentiate benign from malignant:

  • Size (too unreliable as only criterion)

    • the larger the lesion the more likely it is symptomatic

    • with known malignancy

      • 87% of lesions <3 cm are benign

      • 95% of lesions >3 cm are malignant

    • without known malignancy

      • Frequency: 1.5%

      • all malignant lesions were >5 cm

    • change in size:

      • A lesion without change in size over 6 months is likely benign!

  • Endocrinologic subclinical function

    • recommended for lesions >4 cm

      Frequency:	5%
      Cause:	pheochromocytoma (70%), adrenocortical adenoma (30%)
      Secretion:	aldosterone, cortisol, catecholamines

  • NECT attenuation (HU_NECT)

    Sensitivity for adenomas:	56%
    False-positive rate:	4%
    10 HU	= benign lipid-rich adenoma / cyst
    >10 HU	= indeterminate
    Reason:	60 70% of benign adrenocortical tumors contain intracytoplasmic fat

  • CECT for lesions >10 HU

    • 60 sec scan (HU_{CECT 1min})

    • 15-minute delayed scan (HU_{CECT 15min})

      Percentage of relative enhancement washout= [HUCECT 1min HUCECT 15min] / [HUCECT 1min HUNECT] 100
      washout >60%	= lipid-poor adenoma
      washout 60%	= indeterminate mass
      Reason:	malignant vessels have an increased capillary permeability with prolonged retention of contrast material
      Results:	95% sensitive, 97% specific

  • Chemical shift MRI:

    • Reason:  fat protons precess faster than water

    • fat + water summate to intermediate signal intensity on in-phase images

    • fat + water signals cancel each other out to low signal intensity on out-of-phase images = adenoma

    • Results:  10% overlap between benign + malignant; 90% of lesions between 10 HU and 30 HU on CT correctly classified

  • Adrenal biopsy

    Accuracy:	96 100% for malignancy
    Insufficient material:	4 19%
    Cx: 8 12% (bleeding, pneumothorax, infection, tumor tracking); several deaths reported after Bx of pheochromocytoma

  • FDG-PET

    SUV:	>4 for metastatic disease (from lung, colon, melanoma, lymphoma)
    FN:	renal cell carcinoma

  • Large size, irregularity, inhomogeneity are suggestive of malignancy

• mnemonic:  PLAN My HAM

  • Pheochromocytoma

  • Lymphoma

  • Adenoma

  • Neuroblastoma

  • Myelolipoma

  • Hemorrhage

  • Adenocarcinoma

  • Metastasis

P.882

Small Unilateral Adrenal Tumor

• Cortical adenoma (in 1 9% of autopsies)

  • <10 HU imply (in 96%) an adenoma

• Metastasis

• Pheochromocytoma

• Asymmetric hyperplasia

• Granulomatous disease (TB, histoplasmosis)

  • diffuse enlargement / discrete mass

  • central cystic changes calcification

• Myelolipoma

Large Solid Adrenal Mass

• Cortical carcinoma

• Pheochromocytoma

• Neuroblastoma / ganglioneuroma

• Myelolipoma

• Metastasis

• Hemorrhage

• Inflammation

• Abscess (eg, histoplasmosis, tuberculosis)

• Hemangioma

Malignant Adrenal Mass

• Adrenal cortical carcinoma

• Angiosarcoma

• Lymphoma

• Malignant pheochromocytoma

• Metastasis (in 4% without known primary; in 25 72% with known primary)

Cystic Adrenal Mass

• Pseudocyst: old hemorrhage / infarction

• Vascular cystic space (endothelial lining): lymphangioma, hemangioma

• True cyst (epithelial lining): glandular cyst, embryonal cyst, mesothelial inclusion cyst

• Parasitic cyst: hydatid cyst

• Hemorrhagic complication / degeneration of a tumor: cystic adenoma, cystic pheochromocytoma, cystic adenomatoid tumor, cystic adrenocortical carcinoma, schwannoma

• Neuroblastoma (rare)

• Cortical adenoma with low density

Adrenal Calcification

• TUMOR

  • Neuroblastoma

  • Pheochromocytoma

  • Adrenal adenoma

  • Adrenal carcinoma

  • Dermoid

• VASCULAR

  • Hemorrhage (neonatal, sepsis)

• INFECTION

  • Tuberculosis

  • Histoplasmosis

  • Waterhouse-Friderichsen syndrome

• ENDOCRINE

  • Addison disease (TB)

• OTHERS

  • Wolman disease

Kidney

Developmental Renal Anomalies

Numerary Renal Anomaly

• Supernumerary kidney

• Complete / partial renal duplication

• Abortive calyx

• Unicaliceal (unipapillary) kidney

Renal Underdevelopment

• Congenital renal hypoplasia

• Renal agenesis

• Renal dysgenesis

Renal Ectopia

• Normal location of kidneys: 1st 3rd lumbar vertebra

  Incidence:	0.2% (autopsy series)
  Cause:	failure of kidney to ascend by 8 weeks GA
  At risk of:	hydronephrosis due to UPJ obstruction, infection, calculi

• unusual developmental funny-looking calices often misinterpreted as obstructive

• loop-to-loop colon = abnormal looped configuration of colon occupying the renal fossa

Longitudinal Renal Ectopia

• Location:  pelvic, sacral, lower lumbar level, intrathoracic; L > R

• must demonstrate aberrant arteries

• DDx:  displacement through diaphragmatic hernia (nonaberrant); hypermobile kidney

Pelvic kidney

• = ectopic kidney due to failure of renal ascent

• Incidence:  1:725 births

• May be associated with:

  • vesicoureteral reflux

  • hydronephrosis due to abnormally high insertion of ureter into renal pelvis

  • hypospadia (common)

  • contralateral renal agenesis

• blood supply via iliac vessels / aorta

• nonrotation = anteriorly positioned renal pelvis (common)

Crossed Renal Ectopia

= kidney located on opposite side of midline from its ureteral orifice; usually L > R and crossed kidney inferior to normal kidney

Cause:	? faulty development of ureteral bud, vascular obstruction of renal ascent
Associated with:	obstruction urolithiasis, infection, reflux, megaureter, hypospadia, cryptorchidism, urethral valves, multicystic dysplasia

• fused (common)

• separate (rare)

• invariably aberrant renal arteries

• distal ureter inserts into trigone on the side of origin

Renal Fusion

• = lump, cake, disk, horseshoe

P.883




• Cx: aberrant arteries may cross and obstruct ureter

Horseshoe kidney

Discoid / pancake kidney

• = bilateral fused pelvic kidneys

• Associated with:

  • abnormal testicular descent, tetralogy of Fallot, vaginal agenesis, sacral agenesis, caudal regression, anal anomalies

Renal Malrotation

• collecting structures may be positioned ventrally (most common), lateral (rare), dorsal (rarer), transverse (along AP axis)

• funny-looking calices = developmental usually nonobstructive ectasia

Absent Renal Outline on Plain Film

• ABSENT KIDNEY

  • Congenital absence

  • S/P nephrectomy

• SMALL KIDNEY

  • Renal hypoplasia

  • Renal atrophy

• RENAL ECTOPIA

  • Pelvic kidney

  • Crossed fused ectopia

  • Intrathoracic kidney

• OBLITERATION OF PERIRENAL FAT

  • Perirenal abscess

  • Perirenal hematoma

  • Renal tumors

Nonvisualized Kidney on Excretory Urography

• ABSENCE OF KIDNEY

  • Agenesis

  • Surgical absence

  • Renal ectopia

• LOSS OF PERFUSION

  • Chronic infarction

  • Unilateral renal vein thrombosis

• TRAUMA

  • Thrombosis of main renal artery

  • Severe contusion (with renal vascular spasm)

  • Avulsion of renal pedicle

• HIGH-GRADE URINARY OBSTRUCTION

  • Hydronephrosis

  • Ureteropelvic junction obstruction

• REPLACED NORMAL RENAL PARENCHYMA

  • Multicystic dysplastic kidney

  • Unilateral polycystic kidney disease

  • Renal tumor (RCC, TCC, Wilms tumor)

  • Xanthogranulomatous pyelonephritis

Unilateral Large Smooth Kidney

• PRERENAL

  • arterial: acute arterial infarction

  • venous: acute renal vein thrombosis

• INTRARENAL

  • congenital: duplicated pelvicaliceal system, crossed fused ectopia, multicystic dysplastic kidney, adult polycystic kidney (in 8% unilateral)

  • infectious: acute bacterial nephritis

  • adaptation: compensatory hypertrophy

• C. POSTRENAL

  • collecting system: obstructive uropathy

• mnemonic:  AROMA

  • Acute pyelonephritis

  • Renal vein thrombosis

  • Obstructive uropathy

  • Miscellaneous (compensatory hypertrophy, duplication)

  • Arterial obstruction (infarction)

Bilateral Large Kidneys

Average renal length by x-ray: M = 13 cm; F = 12.5 cm

• PROTEIN DEPOSITION

  • amyloidosis, multiple myeloma

• INTERSTITIAL FLUID ACCUMULATION

  • acute tubular necrosis, acute cortical necrosis, acute arterial infarction, renal vein thrombosis

• CELLULAR INFILTRATION

  • Inflammatory cells: acute interstitial nephritis, acute bacterial nephritis

  • Malignant cells: leukemia / lymphoma, bilateral Wilms tumor, nephroblastomatosis

• PROLIFERATIVE / NECROTIZING DISORDERS

  • Glomerulonephritis (GN)

    • acute (poststreptococcal) GN, rapidly progressive GN, idiopathic membranous GN, lobular GN, membranoproliferative GN, IgA nephropathy, glomerulosclerosis, glomerulosclerosis related to heroin abuse

  • Multisystem disease

    • polyarteritis nodosa, systemic lupus erythematosus, Wegener granulomatosis, allergic angitis, diabetic glomerulosclerosis, Goodpasture syndrome (lung hemorrhage + glomerulonephritis), Sch nlein-Henoch syndrome (anaphylactoid purpura), thrombotic thrombocytopenic purpura, focal glomerulonephritis associated with subacute bacterial endocarditis

• URINE OUTFLOW OBSTRUCTION

  • bilateral hydronephrosis: congenital / acquired

• HORMONAL STIMULUS

  • acromegaly, compensatory hypertrophy, nephromegaly associated with cirrhosis / hyperalimentation / diabetes mellitus

• DEVELOPMENTAL

  • bilateral renal duplication, horseshoe kidney, polycystic kidney disease

• MISCELLANEOUS

  • acute urate nephropathy, glycogen storage disease, hemophilia, sickle cell disease, Fabry disease, physiologic response to contrast material and diuretics

mnemonic:  FOG P

Fluid:	edema of kidney (ATN, acute cortical necrosis)
Other:	leukemia, acromegaly, sickle cell anemia, bilateral duplication, acute urate nephropathy
Glomerular disease:	acute GN, lupus, polyarteritis nodosa, diabetes mellitus
Protein deposition:	multiple myeloma, amyloidosis

P.884

Bilateral Small Kidneys

• PRERENAL = VASCULAR

  • Arterial hypotension (acute)

  • Generalized arteriosclerosis

  • Atheroembolic disease

  • Benign & malignant nephrosclerosis

• INTRARENAL

  • Hereditary nephropathies:

    • medullary cystic disease, hereditary chronic nephritis (Alport syndrome)

  • Chronic glomerulonephritis

  • Amyloidosis (late)

• POSTRENAL

  • Papillary necrosis

• CAUSES OF UNILATERAL SMALL KIDNEY

  • occurring bilaterally

• mnemonic: CAPE HANA

  • Chronic glomerulonephritis

  • Arteriosclerosis

  • Papillary necrosis

  • Embolic disease (secondary to atherosclerosis)

  • Hypotension

  • Alport syndrome

  • Nephrosclerosis

  • Amyloidosis (late)

Unilateral Small Kidney

• PRERENAL = VASCULAR

  • Lobar infarction

  • Chronic infarction

  • Renal artery stenosis

  • Radiation nephritis

• INTRARENAL = PARENCHYMAL

  • Congenital hypoplasia

  • Multicystic dysplastic kidney (in adult)

  • Postinflammatory atrophy

• POSTRENAL = COLLECTING SYSTEM

  • Reflux nephropathy = chronic atrophic pyelonephritis

  • Postobstructive atrophy

• mnemonic:  RIP R HIP

  • Reflux atrophy

  • Ischemia (renal artery stenosis)

  • Postobstructive atrophy

  • Radiation therapy

  • Hypoplasia (congenital)

  • Infarction

  • Postinflammatory atrophy

Increased Echogenicity of Renal Cortex

• = RENAL MEDICAL DISEASE

• = diffuse increase in cortical echogenicity with preservation of corticomedullary junction

• Path:  deposition of collagen / calcium in interstitial, glomerular, tubular, vascular disease

• echointensity of cortex greater than liver / spleen equal to renal sinus

• renal size may be normal; enlarged kidneys suggest active stage of renal disease; small kidneys suggest chronic + often end-stage renal disease

• Cause:

  • Acute / chronic glomerulonephritis

  • Renal transplant rejection

  • Lupus nephritis

  • Hypertensive nephrosclerosis

  • Renal cortical necrosis

  • Methemoglobulinuric renal failure

  • Alport syndrome

  • Amyloidosis

  • Diabetic nephrosclerosis

  • Nephrotoxin-induced acute tubular necrosis

  • End-stage renal disease

Hyperechoic Renal Pyramids in Children

• NEPHROCALCINOSIS

  • iatrogenic (most common cause):

    furosemide (Rx for BPD), vitamin D (Rx for hypophosphatemic rickets)

  • noniatrogenic:

    • Idiopathic hypercalcemia

    • Williams syndrome

    • Absorptive hypercalcemia

    • Hyperparathyroidism

    • Milk-alkali syndrome

    • Kenny-Caffey syndrome

    • Distal renal tubular acidosis

    • Malignant tumors

    • Chronic glomerulonephritis

    • Sj gren syndrome (distal RTA)

    • Sarcoidosis

• METABOLIC DISEASE

  • Gout

  • Lesch-Nyhan syndrome (urate)

  • Fanconi syndrome

  • Glycogen storage disease (distal RTA)

  • Wilson disease (distal RTA)

  • Alpha-1 antitrypsin deficiency

  • Tyrosinemia

  • Cystinosis

  • Oxalosis

  • Crohn disease

• HYPOKALEMIA

  • Primary aldosteronism

  • Pseudo-Bartter syndrome

• PROTEIN DEPOSITS

  • Infant dehydration with presumed Tamm-Horsfall proteinuria

  • Toxic shock syndrome

• VASCULAR CONGESTION

  • Sickle cell anemia

• INFECTION

  • Candida / CMV nephritis

  • AIDS-associated Mycobacterium avium-intracellulare

• FIBROSIS OF RENAL PYRAMIDS

• CYSTIC MEDULLARY DISEASE

  • Medullary sponge kidney

  • Congenital hepatic fibrosis with tubular ectasia

P.885




• INTRARENAL REFLUX

  • Chronic pyelonephritis

Iron Accumulation in Kidney

• RENAL CORTEX

  • Paroxysmal nocturnal hemoglobulinuria (= intravascular extrasplenic hemolysis)

  • Sickle cell anemia

• RENAL MEDULLA

  • Hemorrhagic fever with renal syndrome (uncommon viral illness caused by Hanta virus)

    • Triad:

      • renal medullary hemorrhage

      • right atrial hemorrhage

      • necrosis of anterior pituitary

Depression of Renal Margins

• Fetal lobation

  • notching between normal calices

• Splenic impression

  • flattened upper outer margin of left kidney

• Chronic atrophic pyelonephritis

  • indentation over clubbed calices

• Renal infarct

  • normal calices

• Chronic renal ischemia

  • normal calices

Enlargement of Iliopsoas Compartment

• INFECTION

  • from retroperitoneal organs

    • Renal infection

    • Complicated pancreatitis

    • Postoperative aortic graft infection

  • from spine

    • Osteomyelitis / postoperative complication of bone surgery

    • Diskitis / postoperative complication from disk surgery

  • from GI tract

    • Crohn disease

    • Appendicitis

  • others

    • Pelvic inflammatory disease / postpartum infection

    • Sepsis

• HEMORRHAGE

  • Coagulopathy and anticoagulant therapy

  • Ruptured aortic aneurysm

  • Postoperative aneurysm repair / other surgery / trauma

• NEOPLASTIC DISEASE

  • extrinsic

    • Lymphoma

    • Metastatic lymphadenopathy

    • Bone metastases with soft-tissue involvement

    • Retroperitoneal sarcoma

  • intrinsic

    • Muscle tumors

    • Nervous system tumors

    • Lipoma / liposarcoma

• MISCELLANEOUS

  • Pseudoenlargement of psoas muscle compared with de facto atrophy of contralateral side in neuromuscular disease

  • Fluid collections

    • urinoma, lymphocele, pancreatic pseudocyst, enlargement of iliopsoas bursa

  • Pelvic venous thrombosis

    • diffuse swelling of all muscles (edema)

Renal Mass

Bilateral Renal Masses

• MALIGNANT TUMOR

  • Malignant lymphoma / Hodgkin disease

  • Metastases

  • Renal cell carcinoma

  • Wilms tumor

• BENIGN TUMOR

  • Angiomyolipoma

  • Nephroblastomatosis

• CYSTS

  • Adult polycystic kidney disease

  • Acquired cystic kidney disease

Renal Mass in Neonate

• UNILATERAL

  • Multicystic kidney (15%)

  • Hydronephrosis (25%)

    • UPJ obstruction

    • upper moiety of duplication

      

      Most Common Age at Presentation for Solid Renal Neoplasms

  P.886

  
  

  • Renal vein thrombosis

  • Mesoblastic nephroma

    • most common primary renal neoplasm in 1^st month of life

  • Rare: Wilms tumor, teratoma

• BILATERAL

  • Hydronephrosis

  • Polycystic kidney disease

  • Multicystic kidney + contralateral hydronephrosis

  • Nephroblastomatosis

  • Bilateral multicystic kidney

Renal Mass in Older Child

• SINGLE MASS

  • single solid mass

    • Wilms tumor (87%)

    • Clear cell sarcoma of kidney (6%)

    • Mesoblastic nephroma (2%)

    • Rhabdoid tumor (2%)

    • Renal cell carcinoma (<0.5%)

    • Teratoma

    • Intrarenal neuroblastoma

  • single cystic mass

    • Focal hydronephrosis

    • Multilocular cystic nephroma

    • Traumatic cyst, abscess

• MULTIPLE MASSES

  • Nephroblastomatosis

  • Multiple Wilms tumors

  • Angiomyolipoma

  • Lymphoma (<0.5%)

  • Leukemia

  • Adult polycystic kidney disease

  • Abscesses

Growth Pattern of Renal Lesions

Renal Lesion with Expansile Growth Pattern

• Renal cell carcinoma

• Oncocytoma

• Angiomyolipoma

• Juxtaglomerular tumor

• Metastatic tumor (eg, lymphoma)

• Mesenchymal tumor

Renal Lesions with Infiltrative Growth Pattern

• Imaging hallmarks:

  • growth initially respects renal contour

  • invasion of normal structures

  • poorly defined interface between normal renal parenchyma and lesion

  • enlarged kidney with preservation of reniform shape

  • IVP:

    • decreased / absent nephrogram

  • Angio:

    • vascular encasement, pruning, amputation

    • no vascular displacement

  • CT:

    • poorly marginated area of diminished enhancement

    • encasement of collecting system without displacement

    • replacement of renal sinus fat

  • US:

    • poorly circumscribed hypo- / hyperechoic regions

• NEOPLASM

  • lymphoproliferative

    • Lymphoma / leukemia

    • Extramedullary plasmacytoma

  • epithelial tumor of renal parenchyma

    • Renal cell carcinoma (unusual)

    • High-grade and sarcomatoid type of RCC

  • epithelial tumors of the renal pelvis

    • Invasive transitional cell carcinoma

      • mass arises from collecting system

    • Squamous cell carcinoma

  • medullary tumor of uncertain cell origin

    • Collecting duct carcinoma

    • Renal medullary carcinoma

  • metastases, esp. lung cancer

  • renal sarcomas

  • pediatric tumor

    • Mesoblastic nephroma

    • Rhabdoid tumor of the kidney

    • Nephroblastomatosis

    • Primitive neuroectodermal tumor

    • Wilms tumor (unusual)

• INFLAMMATION

  • Bacterial pyelonephritis

  • Xanthogranulomatous pyelonephritis

  • Renal parenchymal malacoplakia

Local Bulge in Renal Contour

• CYST

  • Simple renal cyst

• TUMOR

  • Adenocarcinoma

  • Angiomyolipoma

  • Pseudotumor

• INFECTION

  • Subcapsular abscess

  • XGP

• TRAUMA

  • Subcapsular hematoma

• DILATED COLLECTING SYSTEM

Unilateral Renal Mass

Solid Renal Mass

• TUMORS

  • primary malignant:

    • epithelial tumor of renal parenchyma:

      • adenocarcinoma (83%), papillary neoplasm (14%), chromophobe carcinoma (4%), renal neuroendocrine tumors (carcinoid, small cell carcinoma), Wilms tumor (6%),

    • epithelial tumor of renal pelvis:

      • TCC (8%), squamous cell carcinoma

    • medullary tumor:

      • renal medullary carcinoma, renal collecting duct carcinoma = Bellini duct carcinoma (1%)

    • renal sarcoma (2%)

    P.887

    
    

    in horseshoe kidney:

    • adenocarcinoma (45%), Wilms tumor (28%), transitional cell carcinoma (20%)

  • secondary malignant:

    • malignant lymphoma / Hodgkin disease, metastases, invasive transitional cell carcinoma

  • benign:

    • adenoma, oncocytoma, hamartoma (mesoblastic nephroma, angiomyolipoma, myolipoma, lipoma, leiomyoma, fibroma), hemangioma

• INFLAMMATORY MASSES

  • acute focal pyelonephritis, renal abscess, xanthogranulo- matous pyelonephritis, malacoplakia, tuberculoma

Fluid-filled Mass

• A. CYSTS

  • Simple renal cyst

  • Inherited cystic disease:

    • multicystic dysplastic kidney disease (Potter type II), multilocular cystic nephroma

  • Focal hydronephrosis

• B. VASCULAR

  • Arteriovenous malformation

  • Arteriovenous fistula

    • = single dilated artery + vein

    • tortuous varices over time

    • enlargement of renal vein

    • Cx: hydronephrosis

• Lesions <1 cm often cannot be clearly characterized

• Lesions 1 1.5 cm can often be ignored, particularly in elderly / patients with significant other disease

Calcified Renal Mass

• A calcified renal mass is malignant in 75% of cases!

• Lesions with

  • nonperipheral calcifications are malignant in 87%!

  • peripheral calcifications are malignant in 20%!

• A. TUMOR

  • Renal cell carcinoma (calcifies in 8 20%)

    • calcifications generally nonperipheral, sometimes along fibrous capsule

  • Wilms tumor

  • Transitional cell carcinoma (rare)

  • Osteosarcoma of renal capsule

  • Metastasis

• B. INFECTION

  • Abscess

    • Tuberculous abscess frequently calcifies!

    • Pyogenic abscess rarely calcifies!

  • Echinococcal cyst

    • Renal involvement in 3% of hydatid disease;

    • 50% of echinococcal cysts calcify

  • Xanthogranulomatous pyelonephritis

    • large obstructive calculus in >70%

• C. CYSTS

  • Calcification is related to prior hemorrhage or infection!

  • 1. Simple renal cyst (calcifies in 1 3%)

    • thin peripheral eggshell -like calcification

  • 2. Multicystic dysplastic kidney (in adult)

  • 3. Autosomal dominant polycystic kidney disease

  • 4. Milk of calcium (cyst, caliceal diverticulum, obstructed hydrocalyx)

  • DDx: residual pantopaque used in cyst puncture

• D. VASCULAR

  • Subcapsular / perirenal hematoma

  • Renal artery aneurysm

    • circular cracked eggshell appearance

  • Congenital / posttraumatic arteriovenous malformation

  • Arteriosclerosis in severe atherosclerotic disease, diabetes mellitus, hyperparathyroidism

  • Sloughed papilla in papillary necrosis

Avascular Mass in Kidney

• mnemonic:  CHEAT

  • Cyst

  • Hematoma

  • Edema

  • Abscess

  • Tumor

Hyperechoic Renal Nodule

• MALIGNANT TUMOR

  • Renal cell carcinoma

  • Angiosarcoma

  • Liposarcoma

  • Undifferentiated sarcoma

  • Lymphoma

• BENIGN TUMOR

  • Angiomyolipoma

  • Lipoma

  • Oncocytoma

  • Cavernous hemangioma

• INFARCT

• HEMATOMA

Hyperattenuating Renal Mass on NECT

• BENIGN

  • Complicated benign cyst: hemorrhagic, protein-rich, gelatinous

  • Leiomyoma

  • Angiomyolipoma (rare)

  • Thrombosed renal vein

• MALIGNANT

  • Metastasis from thyroid carcinoma

  • Renal cell carcinoma

Focal Area of Increased Renal Echogenicity

• NONNEOPLASTIC

  • Chronic renal infarction

  • Acute focal bacterial nephritis

• BENIGN TUMOR

  • Angiomyolipoma

  • Cavernous renal hemangioma

  • Oncocytoma

• MALIGNANCY

  • Renal cell carcinoma

  • Angiosarcoma

  • Undifferentiated sarcoma

  • Metastasis

P.888

Fat-containing Renal Mass

• Angiomyolipoma

• Lipoma, liposarcoma

• Teratoma

• Wilms tumor

• Xanthogranulomatous pyelonephritis

• Oncocytoma engulfing renal sinus fat

• Renal cell carcinoma

  • invasion of perirenal fat

  • intratumoral metaplasia into fatty marrow (in 32% if RCCs <3 cm)

• If a lesion contains fat + calcium RCC is likely, not angiomyolipoma!

Renal Sinus Mass

• TUMORS

  • Transitional cell carcinoma

  • Lymphoma

  • Metastasis to sinus lymph nodes

  • Mesenchymal tumor: lipoma, fibroma, myoma, hemangioma

  • Plasmacytoma

  • Myeloid metaplasia

• MISCELLANEOUS

  • Sinus lipomatosis

  • Parapelvic cyst

  • Saccular aneurysm

  • Urinoma

Hypoechoic Renal Sinus

• SOLID

  • Fibrolipomatosis

  • Column of Bertin

  • Duplex kidney

  • TCC / RCC

• CYSTIC

  • Renal sinus cysts

  • Caliectasis

  • Dilated veins, varix

  • Aneurysm, arteriovenous malformation

Renal pseudotumor

• = normal renal tissue mimicking a renal neoplasm

• A. PRIMARY / CONGENITAL

  • Large column of Bertin

    • = large septum / cloison of Bertin = large cloison = focal cortical hyperplasia = benign cortical rest = focal renal hypertrophy

    • = persistence of normal septal cortex / excessive infolding of cortex usually in the presence of partial or complete duplication

    • Location: between upper and interpolar portion

    • mass <3 cm in largest diameter

    • lateral indentation of renal sinus

    • deformation of adjacent calices + infundibula

    • mass continuous with renal cortex

    • enhancement pattern like renal cortex

    • echogenicity similar to cortex

  • Dromedary hump

    • = subcapsular nodule = splenic bump

      Cause:	prolonged pressure by spleen during fetal development
      Location:	in mid portion of lateral border of left kidney

    • triangular contour + elongation of middle calyx

    • enhancement pattern like renal cortex

  • Hilar lip

    • = supra- / infrahilar bulge = medial part of kidney above / below sinus

    • Location:  most frequently medial to left kidney just above renal pelvis (on transaxial scan)

    • enhancement pattern like cortex with medulla

  • Fetal lobation

    • = persistent cortical lobation = ren lobatus

    • = 14 individual lobes with centrilobar cortex located around calices

  • Lobar dysmorphism

    • complete diminutive lobe situated deep within renal substance with its own diminutive calyx in its central portion = calyx of nonresorbed normal junctional parenchyma between upper + lower subkidneys

• ACQUIRED

  • Nodular compensatory hypertrophy

    • areas of unaffected tissue in the presence of focal renal scarring from chronic atrophic pyelonephritis (= reflux nephropathy), surgery, trauma, infarction;

    • hypertrophy usually evident within 2 months; less likely to occur > age 50

    • mass enhances identically to renal parenchyma

      DDx:	accessory spleen, medial lobule of spleen, splenosis, normal / abnormal bowel, pancreatic disease, gallbladder, adrenal abnormalities
      Dx:	static radionuclide imaging / renal arteriography / CT

Pseudokidney Sign

• = sonographic mass of reniform appearance with a central hyperechoic region surrounded by a hyperechoic region

• 1. Intussusception

• 2. Necrotizing enterocolitis

• 3. Midgut volvulus

• 4. Sigmoid volvulus

• 5. Crohn disease

• False-positive:

  • feces in colon, perforated Meckel diverticulum with malrotation + Ladd bands, psoas muscle, hematoma

Renal cystic disease

Potter Classification

• = POTTER SYNDROME

• = any renal condition associated with severe oligohydramnios

• peculiar facies with wide-set eyes, parrot-beak nose, pliable low-set ears, receding chin

  Type I:	infantile PCKD
  Type II:	multicystic dysplastic kidney disease, multilocular cystic nephroma
  IIa:	kidneys of normal / increased size
  IIb:	kidneys reduced in size
  Type III:	adult PCKD, tuberous sclerosis, medullary sponge kidney
  Type IV:	small cortical cysts / cystic dysplasia secondary to ureteropelvic junction obstruction

P.889

Renal Cystic Disease

• GENETIC CYSTIC DISEASE

  • Autosomal dominant polycystic kidney disease

  • Autosomal recessive polycystic kidney disease

  • Medullary sponge kidney

  • Medullary cystic disease

  • Glomerulocystic kidney disease

    • = congenital disease with extremely variable presentation + prognosis

    • Path: cysts within Bowman capsule tubular cysts

    • multiple macroscopic cortical cysts

• OBSTRUCTIVE CYSTIC DISEASE

  • Multicystic dysplastic kidney

  • Segmental / focal renal dysplasia

  • Familial renal dysplasia

• ACQUIRED CYSTIC DISEASE

  • Simple cyst

  • Parapelvic cyst

  • Acquired cystic disease of uremia

  • Infectious cysts (TB, Echinococcus, abscess)

  • Medullary necrosis

  • Pyelogenic cyst

• CYSTS ASSOCIATED WITH SYSTEMIC DISEASE

  • Tuberous sclerosis

  • von Hippel-Lindau disease

• CYSTIC TUMORS

  • Multilocular cystic nephroma

  • Cystic Wilms tumor

  • Cystic renal cell carcinoma

Syndromes with Multiple Cortical Renal Cysts

• Von Hippel-Lindau syndrome

• Tuberous sclerosis

• Meckel-Gruber syndrome

• Jeune syndrome

• Zellweger syndrome = cerebrohepatorenal syndrome

• Conradi syndrome = chondrodysplasia punctata

• Orofacialdigital syndrome

• Trisomy 13

• Turner syndrome

• Dandy-Walker malformation

Multiloculated Renal Mass

• NEOPLASTIC DISEASE

  • Cystic renal cell carcinoma

  • Multilocular cystic renal tumor

    • cystic nephroma

    • cystic partially differentiated nephroblastoma

  • Cystic Wilms tumor

  • Necrotic tumor

    • mesoblastic nephroma

    • clear cell sarcoma

• RENAL CYSTIC DISEASE

  • Localized renal cystic disease

  • Septated cyst

  • Multicystic dysplastic kidney

  • Segmental multicystic dysplasia

  • Complicated cyst

• INFLAMMATORY DISEASE

  • Echinococcus

  • Segmental XGP

  • Abscess

  • Malacoplakia

• VASCULAR LESIONS

  • AV fistula

  • Organizing hematoma

Abnormal nephrogram

Absence of Nephrogram

Global Absence of Nephrogram

• Pathophysiology: complete renal ischemia secondary to occlusion of main renal artery

• Injury to vascular pedicle during blunt abdominal trauma

• Thromboembolic disease

• Renal artery dissection: spontaneous, traumatic, iatrogenic

Segmental Absence of Nephrogram

• SPACE-OCCUPYING PROCESS

  • Neoplasm

  • Cyst

  • Abscess

• FOCAL RENAL INFARCTION

  • Arterial embolus / thrombosis

  • Vasculitis, collagen-vascular disease

  • Sickle cell anemia

  • Septic shock

  • Renal vein thrombosis

Rim Nephrogram

• = rim of cortex receiving collateral blood flow from capsular, peripelvic, and periureteric vessels

• Most specific indicator of renovascular compromise!

• 2 4-mm peripheral band of cortical opacification

• Cause:

  • Acute total main renal artery occlusion: seen in 50% of cases with renal infarction

  • Renal vein thrombosis

  • Acute tubular necrosis

  • 4. Severe chronic urinary obstruction

• DDx: severe hydronephrosis (rim / shell nephrogram surrounding dilated calices)

Unilateral Delayed Nephrogram

• OBSTRUCTIVE UROPATHY

• REDUCTION IN RENAL bloodflow

  • Renal artery stenosis

  • Renal vein thrombosis

Striated Nephrogram

• = streaky linear bands of alternating hyper- and hypoattenuation parallel to axis of tubules + collecting ducts during excretory phase

P.890




• Cause:

  • stasis of contrast material in dilated collecting ducts on background of edematous renal parenchyma (diminished concentration of contrast material in tubules from ischemia + tubular obstruction by inflammatory cells + debris)

• UNILATERAL

  • Acute ureteric obstruction

  • Acute bacterial nephritis / pyelonephritis

  • Renal contusion

  • Renal vein thrombosis

• BILATERAL

  • Acute pyelonephritis

  • Intratubular obstruction: Tamm-Horsfall proteinuria, rhabdomyolysis with myoglobinuria

  • Systemic hypotension

  • Autosomal recessive PCKD

  • Medullary sponge kidney

  • Medullary cystic disease

• mnemonic:  CHOIR BOY

  • Contusion

  • Hypotension (systemic)

  • Obstruction (ureteral)

  • Intratubular obstruction

  • Renal vein thrombosis

  • Bacterial nephritis (acute)

  • Obstruction (ureteral) it is so common!

  • Yes, also cystic diseases: infantile PCKD, medullary cystic disease, medullary sponge kidney

Persistent Nephrogram

• BILATERAL GLOBAL

  • Systemic hypotension

  • Intratubular obstruction from protein:

    • Tamm-Horsfall, Bence Jones, myoglobin

  • Tubular damage by contrast material

• UNILATERAL GLOBAL

  • Renal artery stenosis

  • Renal vein thrombosis

  • Urinary tract obstruction

• SEGMENTAL

  • Obstructed moiety of duplicated collecting system

  • Obstructing renal calculus

  • Obstructing neoplasm

  • Focal stricture

  • Focal parenchymal disease: tubulointerstitial infection

Abnormal Nephrogram due to Impaired Perfusion

• SYSTEMIC HYPOTENSIVE REACTION

  • as reaction to contrast material / cardiac failure / dehydration / shock

  • Pathophysiology:

    • drop in perfusion pressure after contrast reaches kidney leads to increased salt + water reabsorption and slowed tubular transit

  • prolonged bilateral dense nephrograms = persistent increasing nephrogram

  • decrease in renal size

  • loss of pyelogram after initial opacification

  • NUC (use of glomerular filtration agent [eg, Tc-99m DTPA] preferred)

    • prolonged cortical transit + reduced excretion

• RENAL ARTERY STENOSIS

  • decreased nephrographic opacity + rim nephrogram

  • hyperconcentration in collecting system

  • ureteral notching

  • NUC (glomerular filtration agent [eg, Tc-99m DTPA] preferred):

    • decreased perfusion with prolonged excretory phase

• IMPAIRED PERFUSION OF SMALL ARTERIES

  • Trueta shunting = transient rerouting of blood flow from cortex to medulla

  • Cause:

    • reflex spasm during arterial angiography secondary to catheter trauma / pressure injection of highly concentrated contrast medium

    • chronic renal disorders (collagen vascular disease, malignant nephrosclerosis, chronic glomerulonephritis)

    • necrotizing vasculitis (polyarteritis nodosa, scleroderma, hypertensive nephrosclerosis)

  • CT, Angio:

    • inhomogeneous opacification of cortex

    • spotted nephrogram

  • IVP:

    • irregular cortical nephrogram = spotted nephrogram (DDx: scleroderma, hypertensive nephrosclerosis)

• ACUTE VENOUS OUTFLOW OBSTRUCTION

  • in renal vein thrombosis

  • obstructive nephrogram

  • progressive increase in opacity of entire kidney

Abnormal Nephrogram due to Impaired Tubular Transit

• Cause:

  • EXTRARENAL: ureteric obstruction (eg, stone)

    • obstructive nephrogram

    • NUC:

      • before decrease in renal function use of glomerular filtration agent (eg, Tc-99m DTPA); with decrease in renal function use of plasma flow agents (eg, Tc-99m MAG3 / I-123 Hippuran) preferred

    • continuous increase in renal activity

    • dilatation of collecting system

  • INTRARENAL

    • (a) segmental: limb of duplication system, caliceal obstruction, interstitial edema

      • segmental nephrogram

    • (b) protein precipitation: Tamm-Horsfall protein (a normal mucoprotein product of proximal nephrons), Bence Jones protein (multiple myeloma), uric acid precipitation (acute urate nephropathy), myoglobulinuria, hyperproteinuric state

    • striated nephrogram

    • NUC:

      • before decrease in renal function use of glomerular filtration agent (eg, Tc-99m DTPA); with decrease in renal function use of plasma flow agents (eg, Tc-99m MAG3 / I-123 Hippuran) preferred

      P.891

      
      

      • prolonged cortical transit time + prolonged excretory phase

Abnormal Nephrogram due to Abnormal Tubular Function

Pathophysiology:

• PROXIMAL TUBULE

  • reabsorbs almost all of glucose, amino acids, phosphate, bicarbonate

  • glycosuria (Toni-Fanconi syndrome)

  • aminoaciduria (cystinuria)

  • phosphaturia (phosphate diabetes, thiazides)

  • HCO₃^- wasting (proximal renal tubular acidosis)

• DISTAL TUBULE

  • absorbs most of water

  • diabetes insipidus, secretes H⁺

  • distal renal tubular acidosis

• Acute tubular necrosis

  • immediate persistent nephrogram (common)

  • progressive increasing opacity (rare)

• Contrast-induced renal failure

Striated Angiographic Nephrogram

= random patchy densities reflecting redistribution of blood flow from the cortical vasculature to the vasa recta of the medulla

• Obliterative diseases of the renal microvasculature:

  • polyarteritis nodosa, scleroderma, necrotizing angitis, catheter-induced vasospasm

• Acute bacterial nephritis

• Renal vein thrombosis

Increasingly Dense Nephrogram

• = initially faint nephrogram becoming increasingly dense over hours to days

• Mechanism:

  • diminished plasma clearance of contrast material

  • leakage of contrast material into renal interstitial space

  • increase in tubular transit time

• Cause:

  • VASCULAR = diminished perfusion

    • Systemic arterial hypotension (bilateral)

    • Severe main renal artery stenosis (unilateral)

    • Acute tubular necrosis (in 33%):

      • due to contrast material nephrotoxicity

    • Acute renal vein thrombosis

  • INTRARENAL

    • Acute glomerular disease

  • COLLECTING SYSTEM

    • Intratubular obstruction

      • Uric acid crystals (acute urate nephropathy)

      • Precipitation of Bence Jones protein (myeloma nephropathy)

      • Tamm-Horsfall protein (severely dehydrated infants / children)

    • Acute extrarenal obstruction: ureteral calculus

Vicarious Contrast Material Excretion during IVP

• = biliary contrast material detected radiographically following intravenous administration of contrast material

• Normal contrast excretion:

  • <2% of urographic dose of diatrizoates + iothalamates are handled by hepatobiliary excretion

• Pathophysiology:

  • increase in protein binding due to prolonged intravascular contact + acidosis

• Cause:

  • Uremia (reduction in glomerular filtration + uremia-associated acidosis)

  • Acute unilateral obstruction (increase in circulation time + transient intracellular acidosis)

  • Spontaneous urinary extravasation (prolonged vascular contact of contrast material)

Collecting system

Spontaneous Urinary Contrast Extravasation

• = SPONTANEOUS pyelorenal BACKFLOW

• Etiology: physiologic safety valve for obstructed urinary tract with pressures of 80 100 mm Hg in collecting system due to ipsilateral ureteral obstruction from distal stone impaction; pressure is proportional to degree + duration of acute obstruction + dose of contrast material

• Incidence:  0.1 18%; M > F (male ureter less compliant)

• Criteria:

  • absence of recent ureteral instrumentation

  • absence of previous renal / ureteral surgery

  • absence of destructive urinary tract lesion

  • absence of external trauma

  • absence of external compression

  • absence of pressure necrosis due to stone

• Types:

  • Pyelotubular backflow

    • = opacification of terminal portions of collecting ducts (= papillary ducts = ducts of Bellini) as a physiologic phenomenon (in 13% with low osmolality + in 0.4% with high osmolality contrast media), wrongly termed backflow

    • wedge-shaped brushlike lines from calyx toward periphery

  • Pyelosinus backflow

    • = contrast extravasation from ruptured fornices along infundibula, renal pelvis, proximal ureter; most common form

    • Cx: urinoma, retroperitoneal fibrosis

  • Pyelointerstitial backflow

    • = contrast flow from pyramids into subcapsular tubules

  • Pyelolymphatic backflow

    • = contrast extravasation into periforniceal + peripelvic lymphatics

    • visualization of small lymphatics draining medially

  • Pyelovenous backflow

    • = forniceal rupture into interlobar / arcuate veins; rare

Widened Collecting System & Ureter

Fetal pyelectasis

AP diameter of renal pelvis	<5 mm	<20 weeks MA
	<8 mm	20 30 weeks MA
	<10 mm	>30 weeks MA

P.892

• OBSTRUCTIVE UROPATHY

• NONOBSTRUCTIVE WIDENING

  • congenital

    • Megacalicosis

      • underdevelopment of papillae, usually unilateral

    • Congenital primary megaureter

      • = widened ureter with normally tapered distal end

    • Megacystis-megaureter syndrome

    • Prune-belly syndrome

    • Bardet-Biedl syndrome

    • Beckwith-Wiedemann syndrome

    • Megalourethra

  • increased urine volume

    • High-flow states: diabetes insipidus, osmotic diuresis, dehydrated patient undergoing rehydration, unilateral kidney

    • Vesicoureteral reflux

  • atony of renal collecting system

    • Infection: ie, acute pyelonephritis

    • Pregnancy

    • Retroperitoneal fibrosis

  • overdistended urinary bladder

  • previous long-standing significant obstruction:

    • dilatation remains in spite of relief of obstruction

Caliceal Abnormalities

• OPACIFICATION OF COLLECTING TUBULES

  • Pyelorenal backflow

  • Medullary sponge kidney

• PAPILLARY CAVITY

  • Papillary necrosis

  • Caliceal diverticulum

  • Tuberculosis / brucellosis

• LOCALIZED CALIECTASIS

  • Reflux nephropathy = chronic atrophic pyelonephritis

  • Compound calyx

  • Hydrocalyx

  • Congenital megacalyx

  • Localized postobstructive caliectasis

  • Localized tuberculosis / papillary necrosis

• GENERALIZED CALIECTASIS

  • Postobstructive atrophy

  • Congenital megacalices

  • Obstructive uropathy (hydronephrosis)

  • Nonobstructive hydronephrosis

  • Diabetes insipidus

Filling Defect in Collecting System

• mnemonic: 6 C's & 2 P's

  • Clot

  • Cancer

  • Cyst

  • Calculus

  • Candida + other fungi

  • Cystitis cystica

  • Polyp

  • Papilla (sloughed)

Nonopaque Intraluminal Mass in Collecting System

• NONOPAQUE CALCULUS

  • uric acid, xanthine, matrix

  • smooth, rounded, not attached

• TISSUE SLOUGH

  • Papillary necrosis

  • Cholesteatoma

  • Fungus ball = conglomeration of fibrillar hyphae

  • Inspissated debris ( mucopus )

• VASCULAR

  • 1. Blood clot: history of hematuria

  • change in appearance over time

• FOREIGN MATERIAL

  • Air from bladder via reverse peristalsis, direct trauma, renoalimentary fistula

  • Foreign matter

Mucosal Mass in Collecting System

• NEOPLASTIC

  • benign tumor

    • Aberrant papilla = papilla without calyx protruding into major infundibulum

    • Endometriosis

    • Fibroepithelial polyp = fibrous polyp

      • = fibroepithelioma = VASCULAR FIBROUS POLYP = POLYPOID FIBROMA

      • = mesodermal tumor with fibrovascular stroma + normal transitional cell epithelium

      • Age: 20 40 years

      • intermittent abdominal / flank pain

      • gross hematuria (rare)

      • elongated cylindrical filling defect with smooth margins

      • mobile on thin pedicle

  • malignant tumor

    • Uroepithelial tumors

      • Transitional cell carcinoma (85 91%)

      • Squamous cell carcinoma (10 15%)

        • Predisposing factors:

          • calculi (50 60%), chronic infection, leukoplakia, phenacetin abuse

          • infiltrating / superficially spreading

      • Mucinous adenocarcinoma

        • = metaplastic transformation

      • Sarcoma (extremely rare)

    • Metastases: breast (most common), melanoma, stomach, lung, cervix, colon, prostate

• INFLAMMATION / INFECTION

  • Tuberculosis

  • Candidiasis

  • Schistosomiasis

  • Pyeloureteritis cystica

  • Leukoplakia

  • Malacoplakia

  • Xanthogranulomatous pyelonephritis

• VASCULAR

  • submucosal hemorrhage

    • 1. Trauma

    • 2. Anticoagulant therapy

    • 3. Acquired circulating anticoagulants

    • 4. Complication of crystalluria / microlithiasis

    • thumbprinting with progressive improvement

  • vascular notching

    • Ureteropelvic varices

    P.893

    
    

    • Renal vein occlusion

    • IVC occlusion

    • Vascular malformation

    • Retroaortic left renal vein

    • Nutcracker effect on left renal vein between aorta and SMA

    • Polyarteritis nodosa

• PROMINENT MUCOSAL FOLDS

  • Redundant longitudinal mucosal folds of intermittent hydronephrosis (UPJ obstruction, vesicoureteral reflux) or after relief of obstruction

  • Chemical / mechanical irritation

  • Urticaria (Stevens-Johnson syndrome = erythema multiforme bullosa)

  • Leukoplakia (= squamous metaplasia)

  • Ureteral diverticulosis = rupture of the roofs of cysts in ureteritis cystica

Effaced Collecting System

• EXTRINSIC COMPRESSION

  • Unilateral / bilateral global enlargement of renal parenchyma

  • Renal sinus masses

    • Hemorrhage

    • Parapelvic cyst

    • Sinus lipomatosis

• SPASM / INFLAMMATION

  • infection

    • Acute pyelonephritis

    • Acute bacterial nephritis

    • Acute tuberculosis

  • Hematuria

• INFILTRATION

  • Malignant uroepithelial tumors

• OLIGURIA

  • Antidiuretic state

  • Renal ischemia

  • Oliguric renal failure

Renal calcification

Retroperitoneal Calcification

• NEOPLASM

  • Wilms tumor (in 10%)

  • Neuroblastoma (in 50%): fine granular / stippled / amorphous

  • Teratoma: cartilage / bone / teeth, pseudodigits, pseudolimbs

  • Cavernous hemangioma: phleboliths

• INFECTION

  • Tuberculous psoas abscess

  • Hydatid cyst

  • Alkaline-encrusted cystitis and pyelitis

• TRAUMA

  • Old hematoma

Nephrocalcinosis

• = NEPHROLITHIASIS

• = deposition of calcium salts in renal parenchyma

• Incidence:  0.1 6%; M > F

• Cause:  mnemonic:  MARCH

  • Medullary sponge kidney

  • Alkali excess

  • Renal medullary / cortical necrosis, RTA

  • Chronic glomerulonephritis

  • Hyperoxaluria, Hypercalcemia, Hypercalciuria

Medullary Nephrocalcinosis

• = calcifications involving the distal convoluted tubules in the loops of Henle

• Incidence:  95% of all nephrocalcinoses

• Cause:

  • HYPERCALCIURIA

    • endocrine

      • Hyperparathyroidism in 5% (primary >> secondary)

      • Paraneoplastic syndrome of lung + kidney primary (ectopic parathormone production)

      • Cushing syndrome

      • Diabetes insipidus

      • Hyperthyroidism / hypothyroidism

    • alimentary

      • Milk-alkali syndrome (excess calcium + alkali = milk + antacids)

      • Hypervitaminosis D

      • Beryllium poisoning

    • osseous

      • Osseous metastases, multiple myeloma

      • Prolonged immobilization

      • Progressive senile osteoporosis

    • renal

      • Medullary sponge kidney

      • Renal tubular acidosis (in 73% of primary RTA)

      • Bartter syndrome

        • tubular disorder with potassium + sodium wasting, hyperplasia of juxtaglomerular apparatus, hyperaldosteronism, hypokalemic alkalosis, and normal blood pressure

    • drug therapy

      • Furosemide (in infants)

      • Prolonged ACTH therapy

      • Vitamin E (orally)

      • Vitamin D excess

      • Calcium (orally)

      • Nephrotoxic drugs: outdated tetracycline, amphotericin B

    • miscellaneous

      • Sarcoidosis

      • Idiopathic hypercalciuria

      • Idiopathic hypercalcemia

  • HYPEROXALURIA = OXALOSIS

    • Primary hyperoxaluria

      • = Hereditary hyperoxaluria (more common)

      • = rare autosomal recessive inherited enzyme deficiency of carboligase with diffuse oxalate deposition in kidneys, heart, blood vessels, lung, spleen, bone marrow

      • Type I   =    -ketoglutarate-glyoxylate carboxylase deficiency

        • glycolic aciduria

      P.894

      
      

      • Type II   =   D-glycerate dehydrogenase deficiency

        • 1-glyceric aciduria

        • Age:  usually <5 years

        • Prognosis:  early death in childhood

    • Secondary hyperoxaluria

      • = enteric hyperoxaluria (rare)

      • Cause:  disturbance of bile acid metabolism after jejunoileal bypass, ileal resection, blind loop syndrome, Crohn disease, increased ingestion (green leafy vegetables), pyridoxine deficiency, ethylene glycol poisoning, methoxyflurane anesthesia

  • hyperuricosuria

    • Gouty kidney

    • Lesch-Nyhan syndrome

  • URINARY STASIS

    • Milk-of-calcium in pyelocaliceal diverticulum

    • Medullary sponge kidney

  • DYSTROPHIC CALCIFICATION

    • Renal papillary necrosis (especially analgesic nephropathy)

    • Chronic pyelonephritis

    • Sickle cell disease

    • Renal tuberculosis

      • mnemonic:  HAM HOP

        • Hyperparathyroidism

        • Acidosis (renal tubular)

        • Medullary sponge kidney

        • Hypercalcemia / hypercalciuria (sarcoidosis, milk-alkali syndrome, hypervitaminosis D)

        • Oxalosis

        • Papillary necrosis

• normal-sized / occasionally enlarged kidneys (medullary sponge kidney)

• small poorly defined / large coarse granular calcifications in renal pyramids:

  • uniform deposition: hyperparathyroidism / distal renal tubular acidosis (type 1)

  • asymmetric deposition in dilated collecting ducts within papillary tips: medullary sponge kidney

• US:

  • absence of hypoechoic papillary structures (earliest sign)

  • hyperechoic rim at corticomedullary junction + around tip and sides of pyramids

  • solitary focus of hyperechogenicity at tip of pyramid near fornix

  • increased echogenicity of renal pyramids shadowing (no acoustic shadowing with small + light calcifications)

• DDx of hyperechoic medulla in newborns:

  • oliguria with transient tubular blockage by Tamm-Horsfall proteinuria

• Cx: often followed by urolithiasis

Cortical Nephrocalcinosis

• = calcium deposition in renal cortex

• Incidence:  5% of all nephrocalcinoses

• Cause:

  • Acute cortical necrosis

  • Chronic glomerulonephritis

  • Alport syndrome = hereditary nephritis + deafness

  • Congenital oxalosis, primary hyperoxaluria

  • Chronic paraneoplastic hypercalcemia

  • Toxic: ethylene glycol, methoxyflurane

  • Sickle cell disease

  • Rejected renal transplant

    • mnemonic:  COAG

      • Cortical necrosis (acute)

      • Oxalosis

      • Alport syndrome

      • Glomerulonephritis (chronic)

• thin rim of calcification with a tramline appearance

• spotty appearance (= preferential deposition in necrotic glomeruli)

• US:

  • homogeneously increased echogenicity of renal parenchyma > liver echogenicity

Renovascular Disease

Renal Artery Aneurysm

• Prevalence: 0.01 0.1%; 22% of visceral aneurysms

• Types:

  • saccular (most common): near first bifurcation of main renal artery; congenital; associated with medial fibroplasia + atherosclerosis

  • fusiform: in medial fibroplasia; not calcified

  • dissecting: traumatic, spontaneous (atherosclerosis, intimal fibroplasia, perimedial fibroplasia), iatrogenic

• Cx:

  • Hypertension (unusual)

  • Perinephric / retroperitoneal hemorrhage [rare] with increased risk in peripartum women

  • Formation of AV fistula

  • Peripheral renal embolization [from mural thrombus]

  • Thrombosis

  • Hematuria

Extrarenal Aneurysm (2/3)

• True aneurysm

  • Atherosclerotic (most common)

  • Fibromuscular dysplasia

  • Pregnancy

  • Mesenchymal disease: neurofibromatosis, Ehlers-Danlos syndrome

• False aneurysm

  • Trauma; renal artery angioplasty

  • Beh et disease

  • Mycotic aneurysm

    • 2.5% of all aneurysms

    • Cause:  bacteremia, SBE, perivascular extension of inflammation

    • Organism:  Streptococcus, Staphylococcus, Pneumococcus, Salmonella

• incomplete / complete ring of calcification

• variable enhancement (depending on amount of thrombus)

• Rx:

  • conservative in asymptomatic patient for well-calcified aneurysm <2 cm in diameter

  P.895

  
  

  • surgery for (a) interval growth, (b) emboli to kidney, (c) in woman of childbearing age, (d) diminished renal function / ischemia / hypertension / dissection

Intrarenal Aneurysm (1/3)

in interlobar and more peripheral branches

• CONGENITAL (most common)

  • Congenital renal aneurysm

    • Age at Dx: 30 years or older; M:F = 1:1

    • hypertension in 25% (from segmental renal ischemia)

    • saccular aneurysm close to vascular bifurcations, may calcify

    • often bilateral

    • Rx: surgical / endovascular repair for aneurysm >1.0 cm in hypertensive patient / for aneurysm >1.5 cm in asymptomatic normotensive patient

• ARTERITIS

  • Polyarteritis nodosa

  • SLE

  • Allergic vasculitis

  • Wegener granulomatosis

  • Transplant rejection

  • Drug-abuse vasculitis

    • Kidney most commonly affected organ

    • Cause:

      • immunologic injury from circulating hepatitis antigen-antibody complexes producing a necrotizing angitis

      • bacterial endocarditis

      • drug-related

      • impurity-related

    • Drugs:  methamphetamine, heroin, LSD

    • multiple small aneurysms in interlobar branches near corticomedullary junction

    • inhomogeneous spotty nephrogram

• DEGENERATIVE: Atherosclerosis (may calcify)

• TUMOR

  • Neoplasm (RCC in 14%; adult Wilms tumor)

  • Hamartoma (angiomyolipoma in 50%)

  • Metastatic arterial myxoma

  • Vascular malformation

• MESENCHYMAL DISEASE:

  • Neurofibromatosis

  • Fibroplasia

• TRAUMA

• INFECTION: syphilis, tuberculosis

Spontaneous Retroperitoneal Hemorrhage

• RENAL TUMOR (57 63%)

  • malignant tumor (30 33%)

    • RCC (33%)

    • TCC of renal pelvis

    • Wilms tumor

    • Lipo-, fibro-, angiosarcoma

  • benign tumor (24 33%):

    • Angiomyolipoma (16 24%)

    • Lipoma

    • Adenoma

    • Fibromyoma

    • Ruptured hemorrhagic cyst

• VASCULAR DISEASE (18 26%)

  • Ruptured renal artery aneurysm

  • Vasculitis (eg, polyarteritis nodosa in 13%)

  • Arteriovenous malformation

  • Segmental renal infarction

• INFLAMMATION / INFECTION (7 10%)

  • Abscess (in 50% of infections)

  • Acute / chronic nephritis

• COAGULOPATHY

  • Anticoagulant therapy (in 4.3 6.6% of IV heparin, in 01. 0.6% of oral anticoagulants)

    • Source:  idiopathic (42%), tumor (21%), stone disease (17%), hemorrhagic cystitis

  • Bleeding diathesis

  • Long-term hemodialysis

• PRIMARY ADRENAL CYST / TUMOR

  • Pheochromocytoma

    • Massive bleed due to an undiagnosed pheochromocytoma has been lethal in 50%!

  • Pseudocyst

  • Myelolipoma

  • Hemangioma

  • Adrenocortical adenoma / carcinoma

  • Metastasis

• flank pain of sudden onset

• Follow-up CT may be indicated at 3 and 6 months if the source of blood remains indeterminate!

• Surgical exploration must be considered to uncover a small renal tumor if the cause of hemorrhage is not determined radiologically!

Subcapsular Hematoma

• subcapsular mass with flattening of renal parenchyma

• total resorption / formation of pseudocapsule with calcification

• Angio:

  • avascular mass

• Cx: Page kidney (ischemia, release of renin, HTN)

Renal Doppler

• NORMAL RENAL DOPPLER

  • resistive index (RI) of 0.70 = upper limit of normal

  • Elevation of RI:

    • significant systemic hypotension

    • markedly decreased heart rate

    • perinephric / subcapsular fluid collection

    • in neonates + infants

• RENAL MEDICAL DISEASE

  • Elevation of RI more likely with vascular / tubulointerstitial process, less likely with glomerular disease

  • May be useful in predicting clinical outcome in:

    • hemolytic-uremic syndrome

    • acute renal failure

    • nonazotemic patients with severe liver disease

• RENAL ARTERY STENOSIS

• RENAL VEIN THROMBOSIS

P.896

Ureter

Ureteral Deviation

• LUMBAR URETER

  • lateral deviation (common)

    • Hypertrophy of psoas muscle

    • Enlargement of paracaval / paraaortic lymph nodes

    • Aneurysmal dilatation of aorta

    • Neurogenic tumors

    • Fluid collections (abscess, urinoma, lymphocele, hematoma)

  • medial deviation

    • Retrocaval ureter (on right side only)

    • Retroperitoneal fibrosis

• PELVIC URETER

  • medial deviation

    • Hypertrophy of iliopsoas muscle

    • Enlargement of iliac lymph nodes

    • Aneurysmal dilatation of iliac vessels

    • Bladder diverticulum at UVJ (Hutch)

    • Following abdominoperineal surgery + retroperitoneal lymph node dissection

    • Pelvic lipomatosis

  • lateral deviation with extrinsic compression

    • Pelvic mass (eg, fibroids, ovarian tumor)

Ureteral Dilatation

Size of ureter:  >3 mm

• OBSTRUCTION

  • Ureterolithiasis

• CONGENITAL

  • Chronic vesicoureteral reflux

  • Posterior urethral valves

  • Megaureter

  • Prune-belly syndrome

• INFECTION / INFLAMMATION

  • impairing ureteral peristalsis

  • 1. UTI (eg, E. coli, Pseudomonas, Citrobacter)

  • 2. Appendicitis

  • 3. Diverticulitis

• COMPRESSION

  • by pelvic / abdominal mass

Megaureter

• VESICOURETERAL REFLUX

  • primary vesicoureteral reflux

    • Primary reflux megaureter

      • Cause: abnormal ureteral tunnel at UVJ

    • Prune belly syndrome

  • secondary vesicoureteral reflux

    • Hypertonic neurogenic bladder

    • Bladder outlet obstruction

    • Posterior urethral valves

• OBSTRUCTION

  • primary obstruction

    • Intrinsic ureteral obstruction (stone, stricture, tumor)

    • Ectopic ureter

    • Ureterocele

    • Ureteral duplication

      • tortuous dilated ureter of upper moiety

  • secondary obstruction

    • Retroperitoneal obstruction: tumor, fibrosis, aortic aneurysm

    • Bladder wall mass

    • Bladder outlet obstruction: eg, prostatic enlargement

• NONREFLUX-NONOBSTRUCTED MEGAURETER

  • Congenital primary megaureter = megaloureter

  • Polyuria: eg, diabetes insipidus, acute diuresis

  • Infection

  • Ureter remaining wide after relief of obstruction

• mnemonic:  DiaPOUR

  • Diabetes insipidus

  • Primary megaureter

  • Obstruction (recent / old)

  • UVJ obstruction

  • Reflux

Ureteral Stricture

• INTRINSIC CAUSE

  • mucosal

    • Primary ureteral tumors

  • mural

    • Endometriosis

      • common disorder in menstruating women (15%); ureteral involvement is rare and indicates widespread pelvic disease

      • abrupt smooth stricture of 0.5 2.5 cm length

      • rectosigmoid involvement on BE

    • Tuberculosis, schistosomiasis

    • Traumatic

      • ureterolithotomy, endoscopic stone extraction, hysterectomy

    • Amyloidosis

      • distal stricture with submucosal calcification

    • Nonspecific (rare)

• EXTRINSIC CAUSE

  • Endometriosis

    • extrinsic form:intrinsic form = 4:1

  • Abscess

    • tuboovarian, appendiceal, perisigmoidal

  • Inflammatory bowel disease

    • (eg, Crohn disease, diverticulitis)

  • Radiation fibrosis

  • Metastases

    • cervix, endometrium, ovary, rectum, prostate, breast, lymphoma

  • Iliac artery aneurysm (with perianeurysmal fibrosis)

• mnemonic:  MISTER

  • Metastasis (extrinsic / intrinsic)

  • Inflammation from calculus

  • Schistosomiasis

  • Tuberculosis, Transitional cell carcinoma, Trauma

  • Endometriosis + other periureteral inflammatory process

  • Radiation therapy, Retroperitoneal fibrosis

Ureteral Filling Defect

• FIXED

  • neoplasm

    P.897

    
    

    • Urothelial neoplasm

    • Metastasis

    • Fibroepithelial polyp

  • inflammation

    • Ureteritis cystica

    • Tuberculosis

    • Endometriosis

• MOBILE

  • Calculus

  • Sloughed papilla

  • Blood clot

Ureteral Calcification

• URETERAL LUMEN

  • Stone migrated from kidney

  • Stone in ureteral diverticulum / ureterocele

  • Steinstrasse (stone street) = collection of stone fragments in distal ureter following lithotripsy

• URETERAL WALL

  • Schistosomiasis

  • Tuberculosis

  • Amyloid infiltration

  • Ureteral tumor

• DDx:

  • Phlebolith in gonadal vein (multiple, not along course of ureter, centrally radiolucent)

  • Orally administered contrast material trapped in appendix / diverticulum

  • Dermoid cyst with calcification

  • Silastic fallopian tube band

  • Radiation seeds used for prostate cancer

Urinary Bladder

Bilateral Narrowing of Urinary Bladder

• WITH ELEVATION OF BLADDER FLOOR

  • Pelvic lipomatosis

  • Pelvic hematoma

    • Cause:  trauma, anticoagulant therapy, spontaneous rupture of blood vessels, blood dyscrasia (rare), bleeding neoplasm (rare)

  • 3. Chronic cystitis

• WITH SUPERIOR COMPRESSION OF BLADDER

  • Thrombosis of IVC

    • Cause:  trauma, hypercoagulability state (oral contraceptives), extension of thrombi from lower extremity, abdominal sepsis, Budd-Chiari syndrome, compression of IVC by neoplasm

    • collaterals through gonadal veins, ascending lumbar veins, vertebral plexus, retroperitoneal veins, portal vein (via hemorrhoidal veins)

    • notching of distal ureter by ureteral veins

  • Pelvic lymphadenopathy

    • Cause:  lymphoma (most often), prostatic carcinoma

    • polycyclic asymmetric compression of bladder

    • medial displacement of pelvic segment of ureters

    • lateral displacement of upper ureters

  • Hypertrophy of iliopsoas muscles

  • Bilateral pelvic masses

    • bilateral lymphocysts (following radical pelvic surgery)

    • bilateral urinomas

    • bilateral pelvic abscesses

  • Retroperitoneal fibrosis

  • Large iliac artery aneurysms

Inverted Pear-shaped Urinary Bladder

• mnemonic:  HALL

  • Hematoma

  • Aneurysm (bilateral common / external iliac artery)

  • Lipomatosis, pelvic

  • Lymphadenopathy (pelvic)

Small Bladder Capacity

• Cause:

  • Thickened / fibrotic bladder wall

    • Interstitial cystitis

    • Tuberculous cystitis

    • Cystitis cystica

    • Schistosomiasis

    • Trauma: surgical resection, radiation therapy

  • Disuse of bladder

• urinary frequency

• progressive rise in bladder pressure during filling

• reduced bladder compliance

• thickened bladder wall + decreased bladder volume

• vesicoureteral reflux

Bladder Wall Thickening

• Normal bladder wall thickness (regardless of age + gender):

  • <5 mm   in nondistended bladders

  • <3 mm   in well-distended bladders

• TUMOR

  • Neurofibromatosis

• INFECTION / INFLAMMATION

  • Cystitis

• MUSCULAR HYPERTROPHY

  • Neurogenic bladder

  • Bladder outlet obstruction (eg, posterior urethral valves)

• UNDERDISTENDED BLADDER

Urinary Bladder Wall Masses

• CONGENITAL

  • Congenital septum

  • Simple ureterocele

  • Ectopic ureterocele

• BLADDER TUMORS

• INFLAMMATION / INFECTION

  • Cystitis: hemorrhagic cystitis, abacterial cystitis, bullous cystitis, edematous cystitis, interstitial cystitis, eosinophilic cystitis, granulomatous cystitis, emphysematous cystitis, cystitis cystica, cyclophosphamide cystitis, cystitis glandularis (premalignant lesion with villous lesions in bladder dome from proliferation of intestinelike glands in submucosa)

  • Tuberculosis

  • Schistosomiasis

  • Malacoplakia

  P.898

  
  

  • Extravesical inflammation:

    • Diverticulitis

    • Crohn disease

    • endometriosis

• HEMATOMA

  • after instrumentation, surgery, trauma

Bladder Tumor

• Incidence:  2 6% of all tumors

• EPITHELIAL TUMORS (95%)

  • Urothelial carcinoma = transitional cell carcinoma (90%)

  • Squamous cell carcinoma (4% in USA)

    • worst prognosis; secondary to chronic disorders (chronic irritation from indwelling catheters, infection, stricture, calculi), cyclophosphamide, smoking, intravesical bacillus Calmette-Gu rin, bladder diverticula, schistosomiasis (>50% of bladder tumors in contries with endemic bilharziasis)

  • Adenocarcinoma (1%)

    • most common in bladder exstrophy, less common in cystitis glandularis + urachal carcinoma (at dome of bladder in urachal remnant)

    • metastatic adenocarcinoma (colon, prostate, rectum) more common than primary

  • Small cell / neurondocrine carcinoma (<0.5%)

    • = highly aggressive tumor with invasive disease in 94% at presentation

    • Age:  20 91 years; M:F = 3 5:1

    • ematuria (88%)

    • large polypoid / nodular tumor

    • size from 3 to 8 cm

    • Prognosis: 16% 5-year survival rate

  • Carcinoid

    • Mean size:  6 mm

  • Melanoma (extremely rare)

• NONEPITHELIAL / mesenchymal TUMORS

  • primary benign tumors from

    • muscle

      • Leiomyoma (0.43%)

        • Most common nonepithelial tumor

        • Age: 22 78 years; M:F = 1:1

        • hematuria secondary to ulceration

        • Location: arise in submucosa

        • Site: submucosal (7%) / intravesical (63%) / extravesical (30%)

        • solid homogeneous mass

        • smooth indentation of bladder wall

        • intraluminal mass degeneration

      • Rhabdomyoma (rare)

    • nerve

      • Neurofibroma / NF 1 in 60%

        • typically low in attenuation on CT

        • hypointense mass on T1WI

        • target sign on T2WI for plexiform neurofibroma = central hypointense fibrosis surrounded by hyperintense myxoid stroma

      • Paraganglioma = pheochromocytoma (0.1%)

        • 1% of all pheochromocytomas

        • Age: 10 78 years; M < F

        • Origin: from paraganglia of bladder wall

        • adrenergic attack at micturition ( micturition attack ) / bladder filling (headaches, weakness) in 50%

        • intermittent hypertension

        • elevated catecholamine levels

        • submucosal mass

        • ring calcification around circumference

        • marked enhancement (KEY FEATURE)

        • N.B.: biopsy may incite hypertensive crisis!

        • Prognosis: 7% are malignant

    • fat

      • Lipoma

    • fibrous tissue

      • Fibroma

      • Solitary fibrous tumor

    • blood vessels

      • Hemangioma

        • Age: 50% during childhood; 58 (range, 19 76) years during adulthood

        • median size of 7 mm (range, 2 30 mm)

      • Plasmacytoma

      • Nephrogenic adenoma

        • Associated with: cystitis cystica / cystitis glandularis

  • primary malignant tumors

    • Primary lymphoma

      • 2nd most common nonepithelial tumor of urinary bladder

      • Age: 40 years; M:F = 1:3

      • Histo: low-grade B-cell mucosa-associated lymphoid tissue (MALT) / diffuse large B-cell type

      • Location: submucosal; at bladder base + trigone

    • Rhabdomyosarcoma

      • Age: 1st and 2nd decades of life

      • Most common bladder tumor in patients <10 years of age

    • Leiomyosarcoma

      • Most common nonepithelial malignant bladder tumor

      • Age: mainly >40 (range, 25 88) years; M:F = 3:1

      • Location: rarely at trigone

      • poorly circumscribed invasive mass

      • heterogeneous texture from necrosis (common)

      • mean size of 7 cm

    • Osteosarcoma

  • secondary tumors

    • Metastases

      • 1.5% of all bladder malignancies

      • Origin: melanoma > stomach > breast > kidney > lung

      • solitary / multiple nodules

    • Lymphoma

      • bladder involved at autopsy: in 15% of NHL, in 5% of Hodgkin disease

    • Leukemia

      • microscopic involvement in 22% at autopsy

    • Direct extension (common)

      P.899

      
      

      • from prostate, rectum, sigmoid, cervix, ovary

    • Endometriosis

      • Location: on posterior wall

      • urinary symptoms in 80%

Bladder Calcification

Bladder Calculi

• Stasis calculi (70%)

  • in bladder outflow obstruction, bladder diverticula, cystocele, neuropathic bladder dysfunction

  • Associated with:  gram-negative lower urinary tract infection (in 30%), in particular Proteus

• Migrant calculi

  • = renal calculi spontaneously passing into bladder

• Foreign body nidus calculi

  • from self-introduced objects, urinary stent, chronic catheterization, bladder wall-penetrating bone fragments, prostatic chips, nonabsorbable suture material, fragments of Foley balloon catheter, pubic hair, presence of intestinal mucosa (in bladder augmentation, ileal conduit, repaired bladder exstrophy)

• Idiopathic/ primary/ endemic calculi

  • Countries: in North Africa, India, Indonesia

  • Age: in young boys of low socioeconomic class (nutritional deficiency?)

• Incidence: India (13:100,000); less common in western hemisphere

• Number of stones: solitary (86%); multiple (in up to 25%)

• Composition: magnesium ammonium phosphate (50%), calcium salts (31%), uric acid origin (5%)

• hematuria, recurrent UTIs, pelvic pain, irritative / obstructive voiding symptoms

• Rx: surgical extraction, lithotripsy, alkalinization of urine

• Rate of recurrence: 41%

Bladder Wall Calcification

• INFLAMMATION

  • Schistosomiasis (50%)

    • relatively normal distensibility of bladder

    • thin arcuate pattern of calcification

  • Tuberculosis

    • bladder markedly contracted

  • Cystitis:

    • postirradiation cystitis, alkaline incrusted cystitis, cytotoxin cystitis

  • Bacillary UTI (extremely uncommon)

  • Encrusted foreign material

  • Alkaline-encrusted cystitis and pyelitis

• NEOPLASM

  • Primary neoplasm of bladder: TCC, squamous cell carcinoma, leiomyosarcoma, hemangioma, neuroblastoma, osteogenic sarcoma

  • Urachal carcinoma

• mnemonic:  SCRITT

  • Schistosomiasis

  • Cytoxan

  • Radiation

  • Interstitial cystitis

  • Tuberculosis

  • Transitional cell carcinoma

Masses Extrinsic to Urinary Bladder

• NORMAL / ENLARGED ORGANS

  • Uterus, leiomyomatous uterus, pregnant uterus

  • Distended rectosigmoid

  • Ectopic pelvic kidney

  • Prostate cancer / BPH

• SOLID PELVIC TUMORS

  • Lymphadenopathy

  • Bone tumor from sacrum / coccyx

  • Rectosigmoid mass

  • Hip arthroplasty

  • Neurogenic neoplasm, meningomyelocele

  • Pelvic lipomatosis / liposarcoma

• CYSTIC PELVIC LESIONS

  • congenital / developmental

    • Urachal cyst

    • M llerian duct cyst

    • Gartner duct cyst

    • Anterior meningocele

    • Hydrometrocolpos

  • related to trauma

    • Hematoma (eg, rectus sheath hematoma)

    • Urinoma

    • Lymphocele

    • Abscess

    • Aneurysm

    • Mesenteric cyst

  • cyst of genitalia

    • Prostatic cyst

    • Cyst of seminal vesicle

    • Cyst of vas deferens

    • Ovarian cyst

    • Hydrosalpinx

    • Vaginal cyst

  • cyst of urinary bladder

    • Bladder diverticulum

  • cyst of GI tract

    • Peritoneal inclusion cyst

    • Fluid-filled bowel

Voiding Dysfunction

• FAILURE TO STORE URINE

  • urinary frequency, urgency, incontinence

  • bladder causes

    • involuntary detrusor contractions

      • detrusor instability (idiopathic / neurogenic)

      • detrusor hyperreflexia (upper cord lesion)

    • poor bladder compliance

      • detrusor hyperreflexia

      • bladder wall fibrosis

    • sensory urgency

      • infection, inflammation, irritation

      • neoplasia

    • vesicovaginal fistula

    • psychogenic condition

  P.900

  
  

  • sphincter causes

    • Stress incontinence

    • Sphincteric incontinence

  • extravesical ectopic insertion of ureter in females

• FAILURE TO EMPTY BLADDER

  • poor flow, straining, hesitancy

  • inability to completely empty bladder

  • bladder causes

    • Detrusor areflexia (sacral arc lesion)

    • Impaired detrusor contractility (myogenic)

    • Psychogenic condition

  • bladder outlet obstruction:

    • Bladder neck contracture

    • Prostatic enlargement

    • Detrusor-external sphincter dyssynergia

    • Scarring from surgery / radiation therapy

    • Ectopic ureterocele

    • Urethral stenosis

    • Urethral kinking (eg, due to cystocele)

Incontinence

• Stress incontinence

• Vesicovaginal / ureterovaginal fistula

• Urge incontinence

• Psychogenic incontinence

• Overflow incontinence

  • secondary to lesions of sacral spinal cord / sacral reflex arc or severe outlet obstruction

• Reflex voiding

  • hyperreflexive lesion (lesion of upper spinal cord)

  • uninhibited / unstable bladder

• Continual dribbling

  • = extravesical ectopic termination of ureter

Stress Incontinence

• = SPHINCTER WEAKNESS INCONTINENCE

• Cause:

  • Male: S/P prostatectomy with damage to distal sphincter

  • Female: congenital bladder neck weakness, pregnancy, childbirth, aging (secondary to changes in anatomic relationship of urethra + bladder base)

• frequency, urgency (involuntary filling of bladder neck)

• opening of bladder neck during coughing

• impairment of milk-back mechanism (= retrograde emptying of urethra during interruption of voiding phase does not occur)

• urethrovesical descent (in types I + II)

• Chain cystography:

  • posterior urethrovesical angle (= angle between posterior urethra + bladder base) increased >100

  • upper urethral axis (= angle between upper urethra + vertical line) increased >35

Detrusor Instability

• = MOTOR URGE INCONTINENCE = UNSTABLE BLADDER

• Condition resembles that of immature bladder before toilet training

• Patient groups:

  • symptoms of nocturnal enuresis + frequency / incontinence dating back to childhood

  • idiopathic instability occurring in middle age

  • outflow obstruction commonly in men

  • degenerative instability secondary to cardiovascular + neurologic disease later in life

• frequency, urgency, urge incontinence, occasionally nocturia

• hesitancy + difficulty in voiding may occur in men without significant prostatic hypertrophy

• involuntary bladder contractions with no relationship to bladder distension

• progressively vigorous contractions during bladder filling

• postural instability limited to upright position

• impaired milk-back mechanism due to high bladder pressure

• strong after contractions following bladder emptying

• Cx: thickening of bladder wall, bladder diverticula

• Rx: treatment of obstruction, anticholinergic drug (oxybutynin), operative increase in bladder capacity

Sensitive Bladder (Sensory Urgency)

• Cause: cystitis (reduced compliance), some cases of stress incontinence (filling of bladder neck induces urgency)

• frequency, urgency, sometimes nocturia

• patient uncomfortable with low bladder filling

• no abnormal rise in bladder pressure

• normal voiding function

Detrusor-sphincter Dyssynergia

• = overactivity of bladder neck muscle with failure to relax at beginning of voiding

• Cause: spinal cord lesion / trauma above level of sacral outflow

• difficulty in voiding frequency

• lifelong history of poor stream

• collarlike indentation of bladder neck during voiding (= persistent / intermittent narrowing of membranous urethra)

• may have high voiding pressure + reduced flow

• trapping of contrast in urethra during interruption of flow

• massive reflux into prostatic ducts during voiding (due to high pressure within prostatic urethra)

• severely trabeculated Christmas-tree bladder + bilateral hydroureteronephrosis

• Rx: bladder neck incision

Hinman Syndrome

• = nonneurogenic NEUROGENIC BLADDER [NNNB] = DETRUSOR-SPHINCTER DYSSYNERGIA

• Cause: no neurologic / anatomic obstructive disease; distinctly abnormal family dynamics (in 50%)

• Age: some time after toilet training with onset during early / late childhood / puberty

• clinical criteria:

  • intact perineal sensation + anal tone

  • normal anatomy + function of lower extremities

  • absence of skin lesions overlying sacrum

  • normal lumbosacral spine at plain radiography

  • normal spinal cord at MR imaging

• high-pressure uninhibited detrusor contractions

P.901




• lack of coordination between detrusor contraction + periurethral striated sphincter relaxation

• inability to suppress bladder contractions

• normal response of detrusor muscle to reflex stimulation

• increased bladder capacity + pressure

• sphincter activity may increase paradoxically during detrusor contraction

• US:

  • trabeculated bladder

  • dilatation of upper urinary tracts

  • renal damage

• VCUG:

  • urethra normal during early voiding

  • urethral distension after contraction of external sphincter as voiding progresses

  • ureterovesical obstruction / reflux

• Rx: suggestion therapy + hypnosis, bladder retraining, biofeedback, anticholinergic drugs

Wetting

• Enuresis

  • = manifestation of neuromuscular vesicourethral immaturity; M:F = 3:2

  • intermittent wetting, usually at night during sleep

  • often positive history of enuresis from one parent

  • normal physical examination

  • no structural abnormality; urography NOT indicated

• Epispadia

• Sacral agenesis

  • = segmental defect (below S2) with deficiency of nerves that innervate bladder, urethra, rectum, feet

  • Children of diabetic mothers are affected in 17%!

• Extravesical infrasphincteric ectopic ureter

  • only affects girls as boys do NOT have infrasphincteric ureteral orifices

  • ureter draining upper pole of duplex system exits below urethral sphincter (90%)

  • ureter draining single system with ectopic extravesical orifice (10%)

• Synechia vulvae

  • = adhesive fusion of minor labia directs urine primarily into vagina from where it dribbles out post micturition

• Vaginal reflux

  • in obese older girls with fat thighs and fat labia

• Miscellaneous

  • posterior urethral valves, urethral stricture, urethral diverticula

Prostatic Obstruction

• = urethral compression by hypertrophic prostatic tissue

• difficulty in voiding

• reduction in flow rate

• high-pressure bladder

• slow + prolonged flow

• increase in bladder capacity with reduced contractility (late)

Scrotum

Acutely Symptomatic Scrotum

• = acute unilateral scrotal swelling pain

• Cause:

  • epididymitis:torsion = 3:2 <20 years of age

  • epididymitis:torsion = 9:1 >20 years of age

• TORSION

  • Torsion of testis (20%)

    • = most common acute process in prepubertal age

  • Torsion of testicular appendages accounts for 5% of scrotal pathology; both appendages located near upper pole of testes

    • Frequency:

      • appendix testis:appendix epididymis = 9:1

    • 8 9-mm complex mass in superior aspect of scrotum without color Doppler flow signals

    • mildly enlarged epididymis (75%)

    • blood flow increased in epididymis (60%), scrotal wall (53%), testis (13%) simulating acute epididymoorchitis

• INFECTION / INFLAMMATION (75 80%)

  • Acute epididymitis

    • most common acute process in postpubertal age

  • Orchitis

  • Intrascrotal abscess

  • Sch nlein-Henoch purpura

  • Kawasaki syndrome

  • Insect bite

  • Acute hydrocele

• HEMORRHAGE

  • Testicular trauma

    • Location:  hematoma in scrotal wall, between layers of tunica vaginalis (= hematocele), in epididymis, in testis

    • rapid change in echo character over time

    • disruption of tunica albuginea (= testicular rupture)

  • Hemorrhage into testicular tumor

• HERNIA

  • Scrotal fat necrosis

  • Strangulated hernia

Scrotal Wall Thickening

• Acute idiopathic scrotal edema

  • Incidence: 20 30% of all acute scrotal disorders

  • Age: 5 11 years (range 18 months to 14 years)

  • subcutaneous scrotal edema, erythema

  • minimal pain, afebrile, peripheral eosinophilia

• Epididymoorchitis

• Testicular torsion

• Torsion of testicular / epididymal appendage

• Trauma

• Henoch-Sch nlein purpura

• Cx of ventriculoperitoneal shunt

• Cx of peritoneal dialysis (? leakage of fluid into the anterior abdominal wall + dissection into scrotum)

Testicular Blood Flow

Increased Testicular Blood Flow

• Orchitis

• Torsion-detorsion sequence

• Torsion of appendix testis / epididymis

• Abscess

• Tumor

P.902

Decreased Testicular Blood Flow

• Torsion

• Infarct

Scrotal Gas

• Fournier gangrene

• Scrotal abscess

• Scrotal hernia with gas-containing bowel

• Scrotal emphysema from bowel perforation

• Extension of subcutaneous emphysema

• Air leakage + dissection due to faulty chest tube positioning

Groin Mass

• CONGENITAL

  • Encysted hydrocele

    • = peritoneal fluid remnant of processus vaginalis

    • of spermatic cord (male)

    • of canal of Nuck (female equivalent)

  • Retractile testis

• HERNIA

  • Inguinal hernia

  • Femoral hernia

• VASCULAR

  • Hematoma

  • Pseudoaneurysm

  • Varicocele

  • Varices of greater saphenous vein

• INFECTIOUS / INFLAMMATORY

  • Inflammation of ileopectineal bursa

  • Synovial osteochondromatosis of hip joint

  • Groin abscess

• NEOPLASM

  • Lipoma (most common benign tumor)

  • Inguinal lymph node metastases (from cancer of lower vagina, vulva, penis, lower rectum, anus, lower extremity)

Scrotal mass

• Most frequent conditions:

  • Inflammation (48%)

  • Hydrocele (24%)

  • Torsion (9%)

  • Varicocele (7%)

  • Spermatocele (4%)

  • Cysts (4%)

  • Malignant tumor (2%)

  • Benign tumor (0.7%)

• Sonographic differentiation of intra- from extratesticular mass is 80 95% accurate!

Intratesticular Mass

• 90 95% of testicular tumors are malignant!

  • Testicular cancer

  • Inflammation: focal orchitis

  • Abscess

  • Testicular infarction

    • soft to palpation

    • hypoechoic wedge-shaped peripheral defect

  • Hematoma

  • Benign gonadal tumor

  • Granulomatous orchitis

    • TB, syphilis, fungi, parasites

      • tendency to involve epididymis first

    • sarcoidosis (genital tract affected in 5%)

      • multiple hypo- / hyperechoic masses within testis / epididymis

  • Testicular cyst / tunica albuginea cyst

  • Postbiopsy defect

  • Adrenal rest

    • Prevalence: in 7 15% of newborns;in 1.6% of adults

    • Associated with: congenital adrenal hyperplasia, Cushing syndrome

    • increase in cortisol levels (testicular vein sampling is diagnostic)

      • Adrenal rests only form masses after exposure to elevated levels of adrenocorticotropic hormone

  • bilateral eccentric nodular masses <5 mm:

    • predominantly hypoechoic

    • occasionally heterogeneously hyperechoic acoustic shadowing

Multiple Intratesticular Masses

• Lymphoma / leukemia

• Primary testicular tumor

• Chronic infections

• Metastases: prostate, kidney, melanoma

• Granulomatous disease: sarcoidosis

• The prevalence of synchronous / metachronous bilateral testicular neoplasms is 1 3%!

Prepubertal Testicular Mass

• Only 0.5 5% of all intratesticular tumors occur in patients <15 years of age

• Primary tumor

  • Germ cell tumors (70 90%):

    • Yolk sac tumor ( 2 years)

    • Teratoma ( 5 years)

  • Sex cord-stromal tumors (10 30%):

    • Leydig cell tumor (3 9 years)

    • Sertoli cell tumor (commonly <1 year)

    • Gonadoblastoma (after puberty)

    • Fibroma, lipoma, hemangioma, sarcoma, adrenal rest

• Secondary tumor

  • Lymphoproliferative tumor: leukemia, lymphoma

  • Solid tumor: Wilms, neuroblastoma, rhabdomyosarcoma, retinoblastoma

  • Others: sinus histiocytosis, Langerhans cell histiocytosis, tuberculous orchitis

Paratesticular Mass

• Only 4% of all scrotal tumors!

Paratesticular Inflammatory Mass

• Sarcoidosis of epididymis

• Inflammatory nodule of epididymitis

• Sperm granuloma

  • Cause: sperm extravasation with granuloma formation

P.903




• Scrotal calculi = scrotal pearls

  • Cause: fibrinous debris in long-standing hydrocele / following torsion of appendix testis or epididymis

Paratesticular Tumor

• The majority of paratesticular tumors are derived from the spermatic cord!

• Sarcomas are the most common spermatic cord tumors after lipomas!

• EPIDIDYMAL TUMOR

• SPERMATIC CORD TUMOR

  • benign: lipoma > fibroma > dermoid cyst > lymphangioma

  • malignant: sarcoma

• SCROTAL TUNICA TUMOR

• Benign Paratesticular tumor (75%

  • Cord lipoma (vast majority)

  • Adenomatoid tumor (30%)

    • = benign slow-growing mesothelial neoplasm

    • Age: 2nd 4th decade

    • Histo: epithelial-like cells + fibrous stroma

    • Location: epididymis (particularly in globus minor), tunica albuginea, spermatic cord (rare)

    • well-marginated solid mass with echogenicity equal to / greater than testis

    • 0.4 5.0 cm in size

  • Epidermoid inclusion cyst

  • Polyorchidism

  • Leiomyoma

  • Cord fibroma

    • = reactive nodular proliferation of paratesticular tissues

  • Others: herniated omentum, adrenal rest, carcinoid, papillary cystadenoma of epididymis, adrenal rest, cholesteatoma

• Malignant Paratesticular Tumor (25%)

  • Sarcomas:

    • primarily in adults: undifferentiated sarcoma (30%), leiomyo-, lipo-, fibro-, myxochondrosarcoma, malignant fibrous histiocytoma

    • children: rhabdomyosarcoma (20%), embryonal sarcoma

      • Rhabdomyosarcoma is the most common extratesticular neoplasm in children!

  • Mesothelioma of tunica (in 15% malignant)

  • Metastases

Extratesticular Fluid Collection

• Hydrocele, pyocele, hematocele (surgery, trauma, neoplasm)

• Varicocele

• Spermatocele (after puberty)

  • = single / multiple retention cysts filled with fluid + spermatozoa + cellular debris

  • frequently following vasectomy

  • Location: commonly in head of epididymis

  • up to a few cm in size septations

• Epididymal cyst

  • = cyst without spermatozoa (less common than spermatoceles)

  • status post vasectomy

  • Location: anywhere within epididymis

  • wide range of sizes

• Lymphangioma, hemangioma

• Lymphocele

• Abscess

• Scrotal hernia = bowel in inguinal hernia

  • hypoechoic bowel musculature + peristalsis

Cystic Lesion of Testis

• Incidence: 4 10% (increasing with age)

• asymptomatic

• NONNEOPLASTIC

  • Intratesticular cyst

    • Prevalence: 8 10%

    • Cause:? trauma, prior inflammation, surgery

    • Age: >40 years

    • nonpalpable

    • Often associated with: spermatocele, dilated rete testis

    • Location: related to rete testis (in 92%)

    • usually solitary 2 20-mm simple cyst

    • DDx: cystic neoplasm

  • Tunica albuginea cyst

    • = mesothelial rests

    • Cause: fluid within mesothelial rests; fluid from blind-ending efferent ductules

    • Mean age: 40 years

    • palpable firm nodule

    • Location: upper anterior / lateral aspect of testis

    • solitary uni- / multilocular 2 5-mm marginally located cyst

  • Intratesticular tubular ectasia

    • = DILATATION OF RETE TESTIS = CYSTIC TRANSFORMATION OF THE RETE TESTIS

    • Cause: partial / complete obliteration of efferent ductules

    • Age: >55 years

    • Often associated with: spermatocele

    • nonpalpable

    • Location: mediastinum testis, frequently asymmetrically bilateral

    • elliptical hypoechoic branching tubular structures cysts

    • epididymal cysts / spermatoceles

    • MR:

      • hypointense on T1WI

      • iso- to hyperintense on T2WI

    • DDx: teratoma

  • 4. Intratesticular spermatocele

    • = cyst containing mature spermatozoa

    • Location: attached to mediastinum testis

  • Intratesticular varicocele

    • pain (related to passive congestion)

    • multiple anechoic serpiginous tubules

    P.904

    
    

    • characteristic venous flow pattern increasing with Valsalva on Doppler

    • Infrequently associated with: extratesticular varicocele

  • Intratesticular abscess

    • Cause: epididymoorchitis, trauma, testicular infarction, mumps

    • collection with low-level echoes, shaggy irregular wall, occasionally hypervascular margin

  • Intratesticular infarction

    • avascular hypoechoic mass

  • Congenital cystic dysplasia of testis (extremely rare)

• BENIGN TUMOR

  • Epidermoid cyst / keratin cyst of testis

• MALIGNANCY

  • 24% of all testicular tumors have cystic component!

  • palpable

  • in combination with solid elements

• DDx: hematoma, inflammation, seminoma, Leydig cell tumor

Epididymal Enlargement with Hypoechoic Foci

• Epididymitis

• Sperm granulomas

• Tuberculosis

• Lymphogranuloma venereum

• Granuloma inguinale

• Filarial granuloma

• Fungal disease

• Lymphoproliferative disease

• Metastases

Cystic Lesions of Epididymis

• Epididymal cyst

  • Incidence: in up to 40%

  • May be associated with: intratesticular tubular ectasia

  • single / multiple / bilateral

  • DDx: loculated hydrocele

• Spermatocele

  • may contain low-level echoes

• Cystic degeneration of epididymis

Prostate

Large Utricle

• Prune belly syndrome

• Imperforate anus of high type

• Down syndrome

• Hypospadia

• Posterior urethral valves

Prostatic Cysts

• M llerian duct cyst

  • from remnants of paramesonephric (= m llerian) duct which has regressed by 3rd fetal month

  • Prevalence: 4 5% of male newborns; in 1% of men

  • Age: discovered in 3rd 4th decade

  • obstructive / irritative urinary tract symptoms

  • suprapubic / rectal pain

  • hematuria

  • infertility (most common cause of ejaculatory duct obstruction)

  • Location: arise from region of verumontanum slightly lateral to midline

  • No communication with genital tract / urethra; connected by thin stalk

  • Associated with: typically NO other congenital anomalies; renal agenesis (rarely)

  • large intraprostatic cyst usually with extension superolaterally above prostate

  • aspirate contains serous / mucous clear brown / green fluid (hemorrhage + debris), NOT spermatozoa

  • rarely contains calculi

  • MR:

    • increased signal on T1WI (hemorrhage, protein)

  • Cx: infection, hemorrhage, carcinomatous transformation

  • DDx: posterior bladder diverticulum, urethral diverticulum, utricle cyst, vas deferens cyst, seminal vesicle cyst

• Utricle cyst

  • Secondary to dilatation of prostatic utricle (sometimes believed to be a remnant of the m llerian duct)

  • Age: 1st 2nd decade

  • postvoid dribbling

  • obstructive / irritative urinary tract symptoms

  • suprapubic / rectal pain

  • hematuria

  • Often associated with: hypospadia, intersex disorders, incomplete testicular descent, ipsilateral renal agenesis

  • Location: arise in midline from verumontanum

  • Free communication with urethra

  • usually 8 10-mm-long cyst (DDx: m llerian duct cyst usually larger extending above base of prostate)

  • NO extension above prostate

  • Dx: endoscopic catheterization with aspiration of white / brown fluid occasionally containing spermatozoa

  • Cx: infection, hemorrhage, carcinomatous metaplasia

• Ejaculatory duct cyst

  • Cause: congenital / acquired obstruction of ejaculatory duct

  • perineal pain, dysuria, ejaculatory pain

  • hematospermia

  • Location: along expected course of ejaculatory duct

  • intraprostatic cyst within central zone

  • aspirate contains spermatozoa with normal testicular function

  • cyst commonly contains calculi

  • cystic dilatation of ipsilateral seminal vesicle

  • contrast injection into cyst outlines seminal vesicle

• Cystic degeneration of BPH

  • Most common cystic lesion of prostate!

  • Location: transition zone

  • usually small cyst within nodules of benign prostatic hyperplasia

• Retention cyst

  • = dilatation of glandular acini

  • Cause: acquired obstruction of glandular ductule

  • Age: 5th 6th decade

  • Location: transition / central / peripheral zone

  • 1 2-cm smooth-walled unilocular cyst

P.905




• Cavitary / diverticular prostatitis

  • Cause: fibrosis of chronic prostatitis constricts ducts leading to stagnation of exudate + breakdown of intraacinar septa with cavity formation

  • history of long-standing inflammatory condition

  • Swiss cheese prostate

• Prostatic abscess

  • Age: 5th 6th decade

  • fever, chills

  • urinary frequency, urgency, dysuria, hematuria

  • perineal / lower back pain

  • focally enlarged tender prostate

  • hypo- / anechoic mass with irregular wall + septations

• Parasitic cyst (Echinococcus, bilharziasis)

• Cystic carcinoma

  • hemorrhagic aspirate

  • solid tissue invaginating into cyst

Hypoechoic Lesion of Prostate

• Adenocarcinoma (35%)

• Benign prostatic hyperplasia (18%)

  • rarely may originate in the peripheral zone

• Normal prostatic tissue (18%)

  • cluster of prostate retention cysts

  • prominent ejaculatory ducts

• Acute / chronic prostatitis (14%)

• Granulomatous prostatitis (0.8%):

  • most frequently due to intravesical Calmette-Gu rin bacillus (BCG) therapy in treatment of bladder cancer

• Atrophy (10%)

  • occurs in 70% of young healthy men

  • May be confused with carcinoma histologically!

• Prostatic dysplasia (6%)

Urethra

Congenital Urethral Anomalies

• Anomaly of number

  • Duplication of urethra

• Anomalies of form

  • Posterior urethral valves

  • Congenital stricture

  • Congenital polyp

  • Congenital diverticulum

• Malformation of urethral groove

  • Epispadia

    • = absent roof of urethra with opening anywhere between base of bladder and glans penis

    • Associated with: bladder exstrophy

    • urinary incontinence from incompetent bladder neck / urethral sphincter

    • abnormally wide symphysis pubis (>1 cm)

  • Hypospadia

    • = congenital defect of anterior urethra with opening anywhere along ventral aspect of penile shaft

Cowper (Bulbourethral) Gland Lesions

• Analogous to Bartholin glands in females

• Prevalence: 2.3% (autopsy)

• Location: within urogenital diaphragm

  • Retention cyst

    • Cx: prenatal death from urinary obstruction

  • Infectious / traumatic cyst

    • asymptomatic (most)

    • hematuria, bloody urethral discharge

    • postvoid dribbling

Urethral Tumors

Benign Urethral Tumor

• Fibroepithelial polyp

  • Age: in child / young adult

  • Histo: transitional cell epithelium

  • solitary, pedunculated fingerlike filling defect attached near verumontanum

  • Cx: bladder outlet obstruction

  • Transitional cell papilloma

  • Age: older patient

  • Location: in prostatic / bulbomembranous urethra

  • Frequently associated with concomitant bladder papillomas

• Adenomatous polyp

  • Age: young men

  • Histo: columnar epithelium from aberrant prostatic epithelium

  • Location: adjacent to verumontanum

  • hematuria

• Penile squamous papilloma / condyloma acuminata

  • In 5% of patients with cutaneous disease (glans penis)

  • verrucous lesion in distal urethra, rarely extension into bladder

• Others: caruncle, urethral mucosal prolapse, inflammatory tags (in female)

Malignant Urethral Neoplasm

• Incidence: 6th 7th decade, M:F = 1:5

• FEMALE

  • urethral bleeding

  • obstructive symptoms

  • dysuria

  • mass at introitus

  • Squamous cell carcinoma (70%):

    • distal 2/3 of urethra

  • Transitional cell carcinoma (8 24%):

    • posterior 1/3 of urethra

  • Adenocarcinoma (18 28%):

    • from periurethral glands of Skene

• MALE

  • palpable urethral mass

  • periurethral abscess

  • obstructive symptoms

  • cutaneous fistula

  • bloody discharge

  • Site: bulbomembranous urethra (60%); penile urethra (30%); prostatic urethra (10%)

  • Squamous cell carcinoma (70%)

    • secondary to chronic urethritis from venereal disease (44%) + urethral strictures (88%)

  • Transitional cell carcinoma (16%)

    • part of multifocal urothelial neoplasia, in 10% after cystectomy for bladder tumor

  P.906

  
  

  • Adenocarcinoma (6%)

    • in bulbous urethra originating in glands of Cowper / Littre

  • Melanoma, rhabdomyosarcoma, fibrosarcoma (rare)

  • Metastases from bladder / prostatic carcinoma (rare)

Calcifications of Male Genital Tract

• VAS DEFERENS

  • Diabetes mellitus: in muscular outer layer

  • Degenerative changes

  • TB, syphilis, nonspecific UTI: intraluminal

• SEMINAL VESICLES

  • gonorrhea, TB, schistosomiasis, bilharziasis

• PROSTATE

  • calcified corpora amylacea, TB

Ambiguous Genitalia

• = external genitalia that are not clearly of either sex

• Prevalence: 1:1,000 live births

  • cryptorchidism

  • epi- / hypospadia

  • labial fusion

  • clitoromegaly

  • Cause:

    • Abnormal hormone levels

      • Congenital adrenal hyperplasia

      • Transplacental passage of hormones

      • True hermaphroditism

    • Anomalies of external genitalia not hormonally mediated (eg, micropenis)

• Terminology:

  • SEX = what a person is biologically; sex assignment based on

    • karyotype

    • gonadal biopsy

    • genital anatomy

  • GENDER = what a person becomes socially

Female Pseudohermaphroditism

• = FEMALE INTERSEX

• Cause: exposure to excessive androgens in 1st trimester due to

  • congenital adrenogenital syndrome

  • maternal drug ingestion (progestational agents, androgens)

  • masculinizing ovarian tumor

• Karyotype: 46, XX

• masculinized external genitalia:

  • penislike clitoris (due to prominent corpora cavernosa + corpus spongiosum)

  • rugose labioscrotum

• uterus + vagina may be filled with urine through urogenital sinus

• normal ovaries, fallopian tubes, uterus, vagina

• enlarged adrenal glands (adrenal hyperplasia)

• no testicular tissue / internal wolffian duct derivatives

Male Pseudohermaphroditism

• Cause: within fetal testis

  • decreased testosterone synthesis

  • decreased dihydrotestosterone production (= substance responsible for masculinization of external genitalia) due to 5 -reductase deficiency

  • no testosterone production due to early destruction / dysgenesis of testes

  • complete / incomplete androgen insensitivity due to androgen receptor defect (= testicular feminization)

• Karyotype: 46, XY

• incompletely masculinized / ambiguous external genitalia

• [ apparent hypergonadotropic primary amenorrhea]

• commonly undescended normal / mildly defective bilateral testes

• prostatic tissue

• no m llerian duct derivatives (production of m llerian regression factor by testes not affected)

• occasionally blind-ending vaginal pouch emptying into perineum (= pseudovagina) / through urethra (= urogenital sinus)

Gonadal Dysgenesis

characterized by abnormal gonadal organization and function with gonads often partially / completely replaced by fibrous stroma

• Mixed gonadal dysgenesis

  • = testis on one side + gonadal streak on other side

  • Karyotype: 45, XO/46, XY karyotype or other mosaics with a Y chromosome

  • ambiguous external genitalia

  • small / rudimentary uterus + vagina

  • fallopian tube present on side of streak gonad

  • urogenital sinus commonly empties at base of phallus

  • dysgenetic gonads (with inability to secrete m llerian regression factor)

  • Cx: gonadal neoplasia

• Pure XY gonadal dysgenesis

  • Karyotype: 46, XY

  • bilateral streak gonads / dysgenetic testes

  • m llerian + wolffian duct derivatives both absent / partially developed

• XY gonadal agenesis

  • = vanishing testes syndrome = testicular resorption in early fetal life of unknown cause

  • Karyotype: 46, XY

  • ambiguous external genitalia / female phenotype

  • absent testes

  • m llerian + wolffian duct derivatives both absent / partially developed

True Hermaphroditism

• = TRUE INTERSEX

• = condition characterized by presence of ovarian + testicular tissue either separate or in same gonad (= ovotestis in 64%)

• Gonads:

  • ovary on one + testis on other side (30%)

  • ovary / testis on one + ovotestis on other side (50%)

  • bilateral ovotestes (20%)

  • Location: in pelvis predominantly ovarian tissue; in scrotum / inguinal region predominantly testicular tissue

  P.907

  
  

  • Incidence: rare (500 cases in world literature); <10% of all intersex conditions

  • Age: diagnosed within first 2 decades (75%)

  • Karyotype: 46, XX (80%) / 46, XY (10%) / mosaicism (10%)

  • Classification:

    • Class I: normal female genitalia (80%)

    • Class II: enlarged clitoris

    • Class III: partially fused labioscrotal folds

    • Class IV: fused labioscrotal folds

    • Class V: hypoplastic scrotum + penoscrotal hypospadia

    • Class VI: normal male genitalia

• ambiguous external genitalia

• inguinal hernia

• lower abdominal pain (due to endometriosis)

• lower abdominal tumor (dysgerminoma, myomatous uterus)

• Reared as boy:

  • cryptorchidism

  • short penis

  • slight degree of hypospadia

  • urogenital sinus at base of penis

  • penile urethra (extremely rare)

  • effective spermatogenesis (rare)

• Reared as girl:

  • development of breasts

  • hematuria (= menstruation via urogenital sinus opening) in 50%

  • internal female organs + female fertility

  • amenorrhea

  • separate urethral + vaginal openings (uncommon)

  • hypoplastic uterus (in virtually 100%)

  • ovotestis with heterogeneous appearance due to combination of testicular tissue + ovarian follicles

  • internal gonadal duct fits the gonad:

    • deferent duct on side of testis

    • fallopian tube on side of ovary

    • ipsilateral fallopian tube absent (suppression of development by fetal testis)

  • testis / testicular portion of ovotestis usually dysgenetic

Male Infertility

• CONGENITAL

  • Wolffian duct anomalies

    • Renal agenesis / atrophy

    • Vas deferens agenesis / cyst

    • Seminal vesicle agenesis / cyst

    • Ejaculatory duct cyst

  • M llerian duct anomalies

    • M llerian duct cyst

    • Utricle cyst

• ACQUIRED

  • Cowper duct cyst

  • Prostatic cyst in peripheral zone

• INFECTIOUS

  • Prostatitis

• HORMONAL

  • semen low in volume, acid pH, without fructose

  • 1. Seminal vesicle atrophy

    • = seminal vesicles <7 mm in width

  • 2. Seminal vesicle hypoplasia

    • = seminal vesicles <11 mm + >7 mm in width

P.908

Anatomy and Function of Urogenital Tract

Male Metanephros Differentiation

Female Metanephros Differentiation

Urogenital embryology

Pronephros = forekidney

• develops from mesoderm during 3rd week of gestation; involutes during 4th week of gestation;

• vestigial remnant / completely absent

Mesonephros = midkidney

• develops during 4th week of gestation immediately caudal to pronephros, functions as interim kidney; degenerates around 8 weeks of gestation

  • mesonephric tubules

    • paradidymis, epididymis, efferent ductules (M); epinephron (F)

  • mesonephric (wolffian) duct

    • appendix epididymis, vas deferens, ejaculatory duct, seminal vesicles (M); vanishes (F)

Paramesonephric (M llerian) Duct

• (grows along mesonephric duct)

Male:	degenerates due to production of m llerian inhibiting factor (MIF) by Sertoli cells of testis at about 6 weeks GA
	prostatic utricle + appendix testis
Female:	induced by wolffian duct at 5 weeks GA; grows caudally + joins in midline + fuses with outgrowth of urogenital sinus
	uterus, fallopian tubes

P.909

Metanephros = hindkidney = permanent kidney

• metanephric diverticulum (ureteric bud) buds from mesonephric duct near its entry into the cloaca at 4th week; it lengthens + grows toward nephrogenic cord which becomes the metanephric blastema + divides and forms

  • ureter (mesonephric duct)

  • renal pelvis (first 4 dividing generations of duct)

  • calices (second 4 dividing generations of duct)

  • collecting tubules (10 12 generations of duct)

• metanephric blastema (= nephrogenic mesoderm) forms nephrons under the influence of ureteral bud, ie, the end of collecting tubules induce clusters of metanephric blastema cells located at the periphery and along the sides of the medullary ray (= pyramid) except around the papilla

• metanephric vesicles form within clusters of metanephric blastema cells + elongate into S-shaped tubules which, by 12th week of gestation, result in

  • glomerulus

  • proximal convoluted tubule

  • loop of Henle

  • distal convoluted tubule

  • connective tissue

  • Polycystic kidney disease is believed to be a failure of linkage!

Urogenital Sinus

• forms from cloaca

• develops into bladder + urethra (+ prostate)

Bladder

Period:

develops in 2nd 4th embryonal month

Urachus

• = narrowed apex of fetal bladder continuous with allantoic stalk at the umbilicus

• forms median umbilical ligament

• supravesical portion

• intramural portion

• intramucosal portion

Sex development

Indifferent Stage of Sexual Differentiation

Period:

until 7th week of GA

• Composition of Undifferentiated Gonad:

  • Mesenchyme

    • condensation of mesenchyme forms genital ridges on both sides of midline between 6th thoracic and 2nd sacral segments; differentiates into interstitial (Leydig) cells within seminiferous tubules

  • Mesothelium

    • genital ridges are covered by proliferating mesothelium (coelomic epithelium); differentiates into Sertoli / supporting cells of the seminiferous tubules; forms tunica albuginea

  • Germ cells

    • form in wall of yolk sac and migrate along hindgut into genital ridge; differentiate into spermatogonia within seminiferous tubules

Formation of Testis

Period:

around 8 weeks GA

• testis-determining factor localized on short arm of Y chromosome forms seminiferous tubules

• Leydig cells secrete testosterone supporting the mesonephric (wolffian) duct development

• Sertoli cells secrete m llerian-inhibiting factor leading to regression of paramesonephric (m llerian) duct

Testicular Migration

• testes remain near deep inguinal canal until 7th month and then descend through inguinal canal into twin scrotal sacs

Renal anatomy

Adult Kidney

• forms by fusion of superior + inferior subkidneys (= metanephric lobes); the line of fusion runs obliquely forward and upward

  • separation of upper + lower groups of calices

  • indentation of cortical contour + echogenic line (= interrenicular septum = junctional parenchymal defect) delineates junctional parenchyma (often referred to as hypertrophic column of Bertin)

• consists of 20,000 lobules within 14 lobes (reniculi)

• initially located in pelvic region ventral to sacrum, ascending cranially at 9 weeks of gestation secondary to body growth caudal to kidneys + straightening of body curvature

• renal hilum at first ventrally located, eventually rotating medially by 90 degrees with renal ascent

Reniculus = renal lobe

• = central core of medullary tissue enveloped by

• centrilobar cortex (= cortical arch) that covers the base of the pyramid subsequently forming the renal cortex with loss of grooves

• mural cortex that wraps around sides of pyramid and fuses with the mural cortex of adjacent lobe to form renal septum (= column of Bertin)

• renal lobes completed by 28 weeks GA

• ren lobatus (= interlobar surface grooves) present in fetus + infant, rare in adulthood

• assimilation of independent lobes >28 weeks GA makes renal surface smoother

• nephrogenesis completed by 36 weeks GA

Renal Size (in cm)

<1 year of age:	4.98 + 0.155 age (months)
>1 year of age:	6.79 + 0.22 age (years)
adulthood:	R kidney 10.74 1.35 (SD);
	L kidney 11.10 1.15 (SD);

• ratio of renal length (RL) to distance between first 4 lumbar transverse processes (4TP) = 1.04 0.22

P.910

Anatomy of Renal Arteries

Renal Parenchymal Blood Supply

Renal Echogenicity

• ADULTHOOD

  • liver spleen renal cortex > renal medulla

• INFANCY (in neonate up to 6 months of age)

  • cortex may be more echogenic than adjacent normal liver / spleen

    Cause:

    glomeruli occupy 18% of cortex in neonate compared with 9% in adult

  • increase in corticomedullary differentiation

    Cause:

    ratio of cortex to medulla 1.64:1 in neonate compared with 2.59:1 in adult

  • renal sinus echogenicity less prominent

    Cause:

    paucity of fat

Renal Vascular Anatomy

Renal Arteries

1st order:	main renal arteries at level of L1 / upper margin of L2
2nd order:	5 segmental branches = apical, anterior superior, anterior inferior, posterior, basilar

• Anatomic Renal Artery Variants

Resistive index:	<0.70
	1 SD of several measurements = 0.04

• Multiple renal arteries (25 30%)

  • unilaterally (32%); bilaterally (12%)

• Polar artery

  Entry:

  without going through renal hilum directly into renal parenchyma

  • superior polar artery

    Origin:

    main renal artery (12%), aorta (7%)

  • inferior polar artery

    Origin:

    aorta (5.5%), main renal artery (1.4%)

• Supplementary artery

  Entry:	renal hilum
  Origin:	aorta, iliac a., internal spermatic a., SMA, IMA, celiac trunk, middle colic a., lumbar a., middle sacral a., contralateral renal a.
  Supply:	lower pole (72%) > upper pole

• Extrahilar branching

  • = branching of main renal artery prior to reaching hilum

    Entry:

    renal hilum / direct as polar arteries

  • early branching: within 1.5 cm from aorta

• Accessory renal artery

  • = segmental artery originating from aorta / iliac a.

• Aberrant renal artery

  • = segmental artery arising from superior mesenteric artery / internal spermatic artery

• Capsular artery

  • = tiny vessels perfusing the renal capsule

    Origin:

    main renal a., branch renal a., other retroperitoneal aa. (lumbar a.)

Renal Veins

• Single right renal vein (85%) without major extrarenal tributaries

• Single preaortic left renal vein (86%) with several major extrarenal tributaries

  • left adrenal vein

  • left gonadal vein

  • lumbar, ascending lumbar, hemiazygos vv.

Anatomic Renal Vein Variants

• Multiple right renal veins (28 30%)

  • single right renal vein divides just before union with IVC (4%)

  • right gonadal vein joins the renal vein (6%)

  • accessory branch of adrenal vein enters right renal vein (31%)

  • lumbar / azygos vv. enter right renal vein (3%)

• Circumaortic left renal vein (5 17%)

• Single retroaortic left renal vein (2 3%)

• Lumbar veins joining left renal vein (75%)

P.911

Retroperitoneum

• = space between transversalis fascia + parietal peritoneum extending from diaphragm to pelvic brim

Perirenal Compartments

• Anterior border: anterior renal fascia

• Anterior pararenal space

  • superiorly joins with posterior renal fascia and attaches to crux of diaphragm

  • in the middle blends with connective tissues of central prevertebral space around great vessels

  • inferiorly joins with posterior renal fascia and attaches to great vessels

    contains:

    pancreas, duodenum, ascending + descending colon

• Perirenal space

  • subdivided into multiple compartments by incomplete bridging septa that attach to anterior + posterior renal fascia

  • forms inverted cone around adrenal gland + perirenal fat + upper half of kidney

  • forms cone around perirenal fat + lower pole of kidney

  • medially open communicating with central prevertebral space

    contains:

    kidneys, adrenals

• Posterior pararenal space

  contains:

  fat, no organs

• Posterior border:

  • posterior renal fascia (attaches to psoas muscle)

Renal hormones

Antidiuretic Hormone (ADH)

Production site:	supraoptic nuclei of hypothalamus, transported to neurohypophysis
Stimulus:	fluid loss with increase in osmolality
Effects:	(1) 10 increase in permeability of collecting ducts (= concentrated urine)
	(2) decreased blood flow through vasa recta leads to increased hypertonicity of interstitium (= countercurrent multiplier mechanism)

Renin-aldosterone Mechanism

• receptors in juxtaglomerular apparatus register the intra-glomerular capillary hydraulic pressure, which is one of the main determinants of the glomerular filtration rate (GFR);

• the receptors regulate the release of renin as an autoregulatory feedback mechanism to maintain the intraglomerular hydraulic pressure;

• renin mediates conversion of angiotensin to angiotensin-I, which is then cleaved by a converting enzyme into angiotensin-II

Angiotensin-II Effect

• constriction of efferent postglomerular arterioles, which increases intraglomerular capillary hydraulic pressure + GFR

• systemic arteriolar constriction (= most potent vasoconstrictor of biologic systems), which causes systemic hypertension

• release of aldosterone, which increases sodium retention by renal tubules

  • leads to an increase in blood volume + pressure if both kidneys are affected

  • leads to compensatory natriuresis if only one kidney is affected

• ACE inhibitors (eg, captopril) produce a dramatic decrease in blood pressure!

Renal physiology

Perfusion:	1.2 1.3 L of blood per minute (= 20 25% of total cardiac output)
Urine output:	1 L/d
Filtration:	substances of up to 4 nm (excluding substances >8 nm), threshold at molecular weight of approximately 40,000

Gerota's Fascia

Pararenal Spaces

P.912

Glomerular Filtration Rate (GFR)

• [P] GFR = [U] U_vol

• GFR = {[U] U_vol} / [P] = 125 mL/min = 20% of RPF

  Substrate:

  inulin; Tc-99m DTPA

Tubular Secretion (Tm)

• [U] U_vol = [P] GFR + Tm

• Tm ={ [U] U_vol} - {[P] GFR}

  Substrate:

  p-aminohippurate (PAH); I-131 Hippuran

Renal Plasma Flow (RPF)

• [P] RPF = [U] U_vol

• RPF = {[U] U_vol} / [P]

  Substrate:	p-aminohippurate
  [P]	= concentration in plasma
  GFR	= glomerular filtration rate
  [U]	= concentration in urine
  Uvol	= urine volume
  Tm	= transport maximum (across tubular cells)
  RPF	= renal plasma flow

Renal Acidification Mechanism

• Proximal tubule:

  • reabsorption of 90% of filtered bicarbonate by luminal Na⁺/H⁺ exchange and Na⁺/HCO₃ cotransport at basolateral membrane

    regulated by:	luminal carbonic anhydrase
    influenced by:	luminal HCO3 concentration, extracellular fluid volume, parathormone, K+, aldosterone

• Distal nephron:

  • active secretion of H⁺ against a steep urine-to-blood gradient across luminal cell membrane by H⁺-ATPase pump facilitated by Na⁺ reabsorption resulting in reabsorption of 10% of filtered bicarbonate, formation of ammonium (NH₄⁺) and titratable acidity

    

    Renal Acidification

• Ammonium excretion:

  • Ammonia (NH₃) is formed in proximal tubule as a product of catabolism of glutamine + other amino acids; combination with secreted H⁺ to NH₄⁺ takes place in distal nephron

• Titratable acidity:

  • divalent basic phosphate is converted into monovalent acid form in distal tubule

Renal Imaging in Newborn Infant

• Low glomerular filtration rate (GFR):

  on first day of life:	21% of adult values
  by 2 weeks of age:	44% of adult values
  at end of 1st year:	close to adult values

• Limited capacity to concentrate urine

  

  Sodium Reabsorption hypertonicity is maintained within the medullary interstitium by the countercurrent multiplier system of the loop of Henle and the vasa recta; ADH increases permeability of collecting ducts for water

P.913




• IVP:

  • occasional failure of renal visualization

• NUC:

  • improved visualization on radionuclide studies

Normal Nephrographic Phases / Progression

• Vascular phase (= cortical arteriogram)

  • = contrast material visible in interlobular arteries + glomeruli

    Timing after IV injection:	10 15 25 seconds (arm-to-kidney circulation time)
    Duration:	transient vascular phase of <0.5 seconds

• Cortical phase (= cortical nephrogram)

  • = contrast medium within cortical capillaries + peritubular spaces + cortical tubular lumina

    Timing after IV injection:	25 45 70 seconds
    Timing after intraarterial injection:	2 3 seconds

  • CT:

    • exclusive renal cortical enhancement with minimally enhancing renal medulla (= corticomedullary differentiation)

• Parenchymal phase (= generalized / diffuse / tubular nephrogram)

  • = contrast material within loops of Henle + collecting tubules

    Timing after IV injection:

    60 85 120 seconds (max)

  • enhancement of both cortex and medulla

    N.B.:

    most valuable phase for detecting renal masses

• Excretory phase

  • = contrast material within collecting system

    Timing after IV injection:

    beginning at 2 3 5 minutes

Contrast Excretion

• UROGRAPHIC DENSITY depends on[U] = {[P] GFR} / U_vol

• Concentration of contrast material in plasma [P] is a function of

  • total iodine dose

  • contrast injection rate

  • volume distribution

    • Rapid decline of concentration of contrast material in vessels is due to:

      • rapid mixing within vascular compartment

      • diffusion into extravascular extracellular fluid space (capillary permeation)

      • renal excretion

• Glomerular filtration rate (GFR): 99% filtered

• Urine volume (U_vol), ie, activity of ADH:

  • in dehydrated state with increased ADH activity concentrations of contrast material are higher

    • Dehydration is considered a risk-potentiating factor for nephrotoxicity!

  • in volume-expanded state with decreased ADH activity concentrations of contrast material are lower

    • Patients with CHF require higher doses of contrast material!

• MEGLUMINE

  • no metabolization, excreted by glomerular filtration alone

  • Meglumine effect of osmotic diuresis:

    • lower concentration of urinary iodine per mL urine

    • greater distension of collecting system

      N.B.:

      Avoid meglumine in at risk patients (higher incidence of contrast reactions than sodium!)

• SODIUM

  • extensive reabsorption by tubules with delayed excretion

  • Sodium effect of reabsorption:

    • increased concentration of urinary iodine (improved visualization)

    • less distension of collecting system (ureteral compression necessary)

Adrenal anatomy

• from periphery to centrum:

  • renin-angiotensin dependent outer adrenal cortex

    zona glomerulosa

    = mineralocorticoid (aldosterone)

  • corticotropin-dependent inner adrenal cortex:

    zona fasciculata	= cortisol
    zona reticularis	= sex hormones (androgen, estrogen)

  • medulla = norepinephrine, epinephrine

    mnemonic:

    Glomerular Filtration Rate May Give Answers

    • Glomerulosa

    • Fasciculata

    • Reticularis

    • Mineralocorticoids

    • Glucocorticoids

    • Androgens

• @ IN ADULTHOOD

  Normal size

  :3 5 (L) 3 (W) 1 cm (thick)

  • Each limb of the adrenal gland should not be thicker than the crus of the diaphragm

  Normal weight	:3 5 g (5 10 g at birth)
  Visualization by CT	:left side 100%, right side 99%
  by US	:left side 45%, right side 80%

• IN NEONATAL PERIOD

  Normal weight

  :5 10 g at birth

  • Rapid regression of fetal cortex during first 6 weeks of life!

Adrenal Vascular Anatomy

Adrenal Arteries

• 50 60 small adrenal branches from 3 main adrenal arteries form a subcapsular plexus that drains into medullary sinusoids

  Supply:

  inferior phrenic artery, directly from aorta, renal artery

  • all 3 sources in 34%

  • two sources in 61%

  • single source in 5% (renal a. only in 2%)

    • forming superior, middle, inferior adrenal arteries

• The renal artery contributes in 71%!

• Gonadal artery contributes in 60% in fetal circulation!

Adrenal Veins

• Vascular dam = gland is drained by an intrinsically vulnerable network of relatively few venules

• Single right adrenal v. drains into IVC (69%)

• Accessory right adrenal v. drains into renal v. (31%)

• Left adrenal v. almost always enters left renal v.

P.914

Bladder

• Bladder capacity [mL] = (age in years + 2) 30

Layers of Bladder Wall (from inner to outer)

• Uroepithelium = 3 7 layers of stratified flat cells; able to change shape from cuboidal to flattened as the bladder distends (transitional epithelium)

• Lamina propria: very vascular

• Muscularis propria = complex network of interlacing bundles of smooth detrusor muscle; fibers merge with prostate capsule / anterior vagina + pelvic floor muscles

• Adventitia = connective tissue + serosal covering formed by peritoneum at bladder dome

Scrotal anatomy

Scrotal wall thickness:

2 8 mm (3 6 mm in 89%)

• Tunica vaginalis

  • = inferior extension of processus vaginalis of the peritoneum

Hydrocele:

small to moderate in 14% of normals

Testis

Average size of testis:	3.8 3.0 2.5 cm (decreasing with age)
Length of testis:	3 5.5 cm (mature);
	1 1.5 cm (newborn)
Testicular cysts:	in 8% of normals (average size 2 3 mm), numbers increasing with age
Anatomy:	200 300 lobules each containing 400 600 seminiferous tubules; each tubule is 30 80 cm long with a total length of 300 980 m

Histo:	(1) spermatogonia (adjacent to basement membrane) spermatocytes spermatids spermatozoa
	(2) nondividing Sertoli cells provide the support structure; their tight cell junctions are responsible for the blood-testis barrier
	(3) interstitium (= space between seminiferous tubules) contains connective tissue, lymphatics, blood vessels, mast cells, Leydig cells (= principal source of testosterone production)

Appendix Testis

• = small stalked appendage at upper pole of testis

• = remnant of paramesonephric duct

Tunica Albuginea

• = fibrous covering of testis, invaginating into testicular parenchyma at mediastinum testis; externally covered by visceral layer of tunica vaginalis (= flattened layer of mesothelium); internally applied to tunica vasculosa carrying the capsular artery

Mediastinum Testis

• = converging point of ~400 cone-shaped lobules separated by fibrous septa + seminiferous tubules forming larger tubuli recti and draining into the rete testis (= 15 20 efferent ductules)

• = entry and exit point for ducts, nerves, vessels (hilum of testis)

• posteriorly located linear echogenic region extending longitudinally 5 8 mm from the edge

  

  Arterial Supply of Scrotum

Blood Flow To Testis

Peak systolic velocity:	4 10 19 cm/s
End-diastolic velocity:	2 5 8 cm/s
Resistive index:	0.44 0.60 0.75

Epididymis

• = tortuous tightly folded canal forming the efferent route from testis; consists of head (= globus major), body, tail (= globus minor)

Length:	7 cm
Size of globus major:	11 7 6 mm (decreasing with age)
Epididymal cysts:	occur in 30% of normals (average size of 4 mm)
Epididymal calcification:	in 3%
Appendix epididymis	= small stalked appendage of globus major (in 33%); occasionally duplicated

Spermatic Cord

• = testicular + deferential + cremasteric aa., pampiniform plexus of veins, vas deferens, nerves, lymphatics

Gonadal Vascular Anatomy

Gonadal Artery

Origin:

ventral surface of aorta a few cm below the origin of renal arteries (83%); from renal artery / arteries (17%):

• R from renal a. + L from aorta (6%)

• R from aorta + L from renal a. (4%)

• R + L from both renal arteries (4%)

Course:	L anterior to left renal v. (20%);
	R behind IVC + anterior to right renal v.

Gonadal Vein

R:

drains into IVC (93%) / right renal v. (7%)

L: left renal v.

• Multiple gonadal veins (15%)

Zonal Anatomy of Prostate

Normal weight:	20 6 g
Normal size:	2.8 cm (craniocaudad), 2.8 cm (anteroposterior), 4.8 cm (width)

P.915

• Outer gland

  • Central zone:

    • surrounds ejaculatory ducts from their entrance at prostatic base to verumontanum; 25% of glandular tissue

  • Peripheral zone:

    • extends from base of prostate to apex along rectal surface; 70% of glandular tissue

• Inner gland

  • Transition zone:

    • on each side of internal sphincter; 4% of glandular tissue; enlarges with BPH

  • Periurethral zone:

    • surrounding urethra; 1% of glandular tissue

Anatomy of Urethra

Male Urethra

• extends through corpus spongiosum (composed of large venous sinuses)

• Posterior urethra

  • Prostatic urethra

    • = from vesical neck to triangular ligament

    • orifices of ducts from prostatic acini at floor

    • verumontanum = colliculus seminalis

      • = prostatic utricle (fused end of m llerian ducts)

    • orifice of the two ejaculatory ducts

  • Membranous urethra

    • = portion traversing urogenital diaphragm

    • pea-sized bulbourethral glands of Cowper lie laterally + posteriorly between fasciae and sphincter urethrae within urogenital diaphragm

      

      No Caption Available.

• Anterior = cavernous urethra

  • Bulbous urethra

  • Penile (= pendulous) urethra

    • many small branched tubular periurethral glands of Littre terminate in recesses (lacunae of Morgagni)

      Cx:

      recurring urethral discharge following chronic urethritis, latent gonorrheal urethritis, stricture formation

  • Fossa navicularis

Female Urethra

• 3 5 cm in length, 6 mm in diameter

• urethral crest = posteriorly located prominent fold

• Two sets of glands:

  • urethral glands

    • terminate separately along entire length of urethra

  • paraurethral glands = glands of Skene

    • (= homologues of prostatic ducts)

    • formed by an interdependent conducting system

    • exit on either side of midline just posterior to urethral meatus draining into vaginal vestibule

      Cx:

      chronic gonorrheal urethritis

• Intrapelvic urethra

  • = upper 2/3 of urethra that lies behind symphysis pubis

• Membranous urethra

  • surrounded by sphincter membranacea urethrae (weaker less important structure than in male)

• Perineal urethra

  • lower 1/3 extending from superior fascia of urogenital diaphragm to meatus between labia minora

    

    Urethrogram: Normal Urethral Folds in LPO

P.916

Renal, Adrenal, Ureteral, Vesical, and Scrotal Disorders

Abortive Calyx

• = developmental anomaly with short blind-ending outpouching of pyramid without papillary invagination

Location:	(a) renal pelvis
	(b) infundibulum (mostly upper pole)

Acquired Cystic Kidney Disease

• = ACQUIRED CYSTIC DISEASE OF UREMIA

• = development of numerous fluid-filled renal cysts in patients with chronic renal failure undergoing hemodialysis

• Successful transplant probably stops development of additional cysts, but does not affect malignant potential!

Prevalence:	in 10 20% after 1 3 years,
	in 40 60% after 3 5 years,
	in 90% after 5 10 years of hemodialysis;
	in 25% of renal allograft recipients
Proposed etiologies:

• altered compliance of tubular basement membrane

• intra- and extratubal obstruction due to focal proliferation of tubular epithelium

• obstruction of ducts by interstitial fibrosis / oxalate crystals

• toxicity from circulating metabolites (endogenous / exogenous toxins, mutagens, mitogens, growth factors)

• vascular insufficiency

At increased risk:	older men
Histo:	cysts lined by flattened cuboidal / papillary epithelium
Associated with:

• small papillary / tubular / solid clear-cell adenomas (in 13 20%): approximately 1 cm in diameter

• renal cell carcinoma (in 3 6%): 7-year interval between transplantation + detection of RCC

• small end-stage kidneys (<280 g)

• multiple 0.5 3-cm cysts bilaterally (early = small, late = large)

• occasionally progressive renal enlargement due to cysts

Dx:	>3 cysts + NO history of hereditary cystic disease
Cx:	spontaneous hemorrhage into cyst (macrohematuria / retroperitoneal hemorrhage from cyst rupture)

Aids

• azotemia, proteinuria, hematuria, pyuria (in 38 68% sometime during illness)

• progressive renal failure (10%)

• HIV nephropathy (40%)

  • = characterized by nephrotic-range proteinuria + rapidly progressive renal failure, primarily occurring in Black patients

    Histo:

    focal + segmental glomerulosclerosis, sparse interstitial infiltrates, severe tubular degenerative changes, interstitial tubular microcystic ectasia containing protein casts

  • mild hypertension

  • early + rapidly progressive renal failure with 100% mortality within 6 months

  • global enlargement of both kidneys

    US (best screening test):

    • increased cortical echogenicity (33 68%)

  • CT:

    • medullary hyperattenuation (14%)

    • striated nephrogram on CECT

  • MR:

    • loss of corticomedullary differentiation

      Prognosis:

      death within 6 months

• Renal infection with Pneumocystis carinii (8%)

  • More frequent since introduction of prophylactic aerosolized pentamidine therapy encouraging extrapulmonic spread (<1%) due to inadequate systemic distribution of drug!

  • punctate renal calcifications confined to cortex (DDx: CMV, Mycobacterium avium-intracellulare)

  • associated calcifications in spleen, liver, lymph nodes, adrenal glands

• Renal lymphoma (3 12%)

  • AIDS-related lymphoma:

    • highly aggressive B-cell lymphomas (centroblastic, lymphoblastic, immunoblastic); NHL > Burkitt lymphoma, Hodgkin disease

  • bilateral multiple renal masses

  • direct extension of retroperitoneal lymphadenopathy engulfing kidney, renal sinus, ureter

• Cystitis (22%)

  Organism:

  routine gram-negative species, Candida, beta-hemolytic streptococci, Salmonella, CMV

  • bladder wall thickening

Acute Cortical Necrosis

• = rare form of acute renal failure

• Etiology:

  • ischemia due to vasospasm of small vessels

  • toxic damage to glomerular capillary endothelium

  • primary intravascular thrombosis

• At risk:

  • Obstetric patient (most often): abruptio placentae= premature separation of placenta with concealed hemorrhage (50%), septic abortion, placenta previa

  • Children: severe dehydration + fever, infection, hemolytic uremic syndrome, transfusion reaction

  • Adults: sepsis, severe dehydration, acute prolonged shock, myocardial failure, burns, venomous snakebite, abdominal aortic surgery, hyperacute renal transplant rejection

Histo:

patchy / universal necrosis of renal cortex + proximal convoluted structures (secondary to distension of glomerular capillaries with dehemoglobulinized RBCs); medulla and 1 2 mm of peripheral cortex are spared

• protracted + severe oliguria / anuria

Distribution:

diffuse / multifocal; mostly bilateral

• EARLY SIGNS

  • diffusely enlarged smooth kidneys

  • absent / faint nephrogram

  • CT:

    • enhancing interlobar and arcuate arteries adjacent to nonenhancing cortex (arterial phase)

    P.917

    
    

    • reversed rim sign = enhancement of medulla + nonenhancement of hypoattenuating cortex (parenchymal phase)

      Cause:

      sustained hypotension for 1 hour

    • rim of subcapsular cortical enhancement (due to collateral blood flow from cortical vessels)

    • enhancement of juxtamedullary zone of cortex

  • US:

    • loss of normal corticomedullary region with hypoechoic outer rim of cortex

  • NUC:

    • severely impaired renal perfusion

• LATE SIGNS

  • small kidney (after a few months)

  • tramline / punctate calcifications along margins of viable and necrotic tissue (as early as 1 2 months)

  • US:

    • hyperechoic cortex with acoustic shadowing

      Prognosis:

      poor chance of recovery

Acute Diffuse Bacterial Nephritis

• = ACUTE SUPPURATIVE PYELONEPHRITIS

• = more severe and extensive form of acute pyelonephritis, which may lead to diffuse necrosis (phlegmon)

  Organism:	Proteus, Klebsiella > E. coli
  Predisposed:	diabetics (60%)

Acute Interstitial Nephritis

• = infiltration of interstitium by lymphocytes, plasma cells, eosinophils, few PMNs + edema

  Cause:

  allergic / idiosyncratic reaction to drug exposure (methicillin, sulfonamides, ampicillin, cephalothin, penicillin, anticoagulants, phenindione, diphenylhydantoin)

• eosinophilia (develops 5 days to 5 weeks after exposure)

  large smooth kidneys with thick parenchyma

  normal / diminished contrast density

  US:

  • normal / increased echogenicity

Acute Tubular Necrosis

• = temporary reversible marked reduction in tubular flow rate

• Etiology:

  • DRUGS: bichloride of mercury, ethylene glycol (antifreeze), carbon tetrachloride, bismuth, arsenic, uranium, urographic contrast material (especially when associated with glomerulosclerosis in diabetes mellitus), aminoglycosides (gentamicin, kanamycin)

  • ISCHEMIA: major trauma, massive hemorrhage, postpartum hemorrhage, crush injury, myoglobulinuria, compartmental syndrome, septic shock, cardiogenic shock, burns, transfusion reaction, severe dehydration, pancreatitis, gastroenteritis, renal transplantation, cardiac surgery, biliary surgery, aortic resection

    Pathophysiology:

    profound reduction in renal blood flow due to elevated arteriolar resistance

• smooth large kidneys, especially increase in AP diameter >4.63 cm (due to interstitial edema)

• diminished / absent opacification of collecting system

• immediate persistent dense nephrogram (75%)

• increasingly dense persistent nephrogram (25%)

• diffuse calcifications (rare)

• US:

  • normal to diminished echogenicity of medulla

  • sharp delineation of swollen pyramids

  • normal (89%) / increased (11%) echogenicity of cortex

  • elevated resistive index 0.75 (in 91% excluding patients with hepatorenal syndrome); unusual in prerenal azotemia

• Angio:

  • normal arterial tree with delayed emptying of intrarenal vessels

  • slightly delayed / normal venous opacification

• NUC:

  • poor concentration of Tc-99m glucoheptonate / Tc-99m DTPA

  • well-maintained renal perfusion

  • better renal visualization on immediate postinjection images than on delayed images

  • progressive parenchymal accumulation of I-131 Hippuran / Tc-99m MAG3

  • no excretion

Addison Disease

• = PRIMARY ADRENAL INSUFFICIENCY

• 90% of adrenal cortex must be destroyed!

  Course:

  acute (adrenal apoplexy), subacute (disease present for <2 years), chronic

Acute Primary Adrenal Insufficiency

• = addisonian CRISIS = ADRENAL APOPLEXY

  Cause:

  bilateral adrenal hemorrhage most commonly due to stress from surgery / sepsis / hypotension with shock / hemorrhagic diathesis, anticoagulation therapy

• abdominal / back pain

• fever (70%), hyperpyrexia, lethargy, nausea, vomiting

• bilateral adrenal enlargement with areas of increased attenuation

  Cx:

  catastrophic hypotension + shock

Chronic Primary Adrenal Insufficiency

• Cause:

  • Idiopathic adrenal atrophy (60 70%): likely autoimmune disorder

  • Fungal infection: histoplasmosis, blastomycosis, coccidioidomycosis

  • Granulomatous disease: tuberculosis, sarcoidosis

  • Bilateral metastatic disease (rare)

• hyponatremia, hyperkalemia, azotemia, hypercalcemia

• diminutive glands (in idiopathic atrophy + chronic inflammation)

• calcifications (in 25% of chronic course)

Adrenal Cyst

Prevalence:	0.064 0.180%
Age:	3rd 6th decades (most commonly); M:F = 1:3
Path:	(a) endothelial lining (45 48%):

• Lymphangioma (93%)

• Hemangioma

• pseudocyst (39 42%):

  • Previous hemorrhage / infarction

  P.918

  
  

  • Hemorrhagic complication of benign vascular neoplasm / malformation

  • Cystic degeneration / hemorrhage of primary adrenal mass

• epithelial lining = true cyst (9 10%):

  • Glandular / retention cyst

  • Embryonal cyst

  • Cystic adenoma

  • Mesothelial inclusion cyst

• parasitic cyst (7%): usually echinococcal

Location:

mostly solitary; R:L = 1:1; bilateral in 8 10%

• asymptomatic, unless very large / infected / ruptured / bled into

• well-defined uni- / multilocular

• wall thickness of up to 3 mm

• <5 cm in diameter in 50% (up to 20 cm)

• usually homogeneous with near-water density; higher attenuation with hemorrhage / intracystic debris / crystals

• lack of central enhancement wall enhancement

• calcifications:

  • peripheral / mural: rimlike / nodular (51 69%)

  • central: in intracystic septation (19%) / punctate within intracystic hemorrhage (5%)

    Cx:	hypertension; hemorrhage; infection; rupture with retroperitoneal hemorrhage
    DDx:	1. Cystic pheochromocytoma
    	2. Cystic adenomatoid tumor
    	3. Schwannoma
    	4. Cystic adrenocortical carcinoma (thick-walled lesion >7 cm in size; extremely rare)
    	5. Adrenal adenoma (contrast enhancement, no wall, no peripheral calcification)

Adrenal Hemorrhage

Traumatic Adrenal Hemorrhage

Cause:	blunt abdominal trauma, adrenal venous sampling
Prevalence:	2% (in 28% of autopsies)
Location:	R:L = 9:1, bilateral in 20%

• round / oval hematoma (in 83%) located in medulla + stretching cortex around hematoma

• obliteration of gland by diffuse irregular hemorrhage (in 9%)

• uniform adrenal enlargement (in 9%)

• periadrenal hemorrhage causes ill-defined adrenal margin + stranding + asymmetric thickening of diaphragmatic crus

Nontraumatic Adrenal Hemorrhage

• Most common neonatal lesion of adrenal gland

• Cause:

  • NEONATAL STRESS

    • Difficult labor / delivery: forceps / breech delivery

    • Asphyxia / hypoxia due to prematurity

    • Septicemia

    • Hemorrhagic disorders: DIC, hypoprothrombinemia

    • Extracorporeal membrane oxygenation (in 4%)

    • Thrombus extending from renal vein thrombosis

      Predisposed:	infants large for gestational age, infants of diabetic mothers
      Age:	1st week of life
      Site:	R:L = 7:3; bilateral in 10%

  • STRESS

    • Pathophysiology:

      • stress increases endogenous secretion of adrenocorticotropic hormone severalfold causing an increase in adrenal vascularity; venoconstriction + venous thrombosis (due to catecholamines, thrombin, fibrin, endotoxin) during shock lead to intraglandular hemorrhage

    • Surgery: orthotopic liver transplantation

    • Sepsis: Waterhouse-Friderichsen syndrome(= fulminant meningococcemia); Pseudomonas infection; other gram-negative organisms

    • Burns

    • Hypotension

    • Pregnancy

    • Cardiovascular disease

    • Exogenous adrenocorticotropic hormone

    • Exogenous steroids

  • HEMORRHAGIC DIATHESIS & COAGULOPATHY

    • Anticoagulant therapy (heparin, coumadin): during initial 3 weeks

    • Disseminated intravascular coagulopathy

    • Antiphospholipid syndrome systemic lupus erythematosus (hypercoagulable state causes adrenal vein thrombosis + venous infarction)

  • UNDERLYING ADRENAL TUMOR

    • Pseudocyst

    • Myelolipoma

    • Hemangioma

    • Pheochromocytoma

    • Adrenocortical adenoma / carcinoma

    • Metastasis: bronchogenic carcinoma, angiosarcoma, melanoma

• sudden / gradual onset of lower chest / upper abdominal / flank / back pain

• signs of massive blood loss

• acute primary adrenal insufficiency (rare but life-threatening)

• mass displacing kidney inferiorly + IVC anteriorly

• gradual decrease in size over weeks (follow-up for 2 3 months)

• developing rimlike curvilinear / eggshell calcification

• US (modality of choice for neonate):

  • complex solid echogenic mass during early stage

  • mixed echogenicity with centrally hypoechoic region (as liquefaction occurs)

  • completely anechoic / cystlike in chronic stage

  • peripheral calcifications in 1 2 weeks

  • avascular on color Doppler / power Doppler

• CT:

  • round / oval mass (similar to traumatic causes)

  • periadrenal fat stranding

  • mass + hypoattenuating center calcifications in chronic stage = adrenal pseudocyst

  • calcification >1 year

• NECT:

  • high-attenuation mass (50 90 HU) in acute / subacute stage

P.919




• MR:

  • @ acute stage (<7 days):

    • = high concentration of intracellular deoxyhemoglobin with preferential T2 proton relaxation enhancement

    • isointense / slightly hypointense on T1WI

    • markedly hypointense on T2WI

  • @ subacute stage (7 days 7 weeks):

    • = T1 shortening due to paramagnetic effect of free methemoglobin (Fe³⁺) produced by oxidation of hemoglobin (Fe²⁺)

    • hyperintense on T1WI + T2WI appearing at periphery filling in over several weeks

    • hematoma may be multilocular, each locule with its own different signal intensity

  • @ chronic stage (>7 weeks):

    • = T2 proton relaxation enhancement due to hemosiderin deposition + presence of a fibrous capsule

    • hypointense rim on T1WI + T2WI

    • blooming effect (= magnetic susceptibility) of hemosiderin in gradient-echo imaging

      Cx:	acute primary adrenal insufficiency (rare) is life-threatening
      DDx:	neuroblastoma (stippled calcifications, increase in vanillylmandelic acid, no decrease on follow-up)

Adrenocortical Adenoma

Prevalence:	1 2% in general population; age-dependent 6.6 8.7% at autopsies small tumors in 50% of autopsies;
	In a patient with lung carcinoma a solitary small adrenal mass is more likely an adenoma than a metastasis!
Histo:	clear cells arranged in cords with abundant intracytoplasmic lipid
Absence of lipid does not exclude the possibility of a benign lipid-free adenoma!

• well-defined sharply marginated mass <5 cm in size (average size 2.0 2.5 cm)

• mild homogeneous enhancement

• adenoma may calcify

• CT:

  • soft-tissue density / cystic density (mimicked by high cholesterol content) with poor correlation between functional status and HU number:

    • <0 HU on NECT (47% sensitive, 100% specific)

    • <10 HU on NECT (73% sensitive, 96% specific)

    • <18 HU on NECT (85% sensitive, 100% specific)

    • >10% negative pixels on histogram (100% specific)

  • small adenomas <1 cm often go undetected

  • contralateral gland often normal / atrophic

• CECT:

  • <37 HU on delayed CECT (>5 15 minutes after contrast injection) is DIAGNOSTIC of adenoma

  • Added NECT allows determination of wash-out (in HU):

    • 40 wash-out (83% sensitive, 93% specific)

    • 50% washout (93% sensitive, 98% specific)

    • 60% wash-out (highly sensitive + specific)

• Angio:

  • tumor blush + neovascularity; occasionally hypovascular

  • pooling of contrast material

  • enlarged central vein with high flow

  • arcuate displacement of intraadrenal veins

  • bilateral adrenal venous sampling in up to 40% unsuccessful in localizing

• MR:

  • isointense mass relative to liver + hyperintense relative to spleen on T1WI (due to short T1 time of lipid)

  • iso- / hypointense mass (rarely hyperintense) to spleen on T2WI

  • marked hypointensity compared with spleen / skeletal muscle on opposed-phase GRE images (2 to destructive interference of lipid and water signals = phase cancellation of fat + water protons in same voxel) in 95% of adenomas (>90% accurate)

    • signal loss of 20% on opposed-phase image

  • India ink effect = characteristic black lines outlining interface between organ + adjacent fat (chemical shift artifact)

• Gd-MR:

  • adenomas tend to enhance less rapidly + less intensely than metastases on time-enhancement curves

  • relatively rapid washout of contrast material compared with metastases (due to lack of large interstitial spaces of edema + necrosis) with return to baseline at 15 minutes (DDx: metastases tend to have higher signal intensities [however 20 30% overlap])

Nonhyperfunctioning Adrenocortical Adenoma

• characterized by

  • normal lab values of adrenal hormones

  • NO pituitary shutdown of the contralateral gland

  • activity on NP-59 radionuclide scans

    Incidence:

    incidental finding in 0.6 1.5% of CT examinations, in 3 9% at autopsy

• surveillance CT to confirm lack of growth

  Rx:	surgical removal for masses 3 5 cm as indeterminate potentially malignant neoplasms
  DDx:	metastasis

Hyperfunctioning Adrenocortical Adenoma

• Primary hyperaldosteronism = Conn syndrome (80%)

  Pathophysiology:

  secretion of aldosterone by an adenoma is pulsatile

  • ACTH infusion incites a dramatic increase in levels of cortisol + aldosterone for venous sampling

• Cushing syndrome (10%)

• Virilization

  • hirsutism + clitoromegaly in girls

  • pseudopuberty in boys

  • most common type of hormone elevation in children

  • elevated testosterone levels >0.55 ng/mL

• Feminization (estrogen production)

  • contralateral atrophic gland (secondary to ACTH suppression with autonomous adenoma)

  • unilateral focus of I-131 NP-59 radioactivity + contralateral absence of iodocholesterol accumulation (DDx: hyperplasia [bilateral activity])

P.920

Adrenocortical Carcinoma

Prevalence:	1:1,000,000 people; 0.3 0.4% of all pediatric neoplasms (3 times more likely than adrenal adenoma)
Age:	4th 7th decade
May be associated with:	hemihypertrophy, Beckwith-Wiedemann syndrome, astrocytomas
Path:	large lobulated tumor, often with cystic / necrotic / hemorrhagic center
Histo:	differentiation of benign from malignant solely on the basis of histologic features may be difficult

• abdominal pain, palpable abdominal mass

• 20% nonfunctioning

• 50% hyperfunctioning (in 10 15% Cushing syndrome)

  Size:

  usually >5 cm (median size 12 cm; in 16% <6 cm)

• frequently heterogeneous mass with irregular margins

• occasionally calcified (in 30%)

• invasion of IVC, liver, kidney, diaphragm

• metastases to regional lymph nodes, lung, bone, brain

• Metastases are the only reliable sign of malignancy!

• Large size + calcifications suggest malignancy!

• CT:

  • central areas of low attenuation (tumor necrosis)

  • heterogeneous enhancement (foci of hemorrhage + central necrosis)

• CECT:

  • peripheral nodular enhancement (in 88%)

• US:

  • complex echo pattern (due to hemorrhage + necrosis)

• MR:

  • heterogeneously hyperintense to liver on T1WI + T2WI (due to frequent presence of internal hemorrhage + necrosis)

  • nodular enhancement + central hypoperfusion + delayed washout

• Angio:

  • enlarged adrenal arteries

  • neovascularity, occasionally with parasitization

  • AV shunting; multiple draining veins

• NUC:

  • usually bilateral nonvisualization with I-131 NP-59 (carcinomatous side does not visualize because amount of uptake is small for size of lesion; contralateral side does not visualize because carcinoma is releasing sufficient hormone to cause pituitary feedback shutdown of contralateral gland)

  Biopsy:	may appear histologically benign in well-differentiated adenocarcinoma
  	Sampling error with fine-needle aspiration possible; use core biopsy instead
  Prognosis:	0% 5-year survival rate
  DDx:	metastasis (similar signal intensities on MR)

Adrenocortical Neoplasm in Children

Incidence:	3:1,000,000 annually; less common than neuroblastomas but more common than pheochromocytoma
Age:	6 months to 19 years (mean age of 8 years); 2/3 younger than 5 years of age; M:F = 2.2:1.0
Path:	adenoma = solitary spherical well-demarcated unencapsulated tumor of <50 g;
	carcinoma = multinodular tumor with areas of hemorrhage + necrosis of >100 500 g
Histo:	no reliable features to distinguish between adenoma and carcinoma

• Associated with:

  • Congenital hemihypertrophy (3%)

  • Li-Fraumeni syndrome = SBLA (sarcoma, breast and brain tumors, laryngeal carcinoma, adrenocortical carcinoma)

    • alteration of p53 tumor suppressor gene located on short arm of chromosome 17, band 13

• palpable abdominal mass (57%)

• gonadotropin-independent production of endogenous androgens + cortisol (92%):

  • virilization in female

    • = herculean habitus (increased muscle mass), clitoromegaly, facial hair, advanced pubic + axillary hair development, advanced bone age

  • isosexual precocious puberty in male

    • = early development of acne, pubic hair, penile enlargement

  • mixed endocrine syndrome with cushingoid features (less frequent)

• other endocrine abnormalities (unusual):

  • pure Cushing syndrome

  • feminization in boys (caused by secretion of estrogen)

  • Conn syndrome (primary hyperaldosteronism)

• increase in 24-hour urinary ketosteroid excretion

• increased levels of serum cortisol, testosterone, androstenedione, estradiol

Metastases:

lung > liver > tumor invasion of IVC (35%) > peritoneum (29%) > pleura + diaphragm (24%) > abdominal lymph nodes (24%) > kidney (18%)

• US:

  • 3 22-cm round / ovoid well-circumscribed mass

  • lobulated border (common)

  • thin echogenic capsule-like rim (27%)

  • homogeneous mass hypo- / isoechoic to kidney

  • heterogeneous mass with centrally hypoechoic regions (= tumor necrosis) if large

  • tumor calcification (19%)

• CECT:

  • well-circumscribed mass with thin rim

  • heterogeneous enhancement if lesion large

  • calcification (24%)

• MR:

  • isointense to liver on T1WI

  • hyperintense to liver on T2WI

• secondary findings due to excess serum cortisol:

  • hyperattenuating / hyperechoic renal pyramids (due to hypercalcemia of Cushing syndrome)

  • increase in retroperitoneal fatty tissue (obesity due to Cushing syndrome)

Rx:

surgery

• Prognosis of adrenocortical carcinoma:

  • survival rate of 70% for children <5 years of age and 13% for children >5 years of age; death within 1 2 years after diagnosis

P.921

DDx:	(1) Neuroblastoma (encasing vascular structures, punctate calcifications, extradural extension, ill child, often already metastatic, increase in catecholamines)
	(2) Pheochromocytoma (older child, headaches)
	(3) Adrenal hemorrhage (neonate, temporal evolution)
	(4) Metastasis (extremely rare)

Adrenocortical Hyperplasia

• Responsible for 8% of Cushing syndrome and 10 20% of hyperaldosteronism!

• Cause:

  • Corticotropin-dependent (85%): pituitary causes, ectopic corticotropin production, production of corticotropin-releasing factor

  • Primary pigmented nodular adrenocortical hyperplasia

    Associated with:

    Carney complex

  • Primary aldosteronism (rare)

    Incidence:	4 increased in patients with malignancy
    Age:	70 80% in adults; 19% in children
    Types:

  • Smooth hyperplasia (common)

    • bilateral normal-sized glands

    • thickened + elongated glands

  • Cortical nodular hyperplasia (less common)

    • normal glands appreciable micronodular configuration

    • thickened gland with macronodular configuration (nodules up to 2.5 cm)

• Angio:

  • minimally increased hypervascularity

  • focal accumulation of contrast medium

  • normal venogram / may show enlarged gland

• NUC:

  • asymmetric bilateral NP-59 uptake (related to urinary cortisol excretion) without dexamethasone suppression in Cushing syndrome

  • bilateral foci of NP-59 uptake with dexamethasone suppression (nondiagnostic 5 days)

Adrenogenital Syndromes

• CONGENITAL TYPE

  • = impaired cortisol + aldosterone synthesis secondary to enzyme defect (21-hydroxylase) with increased ACTH stimulation by pituitary gland (negative feedback mechanism)

  • M < F

  • excess of androgenic steroids

  • salt wasting due to diminished mineralocorticoids

  • virilization of female fetus

  • precocious puberty in male

  • pseudohermaphroditism (clitoral hypertrophy, ambiguous external genitalia, urogenital sinus)

  • symmetrically enlarged + thickened adrenal glands

    Rx:

    cortisone mineralocorticoids

• ACQUIRED TYPE

  • M < F

  • adrenal hyperplasia / adenoma / carcinoma

  • ovarian / testicular tumor

  • gonadotropin-producing tumor: pineal, hypothalamic, choriocarcinoma

  • virilization

  • Cushing syndrome

Alkaline-encrusted cystitis and pyelitis

• = chronic severe urinary tract infection affecting the urothelial lining

  Cause:	nosocomial infection with urease-producing bacterium, most commonly Corynebacterium (producing alkaline urine)
  Predisposed:	immunocompromised patient (esp. renal transplant patient), after invasive urologic procedure
  Path:	mucosal inflammation + encrustation of urothelial lining with struvite + calcium phosphate

• fever, hematuria, dysuria, suprapubic pain

• ammonia-like smell of urine

• NECT:

  • diffuse thin / coarse regular superficial linear urothelial calcifications

    Site:	collecting system, ureter, bladder; often bilateral
    Dx:	culture positive >48 hours for urea-splitting micro-organism
    Cx:	septic shock, graft failure
    Rx:	antibiotics, oral acidification of urine

Amyloidosis

• = accumulation of extracellular eosinophilic protein substances

• @ Renal involvement

  Incidence:	1 amyloidosis (35%),
  	2 amyloidosis (in >80%)

  • smooth normal to large kidneys with increase in parenchymal thickness (early stage)

  • small kidneys = renal atrophy (late stage)

  • occasionally attenuated collecting system

  • increase in cortical echogenicity (deposition of amyloid in glomeruli and interstitium) + prominence of corticomedullary junction + obscuration of arcuate aa.

  • nephrographic density normal to diminished

  • US:

    • normal to increased echogenicity

Cx:

renal vein thrombosis

Analgesic Nephropathy

• = renal damage from ingestion of salicylates in combination with phenacetin / acetaminophen in a cumulative dose of 1 kg

  Incidence:	United States (2 10%), Australia (20%)
  Age:	middle-aged; M:F = 1:4

• gross hematuria

• hypertension

• renal colic (passage of renal tissue)

• renal insufficiency (2 10% of all end-stage renal failures)

• Analgesic syndrome: history of psychiatric therapy, abuse of alcohol + laxatives, headaches, pain in cervical + lumbar spine, peptic ulcer, anemia, splenomegaly, arteriosclerosis, premature aging

• papillary necrosis

• scarring of renal parenchyma ( wavy outline ); bilateral in 66%, unilateral in 5%

P.922




• renal atrophy

• papillary urothelial tumors in calyces / pelvis (mostly TCC / squamous cell carcinoma), in 5% bilateral

Angiomyolipoma

• = AML = Renal Choristoma (benign tumor composed of tissues not normally occurring within the organ of origin)

  • = Renal Hamartoma (improper name since fat and smooth muscle do not normally occur within renal parenchyma)

• = most common benign mesenchymal tumor of kidney

  Prevalence:	0.3 3%
  Path:	no true capsule, 88% extending through renal capsule, hemorrhage (characteristic lack of complete elastic layer of vessels predisposes to aneurysm formation); tumor continues to grow during childhood + early adulthood
  Histo:	tumor composed of fat, smooth muscle, aggregates of thick-walled blood vessels

  • small lesions are asymptomatic (60%)

    • Angiomyolipomas >4 cm are symptomatic in 82 94%!

  • acute flank / abdominal pain in 87%

  • Wunderlich syndrome = hemorrhagic shock due to massive bleeding into angiomyolipoma or into retroperitoneum

    • AMLs >4 cm bleed spontaneously in 50 60%!

• CT:

  • ordinary AML (in 95%):

    • negative attenuation values

    • Even a small amount of fat within a solid mass on NECT secures the diagnosis!

  • minimal-fat AML (in 5%)

    • = angiomyolipoma with microscopic fat only

    • hyperattenuating (53%) / isoattenuating (26%) / hypoattenuating (21%) mass (DDx: RCC)

    • homogeneous prolonged tumor enhancement

• MR:

  • markedly hyperintense adipose tissue on T1WI

  • prominent signal loss relative to other tissues on fat-suppressed / opposed-phase images with respect to in-phase images

  • decreased signal intensity on Gd-enhanced images (DDx: RCC enhances)

    Rx:	(1) annual follow-up of lesions <4 cm
    	(2) semiannual follow-up of lesions 4 cm
    	(3) emergency laparotomy (in 25%): nephrectomy, tumor resection
    	(4) selective arterial embolization
    DDx:	renal / perirenal lipoma or liposarcoma; Wilms tumor / renal cell carcinoma (occasionally contains fat if large, but also calcium)

Isolated Angiomyolipoma (80%)

• = SPORADIC ANGIOMYOLIPOMA

  Age:

  27 72 (mean 43) years of age; M:F = 1:4

• solitary + unilateral (in 80% on R side) AML, NO stigmata of tuberous sclerosis

Angiomyolipoma associated with Tuberous Sclerosis (20%)

Mean age:

17 years; usually present by 10 years; M:F = 1:1

• In 80% of patients with tuberous sclerosis

• May be the only evidence of tuberous sclerosis

• commonly large + bilateral + multifocal AMLs

Angiomyolipoma associated with Neurofibromatosis and von Hippel-Lindau Syndrome

Arteriovenous Connection

• early enhancement of draining vein + renal vein + IVC

• intraparenchymal / subcapsular / perirenal hematoma (as a result of bleeding)

Rx:

transcatheter intraarterial occlusion, surgery

Arteriovenous Malformation (20 30%)

• Congenital AVM

  • asymptomatic; M < F

• Acquired AVM: trauma, spontaneous rupture of aneurysm, very vascular malignant neoplasm

• Histo:

  • cirsoid AVM = multiple coiled vascular channels grouped in cluster

  • cavernous AVM = single well-defined artery feeding into a single vein (rare)

• gross hematuria

  Location:

  adjacent to collecting system

  • supplied by multiple segmental / interlobar arteries of normal caliber

  • draining into one / more veins

  • large unifocal mass

  • focally attenuated and displaced collecting system

  • homogeneously enhancing mass

  • curvilinear calcification

• US:

  • tubular anechoic structure (DDx: hydronephrosis, hydrocalyx)

    Cx:

    subcapsular / perinephric hematoma (rare)

Arteriovenous Fistula (70 80%)

• M > F

  Cause:	trauma (stab wound, percutaneous needle biopsy, percutaneous nephrostomy, nephrolithotripsy), surgery, tumor, inflammation, erosion of aneurysm into vein
  Path:	single feeding artery + single draining vein

• asymptomatic with abnormal bruit

• persistent / delayed hematuria (common)

• diminished nephrogram cortical atrophy distal to fistula (due to reduced flow to renal segment)

  Cx:	cardiomegaly + CHF (50%), renin-mediated hypertension
  Prognosis:	spontaneous closure within a few months

Benign Prostatic Hypertrophy

• = BENIGN PROSTATIC HYPERPLASIA

  Prevalence:	50% between ages 51 + 60 years;
  	75 80% of all men >80 years of age
  Histo:	fibromyoadenomatous nodule (most common), muscular + fibromuscular + fibroadenomatous + stromal nodules
  Age:	initial growth onset <30 years of age; onset of clinical symptoms at 60 9 years

• sensation of full bladder, nocturia

• trouble initiating micturition

• decreased urine caliber + force

P.923




• dribbling at termination of micturition

  Location:

  transition + periurethral zone proximal to verumontanum forming lateral lobes (82%), median lobe (12%)

• oval (61%) / round (22%) / pear-shaped (17%) enlargement of central gland

• posterior + lateral displacement of outer gland (= prostate proper) creating cleavage plane of fibrous tissue between hyperplastic tissue + compressed prostatic tissue (= surgical capsule) often demarcated by displaced intraductal calcifications

  Cx:	bladder outflow obstruction
  Rx:

  • Surgery: open prostatectomy (glands >80 g), transurethral resection of prostate = TURP (glands <80 g)

    • Only 4 5% of patients need surgical treatment!

  • Drugs: -blockers (for stromal hyperplasia); androgen deprivation (suppression of LHRH / inhibition of Leydig cell synthesis of testosterone / competition for androgen receptor binding sites) + -blockers (for glandular hyperplasia)

Bladder Diverticulum

• = cavity formed by herniation of bladder mucosa through muscular wall, joined to the bladder cavity by a constricted neck

  Prevalence:	1.7% in children
  Average age:	57 years; M:F = 9:1
  Site:	areas of congenital weakness of muscular wall at
  	(a) ureteral meatus
  	(b) posterolateral wall (Hutch diverticulum = paraureteral)
  Cx:	(1) Vesical carcinoma in 0.8 7% secondary to chronic inflammation (average age 66 years)
  	(2) Ureteral obstruction
  	(3) Ureteral reflux

Primary Diverticula (40%)

• = CONGENITAL / IDIOPATHIC diverticula

• in 3% single diverticulum

• with vesicoureteral reflux

  • Hutch diverticulum in paraureteral region

• without vesicoureteral reflux

Secondary Diverticula (60%)

• in 50% multiple diverticula

• postoperative state

• associated with bladder outlet obstruction

  • Posterior urethral valves

  • Urethral stricture

  • Large ureterocele

  • Neurogenic dysfunction

  • Enlarged prostate

  • Bladder neck stenosis

• associated with syndromes

  • Prune belly syndrome

  • Menkes kinky-hair syndrome

  • Williams syndrome

  • Ehlers-Danlos type 9 syndrome

  • Diamond-Blackfan syndrome

Multiple Diverticula in Children

• Neurogenic dysfunction

• Posterior urethral valves

• Prune belly syndrome

Bladder Exstrophy

• = EPISPADIA-EXSTROPHY COMPLEX

  Prevalence:	1:33,000 to 1:40,000 live births
  Etiology:	incomplete retraction of cloacal membrane prevents normal midline migration of mesoderm resulting in incomplete midline closure of infraumbilical abdominal wall; size of persistent cloacal membrane at time of rupture accounts for different degrees of severity

• urinary bladder exposed + open anteriorly

• mucosa everted through abdominal wall defect

• bladder margins continuous with margins of abdominal wall

• epispadia (male); bifid clitoris (female)

• May be associated with:

  • wide linea alba, omphalocele, limb defects (eg, club feet), renal malformation (horseshoe kidney, renal agenesis), incomplete testicular descent, GI obstruction, bilateral inguinal hernias, imperforate anus, cardiac anomalies, hydrocephalus, meningomyelocele

• ventral defect of infraumbilical abdominal wall

• low position of umbilicus

• pubic diastasis = widening of pubic symphysis

  Cx:	urinary incontinence, infertility, pyelonephritis, bladder carcinoma (4%)
  Rx:	primary closure, bladder excision with urinary diversion

Closed Exstrophy = Pseudoexstrophy

• = persistent large cloacal membrane without rupture

• anterior wall of bladder covered by thin bilaminar epithelial membrane

• infraumbilical musculoskeletal defect

• subcutaneous position of bladder

Cholesteatoma

• = keratin ball = keratinized squamous epithelium shed into lumen

  Pathogenesis:

  long-standing urinary infection may result in squamous metaplasia of transitional epithelium

• history of UTIs

• repeated episodes of renal colic with passage of white tissue flakes

  Location:

  renal pelvis > upper ureter

• mottled / stringy onion-skin filling defect in calices / renal pelvis

• dilatation of pelvicaliceal system (with obstruction)

• calcification of keratinized material possible

• Not a premalignant condition!

Chromophobe Carcinoma of Kidney

Prevalence:	4% of renal cell neoplasms
Age:	median in 6th decade (31 75 years)
Histo:	cells with abundant cytoplasm containing numerous microvesicles

• average size of 8 cm (range 1.3 20 cm)

  Prognosis:

  probably better than RCC

P.924

Chronic Glomerulonephritis

Cause:

after acute poststreptococcal glomerulonephritis

• late presentation without prior clinically apparent acute phase

• hypertension

• renal failure

• small smooth kidneys with wasted parenchyma

• normal papillae + calyces

• patchy nephrogram with diminished density of contrast medium

• cortical calcification (uncommon)

• US:

  • increased echogenicity

  • small kidneys with vicarious sinus lipomatosis

• Angio:

  • marked reduction in renal blood flow + reflux of contrast material into aorta

  • severely pruned + tortuous interlobar and arcuate arteries

  • nonvisualization of interlobular arteries

  • delayed contrast clearance from interlobar arteries

Clear Cell Sarcoma of Kidney

• = BONE-METASTASIZING RENAL TUMOR OF CHILDHOOD

• = rare highly malignant renal tumor of childhood with predilection for bone metastasis

  Incidence:	4 5% of renal tumors in childhood
  Age:	peak age at 2 years (range, 1 6 years); M > F
  Path:	soft well-circumscribed tumor
  Histo:	composed of well-defined polygonal to stellate cells with vacuolization, ovoid to rounded nuclei, prominent capillary pattern + tendency toward cyst formation separated by slightly thickened septa

• increasing abdominal girth + palpable abdominal mass

• lethargy, weight loss

• hematuria

• expansile well-demarcated mass (8 16 cm) with dominant soft-tissue component

• cystic component of varying size (few mm to 5 cm) + multiplicity (58%)

• amorphous / linear calcifications (25%)

• renal mass crossing midline (58%)

• WITHOUT intravascular extension

  Metastases to:

  bone, lymph nodes, brain, liver, lung

• US:

  • inhomogeneous renal mass of soft-tissue density

  • well-defined hypoechoic central area (= necrosis)

  • mass of fluid-filled cystic spaces

• CT:

  • inhomogeneous enhancement less than that of normal renal parenchyma

  • low-attenuation areas (= necrosis)

  • water-density areas (= cysts)

    Prognosis:	60 70% long-term survival rate; aggressive behavior (worse than Wilms tumor) with higher rate of relapse + mortality
    DDx:	cystic form of Wilms tumor (vascular invasion), multilocular cystic nephroma, cystic dysplasia

Congenital Renal Hypoplasia

• = miniaturization with reduction in number of renal lobes, number of calyces and papillae, amount of nephrons (+ smallness of cells)

  VARIANT:

  Ask-Upmark kidney = aglomerular focal hypoplasia

• unilateral small kidney

• decreased number of papillae + calyces (5 or less)

• hypertrophied contralateral kidney

• absent renal artery

• hypoplastic disorganized renal veins

Conn Syndrome

• = PRIMARY HYPERALDOSTERONISM = PRIMARY ALDOSTERONISM

• = autonomous excess secretion of the mineralocorticoid aldosterone with hypertension + spontaneous hypokalemia

  Incidence:	0.05 2% of hypertensive population
  Age:	3rd 5th decade; M:F = 1:2

• hypertension (secondary to hypernatremia)

• hypokalemia (80 90%, induced by administering large amounts of sodium chloride for 3 5 days):

  • muscle weakness, cardiac arrhythmia

  • carbohydrate intolerance

  • nephrogenic diabetes insipidus

• depletion of magnesium

• metabolic alkalosis

• increased urinary excretion of aldosterone + metabolites

• nonsuppressible elevation in plasma aldosterone concentration

• suppressed plasma renin levels

• Path:

  • adenoma (65 89%): solitary aldosteronoma (65 70%); multiple (13%); microadenomatosis (6%)

  • bilateral adrenal hyperplasia (11 25 30%):

    • = idiopathic hyperaldosteronism = focal / diffuse hyperplasia of glomerular zone accompanied by micro- / macroscopic nodules

  • adrenocortical carcinoma (<1%)

• small aldosteronoma of 1.7 cm average size (range, 0.5 3.5 cm); L > R, bilateral in 6%:

  • soft-tissue density / low attenuation

    • Among hyperfunctioning adrenal adenomas aldosteronomas have the lowest attenuation!

  • usually hypervascular, rarely hypovascular

• normal / nodular / multinodular adrenal gland(s) (with hyperplasia)

  Adrenal venography	: 76% accuracy
  Adrenal venous blood sampling	: 95% accuracy,
  	75% sensitivity
  CT	: 60 80% sensitivity

• NUC:

  • I-131 NP-59 uptake following dexamethasone suppression:

    • bilateral early visualization (<5 days) implies adrenal hyperplasia

    • unilateral early visualization implies adenoma

    • late bilateral visualization (>5 days) may be normal

      Dx:	elevated plasma aldosterone concentration + suppressed plasma renin activity
      	Diagnostic endocrine tests:   postural stimulation test, short saline infusion test, 18-hydroxycorticosterone concentration
      Rx:	adrenalectomy for neoplasms (75% long-term cure rate for hypertension); medical treatment for hyperplasia

P.925

Contrast Nephropathy

• = CONTRAST-INDUCED RENAL FAILURE

• = increase in serum creatinine of 1 mg/dL 25 50% of the baseline creatinine level after intravascular contrast administration

• Patients at risk:

  • Preexisting renal insufficiency

  • Insulin-dependent diabetes mellitus

  • Large volume of contrast media

  • Concomitant administration of other nephrotoxic drugs: aminoglycosides, nonsteroidal anti-inflammatory agents

  • American Heart Association class IV congestive heart failure

  • Hyperuricemia

  • A serum creatinine level of >4.5 mg/dL causes acute renal failure in 60% of nondiabetics + 100% of diabetics!

• Previously considered but no longer accepted risk factors:

  • dehydration, hypertension, proteinuria, peripheral vascular disease, age >65 years, multiple myeloma

• Mechanism:

  • increase in renal perfusion by vasodilatation (via prostaglandin I2 E2) followed by vasoconstriction (via angiotensin II, norepinephrine, vasopressin)

• Time course:

  • rise in serum creatinine within 1 2 days

  • peak at 4 7 days

  • return to normal by 10 14 days

• persistent nephrogram on plain film

• cortical attenuation >140 HU on CT with 24-hour delay

• Recommendation:

  • Employ nonionic contrast media (LOCM appears safe in patients without renal dysfunction / underlying risk factors in doses as large as 800 mL [300 mg iodine per mL])

  • Do not exceed maximum allowed dose (Cigarroa formula for HOCM):

    

Cushing Syndrome

• = HYPERCORTISOLISM

• = excessive glucocorticoid secretion from either exogenous / endogenous sources

• Etiology:

  • ACTH-INDEPENDENT

    • Exogenous cortisol

    • Primary adrenal abnormality (20%):

      • primary pigmented nodular adrenocortical hyperplasia (children, young adults)

      • adrenocortical adenoma (10 20% of cases; 10% in adults, 15% in children)

      • adrenocortical carcinoma (5 10% of cases; 10% in adults, 66% in children)

  • ACTH-DEPENDENT

    • = overproduction of corticotropin with adrenal hyperplasia (in up to 85%)

  • Exogenous ACTH

  • Paraneoplastic ectopic ACTH production (20%): oat cell carcinoma of lung (8%), liver cancer, prostate cancer, ovarian cancer, breast cancer, bronchial / thymic carcinoid, bronchial adenoma, pancreatic islet cell tumor (10%), medullary carcinoma of thyroid, thymoma, pheochromocytoma

    • Bronchial + thymic carcinoids are often <1 cm at the time they produce Cushing syndrome!

    • Islet cell tumors are large + often metastatic by the time they produce Cushing syndrome!

  • Cushing disease (70% of endogenous causes)

    • = adrenal hyperplasia due to overproduction of pituitary ACTH

    • Cause:

      • basophilic / chromophobe adenoma

      • overactive pituitary

      • ACTH-producing primary elsewhere

  • Hypothalamic dysfunction

  • Production of corticotropin-releasing factor (rare)

    Incidence:	1:1,000 autopsies; M:F = 1:4
    Age:	30 40 years (highest incidence); more often following pregnancy

• central / truncal obesity, buffalo hump, moon face, facial plethora

• purple abdominal striae, acne, hirsutism

• fatigue, proximal muscle weakness, amenorrhea

• impaired glucose tolerance = glycosuria / diabetes

• hypertension, atherosclerosis, edema

• elevated plasma cortisol levels

• excessive excretion of urinary 17-hydroxy-corticosteroids

• dexamethasone suppression test / metyrapone test

• retarded bone maturation

• most often axial osteoporosis

• stippled calvarium

• demineralized dorsum sellae

• excess callus formation

  Cx:	(1) Pathologic fractures of vertebrae + ribs with excessive callus formation
  	(2) Aseptic necrosis of hips
  	(3) Bone infarcts
  	(4) Delayed skeletal maturation in children

Cystitis

• = bacterial infection; M < F

• frequency, dysuria, hematuria

• reduced bladder capacity

• cystogram insensitive

• US:

  • focal / multifocal / circumferential isoechoic bladder wall thickening

  • decrease in bladder wall thickening during bladder distension (eg, instillation of sterile saline via a urethral catheter)

  • bullous lesions

  • intact mucosa

    DDx:

    bladder neoplasm, ureterocele, pseudoureterocele, neurofibromatosis, pseudosarcomatous myofibroblastic proliferations

Cystitis Cystica

• = CYSTITIS follicularis = CYSTITIS GLANDULARIS= BULLOUS CYSTITIS

• = nonspecific inflammatory process of bladder wall

• multiple small round cystlike mucosal elevations

  P.926

  
  

  May be associated with:	pelvic lipomatosis
  Prognosis:	potentially malignant in adults

Emphysematous Cystitis

• = uncommon complication of urinary tract infection by gas-forming organism almost PATHOGNOMONIC of poorly controlled diabetes (= bacterial fermentation of glucose)

  Age:	>50 years; M:F = 1:2
  Predisposed:	diabetes mellitus, neurogenic bladder, bladder outlet obstruction, chronic UTI
  Organism:	E. coli, E. aerogenes, P. mirabilis, S. aureus, streptococci, Clostridium perfringens, Nocardia, Candida
  May be associated with:	emphysematous pyelitis / pyelonephritis

• pneumaturia (rare)

• Plain film:

  • translucent streaky irregular area / ring of air bubbles in bladder wall

  • intraluminal air-fluid level

• US:

  • shadowing echogenic foci within area of bladder wall thickening

• CT (most specific modality)

  DDx:	(a) Gas within bladder:   trauma, urinary tract instrumentation, enterovesical fistula
  (b) Gas external to bladder:   rectal gas, emphysematous vaginitis, pneumatosis cystoides intestinalis, gas gangrene of uterus

Granulomatous Cystitis = Tuberculous Cystitis

• irritable hypertonic bladder with decreased capacity

• disease process usually starts at trigone spreading upward and laterally

• calcification of bladder wall (rare)

Hemorrhagic Cystitis

Cause:

unclear

• nonspecific: negative culture

• bacterial: E. coli (in 17%)

• viral (adenovirus in 19%): negative culture, viral exanthem

• cytotoxic: cyclophosphamide (Cytoxan ), in 15% of patients within 1st year of treatment

• echogenic mobile clumps of solid material (= intraluminal blood clots)

Interstitial Cystitis

Age:

postmenopausal female

• pink pseudoulceration of bladder mucosa characteristically at vertex of bladder (= Hunner ulcer)

Bullous Edema of Bladder Wall

Cause:

continuous internal contact with Foley catheter, involvement of bladder wall by external contact in pelvic inflammatory conditions (eg, Crohn disease, appendicitis, diverticulitis)

• smoothly thickened / polypoid redundant hypoechoic mucosa

Diabetes Mellitus

• = multisystem disorder

  Prevalence:	14 million patients in United States
  Path:	macro- and microvascular disease; neuropathy; increased susceptibility to infection

• CHRONIC EFFECTS

  • Papillary necrosis

  • Renal artery stenosis

  • Vas deferens calcification

• URINARY TRACT INFECTIONS

  • Renal and perirenal abscess

  • Emphysematous pyelonephritis

  • Emphysematous cystitis

  • Fungal infection: Candida, Aspergillus

  • Xanthogranulomatous pyelonephritis

• GENITAL INFECTION

  • Fournier gangrene

  • Postmenopausal tuboovarian abscess

Diabetic Nephropathy

• = defined as persistent proteinuria (>500 mg of albumin/24 hours) + retinopathy + elevated blood pressure

• Most common cause of end-stage renal disease!

  Incidence:	35 45% of IDDM; <20% of NIDDM; M > F
  Histo:	diffuse intercapillary glomerulosclerosis
  Mortality:	90% after 40 years

• Early:

  • renal enlargement (renal hypertrophy with glomerular expansion)

• Late:

  • progressive decrease in size

  • diffuse cortical hyperechogenicity with gradual loss of corticomedullary differentiation

  • resistive index >0.7 (very late)

• IVP:

  • contrast material may induce renal failure (= rise in serum creatinine level 1 5 days after exposure)

  • Keep patient well hydrated with 0.45% saline!

Diabetic Cystopathy

Cause:	autonomous peripheral neuropathy
Histo:	vacuolation of ganglion cells in bladder wall, giant sympathetic neurons, hypochromatic ganglion cells, demyelination

• insidious impairment of bladder sensation

• decreased reflex detrusor activity

• enlarged postvoid residual urine volume

  Cx:

  vesicoureteral reflux, recurrent pyelonephritis, pyohydronephrosis, overflow incontinence

Epididymitis

Acute Epididymitis

• = ACUTE EPIDIDYMOORCHITIS

• Most common acute pathologic process in postpubertal age

  Cause:	ascending urinary tract infection; instrumentation + prostatitis (in older men)
  Incidence:	634,000 cases/year
  Age:	<18 years (common); 19 25 years (very common); >25 years (extremely common); >30 years (almost all cases of scrotal pain)
  Organism:	E. coli + S. aureus (85%), Gonococcus (12%), TB (2%); nonspecific epididymitis in 20%   (a) >35 years of age: Escherichia coli + Proteus mirabilis, CMV with AIDS   (b) <35 years of age: Chlamydia trachomatis, Neisseria gonorrheae

P.927

• fever

• increasing pain over 1 2 days

• hemiscrotal swelling + tenderness + erythema

• pyuria (95%)

• positive urine culture

• leukocytosis (50%)

• dysuria + frequency (25%)

• prostatic tenderness (infrequent)

  Location:

  may have focal involvement as in focal epididymitis (25%) often in epididymal tail

  • Subsequent spread to testis is common: global orchitis (frequent), focal orchitis (10%)

• US:

  • enlarged epididymis with decreased echogenicity:

    • enlarged head suggests hematogenous spread

    • enlarged tail suggest retrograde reflux from prostate / urine

  • reactive hydrocele thickening of scrotal wall

  • enlarged spermatic cord containing hyperechoic fat

  • thickening of tunica albuginea (in severe infection)

• Color Duplex (91% sensitive, 100% specific):

  • increased number + concentration of identifiable vessels in affected region (= hyperemia)

  • peak systolic velocity (PSV) >15 cm/s with PSV ratio >1.9 compared with normal side

  • detection of venous flow

  • diastolic flow reversal in testicular artery (due to epididymal edema with obstruction of venous outflow)

• NUC (true positive rate of 99%):

  • symmetric perfusion of iliac + femoral vessels

  • markedly increased perfusion through spermatic cord vessels (testicular + deferential arteries)

  • curvilinear increased activity laterally in hemiscrotum on static images (also centrally if testis involved)

  • increased activity of scrotal contents on static images (hyperemia + increased capillary permeability)

    Rx:	antimicrobial therapy, scrotal elevation, bed rest, analgesics, ice packs
    Cx:	(1) Focal / diffuse orchitis (20 40%)   (2) Epididymal abscess (6%)   (3) Testicular abscess (6%)   (4) Testicular infarction (3%) from extrinsic compression of testicular blood flow   (5) Late testicular atrophy (21%)   (6) Hydropyocele   (7) Fournier gangrene
    DDx:	(1) Testicular abscess (increased perfusion with centrally decreased uptake)   (2) Hydrocele (normal perfusion, no uptake)   (3) Testicular tumor (slightly increased perfusion; in- / decreased uptake; no associated epididymal hyperemia on CFI; positive tumor markers: hCG, AFP)

Chronic Epididymitis

• US:

  • enlarged hyperechoic epididymis

Erectile Dysfunction

• = IMPOTENCE (term replaced due to negative connotation)

• = inability to have / maintain a penile erection sufficient for vaginal penetration in 50% or more attempts during intercourse

  Incidence:

  10 million Americans

• Physiology:

  • psychogenic phase:

    • stimuli from thalamic nuclei, rhinencephalon, limbic system converge in medial preoptic anterior hypothalamic area

  • neurologic phase:

    • sacral nerve roots (S2 S4) contribute fibers to pelvic sympathetic plexus

    • stimulation of cavernous n. (parasympathetic nerve) causes changes in blood flow resulting in full erection

    • stimulation of pudendal n. (motor nerve) causes contraction of bulbocavernosus + ischiocavernosus muscle resulting in occlusion of veins + rigid erection

      Risk factors:

      hypertension, diabetes, smoking, CAD, peripheral vascular disease, pelvic trauma / surgery, blood lipid abnormalities

• Cause:

  • Organic (majority)

    • Endocrine disorder reducing serum testosterone / increasing serum prolactin

    • Vascular disease (10 20%): increasing with age

      • failure to fill (arteriogenic)

      • failure to store (venogenic)

    • Neurogenic disease (10%) = failure to initiate:

      • neurologic disorder: multiple sclerosis, spinal cord injury, cervical spondylosis, spinal arachnoiditis, pelvic trauma, temporal lobe / idiopathic epilepsy, Alzheimer disease, Parkinson disease, tabes dorsalis, amyloidosis, primary autonomic insufficiency, cerebrovascular accidents, primary / metastatic tumor

      • surgical injury to nerves: damage to pelvic sympathetic nerves / cavernous n. during radical prostatectomy / cystectomy

    • Chronic disease: diabetes mellitus (2 million); drugs (antihypertensives, anticonvulsants, alcohol, narcotics, psychotropic agents)

    • Endorgan disease: priapism

  • PSYCHOGENIC

• Penile-brachial index (normal >1.0)

  • = highest penile artery pressure over mean brachial pressure

  • <0.70 suggests large vessel disease

    Rx:

    (1) Surgery:
        (a) vascular reconstructive surgery
        (b) penile prosthesis placement
           nonhydraulic: semirigid, malleable, positionable
           hydraulic
      (2) Oral / intracavernosal injection of vasoactive agents
      (3) Nonsurgical external devices: vacuum erection devices
      (4) Sex therapy

P.928

Fournier Gangrene

• = FULMINANT FASCIITIS

• [Jean Alfred Fournier (1832 1914), venereologist in Paris, France]

• = uncommon potentially lethal polymicrobial necrotizing fasciitis of the perineal, perianal or genital areas

  Incidence:	500 cases in literature
  Organism:	(a) aerobes: E. coli, S. aureus, Proteus species, enterococci   (b) anaerobes: Bacteroides fragilis, anaerobic streptococci, clostridia
  Path:	obliterative endarteritis with ensuing cutaneous + subcutaneous necrosis and gangrene, cellulitis, myositis, fasciitis (rate of fascial destruction as high as 2 3 cm/h)
  Age:	newborn to elderly; M>>F
  Predisposed:	diabetes mellitus (present in 40 60%)

• SURGICAL EMERGENCY!

• pain, fever, leukocytosis

• scrotal tenderness, erythema, swelling, crepitation

• In 95% primary focus of infection is recognizable (perianal / perirectal / ischiorectal abscess, anal fissure, colonic perforation, urethral stricture with extravasation, urethral instrumentation, chronic UTI, epididymitis, orchitis, superficial soft-tissue injury of genital skin, IM injection, hidradenitis, septic abortion, vulvar / Bartholin gland abscess, hysterectomy, episiotomy, circumcision, insect bite, burn)!

• gas in scrotal wall + perineum

• scrotal skin thickening + normal testes

  Mortality:	7 75%
  Rx:	antibiotic therapy + debridement + hyperbaric oxygen
  DDx:	epididymoorchitis, gas-containing scrotal abscess, scrotal hernia with gas-containing bowel, scrotal emphysema from bowel perforation, extension of subcutaneous emphysema, air leakage + dissection due to faulty chest tube positioning

Ganglioneuroblastoma

• = tumor of sympathetic nervous system that is intermediate in cellular maturity between neuroblastoma and ganglioneuroma; metastatic potential

  Incidence:	less common than neuroblastoma / ganglioneuroma
  Age:	early childhood; M:F = 1:1
  Location:	posterior mediastinum, abdomen

• extension through neural foramen into epidural space

• nerve root / spinal cord compression

Ganglioneuroma

• = benign neoplastic growth of autonomic ganglia

• = may represent end-stage of maturation of a neuroblastoma induced by chemotherapy / occurring spontaneously

  Histo:	mixture of mature ganglion + Schwann cells
  Age:	42 60% <20 years, 39% aged 20 39 years, 19% aged 40 80 years; M:F = 1:1
  Location:	posterior mediastinum (25 43%); abdomen (52%), adrenal gland (20%); pelvis and neck (9%); oral + intestinal ganglioneuromatosis associated with MEN IIb

• respiratory symptoms, local pressure (40%)

• rarely hormone-active: diarrhea, sweating, hypertension, virilization, myasthenia gravis

• spherical / elliptical large well-defined encapsulated slow-growing mass

• tendency to surround blood vessels without compromising the lumen

• dumbbell-shaped large mass extending from paraspinous region through neural foramen into epidural space

• calcifications (8 27%)

• CT:

  • homogeneous attenuation less than that of muscle

• MR:

  • homogeneous + isointense with muscle on T1WI

  • heterogeneous + hyperintense to muscle on T2WI

    DDx:

    neurofibroma (no calcification), schwannoma (no calcification), neuroblastoma (calcified)

Hemangioma of Adrenal Gland

• = rare benign stromal tumor of adrenal gland

• often large mass (usually >10 cm in diameter, up to 22 cm)

• multiple peripheral nodular areas of marked enhancement after contrast bolus injection

• NO complete fill in of contrast material

• calcifications (28 87%) from previous hemorrhage

• CT:

  • central low attenuation (necrosis / fibrosis)

• MR:

  • mass hypointense relative to liver on T1WI + central hyperintensity (due to hemorrhage)

  • markedly hyperintense on T2WI, especially in central portion

  • variable appearance after hemorrhage, thrombosis, necrosis, fibrosis

    Cx:

    hemorrhage

Hemangioma of Urinary Bladder

Incidence:	0.6% of primary bladder neoplasms;
	0.3% of all bladder tumors
Age:	<20 years (in >50%), M:F = 1:1

• May be associated with:

  • additional hemangiomas in 30%

  • Klippel-Trenaunay syndrome

  • Sturge-Weber syndrome

    Histo:

    capillary / venous / cavernous / hemangiolymphomatous form

• recurrent gross painless hematuria

• cutaneous hemangiomas over abdomen, perineum, thighs in 25 30%

  Location:	dome, posterolateral wall
  Site:	limited to submucosa (33%), muscular wall, perivesical tissue

• compressible solitary (2/3) / multiple (1/3) masses:

  P.929

  
  

  • rounded well-marginated intraluminal mass

  • diffuse bladder wall thickening + punctate calcifications (phleboliths)

• IVP:

  • rounded / lobulated filling defect

• US:

  • solid predominantly hyperechoic mass

  • hypoechoic spaces within thickened bladder wall

    CAVE:

    high risk of intractable hemorrhage at biopsy!

Hemolytic-Uremic Syndrome

• Most common cause of acute renal failure in children requiring dialysis!

• = characterized by thrombotic microangiopathy with typical features of DIC

• Cause:

  • Infection: enterotoxic E. coli, Shigella dysenteriae I, Streptococcus pneumoniae, Salmonella typhi, Coxsackie virus, echovirus, adenovirus

  • Associated medical condition: pregnancy, SLE + other collagen vascular disease, malignancy, malignant hypertension

  • Drugs: oral contraceptives, cyclosporine, mitomycin, 5-fluorouracil

    Pathogenesis:	capillary and endothelial injury to kidney leads to mechanical damage of RBCs + formation of hyaline microthrombi within renal vasculature + focal infarction
    Age:	usually children <2 years
    Histo:	microangiopathy including endothelial swelling + thrombus formation in glomerulus + renal arterioles

• CLASSIC TRIAD:

  • microangiopathic hemolytic anemia

  • thrombocytopenia

  • acute oliguric / anuric renal failure leading to uremia

• recent bout of gastroenteritis (commonly with E. coli)

• sudden pallor, irritability

• bloody diarrhea

• dyspnea (due to fluid retention, heart failure, pleural effusion)

• convulsions

• rapid rise in blood urea nitrogen level out of proportion to plasma creatinine level (= result of cell lysis)

• @ Kidney (sometimes only organ involved):

  • kidneys of normal / slightly increased size

  • hyperechoic cortex

  • Doppler-US:

    • diastolic flow absent / reversed / reduced (= increase in resistance to flow)

    • return to normal waveforms predates return of urine output

  • Scintigraphy:

    • lack of renal perfusion

• Liver: hepatomegaly, hepatitis

• Pancreas: diabetes mellitus

• Heart: myocarditis

• Muscle: rhabdomyolysis

• Intestines: perforation, intussusception, pseudomembranous colitis

• Brain (20 50%): drowsiness, personality changes, coma, hemiparesis, seizures (up to 40%)

  Prognosis:

  complete spontaneous recovery (in 85%)

Hereditary Chronic Nephritis

• = ALPORT SYNDROME

• = probably autosomal dominant trait with presence of fat-filled macrophages ( foam cells ) in the corticomedullary junction and medulla

• males: progressive renal insufficiency, death usually < age 50

• females: nonprogressive

• polyuria

• anemia

• salt wasting

• hyposthenuria

• nerve deafness

• ocular abnormalities (congenital cataracts, nystagmus, myopia, spherophakia)

• NO hypertension

• small smooth kidneys

• diminished density of contrast material

• cortical calcifications

Horseshoe Kidney

• = two kidneys joined at poles by parenchymal / fibrous isthmus

  Incidence:	1 4:1,000 births; 0.2 1% (autopsy series); M:F = 2 3:1
  	Most common fusion anomaly

• Associated with:

  • cardiovascular anomaly, skeletal anomaly, CNS anomaly, anorectal malformation, genitourinary anomaly (hypospadia, undescended testis, bicornuate uterus, ureteral duplication), trisomy 18, Turner syndrome (60%)

• In 50% associated with:

  • Caudal ectopia

  • Vesicoureteral reflux

  • Hydronephrosis 2 to UPJ obstruction

• fusion of R + L kidney at lower (90%) / upper (10%) pole

• renal long axis medially oriented

• isthmus at L4-5 between aorta + inferior mesenteric a.

• renal pelves and ureters situated anteriorly

• multiple renal arteries including isthmus artery

  Cx:

  infection, renal calculi

Hydrocele

• = collection of fluid between parietal and visceral layers of tunica vaginalis

• Most common cause of testicular swelling

• Most common type of fluid collection in scrotum

• US:

  • anechoic, good back wall, through transmission

  • COMPLICATED HYDROCELE = hydrocele with low-level echoes septations:

    • hematocele / pyocele / cholesterol crystals

Primary = Idiopathic Hydrocele

• without predisposing lesion as congenital defect of lymphatic drainage

Secondary Hydrocele

• inflammation (epididymitis, epididymoorchitis)

• testicular tumor (in 10 40% of malignancies)

• trauma / postsurgical

  P.930

  
  

  • 50% of acquired hydroceles are due to trauma!

• torsion, infarction

Congenital Hydrocele

• = ascites trapped in scrotum through communication with peritoneal cavity (= open processus vaginalis); may be associated with inguinal hernia

• should resolve within 2 years

Infantile Hydrocele

• = hydrocele with fingerlike extension into funicular process but without communication with peritoneal cavity

Hydronephrosis

• OBSTRUCTIVE UROPATHY = HYDRONEPHROSIS= dilatation of collecting structures without functional deficit

• OBSTRUCTIVE NEPHROPATHY = dilatation of collecting system with renal functional impairment

• US:

  • Grading system of hydronephrosis:

    Grade 0	= homogeneous central renal sinus complex without separation
    Grade 1	= separation of central sinus echoes of ovoid configuration; continuous echogenic sinus periphery; 52% predictive value for obstruction
    Grade 2	= separation of central sinus echoes of rounded configuration; dilated calyces connecting with renal pelvis; continuity of echogenic sinus periphery
    Grade 3	= replacement of major portions of renal sinus; discontinuity of echogenic sinus periphery

  • Amount of collecting system dilatation depends on:

    • duration of obstruction

    • renal output

    • presence of spontaneous decompression

    • Amount of residual renal cortex is of prognostic significance!

Acute Hydronephrosis

• Cause:

  • Passage of calculus

  • Passage of blood clot (from carcinoma, AV malformation, trauma, anticoagulant therapy), sloughed necrotic papilla

  • Suture on ureter

  • Ureteral edema following instrumentation

  • Sulfonamide crystallization in nonalkalinized urine

  • Normal pregnancy

• pain (50%)

• urinary tract infection (36%)

• nausea + vomiting (33%)

• normal-sized kidney with normal parenchymal thickness

• increasingly dense nephrogram

• delayed opacification of collecting system (decreased glomerular filtration)

• increasingly dense nephrogram over time ( obstructed nephrogram )

• dilated collecting system + ureter

• widening of forniceal angles

• delayed images demonstrate site of obstruction at the end of a persistent column of contrast material in a dilated urinary collecting system

• vicarious contrast excretion through gallbladder (uncommon)

• US:

  • separation of renal sinus echoes

    • False-negatives:

      • staghorn calculus filling entire collecting system, hyperacute renal obstruction (system not yet dilated), spontaneous decompression of obstruction, fluid-depleted patient with partial obstruction, dehydrated neonate

    • False-positives:

      • full bladder, increased urine flow (overhydration, medications, following urography, diabetes insipidus, diuresis in nonoliguric azotemia), acute pyelonephritis, postobstructive / postsurgical dilatation, vesicoureteral reflux

    • Imposters:

      • parapelvic cysts, sinus vessels, prominent extrarenal pelvis

  • ureteral jet not detectable / trickling flow

    CAVE:

    in 25% ureteral jets not detectable (insufficient differences in specific gravity between ureteral urine and urine in the bladder)

    • ureteral jet absent in 13% of pregnant patients without ureteral obstruction

      N.B.:

      turning pregnant patient into contralateral decubitus position will make jet visible

• Duplex US:

  • mean RI of 0.77 0.05 (0.63 0.06 in nonobstructed kidney)

    Caution:

    RI often normal in chronic obstruction; nonobstructive renal disease may elevate RIs

  • 0.08 difference in RI in right-to-left comparison with unilateral obstruction

    Cx:

    spontaneous urinary extravasation (10 18%) from forniceal / pelvic tear (= pyelosinus reflux)

Chronic Hydronephrosis

• = most frequent cause of abdominal mass in first 6 months of life (25% of all neonatal abdominal masses)

• Cause:

  • acquired: benign + malignant tumors of the ureter; ureteral strictures; retroperitoneal tumor / fibrosis; neurogenic bladder; benign prostatic hyperplasia; cervical / prostatic carcinoma; pelvic mass (lymphoma, abscess, ovarian); urethral polyps; urethral neoplasm; acquired urethral strictures

  • congenital: ureteropelvic junction obstruction (most common), posterior urethral valves, ectopic ureterocele, congenital ureterovesical obstruction, prune-belly syndrome, primary megaureter

• insidious course

• large kidney with wasted parenchyma

• diminished nephrographic density (decreased clearance)

• early rim sign (= thin band of radiodensity surrounding calyces)

P.931




• delayed opacification of collecting system

• moderate to marked widening of collecting system

• tortuous dilated ureter

• NUC:

  • photopenic area during vascular phase

  • accumulation of radionuclide tracer within hydronephrotic collecting system on delayed images

    Cx:

    superimposed infection (= pyonephrosis)

Congenital Hydronephrosis

• Mostly isolated malformation

  Incidence:	1:100 300 births
  Risk of recurrence:	2 3% for siblings
  Age at presentation:	25% by age 1 year,
  	55% by age 5 years

  • Cause:

    • UPJ obstruction (22 40 67%)

    • Posterior urethral valves (18%)

    • Ectopic ureterocele (14%)

    • Prune belly syndrome (12%)

    • Ureteral + UVJ obstruction (8%)

    • Others: severe vesicoureteral reflux, bladder neck obstruction, hypertrophy of verumontanum, urethral diverticulum, congenital urethral strictures, anterior urethral valves, meatal stenosis

      May be associated with:

      Down syndrome (17 25%)

  • palpable abdominal mass

  • intermittent flank + periumbilical pain

  • failure to thrive

  • vomiting

  • hematuria, infection

    Location:

    70% unilateral

  • OB-US:

    • AP diameter of renal pelvis 5 mm between 15 20 weeks, 8 mm at 20 30 weeks, 10 mm after 30 weeks MA

      • pyelectasis <7.0 mm after 32 weeks EGA is highly predictive of a normal postnatal outcome

    • ratio of AP diameter of renal pelvis to kidney >50%

    • caliceal distension communicating with renal pelvis

      • Postnatal evaluation after 4 7 days of age (because of decreased GFR + relative dehydration in first days of life)!

        Prognosis:

        parenchymal atrophy + renal impairment (dependent on severity + duration)

Focal Hydronephrosis

• = hydrocalicosis = HYDROCALYX

• = obstructed drainage of one portion of kidney

  Cause:	(1) Congenital: partial / complete duplication
  	(2) Infectious stricture: eg, TB
  	(3) Infundibular calculus
  	(4) Tumor
  	(5) Trauma

• unifocal mass, commonly in upper pole

• absent polar group of calyces (early)

• dilated polar group (late) with displacement of adjacent calyces

• delayed opacification in obstructed group

• focally replaced nephrogram

• US:

  • anechoic cystic lesion with smooth margins

• CT:

  • focal area of water density with smooth margin and thick wall

Hydronephrosis in Pregnancy

• Physiologic dilatation

  Incidence:	80%; in up to 90% by 3rd trimester
  Cause:	hormonal (relaxation of ureteric smooth muscle in response to progesterone), mechanical (gravid uterus compresses ureter at pelvic brim near crossing of iliac vessels with right ureter taking a more acute angle)

  • asymptomatic

  • as early as 6 10 weeks of gestation

  • right side (85 90%), left side (15 67%)

  • ureter widened only to pelvic brim

    Prognosis:

    resolution within a few weeks to 6 months after delivery

• Overdistension syndrome

  Cause:

  obstruction by gravid uterus

  • pain mimicking renal colic

• Acute hydronephrosis

  Cause:

  change in position of fetus, diuresis, passage of stone into ureter

  • constant pain nausea and vomiting

Juxtaglomerular Tumor

• = RENINOMA

• = very rare benign tumor arising from renin-producing juxtaglomerular cells

  Incidence:	<30 cases reported
  Age:	mean age of 24 (range, 7 58) years; 50% <21 years; M:F = 1:2
  Origin:	arising from afferent arterioles of glomeruli
  Path:	small foci of hemorrhage + pseudocapsule
  Histo:	tumor resembles hemangiopericytoma

• typical features of primary reninism:

  • marked + sustained hypertension, often accelerated and poorly controlled

  • secondary hyperaldosteronism with hypokalemia

  • hyperreninemia

• moderate to severe headaches

• hypertensive retinopathy

• polydipsia, polyuria, enuresis

  Location:

  just beneath renal capsule

• renal mass of usually 2 3 (range, 0.8 6.5) cm in size

• US:

  • echogenic mass areas of necrosis / hemorrhage

• CT (thin overlapping cuts):

  • isodense tumor on NECT, hypodense on CECT

• MR:

  • early peripheral enhancement on T1WI

  • washout of contrast material from periphery + filling in of central tumor portion on delayed T1WI

• Angio:

  • (easily overlooked) hypo- / avascular tumor (in 43%)

  • renal vein sampling yields high renin level on affected side

    P.932

    
    

    Dx:	combination of elevated renin without renal arterial lesion + hypovascular solid renal mass
    Rx:	surgical excision

• DDx of renin elevation:

  • Wilms tumor, hypernephroma, lung cancer, paraovarian tumor, fallopian tube adenocarcinoma, epithelial liver hamartoma, orbital hemangiopericytoma, pancreatic cancer, angiolymphoid hyperplasia

Leukemia

• = clonal proliferation of lymphoblasts (acute leukemia) or small lymphocytes (chronic leukemia)

• Most common malignant cause of bilateral global renal enlargement!

  Incidence:

  renal involvement in 50% of children + in 65% of adults at autopsy

• DIFFUSE INVOLVEMENT (most common)

  • leukemic cells infiltrate the interstitial tissue + renal sinus; tubules are replaced (more common in lymphocytic than in granulocytic forms); no relationship to peripheral white blood cell count

  • renal impairment (from leukemic infiltrate, hyperuricemia, septicemia, hemorrhage)

  • hypertension

  • moderate to massive nephromegaly bilaterally with smooth contours

  • normal or diminished density on nephrogram

  • occasionally attenuated collecting system (DDx: renal sinus lipomatosis)

  • nonopaque filling defects on IVP (clot, uric acid)

  • renal / subcapsular / perinephric hemorrhage frequent

  • retroperitoneal lymphadenopathy

  • US:

    • loss of definition + distortion of central sinus complex

    • normal to increased coarse echoes throughout renal cortex + preservation of renal medullae

    • single / multiple focal anechoic masses

• FOCAL ACCUMULATION OF LEUKEMIC CELLS (rare)

  • chloroma (= granulocytic sarcoma) of acute myeloblastic leukemia, myeloblastoma, myeloblastic sarcoma

  • may antedate other manifestations of leukemia

  • unifocal mass in renal cortex / renal sinus

    DDx:

    Hodgkin disease, malignant lymphoma, multiple myeloma

Leukoplakia

• = keratinizing SQUAMOUS METAPLASIA / DYSPLASIA = DYSKERATOSIS

  Cause:	chronic infection (80%) / stones (40%)
  Histo:	large confluent areas / scattered patches of squamous metaplasia of transitional cell epithelium with keratinization + cellular atypia in deeper layers
  Peak age:	4th 5th decade;
  	M:F = 1:1 (with involvement of renal pelvis)
  	M:F = 4:1 (with involvement of bladder)

  • hematuria (30%)

  • recurrent UTIs

  • pathognomonic passage of gritty flakes, soft-tissue stones, white chunks of tissue (desquamated keratinized epithelial layers) leading to colic, fever, chills

    Location:

    bladder > renal pelvis > ureter; bilateral in 10%

  • corrugated / striated irregularities of pelvicaliceal walls, localized / generalized

  • plaquelike intraluminal mass with onion skin pattern of contrast material in interstices

  • caliectasis + pyelectasis common (with obstruction)

  • ridging / filling defects of ureter

  • associated with calculi in 25 50%

    Cx:

    premalignant condition for epidermoid carcinoma in 12% (controversial!)

Localized Cystic Disease

• = multiple simple cysts involving only one portion of the kidney

• no family history

  Histo:	dilated ducts and tubules varying in size from mm to several cm
  Prognosis:	not progressive

Lymphoma of Kidney

Incidence:	in 3 8% (by CT), 30 60% (by autopsy)
	The kidneys are one of the most common extranodal sites of lymphoma!

• Types:

  • NON-HODGKIN LYMPHOMA (more common)

    • SECONDARY due to systemic disease

      • renal involvement detected in 3 8% of abdominal CT, in 33 65% of autopsies; occurs usually late in disease

        At risk:

        immunocompromised patients with HIV infection / organ transplantation (esp. after cyclosporine therapy), ataxia-telangiectasia

    • PRIMARY renal lymphoma (rare)

      • arising in renal hilar nodes / renal parenchyma

  • HODGKIN DISEASE (rare)

    • renal involvement in 13% of autopsies

• Patterns of involvement:

  • hematogenous dissemination (bilateral in 75%):

    • single / multiple foci (most common)

      • resembling primary renal neoplasm

    • diffuse infiltration (less common)

      • preservation of renal parenchyma + contour

  • contiguous extension from adjacent pararenal lymphomatous disease, usually extranodal

• clinically silent (50%)

• flank pain, weight loss

• palpable mass, hematuria

• compromised renal function (urinary tract obstruction, renal vein compression, diffuse infiltration of kidney, superimposed infarct, amyloidosis, hypercalcemia)

  Associated with:

  splenomegaly, lymphadenopathy

  • Look for other sites of multisystemic involvement in bone marrow, liver, GI tract, lung, heart, CNS!

• unilateral:bilateral = 1:3

• multiple nodular masses (29 61%), 1 3 cm in size

• spread from retroperitoneal disease (25 30%) with involvement by transcapsular / hilar invasion

• solitary tumor (10 20%): bulky up to 15 cm in size (7%) / small (7 48%)

• perinephric lymphoma:

  • direct extension from retroperitoneal disease

  • transcapsular growth of renal parenchymal disease

    P.933

    
    

    • A tumor surrounding kidney without parenchymal compression or compromise in function is virtually PATHOGNOMONIC of lymphoma

  • renal sinus infiltration

  • small curvilinear areas of high attenuation

  • thickening of fascia of Gerota

  • perirenal nodules / masses of soft-tissue density

  • mass contiguous with retroperitoneal disease

• nephromegaly due to diffuse infiltration of interstitium (6 19%) with sparing of glomeruli and tubules:

  • preservation of renal contour

  • almost always bilateral

  • encasement / deformation of pelvocaliceal system

  • clinically silent poor renal function

• patency of renal vessels despite tumor encasement is CHARACTERISTIC

• CT (nephrographic phase most sensitive for detection):

  • usually homogeneous poorly marginated masses less dense than renal parenchyma + decreased enhancement compared with renal parenchyma

• US:

  • single / multiple anechoic / hypoechoic masses:

    • may show increased through transmission

  • renal enlargement + decreased parenchymal echoes

  • loss of renal sinus echoes

• Angio:

  • neovascularity, encasement, vascular displacement (occasionally palisade-like configuration)

• DDx of nodular mass:

  • RCC (more heterogeneous, vascular invasion)

  • Metastases from lung, breast, synchronous renal cell cancer

• DDx of infiltrative tumor:

  • TCC, acute / xanthogranulomatous pyelonephritis

Malacoplakia

• = malakoplakia [malacoplakia, Greek = soft plaque]

• = uncommon chronic inflammatory response to gram-negative infection

  Frequency:	<200 cases reported
  Organism:	E. coli (in 94%)
  Predisposed:	diabetes mellitus, immunocompromise
  Pathogenesis:	altered host response to infection at the macrophage level = engulfed organisms remain viable + become a source for recurring infection
  Histo:	submucosal histiocytic granulomas containing large foamy mononuclear cells (Hansemann macrophages) with intracytoplasmic basophilic PAS-positive inclusion bodies (Michaelis-Gutmann bodies = calculospherules) consisting of incompletely destroyed E. coli bacterium surrounded by lipoprotein membranes
  Peak age:	5th 7th decade; M:F = 1:4

• history of recurrent urinary tract infections

• hematuria

• raised yellow lesion <3 cm in diameter

• Location:

  • bladder > lower 2/3 of ureter > upper ureter > renal pelvis; multifocal in 75%; bilateral in 50%

  • outside urinary tract

• @ Bladder / ureter

  • multiple nodular dome-shaped smooth mural filling defects of collecting system

  • scalloped appearance if lesions confluent

  • generalized pelvoureteral dilatation (if obstructive)

    DDx:

    pyeloureteritis cystica

• @ Kidney

  • diffuse enlargement of kidney (bilateral involvement unusual)

  • displacement of pelvicaliceal system + distortion of central sinus complex

  • multifocal parenchymal masses may cause diminished / absent nephrogram

  • urinary tract calcification rare

  • US:

    • lesions of variable echogenicity

  • CT:

    • ill-defined low-attenuation lesions

    • perinephric extension

      DDx:

      infiltrative neoplasm; XGP (unilateral, urinary tract calcification)

Malpositioned Testis

• = maldescended TESTIS

• Testicles are normally within scrotum by 28 32 weeks MA

  Prevalence:

  early 3rd trimester in 10%; at birth in 3.7 6% (in babies >2,500 g in 3.4%; in premature babies in 30%); beyond 3 months of age in 1%

• Test sensitivity:

  MR	: modality of choice
  US	: 20 88%; very sensitive in inguinal canal
  CT	: 95% (testis <1 cm cannot be detected)
  	no spermatic cord in inguinal canal
  Venography	: 50 90%
  Laparoscopy	: most reliable method

  Cx:	(1) Sterility
  	(2) Malignancy: most commonly seminoma, 30 50 risk increase = 1:1,000 men/year; 4 11% of all testicular tumors found in cryptorchidism; risk remains increased even after orchidopexy
  	Annual screening until at least age 35!
  	(3) Torsion: 10 risk in cryptorchidism
  Rx:	surgery / orchidopexy at 9 12 months of age
  DDx:	(1) Rudimentary testis
  	(2) Pars intravaginalis gubernaculum = nonatrophied bulbous termination
  	(3) Congenital absence = monorchia / anorchia (in 3 5%)
  	Nonpalpable testes are agenetic in 15 63% of term infants!

Cryptorchidism (20 29%)

• = arrested descent of testis along its normal course

• Pathophysiologic theory:

  • generalized defect in embryogenesis results in bilateral dysgenetic gonads

  • Theory supported by:

    • cancer risk extends to contralateral testis

    • orchiopexy does not decrease cancer risk

    • cancer risk increases with degree of ectopy

P.934




• Associated with:

  • prune belly syndrome (bilateral cryptorchidism), Prader-Willi syndrome, Beckwith-Wiedemann syndrome, Noonan syndrome, Laurence-Moon-Biedl syndrome, trisomies 13, 18, 21

• nonpalpable testis

  Location:

  high scrotal position (50%); canalicular = between internal + external inguinal ring (20%); abdominal (10%); bilateral in 10%

• The most craniad possible point of an undescended testis is the lower pole of the ipsilateral kidney!

• failure to visualize testis within scrotum

• small atrophic testis with generalized decreased echogenicity:

  • identification of mediastinum testis is necessary

    DDx:

    lymph node

Ectopia Testis (1%)

• = deviation from the usual pathway

  Location:

  interstitial = groin (on external oblique muscle), pubopenile = root of penis, perineal, femoral triangle, on opposite side

Pseudocryptorchidism (70%)

• = RETRACTILE TESTIS

• = unusually spastic cremasteric muscle

Undescended Testis

• = retractile testis + cryptorchidism

Meckel-Gruber Syndrome

• = autosomal recessive disease characterized by occipital encephalocele, polycystic kidneys, polydactyly

  Incidence:	1:12,000 50,000; more common among Yemenite Jews
  Risk of recurrence:	25%; carrier frequency of 1:56

• history of affected siblings

• OB-US:

  • large polycystic kidneys containing 2 10-mm cysts

  • occipital encephalocele

  • postaxial polydactyly

  • microcephaly

  • cleft lip and palate

  • moderate-to-severe oligohydramnios (onset midtrimester)

  • inability to visualize urine within fetal bladder

• OB management:

  • Chromosomal analysis to exclude trisomy 13 (if no prior family history)

  • Option of pregnancy termination <24 weeks GA

  • Nonintervention for fetal distress >24 weeks GA

    Prognosis:	invariably fatal at birth due to pulmonary hypoplasia + renal failure
    DDx:	trisomy 13

Medullary Cystic Disease

• = NEPHRONOPHTHISIS

• = salt-wasting nephropathy causing chronic renal failure in adolescents / young adults

  Histo:

  variable number of medullary cysts (100 m to 2 cm) + progressive periglomerular and interstitial fibrosis + tubular atrophy with dilatation of some proximal tubules

• Types:

  • Medullary Cystic Disease = ADULT ONSET

    • autosomal dominant, in young adults, rapidly progressive course with uremia + death in 2 years

  • Juvenile Nephronophthisis = JUVENILE ONSET

    • = UREMIC MEDULLARY CYSTIC DISEASE

    • autosomal recessive, in children 3 5 years, average duration of 10 years before uremia and death occurs

• salt-wasting, polyuria, hyposthenuria, polydipsia

• failure to thrive, growth retardation (in early teens)

• uremia, severe anemia, normal sediment, hypertension (only in late phase)

• bilateral normal / small kidneys with smooth contour

• thin cortex

• IVP:

  • poor opacification of renal collecting system

  • medullary nephrogram = medullary striations persistent for up to 2 hours; occasionally replaced by sharply defined multiple thin-walled lucencies

• Retrograde pyelogram:

  • communication between collecting system + cysts

• US / CT:

  • increased parenchymal echogenicity + loss of corticomedullary junction

  • multiple small corticomedullary / medullary cysts

Medullary Renal Tumor

Incidence:

1 2% of all renal cancers

Collecting Duct Carcinoma

• = BELLINI DUCT CARCINOMA

  Frequency:	~100 cases reported in literature
  Age:	mean age of 55 years (range of 13 80 years)
  Histo:	mostly high-grade tumor

• abdominal pain, flank mass, hematuria

• In 40% metastasized at presentation

• infiltrative neoplasm centered in medulla:

  • renal sinus invasion

  • extension into cortex is frequent

  • coexisting expansile component

• large tumor at presentation

  US:	hyperechoic mass
  Angio:	hypovascular mass
  MR:	hypointense mass on T2WI
  Prognosis:	aggressive clinical course with 33% surviving >2 years

Renal Medullary Carcinoma

• = highly aggressive malignant tumor of epithelial origin occurring almost exclusively in adolescent / young adult blacks with sickle cell trait / hemoglobin SC disease (termed seventh sickle cell nephropathy ) but NOT with hemoglobin SS (sickle cell) disease

  Origin:	distal collecting duct / epithelium of papilla;? aggressive form of collecting duct carcinoma
  Mean age:	20 (range, 11 39) years; M:F = 3:1 (if <24 years of age) and 1:1 (if >24 years of age)
  Histo:	poorly differentiated tumor cells within a desmoplastic stroma + mixed with reticular, yolk saclike, adenoid cystic components

P.935

• abdominal / flank pain, gross hematuria

• palpable mass, weight loss, fever

• metastases at presentation common: regional lymph nodes, liver, lung, bone

• large ill-defined mass centered in renal medulla:

  • heterogeneous due to varying amounts of hemorrhage and necrosis

  • extension into renal sinus and cortex

  • peripheral caliectasis

  • heterogeneous enhancement

• reniform enlargement with shape of kidney preserved

• small peripheral satellite nodules

  Prognosis:	mean survival rate of 15 weeks from diagnosis
  DDx:	transitional cell carcinoma, rhabdoid tumor

Medullary Sponge Kidney

• = dysplastic cystic dilatation of papillary + medullary portions of collecting ducts (first few generations of metanephric duct branchings)

  Incidence:	0.5%
  Age:	young to middle-aged adults; sporadic
  May be associated with:	Ehlers-Danlos syndrome, parathyroid adenoma, Caroli disease

• often asymptomatic

• medullary nephrocalcinosis (40 80%) with one / more calculi of up to 5 mm clustered in papillary region

• bunch of flowers = thick dense streaks of contrast material radiating from pyramids peripherally representing papillary cysts / ectatic ducts (DDx: dense papillary blush in normals)

• may be unilateral in 25%

• may involve only one pyramid / all pyramids (25%)

• US:

  • echogenic medulla (in absence of stones)

    Cx:	urolithiasis, hematuria, infection
    Dx:	(1) opacification of stone-free papillary cysts
    	(2) accumulation of contrast material around calculi within ectatic tubules / cysts

• DDx:

  • Normal variant ( papillary blush without distinct streaks / nephrocalcinosis / pyramidal enlargement)

  • Renal tuberculosis (larger more irregular calcifications + cavitations + strictures + ulcerations)

  • Papillary necrosis (sloughed papilla + caliceal ring sign)

  • Medullary nephrocalcinosis (no ectatic ducts / cysts, calcifications beyond pyramids)

  • Juvenile polycystic kidney disease (bilateral renal enlargement + hepatic periportal fibrosis)

  • Caliceal diverticulum (small, solitary, located between pyramid)

Megacalicosis

• = CONGENITAL MEGACALICES

• = nonprogressive caliceal dilatation caused by hypoplastic medullary pyramids

  Age:	any age; M >> F
  May be associated with:	primary megaureter

• normal glomerular filtration rate

  Site:

  entire kidney / part of kidney; unilateral >> bilateral

• kidney usually enlarged with prominent fetal lobation

• reduced parenchymal thickness (medulla affected, NOT cortex):

  • normal DMSA scintigram

• mosaic-like arrangement of dilated calyces (polygonal + faceted appearance, NOT globular as in obstruction)

• increased number of calyces (>15)

• ABSENT caliceal cupping (semilunar instead of pyramidal configuration of papillae)

• NO dilatation of pelvis / ureters, NORMAL contrast excretion

  Cx:	(1) Hematuria
  	(2) Stone formation

Megacystis-Microcolon Syndrome

• = megalocystis-microcolon-intestinal hypoperistalsis syndrome (MMIH)

• = functional obstruction of bladder + colon characterized by

  • enlarged urinary bladder

  • small colon

  • strikingly short small intestine suspended on a primitive dorsal mesentery

  • markedly enlarged hydronephrotic kidneys with little remaining parenchyma

    Incidence:	26 cases reported; M:F = 1:7
    May be associated with: diaphragmatic hernia, PDA, teeth at birth

• distended abdomen (large bladder + dilated small bowel loops)

• overflow incontinence

• intestinal pseudoobstruction (poor emptying of stomach, NO peristaltic activity of small bowel)

• OB-US:

  • normal amount of amniotic fluid / polyhydramnios (in spite of dilated bladder = nonobstructive obstruction )

  • massive + progressive bladder distension with poor emptying

  • bilateral megaloureters

  • hydronephrosis

  • female sex

• BE:

  • microcolon (transient feature of unused colon ) with narrow rectum + sigmoid

  • malrotation / malfixation or foreshortening of small bowel

• VCUG

  • distended unobstructed bladder with poor / absent muscular function

    Prognosis:

    lethal in most cases (a few months of age)

Megaloureter

• = CONGENITAL PRIMARY MEGAURETER = TERMINAL ureterectasis = ACHALASIA OF URETER = URETEROVESICAL JUNCTION OBSTRUCTION

• = intrinsic congenital dilatation of lower juxtavesical orthotopic ureter

  Cause:	aperistaltic juxtavesical (1.5 cm long) segment secondary to faulty development of muscle layers of ureter with too much collagen / too much muscle (functional, NOT mechanical obstruction) = Hirschsprung disease of ureter
  Incidence:	2nd most common cause of hydronephrosis in fetus and newborn
  Age:	any; M:F = 2 5:1

P.936




• Associated disorders (in 40%):

  • contralateral: UPJ obstruction, reflux, ureterocele, ureteral duplication, renal ectopia, renal agenesis

  • ipsilateral: caliceal diverticulum, megacalicosis, papillary necrosis

• asymptomatic (mostly)

• abdominal mass, pain

• hematuria, infection

  Location:

  L:R = 3:1, bilateral in 15 40%

• Grading system:

  I (mild)	= distal 1/3 of ureter involved
  II (moderate)	= entire ureter involved caliectasis
  III (severe)	= entire ureter + moderate to marked caliectasis

• prominent localized dilatation of pelvic ureter (up to 5 cm in diameter) usually not progressive, but may involve entire ureter + collecting system

• vigorous nonpropulsive to-and-fro motion in dilated segment

• functional beaking (smoothly tapered narrowing) of abnormal distal ureter without peristalsis

• NO reflux, NO stenosis

Mesoblastic Nephroma

• = FETAL RENAL HAMARTOMA = LEIOMYOMATOUS HAMARTOMA = BENIGN CONGENITAL WILMS TUMOR= BENIGN FETAL HAMARTOMA = FETAL MESENCHYMAL TUMOR = FIBROMYXOMA = Bolande TUMOR= CONGENITAL FIBROSARCOMA

• = nonfamilial benign fibromyomatoid mass arising from renal connective tissue

  Incidence:	most common solid renal neoplasm in neonate; 3% of all renal neoplasms in children
  Age:	peak age 1 3 months; 90% within 1st year of life; rare after the age of 6 months; may occasionally go undetected until adulthood; M > F
  Path:	solid unencapsulated mass infiltrating renal parenchyma (derived from early nephrogenic mesenchyme)
  Histo:	monomorphic tumor composed of smooth muscle cells + immature fibroblasts resembling leiomyoma containing trapped islands of embryonic glomeruli, tubules, vessels, hematopoietic cells, cartilage
  In 14% associated with: prematurity, polyhydramnios, GI + GU tract malformations, neuroblastoma

• large palpable flank mass (most common)

• hematuria (20%) / hypertension (4%), anemia

• large usually solid intrarenal mass:

  • usually replaces 60 90% of renal parenchyma

  • typically involves renal sinus

  • may produce multiple cystic spaces (hemorrhage, necrosis)

• infiltrative growth:

  • NO sharp cleavage plane toward normal parenchyma

  • may extend beyond capsule (common)

• calcifications (rare)

• NO venous extension (DDx from Wilms tumor)

• NO invasion of collecting system

• IVP:

  • large noncalcified renal mass with distortion of collecting system

  • usually NO herniation into renal pelvis (DDx from MLCN)

• CECT:

  • uniform enhancement of less than normal renal parenchyma

  • areas of low attenuation in large lesions (hemorrhage / necrosis)

• US:

  • evenly echogenic tumor resembling uterine fibroids

  • concentric rings of alternating echogenicity

  • homogeneously hypoechoic tumor

  • complex heterogeneous mass with hemorrhage + cyst formation + necrosis

• OB-US:

  • premature delivery, increased renin levels

  • polyhydramnios, hydrops

• Angio:

  • hypervascular mass with neovascularity + displacement of adjacent vessels

    Cx:	(1) Transformation to metastasizing spindle cell sarcoma (rare)
    	(2) Metastases to lung, brain, bone (rare)
    Rx:	nephrectomy with wide surgical margin
    Prognosis:	excellent (imaging follow-up for 1 year)

Metanephric Adenoma

• = NEPHROGENIC adenofibroma = EMBRYONAL ADENOMA

  Age:	any (range, 15 months 83 years); M < F
  Histo:	proliferation of spindle-shaped mesenchymal cells encasing nodules of embryonal epithelium; numerous psammoma bodies

• pain, hypertension, hematoma, flank mass, hypercalcemia, polycythemia

• US:

  • well-defined solid hypovascular mass

  • hypo- / hyperechoic / cystic with mural nodule

• CT:

  • iso- / hypoattenuating mass + little enhancement

  • small calcifications

    Rx:

    local resection with sparing of kidney

Metastases to Adrenal Gland

Frequency:	4th most common site of metastatic disease in the body; in 27% with known primary (autopsy series)
50% of adrenal masses in oncologic patients represent benign nonhyperfunctioning adenomas!
	An adrenal mass in a patient with malignancy is a metastasis in 30 40%!
Origin:	lung (40%), breast (20%), melanoma, renal cell carcinoma, pancreas, thyroid, colon, lymphoma

• large heterogeneously attenuating mass with irregular contour and progressive heterogenous enhancement

• MR:

  • low-signal intensity on T1WI (edema, necrosis)

  • heterogeneous high-signal intensity on T2WI

• Gd-MR:

  • strong rapid enhancement

  • prolonged retention of contrast material (due to large interstitial spaces of edema + necrosis)

• PET:

  • F-18 fluorodeoxyglucose uptake in 100% with rare false-positive results

    Dx:	biopsy
    DDx:	adenoma (intracytoplasmic lipid causing chemical shift artifact + significant decrease in signal intensity on out-of-phase GRE)

P.937

Metastases to Kidney

• Most common malignant tumor of the kidney (2 3 times as frequent as primaries in autopsy studies)!

• 5th most common site of metastases (after lung, liver, bone, adrenals)!

• Renal metastases means typically advanced disease!

  Frequency:

  7 13% in large autopsy series

• most common primaries:

  • bronchus, breast, GI tract, opposite kidney, non-Hodgkin lymphoma, colon, neuroblastoma (in children)

• less common primaries:

  • stomach, cervix, ovary, pancreas, prostate, chloroma, myeloblastoma, myeloblastic sarcoma, melanoma (45% incidence), osteogenic sarcoma, choriocarcinoma (10 50% incidence), Hodgkin lymphoma, rhabdomyosarcoma

• usually asymptomatic

• bilateral multiple small masses (due to brief survival of patient)

• solitary exophytic mass (in colon cancer)

• perinephric tumor (in melanoma)

• infiltrative growth pattern

  DDx on CT:

  lymphoma, bilateral RCC, multiple renal infarcts, acute focal bacterial nephritis, infiltrating TCC

Multicystic Dysplastic Kidney

• = MULTICYSTIC DYSGENETIC KIDNEY (MCDK)= MULTICYSTIC KIDNEY (MCK) = Potter Type II

• Second most common cause of an abdominal mass in neonate (after hydronephrosis)!

• Most common form of cystic disease in infants!

  Incidence:	1:4,300 (for unilateral MCDK), 1:10,000 (for bilateral MCDK) live births; M:F = 2:1 (for unilateral MCDK); more common among infants of diabetic mothers
  Risk of recurrence:	2 3%
  Etiology:	sporadic NOT familial; obstruction / atresia of ureter during metanephric stage before 8 10 weeks' GA
  Pathophysiology:	ureteral obstruction / atresia interferes with ureteral bud division + inhibits induction and maturation of nephrons; collecting tubules enlarge into cysts
  Histo:	immature glomeruli + tubules reduced in number + whirling mesenchymal tissue, cartilage (33%), cysts

• abdominal mass

• asymptomatic if unilateral (may go undetected until adulthood)

• recurrent urinary tract infections, intermittent abdominal pain, nausea + vomiting, hematuria, failure to thrive

• fatal due to pulmonary hypoplasia if bilateral

  Fatal form:

  bilateral MCDK (4.5 21%), contralateral renal agenesis (0 11%)

• Location:

  • UNILATERAL multicystic dysplastic kidney

    • most common form (80 90%); L:R = 2:1

    • secondary to pelvoinfundibular atresia

    • In 20 33 50% associated with anomalies of contralateral kidney:

      • Vesicoureteral reflux (15 43%)

      • Ureteropelvic junction obstruction (7 27%)

      • Horseshoe kidney (5 9%)

      • Ureteral anomalies (5%)

      • Renal hypoplasia (4%)

      • Megaloureter

      • Malrotation

      • Renal agenesis

    • Associated with anomalies of ipsilateral kidney:

      • Vesicoureteral reflux (25%)

      • Ectopic ureter

  • SEGMENTAL / focal renal dysplasia

    • = multilocular cyst secondary to

    • high-grade obstruction of upper pole moiety in duplex kidney from ectopic ureterocele

    • single obstructed infundibulum

  • BILATERAL cystic dysplasia

    • in the presence of severe obstruction in utero from posterior urethral valves / urethral atresia with oligohydramnios + pulmonary hypoplasia

      Prognosis:

      lethal

• Potter types:

  • Multicystic kidney (Potter IIa)

    • large kidney with multiple large cysts + little visible renal parenchyma

  • Hypoplastic / diminutive form (Potter IIb)

    • echogenic small kidney

• Time of appearance:

  • Related to site of obstruction

    • @ ureteropelvic junction

      • single / several large / multiple medium-sized cysts in large kidney

    • @ distal ureter / urethra

      • small / no cysts in small kidney

  • Related to time of insult

    • early onset between 8th and 11th week

      • small / atretic renal pelvis + calyces

      • 10 20 cysts + loss of reniform appearance

    • late onset = HYDRONEPHROTIC FORM

      • large central cyst (= dilated pelvis) often communicating with cysts

      • some renal function may be demonstrated

• large kidney with lobulated contour in infancy

• often incidental finding of small kidney in adults (as little as 1 g secondary to arrested growth)

• ipsilateral atretic ureter associated with hemitrigone

• contralateral renal hypertrophy

• calcification: curvilinear / ringlike in wall of cysts in 30% of adults, rarely in children

• NUC (Tc-99m MAG 3):

  • NUC preferred over IVP in first month of life as concentrating ability of even normal neonatal kidneys is suboptimal!

  • no function

    DDx:

    severe hydronephrosis (peripheral activity), UPJ obstruction (minimal uptake)

P.938




• US:

  • normal renal architecture replaced by:

    • random cysts of varying shape + size ( cluster of grapes ) with largest cyst in peripheral nonmedial location (100% accurate)

    • cysts separated by septa (100% accurate)

    • no communication between multiple cysts (93% accurate)

    • cysts begin to disappear in infancy

  • central sinus complex absent (100% accurate)

  • no identification of parenchymal rim or corticomedullary differentiation (74% accurate)

  • oligohydramnios in bilateral MCDK / unilateral MCDK + contralateral urinary obstruction

• Angio:

  • absent / hypoplastic renal artery; angiography unnecessary since a DDx to long-standing functionless kidney is not possible

• OB management:

  • Routine antenatal care + evaluation by pediatric urologist following delivery if unilateral

  • Option of pregnancy termination if 24 weeks GA

  • Nonintervention for fetal distress if >24 weeks GA

    Cx:	(1) Renin-dependent hypertension (rare)
    	(2) Malignancy in <1:330
    Rx:	(1) Follow-up in 3 4-month intervals in first year (isolated reports of developing malignancy)
    	(2) Nephrectomy (in hypertension / massive renal enlargement)
    DDx:	(1) Hydronephrosis
    	(2) Renal dysplasia with cysts (associated with partial obstruction)

Multilocular Cystic Renal Tumor

• = BENIGN MULTILOCULAR CYSTIC NEPHROMA (MLCN)= POLYCYSTIC NEPHROBLASTOMA = WELL-DIFFERENTIATED POLYCYSTIC WILMS TUMOR = BENIGN CYSTIC DIFFERENTIATED NEPHROBLASTOMA = CYSTIC PARTIALLY DIFFERENTIATED NEPHROBLASTOMA= MULTILOCULAR CYSTIC NEPHROMA = Perlman TUMOR = MULTILOCULAR RENAL CYST = CYSTIC ADENOMA / HAMARTOMA / LYMPHANGIOMA = PARTIALLY POLYCYSTIC KIDNEY

• = rare nonhereditary benign renal neoplasm originating from metanephric blastema possibly representing the benign end of a spectrum with solid Wilms tumor at the malignant end

  Age:	biphasic age + sex distribution: <4 years in 73% male, >4 years in 89% female
  	(a) 3 months to 2 years of age (65%), 5 30 years (5%); M:F = 2:1
  	(b)>30 years (30%); M:F = 1:8
  	90% of tumors in males occur in first 2 years of life (peak 3 24 months)!
  	Most of the lesions in females occur between ages 4 and 20 or 40 and 60!
  Path:	solitary large well-circumscribed multiseptated mass of noncommunicating fluid-filled loculi, surrounded by thick fibrous capsule + compressed renal parenchyma; cyst size between mm up to 4 cm
  Histo:	(gross anatomic + radiologic features are identical)

  • Cystic nephroma

    • fibrous tissue septa of undifferentiated mesenchymal and primitive glomerulotubular elements surround cysts lined by flattened cuboidal epithelium;NO blastemal / other embryonal elements

    • typically seen in adult women

  • Cystic partially differentiated nephroblastoma

    • = CPDN

    • predominantly cystic lesion with septa containing primitive metanephric blastema

    • primarily in young boys

    • No association with Wilms tumor!

• commonly asymptomatic painless abdominal mass

• sudden and rapid enlargement

• pain, hematuria, urinary tract infection

  Location:	unilateral, often replacing an entire renal pole (usually lower pole)
  Size:	average size of 10 cm (few cm to 33 cm)

• sharply well-circumscribed (characteristic) multiseptated cystic renal mass

• tumor surrounded by thick fibrous capsule

• cluster of noncommunicating honeycombed cysts of various sizes (several mm to 4 cm) separated by thick septa

• smaller closely spaced cysts appear as solid nodules

• contrast enhancement of septations (secondary to tortuous fine vessels coursing through septa)

• curvilinear to flocculent calcification of septa / capsule

• IVP:

  • distortion of calyces / hydronephrosis secondary to nonfunctional mass

  • tendency for herniation of tumor cysts into renal pelvis (nonspecific, also seen with Wilms tumor + RCC)

• US:

  • cluster of cysts separated by thick septa (SUGGESTIVE PATTERN)

  • occasionally solid echogenic character (due to very small cysts / jellylike contents)

• CT:

  • cysts with attenuation equal to / higher than water (gelatinous fluid)

• MR:

  • multicystic masses of low signal intensity on T1WI + hyperintense on T2WI

  • variable high signal intensity of loculations on T1WI (due to hemorrhage)

    Cx:	local recurrence / coexistent Wilms tumor (extremely rare)
    Rx:	nephrectomy with excellent prognosis
    DDx:	(1) Cystic Wilms tumor (overlapping age, expansile solid masses of nephroblastomatous tissue)
    	(2) Clear cell sarcoma (poor prognosis)
    	(3) Cystic mesoblastic nephroma (most common renal tumor of infancy)
    	(4) Cystic RCC (mean age of 10 years)
    	(5) Segmental form of multicystic dysplastic kidney

Multiple Myeloma

• It is essential that dehydration be avoided!

• Impairment of renal function:

  • Precipitation of abnormal proteins (Bence Jones Tamm-Horsfall protein casts) into tubule lumen (30 50%)

  P.939

  
  

  • Toxicity of Bence Jones proteins on tubules

  • Impaired renal blood flow secondary to increased blood viscosity

  • Amyloidosis

  • Nephrocalcinosis from hypercalcemia

  • Contrast-induced renal failure in multiple myeloma is not seen with greatly increased frequency!

• Tamm-Horsfall proteinuria (tubular cell secretion)

• smooth normal to large kidneys (initially), become small with time

• occasionally attenuated pelvoinfundibulocaliceal system

• normal to diminished contrast material density; increasingly dense in acute oliguric failure

• US:

  • normal to increased echogenicity

• NUC in bone scintigraphy:

  • nonspecific increased parenchymal activity

Mycetoma

• = FUNGUS BALL

  Organism:	typically Candida, Aspergillus, Mucor, Cryptococcus, Phycomycetes, Actinomycetes mostly mycelial (M-form) or occasionally yeast cells (Y-form)
  Predisposed:	diabetics, debilitating illness, prolonged antibiotic therapy, leukemia, lymphoma, thymoma, immunosuppression

• flank pain, passing of tissue, hematuria (extremely rare)

• renal candidiasis associated with candidemia

• Candida cystitis preceded by vaginal candidiasis

• unilateral nonvisualization of kidney (most frequent)

• large irregular filling defect extending into dilated calyces (retrograde contrast study)

• necrotizing papillitis from Candida nephritis (common)

• lacelike pattern (on antegrade contrast study)

Myelolipoma

• = rare benign tumor composed of hematopoietic cells + fat similar to bone marrow

  Prevalence:	0.06 0.2% (autopsy series);3% of all primary adrenal tumors
  Age:	middle-aged adults (not children)
  Cause:	? metaplasia of adrenal cortical cells precipitated by chronic stress / degeneration
  Path:	mature fat interspersed with hematopoietic cells resembling bone marrow + pseudocapsule
  Histo:	variable mixture of myeloid + leukocyte precursor cells, erythroid cells, megakaryocytes, lymphocytes
  Associated with:	endocrine disorders in 7% (Cushing syndrome, 21-hydroxylase deficiency), nonhyperfunctioning adenoma (15%)

• usually clinically occult

• pain (from spontaneous hemorrhage if large)

  Location:	(a) adrenal gland (85%)
  	(b) extraadrenal (15%): retroperitoneal (12%), intrathoracic (3%)
  Site:	unilateral:bilateral = 10:1
  Size:	mean diameter of 10.4 cm

• X-ray:

  • soft lucent mass with rim of residual normal adrenal cortex

  • calcifications (in up to 22% from previous hemorrhage)

• US:

  • heterogeneous predominantly hyperechoic (= fatty + myeloid tissue) mass with interspersed hypoechoic (= pure fat) regions

• CT:

  • fatty tissue mass of 30 to 115 HU

  • large amounts of fat with interspersed smoky areas of higher attenuation of 20 30 HU (= admixture of fat + marrowlike elements)

• MR:

  • hyperintense areas on T1WI heterogeneously distributed in clumps of mature adipose tissue

  • intermediate intensity on T2WI similar to spleen

  • focal reduction in signal intensity on fat-suppressed / opposed-phase images (in fatty areas)

    Cx:	acute retroperitoneal hemorrhage with increase in size (12%)
    Dx:	percutaneous needle biopsy
    Rx:	surgical excision not necessary
    DDx:	liposarcoma, fat-containing adrenocortical carcinoma

Nephroblastomatosis

• = multiple / diffuse nephrogenic rests

• = dysontogenetic process with persistence of embryonic renal parenchyma (= metanephric blastema) within the renal cortex >36 weeks GA

  Incidence:	1% of infant kidneys; in 41% with unilateral Wilms tumor, in 94% with metachronous contralateral Wilms tumor, in 99% with bilateral Wilms tumor
  	Usually absent in infants >4 months of age
  Pathogenesis: metanephric blastema (= persistent embryonal tissue) normally present up to 36 weeks of gestational age; embryonal renal tissue in mature kidney after birth retains potential to form nephroblastoma / Wilms tumor

• PERILOBAR NEPHROGENIC REST (0.87%)

  Path:	multiple rests forming a well-circumscribed smooth band at periphery of lobe
  Histo:	predominant tissue is blastema

  • Associated with:

    • Beckwith-Wiedemann syndrome (gigantism, macroglossia, omphalocele, genitourinary anomalies)

    • Hemihypertrophy

      • 3% develop Wilms tumor

    • Perlman syndrome (visceromegaly, gigantism, cryptorchidism, polyhydramnios, characteristic facies)

    • Trisomy 18 syndrome

    • Abnormal chromosome band 11p15 (Wilms tumor gene 2) in up to 77% of patients with perilobar rests

    • Mean age presenting with neoplasia: 36 months

• Intralobar nephrogenic rest (0.10%)

  Path:	single / few rests with irregular indistinct margins randomly anywhere within lobe
  Histo:	predominant tissue is stroma + epithelium

  • Associated with:

    • Drash syndrome (ambiguous genitalia in genotypic males, progressive renal failure): 78% with intralobar rests + 11% with perilobar rests

    P.940

    
    

    • Sporadic aniridia: 100% with intralobar rests + 20% with perilobar rests

      • 33% likelihood of Wilms tumor

    • WAGR syndrome (Wilms tumor, aniridia, genital abnormalities, mental retardation)

    • Abnormal chromosome band 11p13 (Wilms tumor gene 1)

    • Mean age presenting with neoplasia: 16 months

      Age:

      <2 years of age; neonatal period, infancy, childhood

  • Histologic subtypes:

    • dormant (nascent): nephrogenic rests the size of a glomerulus primarily composed of blastemal + epithelial elements; no malignant potential

    • sclerosing (regressing / obsolescent): microscopic rests primarily composed of stromal elements

    • hyperplastic: spherical / irregular / oval proliferation of most or all cell elements

    • neoplastic: expansile mass due to proliferation of a single cell line

    • clinically occult in vast majority / renal enlargement

    • MR (43% sensitivity, 58% sensitivity with enhancement):

      • homogeneously hypointense lesions on T1WI

      • homogeneously hypointense lesions on T2WI for sclerosing / involuting type of nephroblastomatosis

      • isointense lesions on T2WI for hyperplastic / neoplastic type of nephroblastomatosis

      • hypointense lesions on enhanced T1WI

        Cx:	malignant transformation (enlargement of rest / development of mass) into cystic partially differentiated nephroblastoma / Wilms tumor
        1% of patients with nephrogenic rests undergo neoplastic transformation!
        Screening:	for children with associated syndromes baseline CT at diagnosis / 6 months of age + follow-up sonograms every 3 months until age 7 years
        Rx:	radiologic follow-up / chemotherapy (for biopsy-proved hyperplastic nephrogenic rests similar to stage I Wilms tumor)

Multifocal (juvenile) Nephroblastomatosis

• most common form

• = isolated macroscopic nephrogenic rests

• may escape detection with imaging

• nodular mass effect on pelvicaliceal structures

• kidneys may be enlarged

• lobulated contour of kidney

• US:

  • hypoechoic / isoechoic / hyperechoic nodules

• CECT (preferred study):

  • nodules with less enhancement than renal parenchyma

Superficial Diffuse (Late Infantile) Nephroblastomatosis

• = superficial continuous rind of rests around medulla (= perilobar type)

  Age:

  <2 years

• nephromegaly

• US:

  • loss of corticomedullary differentiation

  • kidneys diffusely echogenic / of normal echogenicity

  • cysts of variable size

• CECT:

  • thick rind at periphery of kidney with poor / striated enhancement

    DDx:

    autosomal recessive polycystic kidney disease, leukemia, lymphoma

• Strong association with Wilms tumor!

Universal / Panlobar (Infantile) Nephroblastomatosis

• rare form

• = entire renal parenchyma diffusely involved

• may develop renal failure

• bilateral renal enlargement (infiltrative growth)

Nephrogenic Adenoma

• = uncommon benign metaplastic response to urothelial injury / prolonged irritation

  Cause:	(a) trauma: pelvic trauma, surgery in lower urinary tract, endoscopic procedure, renal transplantation (after a mean of 50 months)
  	(b) irritation: calculi, chronic bacterial infection, irradiation, intravesical chemotherapy, immunosuppressive therapy
  Age:	3 weeks to 83 years; M:F = 3:1 (more common in females if <20 years of age)
  Path:	discrete raised papillary / polypoid / cystic areas projecting from epithelial surface
  Histo:	variable number of small tubules (resembling loops of Henle and collecting ducts) + cysts + papillae lined with a single layer of cuboidal / low columnar cells

• hematuria, dysuria, bladder instability

• asymptomatic

  Location:	bladder (72%), renal pelvis, ureter, urethra; strong correlation between location + site of insult to urothelium
  Size:	usually 1 mm, up to 7 cm in diameter

• papillary / polypoid filling defect

  Prognosis:	high likelihood of recurrence; rarely malignant transformation
  Rx:	resection / fulguration
  DDx:	inflammatory / malignant urothelial lesions

Neuroblastoma

• Most common solid abdominal mass of infancy (12.3% of all perinatal neoplasms), 3rd most common malignant tumor in infancy (after leukemia + CNS tumors); 2nd most common tumor in childhood (Wilms tumor more common in older children), 8 10% of all childhood cancers; 15% of cancer deaths in children

  Incidence:	1:7,100 to 1:10,000 live births; 500 cases per year in USA; 20% hereditary
  Origin:	neural crest
  Path:	round irregular lobulated mass of 50 150 g with areas of hemorrhage + necrosis
  Histo:	small round cells slightly larger than lymphocytes with scant cytoplasm; Horner-Wright rosettes
  	= one / two layers of primitive neuroblasts surrounding a central zone of tangled neurofibrillary processes
  Age:	peak age at 2 years; 25% during 1st year; 50% <2 years; 79% in <4 years; 97% in <10 years; occasionally present at birth; M:F = 1:1
  Median age:	22 months
  May be associated with:	aganglionosis of bowel, CHD

P.941

• pain + fever (30%)

• palpable abdominal mass (45 54%)

• bone pain, limp, inability to walk (20%)

• cerebellar ataxia:

  • myoclonus of trunk + extremities

  • opsoclonus (20%) = spontaneous conjugate + chaotic eye movements (sign of cerebellar disease)

• orbital ecchymosis / proptosis (12%)

• increased catecholamine production (75 90%):

  • in 95% excreted in urine as vanillylmandelic acid (VMA) / homovanillic acid (HVA)

  • hypertension (up to 30%)

  • intractable diarrhea (9%) due to increase in vasoactive intestinal polypeptides (VIP)

  • acute cerebellar encephalopathy

  • paroxysmal episodes of flushing, tachycardia, headaches, sweating

  • rise in body temperature

  • hyperglycemia

• Stage:

  • I limited to organ of origin

  • II regional spread not crossing midline

  • III extension across midline

  • IV metastatic to distant lymph nodes, liver, bone, brain, lung

  • IVs stages I + II with disease confined to liver, skin, bone marrow WITHOUT radiographic evidence of skeletal metastases

• Metastases:

  • bone (60%), regional lymph nodes (42%), orbit (20%), liver (15%), intracranial (14%), lung (10%)

  • Metastases are first manifestation in up to 60%!

  • Hutchinson syndrome

    • primary adrenal neuroblastoma

    • extensive skeletal metastases, particularly skull

    • proptosis

    • bone pain

  • Pepper syndrome

    • primary adrenal neuroblastoma

    • massive hepatomegaly from metastases

  • Blueberry muffin syndrome

    • primary adrenal neuroblastoma

    • multiple metastatic skin lesions

  • Bone marrow aspirate positive in 50 70% at time of initial diagnosis!

  • 2/3 of patients >2 years have disseminated disease!

  • @ Skeletal metastases:

    • paraplegia / extremity weakness from spinal canal extension

    • periosteal reaction

    • osteolytic focus / multicentric lytic lesions

    • lucent horizontal metaphyseal line

    • vertical linear radiolucent streaks in metadiaphysis of long bones

    • pathologic fracture

    • vertebral collapse

    • widened cranial sutures (subjacent dural metastases)

    • sclerotic lesions with healing

      DDx:

      Ewing sarcoma, rhabdomyosarcoma, leukemia, lymphoma

  • @ Intracranial + maxillofacial metastases:

    Site:

    dura, brain substance

  • @ Pulmonary metastases:

    • nodular infiltrates

    • rib erosion

    • mediastinal + retrocrural lymphadenopathy (common)

      Location:

      anywhere within sympathetic neural chain

    • @ Abdomen

      • adrenal (36%): almost always unilateral

      • both adrenals (7 10%)

      • extraadrenal in sympathetic chain (18%)

    • @ Thorax + posterior mediastinum (14%): aortic bodies

    • @ Neck (5%): carotid ganglia

    • @ Pelvis (5%): organ of Zuckerkandl

    • @ Skull / esthesioneuroblastoma of olfactory bulb, cerebellum, cerebrum (2%)

    • @ Other sites (10%): eg, intrarenal (very rare)

    • @ Unknown (10%)

  • large suprarenal mass with irregular shape + margins (82%):

    • displacement of kidney

    • inseparable from kidney invasion of kidney (10 32%) along the vascular pathways

    • propensity for extension into spinal canal through neural foramen with erosion of pedicles (15%)

    • extension across midline (55%) (DDx: Wilms tumor)

    • stippled / coarse calcifications frequent

  • retroperitoneal adenopathy / contiguous extension (73%)

  • retrocrural adenopathy (27%)

  • encasement of IVC + aorta, celiac axis, SMA (32%):

    N.B.:

    caval involvement = indicator of unresectability

  • liver metastases (18 66%); invasion of liver (5%)

  • IVP:

    • drooping lily sign = displacement of kidney inferolaterally without distortion of collecting system

    • hydronephrosis (24%)

    • calcifications in 36 50% on KUB

  • CT:

    • heterogeneous texture with low-density areas from hemorrhage + necrosis (55%)

    • calcifications in up to 85%

  • MR:

    • hyperintense heterogeneous mass on T2WI

  • Angio:

    • hypo- / hypervascular mass

  • US:

    • hyperechoic poorly defined mass with acoustic shadowing (calcifications):

      • hypoechoic areas (representing necrosis + hemorrhage)

  • NUC:

    • focal uptake of I-131 / I-123 MIBG radioactivity (82% sensitivity; 88% specificity)

    • tracer uptake on bone scan (60%)

  • OB-US:

    • maternal symptoms of catecholamine excess

    • mixed cystic + solid mass in adrenal region

    P.942

    
    

    • may exhibit acoustic shadowing (calcifications)

    • hydrops fetalis (severe anemia secondary to metastases to bone marrow, mechanical compression of IVC, hypersecretion of aldosterone)

    • polyhydramnios

  • Prognosis:

    • 2-year survival rate versus age at presentation:

      60%	if patient's age	<1 year
      20%	if patient's age	1 2 years
      10%	if patient's age	>2 years

      • May revert to benign ganglioneuroma in 0.2%!

      • Survival rate versus stage:

        • 80% for stage I

        • 60% for stage II

        • 30% for stage III

        • 7% for stage IV

        • 75 87% for stage IVs

          DDx:

          adrenal hemorrhage, exophytic Wilms tumor, mesoblastic nephroma, multicystic kidney, retroperitoneal teratoma, infradiaphragmatic extralobar sequestration, hepatic hamartoma / hemangioma, splenic cyst

Neurogenic Bladder

Neuroanatomy:	bladder innervation of detrusor muscle by parasympathetic nerves S2 S4
Etiology:	congenital (myelomeningocele); trauma; neoplasm (spinal, CNS); infection (herpes, polio); inflammation (multiple sclerosis, syrinx); systemic disorder (diabetes, pernicious anemia)

• SPASTIC BLADDER

  • upper motor neuron lesion above conus

• ATONIC BLADDER

  • lower motor neuron lesion below conus

Oncocytoma

• = PROXIMAL TUBULAR ADENOMA = BENIGN oxyphilic ADENOMA

• = rare form of hypervascular adenoma

  Prevalence:	1 2 13% of renal tumors
  Age:	median age around 65 (range of 26 94) years; M:F = 1.6:1 to 2.5:1
  Path:	well-encapsulated tan-colored tumor of well-differentiated proximal tubular cells (benign adenoma) + oncocytes
  Histo:	oncocytes = large epithelial cells with granular oxyphilic / eosinophilic cytoplasm (due to large number of mitochondria); no clear cytoplasm; similar oncocytic tumors seen in thyroid, parathyroid, salivary glands, adrenals

• majority asymptomatic, occasionally hypertension

• renal mass of 6 7.5 cm average size (0.1 26 cm)

• tumor of homogeneous low attenuation / hypoechogenicity (>50%)

• well-demarcated with pseudocapsule

• central stellate scar in 30% (in lesions >3 cm in diameter due to organization of central infarction + hemorrhage after tumor growth has outstripped blood supply)

• invasion of renal capsule / renal vein in large tumors

• MR:

  • mass hypointense on T1WI + hyperintense on T2WI

  • prominent enhancement of mass

  • central stellate scar hypointense on T1WI + hyperintense on T2WI + less enhancement than remainder of mass

• Angio:

  • spoke-wheel configuration (80%), homogeneously dense parenchymal phase (71%)

  • NO contrast puddling / arteriovenous shunting / renal vein invasion

• NUC:

  • photopenic area (tubular cells do not function normally) on Tc-99m DMSA

    Dx:	percutaneous needle biopsy unreliable
    Pathologic diagnosis requires entire tumor because well-differentiated renal cell carcinoma may have oncocytic features!
    Rx:	local resection / heminephrectomy
    Prognosis:	death from malignancy following surgery (3%)

Orchitis

• unusual without epididymitis

• Etiology:

  • bacterial infection

  • viral infection

    • complication of mumps in 20%:

      • in adolescents + young adults; usually developing 4 5 days later; unilateral involvement in >90%; parotitis precedes orchitis in 84%, simultaneous in 3%, later in 4%; without parotitis in 10%

    • Coxsackie virus

  • increased testicular blood flow

  • enlargement of testis

  • hydrocele + thickening of scrotal wall

    DDx:

    neoplasm (mimicked by focal orchitis)

Ossifying Renal Tumor of Infancy

• = rare benign renal mass originating from urothelium

  Incidence:	only 11 cases in literature
  Age:	6 days 14 months; M > F
  Histo:	osteoid core, osteoblasts, spindle cells

• hematuria

  Location:	L > R kidney
  Site:	upper pole

• 2 3-cm polypoid mass:

  • calcified (in 80%)

  • filling defect of collecting system

  • partial obstruction of collecting system

• echogenic mass + shadowing

• poor enhancement on CT

  DDx:

  staghorn calculus

Page Kidney

• = renin-angiotensin mediated hypertension caused by reduction of blood flow to kidney secondary to renal compression in a perinephric / subcapsular location

  Etiology:	(1) Spontaneous hematoma (most common)
  	(2) Blunt trauma with chronic contained subcapsular hematoma / perirenal scarring
  	(3) Cyst
  	(4) Tumor

P.943




• stretching + splaying of intrarenal vessels

• slow arterial washout

• distortion of renal contour + thinning of renal parenchyma

• enlarged + displaced capsular artery

Papillary Necrosis

• = NECROTIZING PAPILLITIS

• = ischemic necrobiosis of medulla (loops of Henle + vasa recta) secondary to interstitial nephritis (interstitial edema) or intrinsic vascular obstruction

• Cause:

  mnemonic:

  POSTCARD

  • Pyelonephritis

  • Obstructive uropathy

  • Sickle cell disease

  • Tuberculosis, Trauma

  • Cirrhosis = alcoholism, Coagulopathy

  • Analgesic nephropathy

  • Renal vein thrombosis

  • Diabetes mellitus (50%)

    also:

    dehydration, severe infantile diarrhea, hemophilia, Christmas disease, acute tubular necrosis, transplant rejection, postpartum state, high-dose urography, intravesical instillation of formalin, thyroid cancer

• Types:

  • Necrosis in situ = necrotic papilla detaches but remains unextruded within its bed

  • Medullary type (partial papillary slough) = single irregular cavity located concentric / eccentric in papilla with long axis paralleling the long axis of the papilla + communicating with calyx

  • Papillary type (total papillary slough)

• Phases:

  • Enlargement of papilla (papillary swelling)

  • Fine projections of contrast material alongside papilla (tract formation)

  • Medullary cavitation / complete slough of papilla

• flank pain, dysuria, fever, chills

• ureteral colic

• acute oliguric renal failure

• hypertension

• proteinuria, pyuria, hematuria, leukocytosis

  Location:	(a) localized / diffuse
  	(b) bilateral distribution (systemic cause)
  	(c) unilateral (obstruction, renal vein thrombosis, acute bacterial nephritis)

• normal or small kidney (analgesic nephropathy) / large kidney (acute fulminant)

• smooth / wavy renal contour (analgesic nephropathy)

• calcification of necrotic papilla: papillary / curvilinear / ringlike

• IVP:

  • lobster claw sign = subtle streak of contrast material extending from fornix parallel to long axis of papilla

  • centric / eccentric, thin and short / bulbous cavitation of papilla

  • widened fornix (necrotic shrinkage of papilla)

  • signet ring sign = ring shadow of papilla (outlining detached papilla within contrast material-filled cavity)

  • club-shaped / saccular calyx (sloughed papilla)

  • intraluminal nonopaque filling defect (sloughed papilla) in calyx / pelvis / ureter

  • diminished density of contrast material in nephrogram; rarely increasingly dense

  • wasted parenchymal thickness

  • displaced collecting system (enlarged septal cortex from edema)

• US:

  • multiple round / triangular cystic spaces in medulla with echo reflections of arcuate arteries at periphery of cystic spaces

    Cx:	higher incidence of transitional cell carcinoma in analgesic abusers (8 x); higher incidence of squamous cell carcinoma
    DDx:	(1) Postobstructive renal atrophy
    	(2) Congenital megacalices (normal renal function)
    	(3) Hydronephrosis (dilated infundibula)

Paroxysmal Nocturnal Hemoglobinuria

• = rare acquired disorder of nonmalignant hematopoietic stem cells

  Cause:

  infection, transfusion, radiographic contrast material, exercise, drugs, immunization, surgery

• Pathophysiology:

  • destruction of abnormally sensitive RBCs + granulocytes + platelets by activated complement; complement activation of abnormal platelets + release of thrombogenic material from lysed RBCs

• increased susceptibility to infections

• intravascular hemolysis:

  • hemoglobinuria

  • pancytopenia / aplasia

  • chronic iron deficiency anemia

• venous thrombosis in uncommon sites:

  • cerebral vein thrombosis

  • acute (tubulointerstitial nephritis) / chronic renal failure (small vessel thrombosis)

  • mesenteric + splenic vein thrombosis

  • hepatic vein thrombosis (= Budd-Chiari syndrome) involving tertiary + secondary venous radicles

  • portal vein thrombosis

• MR:

  • low signal intensity of renal cortex on T1WI + T2WI due to hemosiderin deposition (after intravascular hemolysis free hemoglobin is filtered across renal glomeruli + reabsorbed by proximal convoluted tubular cells)

  • usually decreased iron concentration in liver + spleen unless transfusions were given (DDx to other hemolytic anemias)

    Prognosis:

    venous thrombosis is a major cause of death

Pheochromocytoma

• = ADRENAL PARAGANGLIOMA

• = rare catecholamine-secreting tumor of chromaffin tissue; responsible for 0.1% of hypertensions

  Incidence:	0.13% in autopsy series; sporadic occurrence in 10%
  Origin:	neuroectodermal tissue
  Histo:	chromaffin tumor cells contain chromagranin within secretory granules, tumor tends to form Zellballen (cell balls)
  Age:	5% in childhood

P.944

• symptomatology secondary to excess catecholamine production (norepinephrine / epinephrine):

  • asymptomatic (9%)

  • headaches, sweating, flushing, palpitations, tachycardia, anxiety, tremor

  • nausea, vomiting, abdominal pain, chest pain

  • paroxysmal (47%) / sustained (37%) hypertension

    • elevated catecholamine

    • functional renal vasoconstriction

    • renal artery stenosis (fibrosis, intimal proliferation, tumor encasement)

  • hypoglycemia during hypertensive crisis

  • elevated urine vanillylmandelic acid (VMA) in 54%; in up to 22% false-negative result because VMA not excreted

• Most common cause of spontaneous retroperitoneal hemorrhage from a primary adrenal tumor!

• Associated with heritable conditions (10%):

  • usually with bilateral pheochromocytomas

  • Multiple endocrine neoplasia (MEN):

    • pheochromocytomas occur in 50% of MEN 2 patients (bilateral in up to 50%)

    • malignant transformation in 5%

    • pheochromocytoma small + asymptomatic in 50%

    • Sipple syndrome = MEN type 2A

      • = medullary carcinoma of thyroid + parathyroid adenoma + pheochromocytoma

    • Mucosal neuroma syndrome = MEN type 2B

      • = medullary carcinoma of thyroid + intestinal ganglioneuromatosis + pheochromocytoma

  • Neuroectodermal disorder

    • neurofibromatosis type 1 (in 0.1 5.7%)

    • von Hippel-Lindau disease

    • tuberous sclerosis

    • 10% of patients with neurofibromatosis (NF1) / von Hippel-Lindau disease have pheochromocytoma!

  • Familial pheochromocytosis

  • Carney syndrome

    mnemonic:

    VEIN

    • Von Hippel-Lindau

    • Endocrine neoplasia (MEA 2)

    • Inherited (congenital) pheochromocytoma

    • Neurofibromatosis

      Location:

      anywhere in sympathetic nervous system from neck to sacrum; subdiaphragmatic in 98%

  • adrenal medulla (85 90%) = pheochromocytoma

  • extraadrenal (10 15% in adults, 31% in children)

    • = paraganglioma:

      • paraaortic sympathetic chain (8%), organ of Zuckerkandl at origin of inferior mesenteric artery (2 5%), gonads, urinary bladder (1%)

        Multiplicity:	10% in nonfamilial adult cases
        	32% in nonfamilial childhood cases
        	65% in familial syndromes

• RULE OF TENS ( ten-percent tumor ):

  10% bilateral / multiple	10% extraadrenal
  10% malignant	10% familial

• discrete round / oval mass with a mean size of 5 cm (range 3 12 cm)

• speckled calcifications in 10 12%

• CT (93 100% sensitive):

  • Localization accurate in 91% with tumor >2 cm in size; up to 40% in extraadrenal location are missed by CT

  • solid / cystic / complex mass with low-density areas secondary to hemorrhage / necrosis

  • marked avid contrast enhancement

  • IV injection of iodinated contrast material may precipitate hypertensive crisis in patients not on alpha-adrenergic blockers! Nonionic IV contrast media can safely be used without a-adrenergic blockage!

• NUC: I-131 / I-123 MIBG (metaiodobenzylguanidine) scan (80 90% sensitive; 98% specific):

  • Useful:

    • with clear clinical / laboratory evidence of tumor but no adrenal abnormality on CT / MR

    • in detecting extraadrenal pheochromocytomas by whole-body scintigraphy

• US:

  • well-marginated ovoid purely solid (68%) / complex (16%) / cystic tumor (16%)

  • homo- (46%) / heterogeneously (54%) solid tumor: isoechoic + hypoechoic (77%) / hyperechoic (23%) to renal parenchyma

  • heterogeneity introduced by hemorrhage / necrosis

• MR (method of choice):

  • iso- / slightly hypointense to liver on T1WI

  • may contain areas of high signal intensity on T1WI due to hemorrhage (20%)

  • extremely hyperintense compared with spleen on T2WI (in 60%) due to intratumoral cystic regions

  • contains central heterogeneous areas of decreased signal intensity in 35% (due to necrosis / hemorrhage / calcifications) on T2WI

  • rapid marked homo- / inhomogeneous enhancement (not routinely used as it does not increase sensitivity)

  • no change in signal intensity between in-phase + opposed-phase T1WI images

• Angio:

  N.B.:

  intraarterial injection CONTRAINDICATED (induces hypertensive crisis)

  • localization by aortography in >91%

  • usually hypervascular lesion with intense tumor blush

  • slow washout of contrast material

  • enlarged feeding arteries + neovascularity ( spoke-wheel pattern)

  • parasitization from intrarenal perforating branches

  • venous blood sampling (at different levels in IVC)

    Cx:	(1) malignancy in 2 14% with metastases (may be hormonally active) to bone, lymph nodes, liver, lung
    	(2) Spontaneous retroperitoneal hemorrhage (is lethal in 50% if tumor previously undiagnosed)
    Rx:	(1) Surgical removal curative
    	(2) Alpha-adrenergic blocker (phenoxybenzamine / phentolamine)
    	(3) Beta-adrenergic blocker (propranolol)
    	(4) I-131 MIBG used to treat metastases
    DDx:	nonfunctioning adrenal adenoma, adrenocortical carcinoma, adrenal cyst

P.945

Plasmacytoma of Kidney

• = group of malignant disorders involving differentiated B lymphocytes or plasma cells

• Classification:

  • solitary = plasmacytoma (5%)

  • multiple = multiple myeloma (95%):

    • involvement of kidney in 17% at autopsy

• Distribution of primary extramedullary plasmacytoma:

  • skeleton (95%)

  • nonskeletal sites (5%): upper respiratory tract

• monoclonal immunoglobulin / Bence Jones proteinuria

• well-circumscribed mass / infiltrative lesion

  DDx:

  indistinguishable from other renal primaries

Polycystic Kidney Disease

Autosomal Dominant Polycystic Kidney Disease

• = ADULT POLYCYSTIC KIDNEY DISEASE = ADPKD = Potter type III

• = slowly progressive disease with nearly 100% penetrance and great variation in expressivity

  Cause:	gene located on short arm of chromosome 16 (in 90%); spontaneous mutation in 10%
  Incidence:	1:1,000 people carry the mutant gene; 3rd most prevalent cause of chronic renal failure
  Risk of recurrence:	50%
  Histo:	abnormal rate of tubule divisions (Potter type III) with hypoplasia of portions of tubules left behind as the ureteral bud advances; cystic dilatation of Bowman capsule, loop of Henle, proximal convoluted tubule, coexisting with normal tissue

• Mean age at diagnosis:

  • 43 years (neonatal / infantile onset has been reported); M:F = 1:1

  • Onset of cyst formation:

    • 54% in 1st decade

    • 72% in 2nd decade

    • 86% in 3rd decade

    • morphologic evidence in all patients by age 80

• Criteria in screening exam for cysts:

  18 29 years	5 cysts
  30 44 years	6
  45 59 years	6 cysts in females, 9 in males

• Associated with:

  • Cysts in: liver (25 50 80%), pancreas (9%); rare in lung, spleen, thyroid, ovaries, uterus, testis, seminal vesicles, epididymis, bladder

  • Aneurysm: saccular berry aneurysm of cerebral arteries (3 13%), aortic aneurysm

  • Mitral valve prolapse

  • Colonic diverticulosis

  • Consider ADPKD a systemic disease due to a generalized collagen defect!

• symptomatic at mean age of 35 years (cysts are growing with age)

• hypertension (50 70%)

• azotemia

• hematuria, proteinuria

• lumbar / abdominal pain

• bilaterally large kidneys with multifocal round lesions; unilateral enlargement may be the first manifestation of the disease

• cysts may calcify in curvilinear rim- / ringlike irregular amorphous fashion

• elongated + distorted + attenuated collecting system

• nodular puddling of contrast material on delayed images

• Swiss cheese nephrogram = multiple lesions of varying size with smooth margins

• polycystic kidneys shrink after beginning of renal failure, after renal transplantation, or on chronic hemodialysis

• NUC: poor renal function on Tc-99m DTPA scan

  • multiple areas of diminished activity, cortical activity only in areas of functioning cortex

• US:

  • multiple cysts in cortical region (usually seen in 50% by 10 years of age)

  • diffusely echogenic when cysts small (children)

  • renal contour poorly demarcated

• OB-US:

  • large echogenic kidneys similar to infantile PCKD (usually in 3rd trimester, earliest sonographic diagnosis at 14 weeks), can be unilateral

  • macroscopic cysts (rare)

  • normal amount of amniotic fluid / oligohydramnios (renal function usually not impaired)

• Atypical rare presentation:

  • unilateral adult PCKD

  • segmental adult PCKD

  • adult PCKD in utero / neonatal period

• Cx:

  • Death from uremia (59%) / cerebral hemorrhage (secondary to hypertension or ruptured aneurysm [13%]) / cardiac complications (mean age 50 years)

  • Renal calculi (20%): mostly urate

  • Urinary tract infection

  • Cyst rupture

  • Cyst hemorrhage (66%):

    • common cause of acute flank pain

    • hyperattenuated cyst content on CT

    • calcifications frequent, which may take years

  • Renal cell carcinoma (increased risk if in renal failure)

• DDx:

  • Multiple simple cysts (less diffuse, no family history)

  • von Hippel-Lindau disease (cerebellar hemangioblastoma, retinal hemangiomas, occasionally pheochromocytomas)

  • Acquired uremic cystic disease (kidneys small, no renal function, transplant)

  • Infantile PCKD (usually microscopic cysts)

Autosomal Recessive Polycystic Kidney Disease

• = INFANTILE POLYCYSTIC KIDNEY DISEASE = POLY-CYSTIC DISEASE OF CHILDHOOD = Potter Type I

  Frequency:	1: 6,000 to 1:55,000 live births; F > M; carrier frequency of 1:70
  Cause:	chromosomal abnormality on 6p21 (gene not yet identified) resulting in abnormal epithelium

P.946




• Pathogenesis:

  • symmetric circumferential epithelial proliferation results in tubular lengthening + fusiform dilatation of collecting ducts; abnormal epithelium becomes secretory instead of resorptive; secreted fluid is rich in epithelial growth factors stimulating further epithelial proliferation

• Path:

  • @ Kidney:

    • numerous dilated + elongated collecting tubules with radial orientation extending from medulla into cortex; associated renal interstitial edema + fibrosis; increased separation of a normal number of glomeruli

    • spongelike texture of renal parenchyma

    • azotemia

    • diminished concentrating ability of kidneys

  • @ Liver:

    • congenital hepatic fibrosis = irregularly formed dilated nonobstructive intrahepatic bile ducts increased in number with atypical branching pattern + fibrosed portal tracts

  • @ Pancreas:

    • pancreatic fibrosis

• The greater the percentage of abnormal collecting tubules, the more severe the renal compromise and the earlier the clinical presentation!

• The less severe the renal findings, the more severe the hepatic findings!

• Blythe & Ockenden classification:

  • PERINATAL FORM (most common)

    • 90% of tubules show cystic changes

    • onset of renal failure in utero

    • Potter sequence

    • both kidneys enlarged

    • oligohydramnios and dystocia (large abdominal mass)

      Prognosis:

      death from renal failure / respiratory insufficiency (pulmonary hypoplasia) within 24 hours in 75%, within 1 year in 93%; uniformly fatal

  • NEONATAL FORM

    • 60% of tubules show ectasia + minimal hepatic fibrosis + bile duct proliferation

    • onset of renal failure within 1st month of life

      Prognosis:

      death from renal failure / hypertension / left ventricular failure within 1st year of life

  • INFANTILE FORM

    • 25% of renal tubules involved + mild / moderate periportal fibrosis

    • disease appears by 3 6 months of age

      Prognosis:

      death from chronic renal failure / systemic arterial hypertension / portal hypertension

  • JUVENILE FORM

    • 10% of tubules involved + gross hepatic fibrosis + bile duct proliferation

    • disease appears at 6 months to 5 years of age

      Prognosis:

      death from portal hypertension

• @ Abdominal radiograph

  • abdominal distension

  • gas-filled bowel loops deviated centrally

• @ Lung

  • severe pulmonary hypoplasia

  • pneumothorax / pneumomediastinum

• @ Liver

  • portal venous hypertension (between 5 and 13 years of age)

  • tubular cystic dilatation of small intrahepatic bile ducts

  • patchy / diffuse increase in liver echogenicity

  • increased echogenicity of portal tracts

  • hepatosplenomegaly

  • enlarged splenic and portal veins

• @ Kidneys

  • bilateral gross smooth renal enlargement

  • faint nephrogram + blotchy opacification on initial images

  • increasingly dense nephrogram

  • poor visualization of collecting system

  • sunburst nephrogram = striated nephrogram with persistent radiating opaque streaks (collecting ducts) on delayed images

  • prominent fetal lobation

  • poor opacification + contrast excretion with impaired renal function

  • CT:

    • kidneys low in attenuation

    • prolonged corticomedullary phase

    • striated pattern of contrast media excretion (due to contrast material in dilated tubules)

  • MR:

    • hyperintense renal parenchyma on T2WI

  • US:

    • hyperechoic enlarged kidneys (unresolved 1 2-mm cystic / ectatic dilatation of renal tubules increases the number of acoustic interfaces)

    • increased renal through-transmission (due to fluid content of cysts)

    • loss of corticomedullary differentiation, poor visualization of renal sinus + renal borders

    • thin rim of hypoechoic cortex

    • occasionally discrete macroscopic cysts <1 cm with tendency to become larger + more numerous over time (in older children resembling adult medullary sponge kidney)

    • compressed / minimally dilated collecting system

    • small bladder

  • OB-US (diagnostic as early as 17 weeks GA):

    • decreased fetal urine output

    • Potter facies: low-set + flattened ears, short + snubbed nose, deep eye creases, micrognathia

    • progressive massive renal enlargement (10 20 larger than normal):

      • renal:abdominal circumference ratio >0.30

    • hyperechoic renal parenchyma

    • nonvisualization of urine in fetal bladder (in severe cases)

    • oligohydramnios (33%)

    • small fetal thorax with pulmonary hypoplasia

    • club foot

  P.947

  
  

  • OB management:

    • Chromosome studies to determine if other malformations present (eg, trisomy 13 / 18)

    • Option of pregnancy termination <24 weeks

    • Nonintervention for fetal distress >24 weeks if severe oligohydramnios present

      Risk of recurrence:	25%
      DDx:	Meckel-Gruber syndrome, adult polycystic kidney disease

Posterior Urethral Valves

• = congenital thick folds of mucous membrane located in posterior urethra (prostatic + membranous portion) distal to verumontanum

  Type I:	(most common) mucosal folds (vestiges of wolffian duct) extend anteroinferiorly from the caudal aspect of the verumontanum, often fusing anteriorly at a lower level
  Type II:	(rare) mucosal folds extend anterosuperiorly from the verumontanum toward the bladder neck (nonobstructive normal variant, probably a consequence of bladder outlet obstruction)
  Type III:	diaphragm-like membrane located below the verumontanum (= abnormal canalization of urogenital membrane)
  Incidence:	1:5,000 8,000 boys; most common cause of urinary tract obstruction + leading cause of end-stage renal disease among boys
  Time of discovery:	prenatal (8%), neonatal (34%), 1st year (32%), 2nd 16th year (23%), adult (3%)

• urinary tract infection (fever, vomiting) in 36%

• obstructive symptoms in 32% (hesitancy, straining, dribbling [20%], enuresis [20%])

• palpable kidneys / bladder in neonate (21%)

• failure to thrive (13%)

• hematuria (5%)

• VCUG:

  • vesicoureteral reflux, mainly on left side (in 33%)

  • fusiform distension + elongation of proximal posterior urethra persisting throughout voiding

  • transverse / curvilinear filling defect in posterior urethra

  • diminution of urethral caliber distal to severe obstruction

  • hypertrophy of bladder neck

  • trabeculation + sacculation of bladder wall

  • large postvoid bladder residual

• US:

  • male gender

  • oligohydramnios (related to severity + duration of obstruction)

  • hypoplastic / multicystic dysplastic kidney (if early occurrence)

  • bilateral hydroureteronephrosis (+ pulmonary hypoplasia)

  • dilated renal pelvis may be absent in renal dysplasia / rupture of bladder / pelvoureteral atresia

  • overdistended urinary bladder (megacystis) in 30%

  • thick-walled urinary bladder + trabeculations (best seen after decompression)

  • urine leak: urinoma, urine ascites, urothorax

  • pear / keyhole bladder = posterior urethral dilatation (on perineal scan)

  • dilated utricle (perineal scan)

• OB management:

  • Induction of labor as soon as fetal lung maturity established if diagnosed during last 10 weeks of pregnancy

  • Vesicoamniotic shunting may be contemplated if diagnosed remote from term (68% survivors) with good prognostic parameters of fetal urinary sodium <100 mEq/dL + chloride <90 mEq/dL + osmolality <210 mOsm/dL

    Cx:	(1) Neonatal urine leak (ascites, urothorax, urinoma) in 13%
    	(2) Neonatal pneumothorax / pneumomediastinum in 9%
    	(3) Prune belly syndrome
    	(4) Renal dysplasia (if obstruction occurs early during gestation)
    Prognosis:	depends upon duration of obstruction prior to corrective surgery; poor prognosis if associated with vesicoureteral reflux; nephrectomy for irreversible damage (13%)
    DDx:	(1) UPJ obstruction
    	(2) UVJ obstruction
    	(3) Primary megaureter
    	(4) Massive vesicoureteral reflux
    	(5) Megacystis-microcolon-intestinal hypoperistalsis syndrome

Postinflammatory Renal Atrophy

• = acute bacterial nephritis with irreversible ischemia as an unusual form of severe gram-negative bacterial infection in patients with altered host resistance in spite of proper antibiotic treatment

  Histo:

  occlusion of interlobar arteries / vasospasm

• small smooth kidney

• papillary necrosis in acute phase

Postobstructive Renal Atrophy

• = generalized papillary atrophy usually following successful surgical correction of urinary tract obstruction and progressing in spite of relief of obstruction

• small smooth kidney, usually unilateral

• dilated calyces with effaced papillae

• thinned cortex

Priapism

• = prolonged penile erection not associated with sexual arousal

• Types:

  • Low-flow form = venoocclusive form (common):

    • characterized by ischemia, venous stasis, pooling of blood within corpora cavernosa

      Cause:

      sickle cell disease, hematopoietic malignancy, hypercoagulable state

    • painful erection

    • sluggish intracavernosal flow

    • decreased venous outflow

    • decreased arterial inflow

    • intracavernosal thrombosis

      Rx:	cavernosal aspiration + irrigation, anticoagulation, shunt procedure
      Cx:	impotence (in 50% in spite of Rx)

  P.948

  
  

  • High-flow form (rare):

    • characterized by unregulated arterial inflow of blood into corpora cavernosa usually due to arterial injury

      Cause:

      perineal / penile trauma

    • subsequent persistent painless erection

    • Color Doppler US:

      • focal blush of abnormal intracavernosal flow adjacent to cavernosal artery from arterial-sinusoidal fistula

        Rx:

        percutaneous transcatheter embolization; arterial ligation

Prostate Cancer

• Incidence:

  • doubles with each decade after age 50; 250:100,000 for 65-year old Caucasian, 1,000:100,000 in 85-year old Caucasian; 180,400 new cases + 31,900 deaths in USA (2000); 2nd most common malignancy in males (after lung cancer); in 35% of men >45 years of age (autopsies)

  • One out of 11 males will develop prostate cancer!

    Racial factors:	8.7% in White males, 9.4% in Black males; less common in Asians
    Risk factors:	advancing age, presence of testes, cadmium exposure, animal fat intake; 1 first-degree relative
    Histo:	adenocarcinoma (common); rare cancers: transitional cell cancer, adenoid cystic cancer, endometrioid neoplasm of verumontanum, carcinosarcoma, sarcoma, lymphoma

• Histo for adenocarcinoma:

  • nuclear anaplasia + large nucleoli in secretory cells, disturbed architecture, invasive growth

  • Premalignant change:

    • Prostatic intraepithelial neoplasia (PIN)

      • = premalignant lesion frequently associated with invasive carcinoma next to it / elsewhere in the gland

    • Atypical adenomatous hyperplasia = proliferation of newly formed small acini

      Staging of Prostate Cancer American Urological Association System (modifi ed Jewitt-Whitmore Staging System)

      A	No palpable lesion
      A1	focal well-differentiated tumor <1.5 cm
      A2	diffuse poorly differentiated tumor; >5% of chips from transurethral resection contain cancer
      B	Palpable tumor confi ned to prostate
      B1	lesion <1.5 cm in diameter confi ned to one lobe
      B2	tumor 1.5 cm / involving more than one lobe
      C	Localized tumor with capsular involvement
      C1	capsular invasion
      C2	capsular penetration
      C3	seminal vesicle involvement
      D	Distant metastasis
      D1	involvement of pelvic lymph nodes
      D2	distant nodes involved
      D3	metastases to bone / soft tissues / organs

  • Grading (Gleason score 2 10):

    1,2,3	glands surrounded by 1 row of epithelial cells
    4	absence of complete gland formation
    5	sheets of malignant cells

    • low numbers refer to well-differentiated, high numbers to anaplastic tumors; primary predominant grade (1 5) is added to secondary less representative area with highest degree of dedifferentiation (1 5)

    • Gleason grading is in only 80% reproducible!

    • Gleason grade 7 has worse prognosis

• Clinical categories:

  • Latent carcinoma = usually discovered at autopsy of a patient without signs or symptoms referable to the prostate (26 73%)

  • Incidental carcinoma = discovered in 6 20% of specimens obtained during transurethral resection for clinically benign prostatic hyperplasia

  • Occult carcinoma = found at biopsy of metastatically involved bone lesion / lymph node in a patient without symptoms of prostatic disease

  • Clinical carcinoma = cancer detected by digital rectal examination based on induration / irregularity / nodule

    • digital rectal exam is 30 60% accurate for differentiating stage B from stage C disease

      P.949

      
      

      Staging of Prostate Cancer American Joint Committee on Cancer

      T0	No evidence of primary tumor
      T1	Clinically inapparent nonpalpable nonvisible tumor
      T1a	<3 microscopic foci of cancer / <5% of resected tissue
      T1b	>3 microscopic foci of cancer / <5% of resected tissue
      T1c	tumor identifi ed by needle biopsy
      T2	Tumor clinically present + confi ned to prostate
      T2a	tumor 1.5 cm, normal tissue on 3 sides
      T2b	tumor <1.5 cm / in one lobe (unilateral)
      T2c	tumor involves both lobes (bilateral)
      T3	Extension through prostatic capsule
      T3a	unilateral
      T3b	bilateral
      T3c	invasion of seminal vesicles
      T4	Tumor fi xed / invading adjacent structures other than seminal vesicles
      T4a	invasion of bladder neck, external sphincter, rectum
      T4b	invasion of levator anus muscle and/or fi xed to pelvic wall
      N	Involvement of regional lymph nodes
      N1	metastasis in a single node 2 cm
      N2	metastasis in a single node <2 and <5 cm / multiple lymph nodes affected
      N3	metastasis in a lymph node 5 cm
      M	Distant metastasis
      M1a	nonregional lymph nodes
      M1b	bone
      M1c	other site

  • elevated Prostate-Specific Antigen (PSA)

    • (= glycoprotein produced by prostatic epithelium) is measured by a monoclonal radioimmunoassay (Hybritech , most commonly used: normal value of 0.1 4 ng/mL)

      • Cancers of <1 mL usually do not elevate PSA!

      • 16% of normal men have PSA >4 ng/mL

      • 19 30% of prostate cancers have normal PSA!

      • Benign conditions with PSA elevation: benign prostatic hypertrophy, prostatitis, prostatic intraepithelial neoplasia

      • Confined disease (stage B and less) & PSA level:

        75%	of patients with PSA of	<4 ng/mL
        53%	of patients with PSA of	4 10 ng/mL
        2%	of patients with PSA of	>30 ng/mL

    • decreased free-to-total PSA ratio:

      • <15% is highly suggestive of cancer,

      • <25% detects 95% of detectable cancers

      • elevated PSA density

        • = volume corrected PSA level [= prostate volume (height width length 0.523) / PSA value]:

          • >0.12 (90% sensitive, 51% specific for cancer)

        • Each gram of malignant prostate tissue produces 3.5 ng/mL PSA versus 0.3 ng/mL PSA for BPH!

      • elevated PSA velocity = serial PSA evaluation

        • >0.75 ng mL^-1 y^-1

    • Staging:

      • At initial presentation >75% have stage C + D!

      • 40% of patient believed to have organ-confined disease have extraprostatic disease at radical prostatectomy

      • Escape routes through prostatic capsule are:

        • capsular margin at neurovascular bundle posterolaterally (80%) due to intrinsic weakness of capsule at this location

        • apex

        • seminal vesicles!

      • Staging accuracy for local / advanced disease:

        • 46 / 66% for US, 57 / 77% for MR

      • Extracapsular disease is common at a tumor volume of >3.8 cm³!

    • Metastases to lymph nodes:

      • 0% in stage A₁, 3 7% in stage A_2,5% in stage B₁, 10 12% in stage B₂, 54 57% in stage C; 10% with Gleason grade 5, 70 93% with Gleason grade 9 / 10

        Location:

        peripheral zone (80%), transition zone (15%), central zone (5%); multifocal in 40%

    • US (21% positive predictive value):

      • hypoechoic (61%) / mixed (2%) / hyperechoic (2%) lesion; not detectable isoechoic lesion (35%)

      • asymmetric enlargement of gland

      • deformed contour of prostate = irregular bulge sign (75% PPV)

      • heterogeneous texture

      • Size versus rate of detection:

        • 5 mm (36%), 6 10 mm (65%), 11 15 mm (53%), 16 20 mm (84%), 21 25 mm (92%), 26 mm (75%)

      • DDx of hypoechoic lesion:

        • external sphincter, veins, neurovascular bundle, seminal vesicle, dilated duct, small prostatic cyst, acute prostatitis, benign prostatic hyperplasia, dysplasia, sonographic artifact

    • MR:

      • low-signal abnormality within the normally high-signal glandular tissue of the peripheral zone on T2WI

      • tumor isointense relative to surrounding gland on T1WI

      • capsule optimally depicted on T1WI due to demarcation by high signal-intensity periprostatic fat

      • extracapsular extension (90% specific, 15% sensitive):

        • direct tumor extension beyond prostate

        • decreased signal intensity in periprostatic fat adjacent to capsule near the tumor on T1WI + T2WI

        • capsular thickening

        • irregular focal bulge in contour of capsule near the tumor

        • flattening / obliteration of rectoprostatic angle

        • asymmetry of neurovascular bundle

        • low-signal lesion on T2WI within seminal vesicles that are normally of high-signal intensity

          DDx:	post-biopsy hemorrhage (low signal on T2WI + high signal on T1WI)
          Prognosis:	increase in tumor volume increases probability of capsular penetration, metastasis, histologic dedifferentiation
          Mortality:	2.6% for White males, 4.5% for Black males; 34,000 deaths/1992

      • Screening recommendation (American Urological Association, American Cancer Society):

        • PSA level measurements + digital rectal exam annually

          Rx:	(1) Watchful waiting
          	(2) Radical prostatectomy for disease confined to capsule + life expectancy >15 years
          	(3) Radiation therapy for
          	(a) disease confined to capsule, life expectancy <15 years
          	(b) disease outside capsule, no spread
          	(4) Hormonal therapy (orchiectomy, diethylstilbestrol, leuprolide acetate) for widely metastatic disease
          	(5) Cryosurgery
          	(6) Chemotherapy

Prune Belly Syndrome

• = EAGLE-BARRETT SYNDROME

• = congenital nonhereditary multisystem disorder; almost exclusively in males

  TRIAD:	1. Abdominal wall muscle deficiency (wrinkled prune belly appearance of abdominal wall)
  	2. Nonobstructed markedly distended redundant ureters hydronephrosis and variable degree of renal dysplasia
  	Bilateral undescended testes (cryptorchidism)

• Etiology:

  • primary mesodermal arrest at 6 10 weeks GA:

    • abundance of fibrous tissue with sparsely placed smooth muscle throughout urinary tract

  • massive abdominal distension with pressure effects on abdominal wall musculature:

    • secondary to bladder outlet obstruction (10 20%) / urine ascites / intestinal perforation with ascites / cystic abdominal masses / megacystis-microcolon-intestinal hypoperistalsis syndrome causing pressure atrophy of abdominal wall muscles; bladder distension interferes with descent of testes

  P.950

  
  

  • dysgenesis of yolk sac

    Incidence:

    1:29,000 to 1:50,000 live births; M:F = 19:1; increased prevalence in Nigeria + Saskatchewan, Canada

• Groups:

  • Severe urethral obstruction (urethral atresia [most commonly] / valves)

    • Associated with:

      • malrotation (most common anomaly), intestinal atresia, imperforate anus, skeletal abnormalities (meningomyelocele, scoliosis, pectus carinatum /excavatum, arthrogryposis, clubfoot, dislocation of hip, lower limb hemimelia, sacral agenesis, polydactyly), CHD (VSD, pulmonary artery stenosis), Hirschsprung disease, congenital cystic adenomatoid malformation of lung

    • bladder wall hypertrophy

    • bilateral cystic renal dysplasia

      Prognosis:

      in 20% death within 1 month; in 50% death within 2 years (due to renal failure pulmonary insufficiency)

  • Functional abnormality of bladder emptying (more common) with no associated abnormalities

    • large floppy urinary bladder

    • large urachal remnant

    • dilated posterior urethra (without obstruction)

    • utricle

    • vesicoureteral reflux

    • dilated tortuous ureters + focal areas of narrowing

    • lobulated kidneys with dilated collecting system of bizarre shape

      Prognosis:

      chronic urinary tract problems

• wrinkled flaccid appearance of hypotonic abdominal wall with bulging flanks (agenesis / hypoplasia of muscles in lower parts of abdominal wall ventrally + laterally):

  • transverse m. > rectus abdominis m. below umbilicus > internal + external oblique m. > rectus abdominis m. above umbilicus

• bilateral cryptorchidism (ESSENTIAL COMPONENT) with increased risk for malignant degeneration

• impaired renal function

• OB-US:

  • enlarged bladder, dilated ureters

  • abnormal abdominal wall

  • normal / decreased AFI

    DDx:

    posterior urethral valves

• @ Bladder

  • thickened bladder wall without trabeculations (due to replacement by fibrocytes + collagen)

  • large distended urinary bladder with a capacity of 600 800 mL

  • intramural bladder calcifications

  • persistence of patent urachus calcification

  • widely patent bladder neck

  • laterally placed ureteric orifices

• @ Urethra

  • elongated + dilated prostatic urethra with tapering of the membranous urethra

  • small / absent verumontanum

  • absent / markedly hypoplastic prostate (cause of infertility and enlarged prostatic urethra)

  • enlarged prostatic utricle (= small epithelium-lined diverticulum representing the remnant of the fused caudal ends of the m llerian ducts)

  • urethral obstruction (stenosis / atresia / dorsal chordae / posterior urethral valves) in 20%

  • scaphoid megalourethra (70%)

    • complete / fusiform megalourethra (rare)

      • = complete absence / marked deficiency of corpora cavernosa + corpus spongiosum

    • incomplete / scaphoid megalourethra (common)

      • = congenital absence / deficiency of corpus spongiosum with a normal glans + navicular fossa

• @ Ureters

  Histo:

  diffuse increase in connective tissue with replacement of smooth muscle

  • massively dilated tortuous elongated ureters affecting the lower third more profoundly (HALLMARK)

  • poor ureteral peristalsis (due to decrease in number of nerves + degeneration of nonmyelinated Schwann fibers)

  • alternating narrowed + dilated ureteral segments

  • vesicoureteral reflux (>70%)

• @ Kidneys

  • asymmetry of renal size + lobulated contours

  • no / mild (>50%) hydronephrosis

  • caliceal dilatation diverticula

  • renal calcifications

  • renal dysplasia with cystic dysplastic changes oligohydramnios, pulmonary hypoplasia (in severe cases due to a combination defect of ureteric bud + metanephron)

• @ Lung (55%)

  • pulmonary hypoplasia

  • cystic adenomatoid malformation

    Cx:

    respiratory infections (ineffective cough)

• @ Musculoskeletal (50%)

  • scoliosis, pectus deformity, arthrogryposis, clubfoot, valgus foot, hemimelia, dislocation of hip, sacral agenesis, polydactyly

• @ Gastrointestinal anomalies (30%)

  • malrotation, atresia, stenosis, volvulus, imperforate anus, Hirschsprung disease, gastroschisis

• @ Cardiovascular (10%)

  • VSD, PDA, tetralogy of Fallot

    Cx:	chronic renal failure / urosepsis / respiratory failure (30% die within first 2 years of life)
    Rx:	internal urethrotomy, cutaneous vesicostomy, reduction cystoplasty, ureteral reimplantation, orchidopexy at 1 2 years of age, renal transplantation after bilateral nephroureterectomy, abdominoplasty

Pyelocaliceal Diverticulum

• = PYELOGENIC CYST = pericaliceal CYST = CALICEAL DIVERTICULUM

• = uroepithelium-lined pouch extending from a peripheral point of the collecting system into adjacent renal parenchyma

P.951




• TYPE I (calyx):

  • more common; connected to caliceal cup, usually at fornix; bulbous shape; narrow connecting infundibulum of varying length; few millimeters in diameter; in polar region especially upper pole

• TYPE II (pelvis):

  • interpolar region; communicates directly with pelvis; usually larger and rounder; neck short and not easily identified

• Cause:

  • Developmental origin from ureteral bud remnant (obstruction of peripheral aberrant minicalyx )

  • Acquired: reflux, infection, rupture of simple cyst / abscess, infundibular achalasia / spasm, hydrocalyx secondary to inflammatory fibrosis of an infundibulum

• formation of single / multiple stones (50%) or milk of calcium (fluid-calcium level)

• opacification may be delayed and remain so for prolonged period

• mass effect on adjacent pelvicaliceal system if large enough

  Cx:	recurrent infection
  DDx:	ruptured simple nephrogenic cyst, evacuated abscess / hematoma, renal papillary necrosis, medullary sponge kidney, hydrocalyx due to infundibular narrowing from TB / crossing vessel / stone / infiltrating carcinoma

Pyelonephritis

• = upper urinary tract infection with pelvic + caliceal + parenchymal inflammation

• Society of Uroradiology recommends eliminating the terms (acute focal) bacterial nephritis, lobar nephritis, lobar nephronia, preabscess, renal cellulitis, renal phlegmon, renal carbuncle!

Acute Pyelonephritis

• = episodic bacterial infection of kidney with acute inflammation, usually involving pyelocaliceal lining + renal parenchyma centrifugally along medullary rays

• Risk factors:

  • Vesicoureteral reflux in children

  • Obstruction, stasis, stone in adults (5%)

• Pathway of infection:

  • ascending bacterial infection usually due to P-fimbriated E. coli (fimbriae facilitate adherence to mucosal surface): initial colonization of ureter in areas of turbulent flow leads to paralysis of ureteral smooth muscle function with dilatation + functional obstruction of collecting system

  • vesicoureteral reflux + pyelotubular backflow:

    • P-fimbriated E. coli not necessary for infection

  • hematogenous spread (12 20%) with gram-positive cocci

    Path:	thickened urothelium with multifocally / globally edematous kidney; radiating yellow-white stripes / wedges extending from papillary tip to cortical surface in a patchy distribution + sharply demarcated from adjacent spared parenchyma by 48 72 hours
    Histo:	tubulointerstitial nephritis = leukocytic migration from interstitium into lumen of tubules with destruction of tubule cells by released enzymes, bacterial invasion of interstitium by 48 72 hours
    Organism:	E. coli > Proteus > Klebsiella, Enterobacter, Pseudomonas
    Age:	most commonly 15 30 years; M << F
    Prevalence:	1 2% of all pregnant women

• fever, chills, flank pain + tenderness

• leukocytosis

• pyuria, bacteriuria, positive urine culture

• microscopic hematuria / bacteremia

• Indication for imaging in adults:

  • diabetes

  • analgesic abuse

  • neuropathic bladder

  • history of urinary tract stones

  • atypical organism

  • poor response to antibiotics

  • frequent recurrences

  • immunocompromised

  • atypical organism (eg, proteus)

• IVP (abnormal in 25%):

  • smooth normal / enlarged kidney(s), focal >> diffuse involvement of kidney

  • diminished nephrographic density (global / wedge-shaped / patchy)

  • immediate persistent dense nephrogram, rarely striated

  • nonvisualization of kidney (in severe pyelonephritis, rare)

  • tree-barking = mucosal striations (rare)

  • compression of collecting system (edema)

  • delayed opacification of collecting system

  • nonobstructive ureteral dilatation (rare, effect of endotoxins)

• CT:

  • thickening of Gerota fascia + thickened bridging septa / stranding (= perinephric inflammation)

  • generalized renal enlargement / focal swelling

  • obliteration of renal sinus

  • thickening of walls of renal pelvis + calices

  • mild dilatation of renal pelvis + ureter

  • area of high attenuation on unenhanced scan

    • (= hemorrhagic bacterial nephritis)

• CECT (abnormal in 65 90%):

  • hypoattenuating (80 90 HU) wedge-shaped area of cortex extending from papilla to renal capsule during nephrographic phase (= lobar segments of hypoperfusion + edema)

  • striated nephrogram

  • poor corticomedullary differentiation

  • dense parenchymal staining on scan delayed 3 6 hours in area of earlier diminished enhancement (= functioning renal parenchyma)

  • soft-tissue filling defect in collecting system

    • (= papillary necrosis, inflammatory debris, blood clot)

  • caliceal effacement

• US (abnormal in <50%):

  • Pyelonephritis is difficult to detect sonographically

  • swollen kidney of decreased echogenicity

  • loss of central sinus complex

  • wedge-shaped hypo- / isoechoic zones, rarely hyperechoic (due to hemorrhage)

  • thickened sonolucent corticomedullary bands

  • blurred corticomedullary junctions

  P.952

  
  

  • localized increase in size + echogenicity of perinephric fat fat within renal sinus

  • localized perinephric exudate

  • thickening of wall of renal pelvis

  • focally decreased blood flow on power Doppler

• MR:

  • wedge-shaped foci of persistent increased signal intensity on contrast-enhanced fast inversion recovery / T2WI

• Renal cortical scintigraphy (Tc-99m DMSA):

  • focal areas of diminished uptake (in 90%)

• Prognosis:

  • Quick response to antibiotic treatment will leave no scars

  • Delayed treatment of acute pyelonephritis during first 3 years of life can severely affect renal function later in life: decreased renal function, hypertension (33%), end-stage renal disease (10%)

    Cx:	(1) Renal abscess (near-water density lesion without enhancement)
    	(2) Scarring of affected renal lobes often in children + in up to 43% in adults
    	(3) Maternal septic shock (3%)
    	(4) Premature labor (17%)

Acute Focal Pyelonephritis

• = LOBAR NEPHRONIA = ACUTE FOCAL BACTERIAL NEPHRITIS = CARBUNCLE = RENAL CELLULITIS = RENAL PHLEGMON

  • = focal variant of acute pyelonephritis with single / multiple areas of suppuration + necrosis

    Organism:	E. coli > Proteus > Klebsiella
    Predisposed:	patients with altered host resistance (diabetes [60%], immunosuppression), chronic catheterization, mechanical / functional obstruction, trauma

• fever, flank pain, pyuria

  Site:

  usually involves entire renal lobe

• Ga-67 uptake

• vesicoureteral reflux often present

• IVP:

  • focal area of absent nephrogram / distorted pyelogram

• US:

  • hypoechoic mass with ill-defined margins and disruption of corticomedullary border

  • NOT a fluid collection

• CT:

  • hypoattenuating zone with poorly defined transition to surrounding parenchyma

  • less than normal parenchymal enhancement

• MR:

  • area of low signal intensity on T1WI

  • hyperintense center (due to fluid, necrosis) on T2WI

• Angio:

  • renal arteries displaced, renal veins compressed

    DDx:	abscess (no enhancement on CT)
    Cx:	scarring, abscess

Emphysematous Pyelitis

• = gas confined to renal pelvis + calyces

  Organism:	E. coli
  Predisposed:	diabetes mellitus (50%); M:F = 1:3
  May be associated with:	emphysematous cystitis (rare)

• pyuria

• gas pyelogram outlining pelvicaliceal system

• dilated renal collecting system (frequent)

• gas in ureters

  DDx:

  reflux of gas / air from bladder or urinary diversion

Emphysematous Pyelonephritis

• = life-threatening acute fulminant necrotizing infection of kidney and perirenal tissues associated with gas formation

  Organism:	E. coli (68%), Klebsiella pneumoniae (9%), Proteus mirabilis, Pseudomonas, Enterobacter, Candida, Clostridia (exceptionally rare)
  Path:	acute and chronic necrotizing pyelonephritis with multiple cortical abscesses
  Mechanism:	pyelonephritis leads to ischemia + low O2 tension with anaerobic metabolism; facultative anaerobe organisms form CO2 with fermentation of necrotic tissue / tissue glucose
  Predisposed:	immunocompromised patients, esp. diabetics (in 87 97% of cases); ureteral obstruction (in 20 40%)
  Average age:	54 years; M:F = 1:2
  May be associated with:	XGP

• features of acute severe pyelonephritis (chills, fever, flank pain, lethargy, confusion) not responding to Rx

• positive blood + urine cultures (in majority)

• urosepsis, shock

• fever of unknown origin + NO localizing signs in 18%

• multiple associated medical problems: uncontrolled hyperglycemia, acidosis, dehydration, electrolyte imbalance

  Location:

  in 5 7% bilateral

• Type I (33%):

  • streaky / mottled gas in interstitium of renal parenchyma radiating from medulla to cortex

  • crescent of subcapsular / perinephric gas

  • NO fluid collection (= no effective immune response)

    Prognosis:

    69% mortality

• Type II (66%):

  • bubbly / loculated intrarenal gas (infers presence of abscess)

  • renal / perirenal fluid collection

  • gas within collecting system (85%)

    Prognosis:

    18% mortality

• parenchymal destruction

• absent / decreased contrast excretion (due to compromised renal function)

• US:

  • high-amplitude echoes within renal sinus / renal parenchyma associated with dirty shadowing / comet tail reverberations

    CAVE:	(1) kidney may be completely obscured by large amount of gas in perinephric space (DDx: surrounding bowel gas)
    	(2) gas may be confused with renal calculi

• CT (most reliable + sensitive modality):

  • mottled areas of low attenuation extending radially along the pyramids

  P.953

  
  

  • extensive involvement of kidney + perinephric space

  • air extending through Gerota's fascia into retroperitoneal space

  • occasionally gas in renal veins

• MR:

  • signal void on T1WI + T2WI (DDx: renal calculi, rapidly flowing blood)

    Mortality:	60 75% under antibiotic Rx; 21 29% after antibiotic Rx + nephrectomy; 80% with extension into perirenal space
    Rx:	antibiotic therapy + nephrectomy; drainage procedure with coexisting obstruction
    DDx:	emphysematous pyelitis (gas in collecting system but not in parenchyma, diabetes in 50%, less grave prognosis)

Fungal Pyelonephritis

Organism:	Candida, Aspergillus, Mucor, Coccidioides, Cryptococcus, Actinomyces, Nocardia, Torulopsis
At risk:	diabetes, drug addiction, leukemia, immunosuppression, debilitation

• pyelonephritis, papillary necrosis, renal abscess

• fungus ball

Xanthogranulomatous Pyelonephritis

• = chronic suppurative granulomatous infection in chronic renal obstruction (calculus, stricture, carcinoma) arising from an abnormal host response to bacterial infection

  Incidence:	681,000 surgically proven cases of chronic pyelonephritis
  Organism:	Proteus mirabilis, E. coli, S. aureus
  Path:	replacement of corticomedullary junction with soft yellow nodules; calyces filled with pus and debris
  Histo:	diffuse infiltration by plasma cells + histiocytes + lipid-laden macrophages (xanthoma cells)
  Pathophysiology:	infection of renal pelvis, which the host is unable to eradicate; macrophages become enlarged with undigested bacteria gradually replacing the renal parenchyma + perinephric space
  Peak age:	45 65 years; all ages affected, may occur in infants; M:F = 1:3 1:4

• pyuria (95%)

• flank pain (80%)

• fever (70%)

• palpable mass (50%)

• weight loss (50%)

• microscopic hematuria (50%)

• elevated ESR

• reversible elevated liver function tests (50%) caused by inflammation in portal triads

• Symptomatic for 6 months prior to diagnosis in 40%!

• DIFFUSE XGP (83 90%)

• SEGMENTAL / FOCAL XGP (10 17%)

  • = tumefactive form due to obstructed single infundibulum / one moiety of duplex system

    DDx:

    renal cell carcinoma

  • kidney globally enlarged (smooth contour uncommon) / focal renal mass (less frequent)

  • contracted pelvis with dilated calyces

  • totally absent / focally absent nephrogram (80%)

  • centrally obstructing calculus:

    • staghorn calculus in 75%

  • extension of inflammation into perirenal space, pararenal space, ipsilateral psoas muscle, colon, spleen, diaphragm, posterior abdominal wall, skin

  • Retrograde:

    • complete obstruction at ureteropelvic junction / infundibulum / proximal ureter

    • contracted renal pelvis, dilated deformed calyces + nodular filling defects

    • irregular parenchymal masses with cavitation

  • CT:

    • low-attenuation fatty masses replacing renal parenchyma (= replacement fibrolipomatosis with attenuation values of less than water)

  • US:

    • hypoechoic dilated calyces with echogenic rim

    • hypoechoic masses frequently with low-level internal echoes replacing renal parenchyma

    • loss of corticomedullary junction

    • parenchymal calcifications are uncommon

  • Angio:

    • stretching of segmental / interlobar arteries around large avascular masses

    • hypervascularity / blush around periphery of masses in late arterial phase (= granulation tissue)

    • venous encasement + occlusion

      DDx:	hydronephrosis, avascular tumor
      Rx:	nephrectomy

Pyeloureteritis Cystica

• = hyperplastic transitional epithelial cell collections projecting into ureteral lumen

• Indicative of past / present urinary tract infection!

  Cause:	chronic urinary tract irritant (stone / infection)
  Histo:	numerous small submucosal epithelial-lined cysts representing cystic degeneration of epithelial cell nests within lamina propria (cell nests of von Brunn) formed by downward proliferation of buds of surface epithelium that have become detached from the mucosa
  Organism:	E. coli > M. tuberculosis, Enterococcus, Proteus, schistosomiasis
  Predisposed:	diabetics
  Age:	6th decade; more prevalent in women

• no specific symptoms; hematuria

  Location:

  bladder >> proximal 1/3 of ureter > ureteropelvic junction; unilateral >> bilateral

• multiple small round smooth lucent filling defects of 1 3 mm in size; scattered discrete / clustered

• persist unchanged for years in spite of antibiotic therapy

  Cx:	increased incidence of transitional cell carcinoma
  DDx:	(1) Spreading / multifocal TCC
  	(2) Vascular ureteral notching
  	(3) Multiple blood clots
  	(4) Multiple polyps
  	(5) Allergic urticaria of mucosa
  	(6) Submucosal hemorrhage (eg, anticoagulation)

P.954

Pyonephrosis

• = presence of pus in dilated collecting system (= infected hydronephrosis)

  Path:	purulent exudate composed of sloughed urothelium + inflammatory cells from early formation of microabscesses + necrotizing papillitis
  Organism:	most commonly E. coli

• US:

  • dispersed / dependent internal echoes within dilated pelvicaliceal system

  • shifting urine-debris level

  • dense peripheral echoes in nondependent location + shadowing (gas from infection)

    Cx:	(1) Renal microabscesses + necrotizing papillitis
    	(2) XGP
    	(3) Renal / perinephric abscess
    	(4) Fistula to duodenum, colon, pleura

Radiation Nephritis

Histo:	interstitial fibrosis, tubule atrophy, glomerular sclerosis, sclerosis of arteries of all sizes, hyalinization of afferent arterioles, thickening of renal capsule
Threshold dose:	2,300 rads over 5 weeks

• clinically resembling chronic glomerulonephritis

• normal / small smooth kidney consistent with radiation field

• parenchymal thickness diminished (globally / focally; related to radiation field)

• diminished nephrographic density

Reflux Atrophy

Cause:

increased hydrostatic pressure of pelvicaliceal urine with atrophy of nephrons secondary to long-standing vesicoureteral reflux

• small smooth kidney with loss of parenchymal thickness

• widened collecting system with effaced papillae

• longitudinal striations from redundant mucosa when collecting system is collapsed

• Do NOT confuse with reflux nephropathy!

Reflux Nephropathy

• = CHRONIC ATROPHIC PYELONEPHRITIS

• = ascending bacterial urinary tract infection secondary to reflux of infected urine from lower tract + tubulointerstitial inflammation in childhood (hardly ever endangers adult kidney); most common cause of small scarred kidney

  Etiology:

  3 essential elements:

  • Infected urine

  • Vesicoureteral reflux

  • Intrarenal reflux

    Age:

    usually young adults (subclinical diagnosis starting in childhood); M < F

• fever, flank pain, frequency, dysuria

• hypertension, renal failure

• may have no history of significant symptoms

  Site:

  predominantly affecting poles of kidneys secondary to presence of compound calyces having distorted papillary ducts of Bellini (= papillae with gaping openings instead of slitlike openings of interpolar papillae)

• normal / small kidney; uni- / bilateral; uni- / multifocal

• focal parenchymal thinning with contour depression in upper / lower pole (more compound papillae in upper pole), scar formation only up to age 4

• retracted papilla with clubbed calyx subjacent to scar

• contralateral / focal compensatory hypertrophy (= renal pseudotumor)

• dilated ureters (secondary to reflux) sometimes with linear striations (redundant / edematous mucosa)

• US:

  • focally increased echogenicity within cortex (scar)

• Angio:

  • small tortuous intrarenal arteries, pruning of intrarenal vessels

  • vascular stenoses, occlusion, aneurysms

  • inhomogeneous nephrographic phase

• NUC (Tc-99m glucoheptonate / DMSA with SPECT most sensitive method):

  • focal / multifocal photon-deficient areas

    Cx:	(1) Hypertension
    	(2) Obstetric complications
    	(3) Renal failure

Renal / Perirenal Abscess

• = usually complication of renal inflammation with liquefactive necrosis; 2% of all renal masses

• Pathway of infection:

  • ascending (80%): associated with obstruction (UPJ, ureter, calculus)

    Organism:

    E. coli, Proteus

  • hematogenous (20%): infection from skin, teeth, lung, tonsils, endocarditis, intravenous drug abuse

    Organism:	staphylococcus aureus
    Predisposed:	diabetics (twice as frequent compared with nondiabetics)

• positive urine culture in 33%

• positive blood culture in 50%

• pyuria, hematuria (absent if abscess isolated within parenchyma)

Renal Abscess

• may have negative urine analysis / culture (in up to 20%)

• IVP:

  • focal mass displacing collecting system

• CT:

  • hypoattenuating irregular / sharply defined focal renal mass:

    • thick enhancing wall / pseudocapsule

    • no enhancement of center of abscess

    • presence of gas

  • thickened septa + Gerota fascia

  • perinephric fat obliteration

• US:

  • slightly hypoechoic (early), hypo- to anechoic (late) mass with irregular margins + increased through-transmission septations microbubbles of gas

• NUC (Ga-67 citrate / In-111 leukocytes):

  • hot spot

    DDx:

    cystic renal cell carcinoma

P.955

Carbuncle

• = multiple coalescent intrarenal abscesses

• Term should not be used in radiology reports!

Perinephric Abscess

• Cause:

  • acute pyelonephritis with extension of renal abscess through capsule

  • from adjacent retroperitoneal infection (eg, perforation of colon cancer, psoas abscess)

  • deep penetration from SQ abscess

  • hematogenous spread

    Predisposed:	diabetics (in 30%), urolithiasis, septic emboli
    Organism:	in up to 30% different from abscess

• 14 75% of patients with perinephric abscess have diabetes mellitus!

• loss of psoas margin / obscuration of renal contour

• renal displacement

• focal renal mass

• scoliosis concave to involved side

• respiratory immobility of kidney = renal fixation

• occasionally gas in renal fossa

• unilateral impaired excretion

• pleural effusion

Renal Adenoma

• Small adenoma <3 cm should be considered a renal cell carcinoma of low metastatic potential = borderline renal cell carcinoma!

  Incidence:	in 7 15 23% of adults (autopsies); most common cortical lesion; increasing with age (in 10% of patients >80 years of age); increased frequency in tobacco users + patients on long-term dialysis
  Age:	usually >30 years; M:F = 3:1

• Types:

  • Papillary / cystadenoma (38%)

  • Tubular adenoma (38%)

  • Mixed type adenoma (21%)

  • Alveolar adenoma (3%) = precursor of RCC

• solitary in 75%, multiple in 25%

• usually <3 cm in size; subcapsular cortical location

• impossible to differentiate from renal cell carcinoma

  Cx:	premalignant / potentially malignant
  Prognosis:	average growth rate of 0.4 (range, 0.2 3.5) cm/year; tumors growing <0.25 cm/year rarely metastasize; tumors growing >0.6 cm/year frequently metastasize

Renal Agenesis

• Mechanism:

  • formation failure

    • = failure of ureteral bud to form

    • hemitrigone = absence of ipsilateral trigone + ureteral orifice

  • induction failure

    • = failure of growing ureteral bud to induce metanephric tissue

    • blind-ending ureter

Unilateral Renal Agenesis

Incidence:	1:600 1,000 pregnancies; M:F = 1.8:1
Risk of recurrence:	4.5%

• Often coexisting with other anomalies:

  • Genital abnormalities:

    • in male (10 15%): hypoplasia or agenesis of testis / vas deferens, seminal vesicle cyst (Zinner syndrome)

    • in female (25 50%): unicornuate / bicornuate / hypoplastic / absent uterus, absent / aplastic vagina

      • 90% of women with renal agenesis have uterine anomalies

      • 30 40% of women with uterine anomalies have renal agenesis

  • Turner syndrome, trisomy, Fanconi anemia, Laurence-Moon-Biedl syndrome

  Location:

  L > R

• visualization of single kidney (DDx: additional kidney in ectopic location)

• absent adrenal gland (11%)

• absent / rudimentary renal vessels

• colon occupies renal fossa

• compensatory contralateral renal hypertrophy (50%)

Bilateral Renal Agenesis

• = Potter syndrome

  Incidence:	1:3,000 to 1:10,000 pregnancies; M:F = 2.5:1
  Risk of recurrence:	<1%

• Potter's facies = low-set ears, redundant skin, parrot-beaked nose, receding chin

• US sensitivity is ONLY 69 73% due to decreased visualization from oligohydramnios + discoid-shaped adrenal glands simulating kidneys!

• severe oligohydramnios (after 14 weeks MA)

• bilateral absence of kidneys (after 12 weeks), ureters, renal arteries

• inability to visualize renal arteries by color duplex

• inability to visualize urine in fetal bladder (after 13 weeks) = bladder agenesis / hypoplasia; negative furosemide test (20 60 mg IV) not diagnostic (fetuses with severe IUGR may not be capable of diuresis)

• flattened discoid shape of adrenals (due to absence of pressure by kidney)

• bell-shaped thorax (pulmonary hypoplasia) in mid to late 3rd trimester

• compression deformities of extremities = clubfoot, flexion contractures, joint dislocations (eg, hip)

  Prognosis:	stillbirths (24 38%); invariably fatal in the first days of life (pulmonary hypoplasia)
  DDx:	functional cause of in utero renal failure (eg, severe IUGR)

Potter Sequence

• = hypoplasia of lungs, bowing of legs, broad hands, loose skin, growth retardation associated with long-standing severe oligohydramnios

  Cause:

  renal agenesis, urethral obstruction, prolonged rupture of membranes, severe IUGR

P.956

Renal Artery Stenosis

Prevalence:

1 2 4% of hypertensive individuals; 4.3 % of autopsies; 10% of hypertensive individuals with coronary artery disease; 25% of patients with hypertension that is difficult to control; in 45% of patients with malignant hypertension; in 45% of patients with peripheral vascular disease

• Cause:

  • Atherosclerosis (60 90%) mostly in proximal 2 cm of main renal artery

    • Any of multiple renal arteries (occurring in 14 28% of the population) may be affected!

  • Fibromuscular dysplasia (10 30%)

  • Others (<10%): thromboembolic disease, arterial dissection, infrarenal aortic aneurysm, arteriovenous fistula, vasculitis (Buerger disease, Takayasu disease, polyarteritis nodosa, postradiation), neurofibromatosis, retroperitoneal fibrosis

• Pathophysiology:

  • decreased perfusion pressure of glomeruli stimulates production of renin in juxtaglomerular apparatus + angiotensin II in kidney; renin converts circulating angiotensinogen ( ₂-globulin) into angiotensin I, sub-sequently converted by angiotensin-converting enzyme (ACE present in vascular endothelium) into angiotensin II, which releases aldosterone; aldosterone increases salt + water retention; angiotensin II + aldosterone vasoconstrict vessels (especially intraglomerular efferent arteriole to maintain filtration pressure)

  • ACE inhibition may impair overall renal function due to disruption of autoregulatory mechanism of GFR (with renal artery stenosis in both kidneys / solitary kidney)

• Renin production stimuli:

  • baroreceptors in the afferent glomerular arteriole sense a decreased stretching of arteriolar wall with diminished blood flow

  • chemoreceptors of the macula densa located in first part of the distal tubule sense a decreased amount of sodium and chloride (which have been largely reabsorbed due to a low GFR)

    Histo:

    tubular atrophy and shrinkage of glomeruli

• abdominal / flank pain

• hematuria

• oliguria, anuria

• hypertension (= renin-mediated hypertension in response to ischemia)

• low urine sodium concentration

• Hemodynamic significance determined by:

  • elevated renin levels in ipsilateral renal vein 1.5:1

  • presence of collateral vessels

  • greater than 70% stenosis with poststenotic dilatation

  • transstenotic pressure gradient 40 mm Hg

  • decrease in renal size

  • 15 20% of patients remain hypertensive after restoration of normal renal blood flow (= renal artery stenosis without renovascular hypertension)!

• Patient selection criteria for screening test

  • = clinical signs associated with moderate-to-high risk of renovascular hypertension (HTN):

    • Abrupt onset or severe HTN

    • HTN resistant to 3-drug therapy in compliant patient

    • Abdominal / flank bruits

    • Unexplained azotemia in elderly patient with HTN

    • Worsening renal function during antihypertensive therapy, especially with ACEIs

    • Grade 3 / 4 hypertensive retinopathy

    • Occlusive disease in other vascular beds

    • Onset of HTN <30 years or >55 years of age

    • Recurrent pulmonary edema in elderly patient with HTN

    • HTN in infants with an umbilical artery catheter

    • HTN in children

• normal / decreased renal size (R 2 cm < L; L 1.5 cm < R) with smooth contour

• vascular calcifications (aneurysm / atherosclerosis)

• IVP (60% true-positive rate, 22% false-negative rate):

  • delayed appearance of contrast material (decreased glomerular filtration)

  • increased density of contrast material (increased water reabsorption)

  • delayed washout of contrast material (prolonged urine transit time)

  • lack of distension of collecting system

  • global attenuation of contrast density; urogram may be normal with adequate collateral circulation

  • notching of proximal ureter (enlargement of collateral vessels)

• CT:

  • prolongation of cortical nephrographic phase + persistent corticomedullary differentiation

  • CT angiography (2 3-mm collimation, pitch 1.5 2.0): specificity of real-time interactive volume rendering > maximum-intensity projection > shaded-surface display

• MRA (>95% sensitive, >90% specific):

  • tendency to overestimate stenosis

  • Limitations:

    • evaluation of branch vessels

    • presence of metallic stent

    • detection of accessory arteries

    • evaluation of small renal arteries

• Angiography:

  • conventional angiography = gold standard test

  • intravenous digital subtraction angiography:

    • does not address hemodynamic significance

• NUC:

  • ACE inhibitor scintigraphy (51 96% sensitive, 80 93% specific)

• Duplex US:

  • direct signs = visualization of renal artery stenosis

    • peak systolic velocity >150 cm/sec for angles <60 or 180 cm/sec for angles >70 (with many false positives due to suboptimal Doppler angles)

    • ratio of peak renal artery velocity to peak aortic center stream velocity >3.5 (for >60% stenosis; 0 91% sensitive, 37 97% specific)

    • poststenotic spectral broadening flow reversal

    • absence of blood flow during diastole (for >50% stenosis)

    • no detectable Doppler signal with good visualization of renal artery (= arterial occlusion)

      P.957

      
      

      

      Variants of Normal Renal Artery Doppler Waveforms

      Type A: early systolic peak (ESP) at the end of the early rise

      Type B: no peak but rise remains straight

      Type C: abnormal spectra with slowed rise time

      AT = acceleration time; V = velocity difference between ESP velocity and late diastolic velocity; ESP = early systolic peak;

      LSP = late systolic peak; acceleration index (AI) = V/AT

      • Problems:

        • technically inadequate examination (gas, corpulence, respiratory motion) in 6 49%; usually limited to children + thin adults

        • multiple renal arteries in 16 28%

        • false tracings from large collateral vessels / reconstituted segments of main renal artery

        • need to visualize entire length of renal artery

        • transmitted cardiac / aortic pulsations obscure renal artery waveform recordings

  • indirect signs = analysis of intrarenal arterial Doppler waveforms

    • pattern recognition

      • dampened appearance = tardus-parvus pulse (tardus = late arrival, parvus = attenuated peak)

      • loss of early systolic peak (not necessarily abnormal!)

      • segmental arterial flow detectable with renal artery occlusion (due to collateral circulation)

    • quantitative criteria

      • acceleration index of <370 470 cm/s² = V/ T = tangential inclination of Doppler waveform in early systole (single most sensitive screening parameter)

        Duplex Results for >60% Renal Artery Stenosis:

        	Sensitivity	Specifi city	Accuracy
        AT 0.07 s	81%	95%	91%
        AI < 300 cm/s2	89%	86%	87%
        Absent ESP	92%	96%	95%

      • delay in acceleration / pulse rise time of >0.05 0.08 seconds = gradual slope of Doppler waveform during early systole

      • RI >5% between both kidneys (82% sensitive + 92% specific for stenosis >50%, 100% sensitive + 94% specific for stenosis 60%)

      • RI <0.56

      • attenuated (= parvus) Doppler waveform amplitude = decrease in peak systolic velocity to <20 30 cm/s

        Problems:	technically inadequate examination in 0 2%
        False-negative US:	stenosis in accessory renal artery
        False-positive US:	coarctation

Arteriosclerotic Renal Artery Disease

Incidence:	in up to 6% of hypertensive patients; most common cause of secondary hypertension
Age:	>50 years; M > F
Path:	lesion primarily involving intima

• worsening of preexistent hypertension

• abrupt onset of severe hypertension >180/110 mm Hg

• vascular bruit in 40 50% (present in 20% of hypertensive patients without renal artery stenosis)

Associated with:	severe arteriosclerosis of aorta, cerebral, coronary, peripheral arteries
Location:	main renal artery (93%) + additional stenosis of renal artery branch (7%); bilateral in 31%

• eccentric stenosis in proximal 2 cm of renal artery, frequently involving orifice

• decrease in renal length over time (= high-grade renal artery stenosis with risk for occlusion)

  Prognosis:	progression of atherosclerotic lesion (40 45%) to renal atrophy, arterial occlusion, ischemic renal failure
  Cx:	azotemia with
  	(a) bilateral renal artery stenoses
  	(b) unilateral renal artery stenosis + poorly functioning contralateral kidney
  Reversible azotemia may be induced by treatment with angiotensin-converting enzyme inhibitors / sodium nitroprusside!
  Rx:	(1) Three-step antihypertensive therapy (control of hypertension difficult)
  	(2) Angiotensin-converting enzyme inhibitors (eg, captopril PO, enalaprilat IV)
  	(3) Renal artery angioplasty (80% success for nonostial lesion, 25 30% for ostial lesion)
  	(4) Surgical revascularization (80 90% success for any lesion location)
  	hypertension improved in 66%
  	improvement / stabilization of renal function in 27 80%

Fibromuscular Dysplasia of Renal Artery

Incidence:	35% of renal artery stenoses; 1,100 patients reported (by 1982) with involvement of renal artery in 60% + extracranial carotid artery in 30%; 25% of all cases of renovascular hypertension
Age:	most common cause of renovascular hypertension in children + young adults <30 40 years; M:F = 1:3
Associated with:	fibromuscular dysplasia of other aortic branches in 1 2%: celiac a., hepatic a., splenic a., mesenteric a., iliac a., internal carotid a.

P.958

• hypertension

• progressive renal insufficiency

  Sites:

  mid and distal main renal artery (79%), renal artery branches (4%), combination (17%); proximal third of main renal artery spared in 98%; bilateral in 2/3; R:L = 4:1

  • Types:

    • Intimal fibroplasia = intimal hyperplasia

      • narrow annular radiolucent band in main renal artery + major segmental branches; often bilateral

      • poststenotic fusiform dilatation

    • Medial fibroplasia with microaneurysm

      • string-of-beads sign = alternating areas of stenoses + aneurysms in mid + distal renal artery + branches; usually bilateral

    • Medial / fibromuscular hyperplasia

      • long smooth tubular narrowing of main renal artery and branches

    • Perimedial fibroplasia

      • beading without aneurysm formation of distal (mostly right) main renal artery

    • Medial dissection

      • false channel in main renal artery + branches

    • Adventitial fibroplasia

      • long segmental stenosis of main renal artery + large branches

        Prognosis:	progression of lesions in 20% causing decline in renal function
        Cx:	(1) Giant aneurysm
        	(2) AV fistula between renal artery + vein (in medial fibroplasia)
        Rx:	(1) Resection of diseased segment with end-to-end anastomosis
        	(2) Replacement by autogenous vein graft, excision + repair by patch angioplasty
        	(3) Transluminal balloon angioplasty (90% success rate with very low restenosis rate)

Neurofibromatosis

• Hypertension in neurofibromatosis due to:

  • Pheochromocytoma

  • Renal artery stenosis

• Renal artery involvement mainly seen in children!

• Types:

  • mesodermal dysplasia of arterial wall with fibrous transformation (common)

  • narrowing of main renal artery by periarterial neurofibroma (rare)

• saccular funnel-shaped aneurysm involving aorta / main renal artery

• smooth / nodular stenosis (mural / adventitial neurofibroma) in proximal renal artery

• intrarenal aneurysm (rare)

  DDx:

  fibromuscular dysplasia; congenital renal artery stenosis

Renal Cell Carcinoma

• = RCC = RENAL ADENOCARCINOMA = HYPERNEPHROMA

  Incidence:	80 90% of all renal malignant primaries in adults; 2% of all visceral cancers (frequency approximates ovarian cancer, gastric cancer, pancreatic cancer, leukemia); 31,200 new RCCs in the USA diagnosed in 2000
  Age:	6th 7th decade (generally >40 years); median age of 55 years; 2% occur in children in first 2 decades of life; M:F = 1.6:1; frequency increasing with age
  Path:	arises from proximal tubular cells; 30% found incidentally with imaging;

  • Tumor growth pattern:

    • papillary (5 15%, best prognosis); trabecular / tubular / cystic / solid (poorer prognosis)

• Histo subtypes:

  • clear cell (70 80%) = rich in cytoplasmic glycogen + lipid content, which wash away during histologic preparation

  • papillary (10 15%)

  • chromophobe (5%)

  • sarcomatoid (1.5%)

• Predisposed:

  • von Hippel-Lindau syndrome (10 25%): multiple often small intracystic tumors (hemangioblastoma, retinal angioma, renal cysts) manifesting at a young age

  • Hemodialysis (in 1.4 2.6%)

  • Acquired cystic disease of uremia (3.3 6.1%; 7 increased risk)

  • Tobacco; phenacetin abuse

• Staging:

  Staging accuracy:	84 91% for CT82 96% for MRpoor for US
  Regional extension:	into lymph nodes (9 23%);into main renal vein (21 35%);into IVC (4 10%)

  Staging Classifi cation for Renal Cell Carcinoma

  Robson Stage	TNM Class
  I		tumor confi ned within renal capsule sharply defi ned convex interface with perirenal fat
  	T1	tumor <7 cm
  	T2	tumor 7 cm
  II	T3	extension into perinephric fat but confi ned to Gerota fascia irregular interface between tumor + fat
  III A		extension into renal vein or IVC
  	T3b	renal vein only
  	T3c	infradiaphragmatic IVC
  	T4b	supradiaphragmatic IVC
  III B	N	regional lymph nodes metastases
  III C		extension into renal vein + lymph nodes
  IV A	T4a	invasion of adjacent organs (other than ipsilateral adrenal)
  IV B	M	distant metastases

  P.959

  
  

  Multiple RCC:

  commonly in von Hippel-Lindau syndrome; hereditary RCC; sporadic in 4 15%; bilateral in 1 3%

• Metastases:

  • bone pain, cough, hemoptysis (as initial symptoms of metastatic disease present in 9%)

  • 28% of patients have clinically apparent multiple distant metastases at presentation!

  • tumor metastases tend to be hypervascular

• Spread to:

  • lung (55%); lymph nodes (34%); liver (33%); bone (32%); adrenals (4.3 19%); contralateral kidney (11%); brain (6%); heart (5%); spleen (5%); bowel (4%); skin (3%); ureter (rare)

• Incidence of metastatic disease:

  (a)tumors	<3 cm:	2.6%
  (b) tumors	3 5 cm:	15.4%
  (c) tumors	>5 cm:	78.6%

• hematuria (56%), flank pain (36%), weight loss (27%), fever (11 15%)

• classic triad of flank pain + gross hematuria + palpable renal mass (4 9%)

• varicocele (2%)

• normochromic normocytic anemia (28 40%)

• Stauffer syndrome (15%) = nephrogenic hepatopathy = hepatosplenomegaly + abnormal liver function in absence of hepatic metastases (? tumor hepatotoxin)

• Paraneoplastic syndromes: erythrocytosis (2%); hypercalcemia (parathormone, prostaglandin, vitamin D metabolites)

• well-marginated often lobulated solitary mass:

  • focal bulge in renal contour

  • enlargement of affected part of kidney

• calcification (15 20%): usually central + amorphous or peripheral + curvilinear in cystic RCC

• extrinsic compression / displacement / invasion of renal pelvis + calyces

• cysts:

  • cystic necrotic tumor (40%)

  • cystadenocarcinoma (2 5%)

  • renal cell carcinoma in wall of cyst (3%)

• tumor growth into renal vein / IVC (in up to 16%) conveys poor prognosis

• infiltrative growth pattern (6%) with ill-defined margin

• IVP:

  • diminished function (parenchymal replacement, hydronephrosis)

  • absence of contrast excretion (renal vein occlusion)

  • pyelotumoral backflow = necrotic part of tumor fills with contrast material

• NECT:

  • homogeneous (if 3 cm) solid lesion of >20 HU

  • heterogeneous mass (if >3 cm) due to hemorrhage / necrosis

  • calcifications in up to 30%

  • perinephric fat stranding (50%) due to edema, vascular engorgement, previous inflammation, tumor invasion

• CECT:

  • mostly heterogeneous enhancement (due to cystic areas or necrosis):

    • enhancement of >12 HU compared with NECT

  • enhancing nodule in perinephric space (46% sensitive for perinephric spread)

  • renal vein thrombus (92% PPV, 97% NPV):

    • low-attenuation filling defect in corticomedullary phase (most specific sign)

    • abrupt change in caliber of vein

    • presence of collateral veins

    • heterogeneous enhancement of malignant thrombus

  • subcapsular / perinephric hemorrhage

  • nodal enlargement of >1 cm (4% FN) (DDx: benign inflammation as reactive immune response in >50%)

  • False negatives in corticomedullary phase:

    • in a small tumor may enhance to the same degree as renal parenchyma

    • centrally located tumor mistaken for medulla

• US:

  • hyperechoic (50 61%), mostly in small tumors <3 cm (78%), occasionally in large tumors (32%):

    • markedly hyperechoic, ie, isoechoic to renal sinus fat in 4 12% of small tumors (DDx: angiomyolipoma)

    • anechoic rim (in 84% of small hyperechoic RCCs), probably due to pseudocapsule of compressed renal tissue (NOT seen in angiomyolipoma)

  • isoechoic (30 86%) / hypoechoic (10 12%), mostly in larger tumors

  • cystic lesion with increase in acoustic transmission (2 13%) due to extensive liquefaction necrosis (DDx: complicated cyst)

  • inhomogeneity due to hemorrhage, necrosis, cystic degeneration

• MR (best modality to assess stage III + IV disease):

  • hyper- / iso- (most) / hypointense relative to renal parenchyma:

    • often low to medium signal intensity on T1WI

    • areas hyperintense on T1WI + hypointense on T2WI are usually due to hemorrhage

  • heterogeneous signal intensity on T2WI

  • mild decrease in signal intensity on opposed-phase images indicates minimal diffuse intracellular lipid (for the most frequent subtype of clear cell carcinoma)

  • imaging at 2 to 5 minutes post contrast injection is critical for the detection of small renal mass (less enhancement than in normal renal tissue)

• Angio:

  • typically hypervascular (95%) with puddling of contrast + occasional AV shunting

  • enlarged tortuous poorly tapering feeding vessels

  • coarse neovascularity + formation of small aneurysms

  • parasitization of lumbar, adrenal, subcostal, mesenteric artery branches

  • poorly defined tumor margins

• Prognosis:

  • Tumor stage + histologic grade are the most important prognosticators!

    • 5-year survival rates for stages I, II, III, IV are 85 100%, 45 65%, 20 40%, 0 10%;

    • 10-year survival rates for stages I, II, III, IV are 56%, 28%, 20%, 3%

    • 4% 3-year survival rate if untreated

    P.960

    
    

    • papillary carcinomas have a better prognosis than nonpapillary carcinomas!

    • clear cell + granular cell cancers have a better prognosis than spindle cell + anaplastic cancers

      Recurrence:

      in 11% after 10 years

• Rx:

  • Radical nephrectomy (2 5% operative mortality)

  • Nephron-sparing surgery (partial nephrectomy) with solitary functioning kidney, compromised renal function, multiple bilateral tumors, small RCC (<4 cm in diameter, polar, cortical, far from renal hilum / collecting system)

Cystic Renal Cell Carcinoma

• UNILOCULAR CYSTIC RCC (50%)

  • = extensive necrosis of a previously solid RCC / intrinsic cystic growth of a cystadenocarcinoma

  • fluid-filled mass without criteria of a renal cyst

• MULTILOCULAR RCC (30%)

  • = intrinsic multilocular growth

  • impossible to distinguish from multilocular cystic nephroma

• MURAL NODULE IN CYSTIC RCC (20%)

  • asymmetric cystic tumor necrosis

  • tumor arising in wall of preexisting cyst

  • tubular dilatation with secondary cyst formation from tumor obstruction

Papillary Renal Cell Carcinoma

Incidence:	5 15% of all RCC
Age:	40 50 years
Path:	cystic necrosis + degeneration frequent; familial form associated with trisomy 17
Histo:	cells surrounding fronds of fibrovascular stroma; macrophages infiltrating the papillary stalks

• slow growing well-encapsulated tumor

• peripheral calcification frequent

• usually hypovascular

• little / no contrast enhancement

• frequently hypoechoic mass

Prognosis:

favorable (metastasize late)

Renal Cell Carcinoma in Childhood

Incidence:	7% of all primary renal tumors during first 2 decades of life;
	in childhood:	Wilms tumor:RCC = 30:1
	in 2nd decade:	Wilms tumor:RCC = 1:1
Mean age:	9 years

• palpable abdominal mass (60%)

• abdominal pain (50%)

• hematuria (30 60%)

• hypertension due to renin production

• polycythemia due to erythropoietin production

• bone resorption due to parathyroid hormone production

• Increased risk of renal cell carcinoma:

  • von Hippel-Lindau disease in 10 25% (cerebellar hemangioblastoma, retinal angioma, pancreatic cysts + tumors, pheochromocytoma, renal cysts + tumors)

Metastases (20%):	lung, bone, liver, brain
Cx:	intravascular extension (25%)
Prognosis:	64% overall survival rate
DDx:	Wilms tumor (younger age, larger at presentation, calcifications less frequent [9% versus 25%], less dense / homogeneous)

Renal Cyst

Simple Cortical Renal Cyst

• = acquired lesion possibly secondary to tubular obstruction; accounts for 62% of all renal masses

  Incidence:	in 1 2% of all urograms; in 3 5% of all autopsies
  Age:	peak incidence after age 30 years; increasing frequency with age (in 0.22% in pediatric age group, in 50% over age 50)
  Path:	low cuboidal / flattened epithelium surrounded by 1 2-mm-thick fibrous wall containing clear / slightly yellow serous fluid

• May be associated with:

  • tuberous sclerosis, von Hippel-Lindau disease, Caroli disease, neurofibromatosis

• large and unifocal when peripheral

• focal attenuation + displacement of collecting system

• focally replaced nephrogram with smooth margin

• beak / claw sign = effaced wedge of renal parenchyma

• delicate filamentous often undulating septa (10 15%)

• curvilinear calcification (1%) in wall / septa

• US (90 100% accuracy of US & CT):

  • spherical / ovoid in shape

  • anechoic without internal echoes

  • smooth clearly demarcated walls

  • acoustic enhancement beyond cyst

• CT:

  • near-water density lesion (<20 HU), thin wall, smooth interface with renal parenchyma, no enhancement

• MR:

  • most sensitive modality for cysts <10 mm

• Cystography:

  • smooth wall, clear aspirate with low lactic dehydrogenase, no fat content

Cx:	(1) Hemorrhage in 1 11.5%
	(2) Infection in 2.5%
	(3) Tumor within cyst in <1%

Atypical / Complicated Renal Cyst

Dx:	cyst puncture
DDx:	renal abscess, hematoma, renal artery aneurysm, cystic tumor
Rx:	surgery, aspiration, serial follow-up

Hemorrhagic Renal Cyst

Cause:

trauma, varices, bleeding diathesis

• rust-colored puttylike material

• uni- / multilocular cyst separated by thick septa

• thick fibrous calcified wall

• fibrin ball inside cyst (rare)

• CT:

  • increased density secondary to acute hemorrhage / high protein contents (= hyperattenuating cyst with approximately 60 90 HU)

  • no contrast enhancement

P.961




• MR:

  • usually iso- to hyperintense on T1WI (owing to methemoglobin) + hyperintense on T2WI (due to lysis of RBCs)

  • variable signal intensities (dependent on amount + acuity of hemorrhage, hemoglobin degradation product, degree of RBC lysis, protein content)

  • hematocrit effect (= RBCs settle to cyst bottom)

Infected Renal Cyst

Cause:	hematogenous dissemination of bacteria, ascending urinary tract infection
Mean age:	61 years; in 94% females

• history of no response to antibiotic Rx for acute pyelonephritis

• leukocyturia

• US:

  • thickened irregular cyst wall (22%)

  • internal septations (11%)

  • wall calcification (occasionally)

  • minute debris either diffusely / fluid-fluid level in dependent portion of cyst

  • amorphous solid conglomerates

  • round sharply marginated lesion

High-density Renal Cyst

• = cyst content 20 HU

• Proteinaceous content

• Hemorrhage

• Infection

• Calcification

• Communication with calyx

• Streak artifact

CT / MRI Features of Cystic Renal Lesions Bosniak Classifi cation

I	simple cyst	well-defi ned round mass of water attenuation hairline-thin imperceptible wall no enhancement
II	minimally complicated cystic lesion	cluster of cysts / septated cyst minimal curvilinear calcifi cation minimally irregular wall high-density content
IIF	follow-up lesion	hairline-thin septum / wall with perceived enhancement intrarenal lesion >3 cm with high-density content
III	complicated (surgical) lesion: hemorrhagic / infected cyst, MLCN, cystic neoplasm	irregular thickened septa measurable enhancement coarse irregular calcifi cation irregular margin multiloculated lesion uniform wall thickening nonenhancing nodular mass
IV	clearly malignant cystic lesion	large cystic / necrotic component irregular wall thickening solid enhancing elements

Differentiation of Renal Lesions by CT

CT Feature	Cyst	Neoplasm
Shape	round, oval	irregular
Margin	smooth	lobulated
Wall	thin, not measurable	thick
Interface	sharp, distinct	indistinct
Density	0-20 HU	>30 HU
Enhancement	<10 20 HU	>10 20 HU
Portal venous phase	<70 HU	>70HU
Vascular Invasion	none	yes

• Considered a Bosniak Class II lesion if:

  • 3 cm in size, partially exophytic, round, sharply marginated, homogeneous, nonenhancing

• An incidental renal mass with attenuation >70 HU during the portal venous phase is more likely a RCC than a high-density renal cyst!

Renal Sinus Cyst

• = PERIPELVIC / PARAPELVIC CYST = PARAPELVIC LYMPHANGIECTASIA = PARAPELVIC LYMPHATIC CYST

• = spherical fluid-filled masses intimately attached to renal pelvis without connection to pelvicaliceal system arising either from renal sinus or parenchyma

  Incidence:

  1.5% (autopsies); 4 6% of all renal cysts

• Etiology:

  • probably ectatic lymphatic channels from lymphatic obstruction;? posttraumatic extravasation of urine / blood;? protrusion of parenchymal cysts into sinus;? mesonephric remnant;? remnant of wolffian body;? outpouchings of renal pelvis;? duplication anomaly

    Age:

    mostly during 5th 6th decade

• almost always asymptomatic

• pain (from obstructive caliectasis)

• renal vascular hypertension (compression of renal aa.)

• clear straw-colored serous fluid

• soft-tissue density in renal sinus

• focal displacement + smooth effacement of collecting system

• stretching of collecting system when generalized (indistinguishable from sinus lipomatosis)

• rarely curvilinear calcification of cyst wall (4%)

• US:

  • anechoic mass(es) with acoustic enhancement, irregular shape

Cx:	obstructive caliectasis (rarely hydronephrosis)
Rx:	cyst ablation with 95% ethanol if symptomatic
DDx:	hydronephrosis

Renal Dysgenesis

• = undifferentiated tissue of renal anlage

• Pathologic NOT radiologic diagnosis

• renal vessels usually absent; occasionally small vascular channels

P.962

Renal Infarction

• Causes:

  • TRAUMA: blunt abdominal trauma with traumatic avulsion / occlusion of renal artery, penetrating vascular injury, surgery

  • EMBOLISM:

    • Cardiac: rheumatic heart disease with arrhythmia (atrial fibrillation), myocardial infarction, prosthetic valve, myocardial trauma, left atrial / mural thrombus, myocardial tumor, subacute bacterial endocarditis (septic emboli)

    • Catheters: angiographic catheter manipulation, transcatheter embolization, umbilical artery catheter above level of renal arteries

  • ARTERIAL THROMBOSIS:

    • arteriosclerosis, aneurysm or dissection of aorta / renal artery, thrombangitis obliterans, polyarteritis nodosa, syphilitic cardiovascular disease, sickle cell disease, paraneoplastic syndrome (Trousseau syndrome), hypercoagulable state

  • VASCULITIS

    • polyarteritis nodosa, SLE, drug-induced vasculitis

  • Sudden complete renal vein thrombosis

Acute Renal Infarction

• sudden onset of flank / back pain

• hematuria, proteinuria, fever, leukocytosis

• normal / large kidney with smooth contour

• normal / expanded parenchymal thickness

• normal / attenuated collecting system, often only opacified by retrograde pyelography

• absent / diminished nephrogram with cortical rim enhancement, rarely striations

• CT:

  • wedge-shaped area of absent enhancement

  • edematous enlargement of kidney (with large infarct)

  • cortical rim sign within several days after global infarction

• US:

  • diminished echogenicity (within <24 hours)

  • normal echogenicity (echoes appear within 7 days)

• NUC (SPECT imaging with Tc-99m DMSA):

  • photon-deficient area

Rx:

thrombolytic therapy, supportive hemodialysis, transcatheter thrombembolectomy, surgery

Lobar Renal Infarction

• EARLY SIGNS:

  • focal attenuation of collecting system (tissue swelling)

  • focally absent nephrogram (triangular with base at cortex)

• LATE SIGNS:

  • normal / small kidney(s)

  • focally wasted parenchyma with NORMAL interpapillary line (portion of lobe / whole lobe / several adjacent lobes)

• CT:

  • nonperfused area corresponding to vascular division

  • cortical rim sign (subacute) = thin rim of preserved subcapsular perfusion due to capsular perforators

• US:

  • focally increased echogenicity

Chronic Renal Infarction

Path:

all elements of kidney atrophied with replacement by interstitial fibrosis

• normal / small kidney with smooth contour

• globally wasted parenchyma

• diminished / absent contrast material density

• US:

  • increased echogenicity (by 17 days)

• Angio:

  • normal intrarenal venous architecture

  • late visualization of renal arteries on abdominal aortogram

Atheroembolic Renal Disease

• = dislodgment of multiple atheromatous emboli from the aorta into renal circulation (below level of arcuate arteries)

• normal / small kidneys with smooth contour or shallow depressions

• wasted parenchymal thickness

• diminished density of contrast material

• CT:

  • patchy nephrographic distribution

• Angio:

  • embolic occlusion

Arteriosclerotic Renal Disease

• = disseminated process involving most of the interlobar + arcuate arteries causing uniform shrinkage of kidney

  Age:

  generally over 60 years

• Accelerated development in:

  • scleroderma, polyarteritis nodosa, chronic tophaceous gout

• often associated with hypertension (nephrosclerosis)

• normal / small kidneys

• smooth contour with random shallow contour depressions (infarctions)

• uniform loss of cortical thickness

• normal / effaced collecting system (fat proliferation)

• increased pelvic radiolucency (vicarious sinus fat proliferation)

• calcification of medium-sized intrarenal arteries

• US:

  • increased echogenicity possible

  • increased size of renal sinus echoes (fatty replacement)

Nephrosclerosis

Histo:

thickening + hyalinization of afferent arterioles, proliferative endarteritis, necrotizing arteriolitis, necrotizing glomerulitis

• arterial hypertension

• (a) BENIGN NEPHROSCLEROSIS

• (b) MALIGNANT NEPHROSCLEROSIS (rapid deterioration of renal function)

• radiographic appearance similar to arteriosclerotic kidney

Renal Leiomyoma

• = capsuloma

  P.963

  
  

  Prevalence:	5% at autopsy (average size of 5 mm)
  Median age:	42 years; M < F
  Associated with:	tuberous sclerosis
  Path:	well-encapsulated solid mass with mean size of 12 cm containing hemorrhage (17%) / cystic degeneration (27%)
  Histo:	smooth muscle cells in a whorled arrangement
  Location:	53% subcapsular, 37% capsular, 10% attached to renal pelvis

• palpable mass (50%), hematuria (20%)

• well-circumscribed exophytic solid lesion cleavage plane between tumor and cortex

• dense calcifications

• Angio:

  • hypo- to hypervascular nonspecific mass

DDx:

renal leiomyosarcoma, adenocarcinoma

Renal Sarcoma

Frequency:	1% of malignant renal parenchymal tumors
Subtypes:	leiomyosarcoma (>50%), angiosarcoma, hemangiopericytoma, rhabdomyosarcoma, fibrosarcoma, osteosarcoma

• considerable variation in growth pattern:

  • expansile mass (most commonly)

  • infiltrative growth (rhabdomyosarcoma, angiosarcoma)

Dx:

by exclusion of sarcomatoid renal carcinoma + primary retroperitoneal sarcoma with direct extension into kidney

Renal Transplant

Frequency:

11,000 transplants per year in USA (1994)

• Complications in 10%:

  • Problematic period between 4 days and 3 weeks after surgery!

  • hypertension in 50% (from rejection / arterial stenosis)

Prognosis:

organ survival at 1 year in 80 95%; 13 24 years half-life for transplant from living related donor

Acute Tubular Necrosis in Renal Transplant

• = primary nonfunction within 72 hours of transplantation followed by improvement within a few days to 1 month

• Most common cause of delayed graft function

  Cause:	prolonged ischemia (cold ischemia time >24 30 hours), reperfusion injury
  	ATN more frequent in cadaveric than living-related donor transplant (donor hypotension)
  	ATN greater in transplants with more than one renal artery
  	ATN related to length of ischemic interval (prolonged organ storage)

• no constitutional symptoms

• elevated urine sodium

• oliguria may begin immediately after transplantation / may be delayed for several days

• US:

  • transient enlargement of transplant

  • transient increase in resistive index

• Scintigram:

  • normal / slightly decreased transplant perfusion:

    • delayed time from T_max to one-half maximal activity

  • decreased + delayed radiopharmaceutical uptake:

    • delayed transit time + delayed T_max

  • delayed / decreased / absent excretion of Tc-99m with parenchymal retention:

    • high 20-minute to 3-minute ratio

DDx:

acute rejection (serial renal studies help to differentiate)

Rejection of Renal Transplant

• Most common cause of parenchymal failure!

• Rejection occurs in all transplants to some degree!

Hyperacute Rejection of Renal Transplant (rare)

• = humeral rejection with preformed circulating antibodies present in recipient at time of transplantation, usually following retransplantation

  Path:	thrombosed arterioles + cortical necrosis
  Time of onset:	within minutes after transplantation

• complete absence of renal perfusion + renal function on Tc-99m DTPA scan (DDx: complete arterial / venous occlusion)

Rx:

requires immediate reoperation

Accelerated Acute Rejection of Renal Transplant

• = combination of antibody + cell-mediated rejection

Time of onset:

2 5 days after transplantation

Acute Rejection of Renal Transplant

• = cellular rejection predominantly dependent on cellular immunity

  Time of onset:	any time, typically within 5 days to 6 months; peak incidence at 2nd 5th week
  Prevalence:	in 50% at least 1 episode in 1st year

• Path:

  • acute interstitial rejection

    • = edema of interstitium with lymphocytic infiltration of capillaries + lymphatics

  • acute vascular rejection (rare)

    • = proliferative endovasculitis + vessel thrombosis

• malaise, fever, weight gain

• tenderness of transplant

• low urine sodium, increase in serum creatinine

• hypertension, oliguria

• US (30 50% negative predictive value):

  • increase in renal volume from edema:

    • decreased renal sinus fat + increased cortical thickness (most predictive)

  • conspicuous pyramids + decreased cortical echogenicity

  • thickening of pelvoinfundibular wall

  • diminished echogenicity of renal sinus fat

  Causes of Renal Allograft Dysfunction

  Immediate to 1st 48 hours	Day 2 to day 7
  1. Hyperacute rejectyion	1. ATN
  2. renal vein thrombosis	2. RVT
  3. Discordant sizer
  >1 week post-op	Delayed
  1. Acute rehjection	1. Chronic rejection
  2. ATN	2. Drug toxicity
  	3. Obstruction
  	4. Infection
  	5. Extrinsi compression

  P.964

  
  

  Renal Transplant Scintigram

  	Early study (<24 hours post transplantation)		Late study (>5 days post transplantation)
  	Flow	Excretion	Flow	Excretion
  Acute tubular necrosis	normal /		normal /
  Hyperacute rejection	absent	absent
  Acute rejection			worsening	worsening
  Chronic rejection

• Doppler US (higher accuracy than morphologic parameters):

  • initially decrease in resistive index (? autoregulatory mechanism)

  • increase in resistive index > 0.80 (with increasing severity of rejection)

    • 0.70 without any form of rejection (57% negative predictive value)

    • >0.90 (100% positive predictive value, 26% sensitivity)

  • reversal of diastolic flow

• NUC:

  • may show decreased renal perfusion + renal function

  • initially perfusion may be normal with only function decreased (DDx to ATN may not be possible on single study)

  • subsequent exams (1 3-day intervals) demonstrate decreasing renal perfusion

  • prolonged excretory phase

  • poor and inhomogeneous nephrogram

• Angio:

  • rapid tapering + pruning of interlobar arteries

  • multiple stenoses + occlusions

  • nonvisualization of interlobular arteries

  • prolonged arterial opacification (normally <2 s)

DDx:

acute tubular necrosis (develops within first few days)

Chronic Rejection of Renal Transplant

• = slow relentless progressive process resulting in interstitial scarring

• Most common cause of late graft loss

  Histo:	endothelial proliferation in small arteries + arterioles; interstitial cellular infiltration + fibrosis; tubular atrophy; glomerular lesions (? recurrence of patient's original glomerulonephritis)
  Time of onset:	months to years after transplantation

• progressive decline of renal function

• small kidney with thin cortex

• diminished number of intrarenal vessels

• vascular pruning / stenoses / occlusions

• mild hydronephrosis

• NUC:

  • diminished uptake of radiopharmaceuticals

  • normal parenchymal transit

  • abnormal cortical retention

Drug Nephrotoxicity

• Nephrotoxic potential:

  • cyclosporine (vasoconstrictive effect on afferent glomerular arterioles) > OKT3 > FK506

  • Effects are dose-dependent and accentuated by dehydration + decreased renal perfusion

    Action:	impedes rejection process with narrow therapeutic window
    Histo:	(a) acutely: damage to tubules, microthrombosis of kidney (secondary to activation of coagulation cascade)
    	(b) chronically: hyaline deposition within arterial walls

• no change in renal size

• no change (?) / elevation of resistive index

• NUC:

  • depressed effective renal plasma flow

  • no parenchymal retention

Urologic Problems with Renal Transplant

Ureteral Obstruction of Renal Transplant (5%)

• acute: secondary to technical problems

• late: secondary to ischemia or previous extravasation

Cause:

stricture (most commonly at ureterovesical junction), ureteral kinking, (transient) edema at ureteroneocystostomy, ureteropelvic fibrosis, crossing vessels, blood clot, hematoma, lymphocele, fungus ball, calculus

• rising creatinine level

• pyelocaliectasis

• normal resistive index strongly argues against obstruction unless ureteral leak is present

DDx:

diminished ureteral tone due to denervation

Urine Extravasation of Renal Transplant (3 10%)

• Cause:

  • Distal ureteral necrosis secondary to interruption of blood supply (early) / vascular insufficiency due to rejection (late)

  • Leakage from ureteroneocystostomy site (related to surgical technique / distal ureteral necrosis)

  • Leakage from anterior cystostomy closure site

  • Segmental renal infarction

• high creatinine level in fluid collection

Prognosis:

high morbidity + mortality (death from transplant infection + septicemia)

Paratransplant Fluid Collection (in up to 50%)

Dx:	percutaneous fluid aspiration
Cx:	Page kidney

• Lymphocele (in up to 15%)

  Onset:

  within 4 8 weeks after transplantation

  • mostly asymptomatic

  P.965

  
  

  • creatinine + urea nitrogen + protein + electrolyte components similar to serum

  • predominantly lymphocytes, few leukocytes

  • mean diameter of 11 cm

  • thick septa (50%) + internal debris

  • photopenic region with displacement / impression on renal transplant / urinary bladder

    Cx:	hydronephrosis; edema of leg / abdominal wall / scrotum / labia
    Rx:	sclerotherapy with povidone-iodine / ethanol; long-term catheter drainage / surgical marsupialization

• Urinoma (rare)

  • pain, swelling, discharge from wound (in early postoperative period)

  • rarely septated + smaller than lymphoceles

  • progressive radiotracer activity within collection

• Hematoma, seroma, abscess

  • small crescentic peritransplant fluid collection (as normal sequelae of surgery)

  • photopenic region with displacement / impression on renal transplant / urinary bladder

Prognosis:	small hematomas typically resolve spontaneously within a few weeks
mnemonic:	HAUL

• Hematoma

• Abscess

• Urinoma

• Lymphocele

Vascular Problems with Renal Transplant (10%)

• PRERENAL

  • Renal artery stenosis (1 4%)

    • Transient elevation of velocities in immediate postoperative period is due to vessel wall edema / arterial spasm!

      Time of onset:

      within 3 years; cadaver kidney > young donor kidney > living-related donor kidney

    • Location:

      • short-segment stenosis at anastomosis: technical (75%), use of clamp / cannula, trauma, ischemia of donor vessel

      • long-segment stenosis of proximal artery (close to anastomosis) > distal artery: trauma during allograft harvesting, faulty operative technique, chronic rejection, atherosclerosis, kinking, scar formation

    • recent onset of hypertension / severe hypertension refractory to medical therapy

      • 65% of transplant recipients have nonrenovascular hypertension

    • unexplained graft dysfunction

    • audible bruit over graft site (occasionally)

    • increase in peak systolic velocity >180 210 cm/sec

    • 2:1 ratio between peak stenotic and poststenotic velocities

    • main renal artery / external iliac artery ratio >3.5

    • marked poststenotic turbulence (supportive evidence)

    • dampened signals distal to stenosis (= tardus-parvus waveform)

    • increase in acceleration time (= pulse rise time) of intrarenal arteries

    • Angio:

      • standard test for detection of arterial stenosis intravascular treatment

        Cx (0.5 2.3%):

        hemorrhage, intimal flap, arteriovenous fistula

    • Renal artery thrombosis (1 5%)

      Cause:	rejection, faulty surgical technique
      Time of onset:	within 1st week
      Predisposed:	allografts with disparate vessel size, multiple anastomoses, intramural vessel injury due to faulty handling, rejection

    • early sudden onset of anuria

    • graft tenderness + swelling

    • (a) global

      • absence of perfusion, uptake, excretion

      • failure to demonstrate intrarenal arterial / venous flow

        Prognosis:

        graft loss

    • segmental

      • segmental infarction due to occlusion of polar artery

      • hypo- / hyperechoic area cortical thickening

      • no flow in affected area

  • Pseudoaneurysm (in up to 17%)

    Cause:

    percutaneous biopsy with vascular injury, faulty surgical technique, perivascular infection

    • Location:

      • extrarenal at anastomotic site: due to suture rupture, anastomotic leakage, vessel wall ischemia

      • intrarenal, mostly of arcuate arteries: following needle biopsy, mycotic infection

    • mimics renal cyst

    • disorganized flow / to-and-fro waveform

      Prognosis:	spontaneous regression frequent
      Cx:	spontaneous rupture

  • Arteriovenous fistula (in 2 18%)

    Cause:

    percutaneous biopsy with vascular injury, faulty surgical technique, perivascular infection

    • hypertension, hematuria, high-output cardiac failure

    • US:

      • high-velocity low-resistance flow in feeding artery

      • pulsatile arterialized waveform in draining vein

      • turbulence + high-frequency velocity shift

      • exaggerated focal color around lesion (= bruit = perivascular soft-tissue vibration)

    • Angio (gold standard + allows treatment):

      • rapid contrast appearance in IVC

      • decreased density on nephrogram

    Cx:

    renal ischemia (with large lesion)

  P.966

  
  

  • Renal allograft necrosis

    • = total lack of perfusion in an area of renal cortex associated with variable degrees of medullary necrosis

      Cause:

      rejection, surgical ligature, preexistent arterial lesion, severe ATN, prolonged time of warm ischemia

    • Pattern:

      • Small focal necrosis

      • Large isolated area of infarction (segmental arterial occlusion)

      • Outer cortical necrosis

      • Cortical necrosis with large patches

      • Diffuse cortical necrosis

      • Cortical + medullary necrosis

      • Necrosis of whole kidney (occlusion of main renal artery)

    • MR:

      • slightly hyperintense (ischemic necrosis) / hypointense (hemorrhagic necrosis) / isointense area on T2WI

      • hypointense areas on Gd-DTPA images

    • US:

      • hypoechoic (ischemic necrosis) / iso- or hyperechoic (hemorrhagic necrosis) areas

      • swollen area (probably cortical edema)

      • absence of arterial perfusion by color duplex (not sensitive for small infarcts / superficial cortical necrosis)

      • elevated resistive indexes + no / reversed diastolic flow

• POSTRENAL

  • Renal / iliac vein thrombosis (4.2 5%)

    • Cause:

      • immediately: injury to epithelium at site of renal vein anastomosis, extrinsic compression by fluid collection

      • after 1st week: acute rejection, reduced intrarenal arterial flow, hypovolemia

    • abrupt onset of oliguria

    • graft tenderness

    • hematuria, proteinuria

    • enlarged hypoechoic transplant

    • prolonged arterial transit time without arterial occlusions + arterial spasms

    • diminished cortical perfusion

    • absent venous flow

    • U-shaped / plateau-like reversal of diastolic arterial flow

    • decreased systolic rise time

  • Renal vein stenosis

    Cause:

    perivascular fibrosis, compression from adjacent perinephric fluid collection

    • color aliasing

    • 3 4-fold increase in velocity

High Vascular Impedance of Renal Transplant

• = pulsatility index (A B / mean) greater than 1.8 or resistive index (A B / B) of Doppler signals of 0.75 0.80 indicate a reduction in diastolic flow velocity

• Causes:

  • intrinsic vascular obstruction

    • Acute vascular rejection (later stage)

    • Renal vein obstruction

  • increased intraparenchymal pressure

    • Severe ATN

    • Severe pyelonephritis:

      • CMV, herpes, E. coli, C. albicans

    • Extrarenal compression:

      • large collection, hematoma, discordant size

    • Urinary obstruction (doubted!)

    • Excessive pressure by transducer

Gastrointestinal Problems with Renal Transplant

Incidence:

40%

• Gastrointestinal hemorrhage

  • Upper GI tract bleeding

    • gastric erosions, gastric / duodenal ulcers

      Mortality rate:

      2 3 of normal

  • Lower GI tract bleeding

    • hemorrhoids, pseudomembranous colitis, cecal ulcers, colonic polyps

• GI tract perforation (3%)

Cause:	spontaneous, antacid impaction, perinephric abscess, diverticular disease
Location:	colon > small bowel > gastroduodenal
Mortality rate:	approaches 75% (because of delayed diagnosis)

Hypertension with Renal Transplant

• Leading cause of death in renal transplant recipient!

  Prevalence:

  up to 60% 1 year after transplantation

• Cause:

  • TRANSPLANT RELATED

    • Acute transplant rejection

    • Chronic rejection

    • Cyclosporine toxicity

    • Ureteral obstruction

    • Renal artery stenosis

      • Accelerated atherosclerosis

      • Postsurgical fibrosis at anastomosis

  • NOT TRANSPLANT RELATED

    • Renin production of native kidney

    • Original renal disease involving transplant

    • Development of essential hypertension

Aseptic Necrosis with Renal Transplant

• Most common long-term disabling complication; femoral head most common site, bilateral in 59 80%

  Frequency:	6 15 29% within 3 years after surgery
  Time of onset:	symptoms develop 5 126 (mean 9 19) months after transplantation

• Risk factors:

  • dose + method of glucocorticoid administration, duration + quality of dialysis before transplantation, secondary hyperparathyroidism, allograft dysfunction, liver disease, previous transplantation, iron overload, increased protein catabolism during dialysis

P.967




• Pathophysiology of corticosteroid therapy:

  • Fat embolism (fat globules occlude subchondral end arteries)

  • Increase in fat cell volume in closed marrow space (increase in intramedullary pressure leads to diminished perfusion)

  • Osteopenia (increased bone fragility)

  • Reduced sensibility to pain (loss of protection against excessive stress)

    Histo:

    fragmentation, compression, resorption of dead bone, proliferation of granulation tissue, revascularization, production of new bone

• 40% asymptomatic

• joint pain

• restriction of movement

  Sites:

  femoral head, femoral condyles (lateral > medial condyle), humeral head

• subchondral bone resorption

• patchy osteosclerosis

• collapse / fragmentation of bone

• MR with abbreviated T1WI protocol = test of choice!

  • see AVASCULAR NECROSIS

Posttransplant Lymphoproliferative Disease

• = abnormal proliferation of B-cell lymphocytes strongly associated with Epstein-Barr virus infection (in 80%); up to 11% may arise from T-cell lymphocytes

• Incidence:

  0.6%	after bone marrow transplantation,
  1 6%	after kidney transplantation (in 20% NHL, especially affecting CNS)
  1.8 20%	after cardiac transplantation

  • Prevalence of NHL is 35 greater than in general population!

    Cause:

    sequelae of chronic immunosuppression with limited ability to suppress neoplastic activity

• Types:

  • Polyclonal B-cell hyperplasia (nearly identical to infectious mononucleosis)

  • Monoclonal non-Hodgkin lymphoma

    Time of onset:

    as early as 1 month after transplantation depending on immunosuppressive regimen

• Location:

  • @ Lymph nodes: tonsils, cervical neck nodes

  • @ Gastrointestinal tract

    Cx:

    visceral perforation (frequent)

  • @ Thorax

    • multiple / solitary well-circumscribed pulmonary nodules mediastinal lymphadenopathy (DDx: cryptococcosis, fungus, Kaposi sarcoma)

    • patchy airspace consolidation (DDx: edema, infection, rejection)

DDx:	lymphoid hyperplasia (spontaneous resolution)
Rx:	(1) Antiviral agents (controversial)
	(2) Reduction / cessation of immunosuppressive agents
	(3) Surgical resection of tumor mass (complete resolution in 63%)

Renal Tubular Acidosis

• = clinical syndrome characterized by tubular insufficiency to resorb bicarbonate, excrete hydrogen ion, or both (= nonanion gap metabolic acidosis)

• failure to thrive

Proximal Renal Tubular Acidosis

• = TYPE 2 RTA

• = impaired capacity to absorb HCO₃^- in proximal tubule leads to presence of bicarbonate in urine at lower plasma levels than normal

• Pathogenesis:

  • ? defect in Na⁺/HCO₃^- cotransport at basolateral membrane; deficit of carbonic anhydrase; parathyroid hormone activates cyclic AMP, which inhibits carbonic anhydrase (hypocalcemia of hyperparathyroidism + various types of Fanconi syndrome)

• self-limited acidosis (bicarbonate loss stops once bicarbonate threshold of about 15 mEq/L is reached)

• unimpaired ability to lower urine pH (pH 4.5 7.8 depending on level of plasma bicarbonate) by normal excretion of hydrogen ions

• hypokalemia (due to hyperaldosteronism secondary to decreased proximal resorption of NaCl)

• rickets / osteomalacia

N.B.:	NEVER nephrocalcinosis / nephrolithiasis (due to normal urinary citrate excretion, low urine pH, self-limited less severe acidosis with less calcium release from bone
Dx:	bicarbonate titration test, large requirement of alkali to sustain plasma bicarbonate level at 22 mmol/L
Rx:	administration of alkali potassium hydrochlorothiazide

Infantile Type of Primary Proximal RTA

Age:

diagnosed within first 18 months of life; usually male patients

• excessive vomiting in early infancy

• growth retardation (<3rd percentile)

• metabolic hyperchloremic acidosis

• normal quantities of net acid excretion

Prognosis:

transient type with spontaneous remission

Secondary Proximal RTA

• = tubular defect of bicarbonate resorption associated with other tubular dysfunction / generalized disease

• Cause:

  • Fanconi syndrome, cystinosis, Lowe syndrome, hereditary fructose intolerance, glycogen storage disease, galactosemia, tyrosinemia, Wilson disease, Leigh syndrome

  • 1 + 2 hyperparathyroidism, vitamin D deficiency, mineralocorticoid deficiency, osteopetrosis

  • medullary cystic disease, renal transplantation, vascular accident to kidney in newborn period, multiple myeloma, amyloidosis, nephrotic syndrome, cyanotic CHD, Sj gren syndrome

  • intoxication with cadmium, outdated tetracycline, methylchromone, 6-mercaptopurine

P.968

Distal Renal Tubular Acidosis

• = TYPE 1 RTA (first type discovered)

• = impaired ability to secrete H⁺ in distal tubule despite low levels of plasma bicarbonate (urine cannot be acidified with pH invariably high at >5.5 6.0)

• Pathophysiology:

  • primary defect of nonacidification of urine followed by

    • hyperchloremia

      • small constant loss of serum sodium bicarbonate (NaHCO₃) without concomitant loss of chloride (NaCl retention) leads to shrinkage of ECF volume

    • chronic severe + progressive acidosis (due to inability to excrete the usual endogenously produced nonvolatile acid) leads to

      • mobilization of calcium + phosphate from bone (osteomalacia)

      • growth retardation

      • hypercalciuria (+ 2 hyperparathyroidism)

      • loss of phosphate (osteomalacia / rickets)

    • nephrocalcinosis + nephrolithiasis (due to combination of hypercalciuria + elevated urine pH + marked reduction in urinary citrate)

    • potassium wastage with hyperkaliuria + hypokalemia (due to constant small loss of sodium bicarbonate in urine, reduction of ECF space, 2 hyperaldosteronism, increase in sodium-potassium exchange in distal tubule)

  Path:

  calcium deposits accompanied by chronic interstitial nephritis with cellular infiltration, tubular atrophy, glomerular sclerosis

• muscle weakness, hyporeflexia, paralysis (due to hypokalemia)

• bone pain (due to osteomalacia)

• polyuria (from defect in urinary concentrating ability as a result of nephrocalcinosis + potassium deficiency)

• low plasma bicarbonate

• hyperchloremic acidosis (from impaired ability to excrete the usual endogenous load of nonvolatile acid)

• alkaline urine (pH >5.0 5.5)

• hypokalemia, loss of sodium

• hypercalciuria (continued mobilization of calcium phosphate from bone due to metabolic acidosis)

• hypocitraturia (increased proximal tubular reabsorption of citrate)

Dx:	acid load test with ammonium chloride (NH4Cl)
Rx:	administration of mixture of sodium + potassium bicarbonate
Cx:	interstitial nephritis, chronic renal failure (damage from nephrocalcinosis + secondary pyelonephritis), bone lesions, nephrocalcinosis, nephrolithiasis

Permanent Distal Renal Tubular Acidosis

• = ADULT TYPE OF PRIMARY DISTAL RTA = BUTLER-ALBRIGHT SYNDROME

  Genetics:	mostly sporadic, may be autosomal dominant
  Age:	children + adults (usually not diagnosed before age 2); F > M

• vomiting, constipation, polyuria, dehydration

• failure to thrive, growth retardation, anorexia

• polyuria (due to renal concentrating defect)

• potassium loss resulting in flaccid paralysis

• bone pain + pathologic fractures in adolescents + adults (from osteomalacia)

• low serum pH, low bicarbonate concentration

• elevation of chloride

• urinary pH of 6.0 6.5

• rickets / osteomalacia

• moderately retarded bone age

• medullary nephrocalcinosis / nephrolithiasis (as early as 1 month of age)

Secondary Distal Renal Tubular Acidosis

• systemic conditions:

  • starvation, malnutrition, sickle cell disease

  • primary hyperthyroidism + nephrocalcinosis, 1 hyperparathyroidism + nephrocalcinosis, vitamin D intoxication, idiopathic hypercalcemia, idiopathic hypercalciuria + nephrocalcinosis

  • amphotericin B nephropathy, toxicity to lithium, toluene sniffing

  • hepatic cirrhosis, fructose intolerance with nephrocalcinosis, Ehlers-Danlos syndrome, Marfan syndrome, elliptocytosis

• renal conditions:

  • renal tubular necrosis, renal transplantation, medullary sponge kidney, obstructive uropathy

• hypergammaglobulinemic states (? autoimmune process):

  • idiopathic hypergammaglobulinemia, chronic active hepatitis, hyperglobulinemic purpura, Sj gren syndrome, cryoglobulinemia, systemic lupus erythematosus, lupoid hepatitis, fibrosing alveolitis

Transient Distal Renal Transient Acidosis

• = INFANTILE TYPE OF PRIMARY DISTAL RTA

  • = LIGHTWOOD SYNDROME = salt-losing nephritis

• = transient self-limited form of infancy (only observed within 1st year of life) with unclear pathophysiology, probably due to vitamin D intoxication

• NO nephrocalcinosis

Renal Vein Thrombosis

Prevalence:

0.5% (autopsy)

• Causes:

  • Intrinsic

    • = thrombotic process begins intrarenally within small intrarenal veins due to acidosis, hemoconcentration, disseminated intravascular coagulation, intrarenal arteriolar constriction reducing venous flow

    • (a) antenatally: abruptio placentae

    • (b) neonates (most common): advanced maternal age, glycosuria in infants of diabetic mothers, dehydration from vomiting, diarrhea, enterocolitis, sepsis, polycythemia, birth trauma, left adrenal hemorrhage, prematurity

    • (c) adults: pyelonephritis, amyloidosis, polyarteritis nodosa, sickle cell anemia, thrombosis of IVC, low flow states (CHF, constrictive pericarditis), diabetic nephropathy, sarcoidosis

      • hypercoagulable state

        • nephrotic syndrome:

          P.969

          
          

          • membranous + membranoproliferative glomerulonephritis (most common), lupoid nephrosis

        • SLE

        • inherited hypercoagulable state:

          • antithrombin III deficiency, protein C deficiency, protein S deficiency

      • mechanical process

        • trauma

        • neoplasm: renal neoplasia (50%: RCC, TCC, Wilms tumor), left adrenal carcinoma

        • abscess

        • aneurysm

      • left ovarian vein thrombosis

  • Extrinsic

    • umbilical vein catheterization, thrombosis of IVC with extension into renal vein, malpositioned IVC filter, carcinoma of pancreatic tail invading renal vein (in 75%), pancreatitis, lymphoma, retroperitoneal sarcoma, retroperitoneal fibrosis, metastases to retroperitoneum (bronchogenic carcinoma)

      mnemonic:

      TEST MAN

    • Thrombophlebitis

    • Enterocolitis (dehydration)

    • Sickle cell disease, Systemic lupus erythematosus

    • Trauma

    • Membranous glomerulonephritis

    • Amyloidosis

    • Neoplasm

• Radiographic appearance varies with:

  • rapidity of venous occlusion

  • extent of occlusion

  • availability of collateral circulation

  • site of occlusion in relation to collateral pathways

Pathophysiology:	formation of collateral channels develops at 24 hours + peaks at 2 weeks after onset of occlusion
Collaterals:	ureteral v. to vesicular vv., pericapsular vv. to lumbar vv., azygos v., portal v.
	on left: in addition gonadal v., adrenal v., inferior phrenic vv.

Acute Renal Vein Thrombosis

Path:

hemorrhagic renal infarction from ruptured venules + capillaries without time for effective development of collaterals

• gross hematuria, proteinuria

• asymptomatic / painful flank mass

• consumptive thrombocytopenia

• anuria, hypertension, azotemia

  Location:

  more common on left (longer left renal vein)

• focal hemorrhagic infarction + capsular rupture

• smooth enlargement of kidney (edema + blood)

• IVP:

  • initially faint + delayed dense nephrogram

  • completely normal to pyelocaliceal nonvisualization

• US:

  • focal / generalized areas of increased echogenicity (from hemorrhage / edema)

  • loss of corticomedullary differentiation

  • thrombus within distended renal vein / IVC

• Doppler-US:

  • venous flow present in segmental veins + collateral veins overlying renal hilum mimicking patency of main renal vein

  • steady / less pulsatile venous flow compared with contralateral main renal vein

  • main renal vein not traceable into IVC on color Doppler

  • elevated resistive index >0.70 reversed end-diastolic renal arterial flow in native kidney

• CT:

  • prolonged cortical nephrographic phase with coarse striations + persistent corticomedullary differentiation

  • edema in renal sinus + perinephric space

  • thickened renal fascia + perirenal stranding

  • development of collateral venous vessels

  • retroperitoneal hemorrhage

• MR:

  • high signal intensity on T1WI + T2WI

• Angio:

  • poorly filling cortical arteries

  • absent inflow from renal vein into IVC

  • thrombus extending into IVC

• NUC:

  • no characteristic pattern on sequential functional study

Cx:	(1) Pulmonary emboli (50%)
	(2) Severe renal atrophy (may show complete recovery)

Subacute Renal Vein Thrombosis

• = good collateral drainage; impaired function with steady state or recanalization

• enlarged edematous boggy kidney

• slightly diminished / normal nephrographic density (may increase over time)

• compression of collecting system ( spidery calyces )

• hypoechoic large kidney

• collateral veins allow venous efflux normalizing arterial waveform

• main renal vein appears small due to recanalization

Chronic Renal Vein Thrombosis

• = indolent stage

• 80 90% asymptomatic

• nephrotic syndrome (proteinuria, hypercholesterolemia, anasarca)

• normal excretory urogram in 25% (with good collateral circulation especially if left side affected)

• notching of collecting system + proximal ureter

• retroperitoneal dilated collaterals

• lacelike intrarenal pattern of calcifications

• US:

  • branching linear calcifications (calcified thrombus)

  • small atrophic echogenic kidney

• CT:

  • attenuated renal vein (due to retraction of blood clot) + IVC thrombus (24%)

  • collaterals along proximal + middle ureter + perirenal

  • prolonged corticomedullary differentiation

  • delayed / absent pyelocaliceal opacification + attenuated collecting system

  P.970

  
  

  • thickening of Gerota fascia

• Arteriography:

  • enlarged venous collaterals on delayed images

Retrocaval Ureter

• = circumcaval URETER

  Etiology:	abnormality in embryogenesis of IVC with persistence of right posterior cardinal vein ventral to ureter + failure of right supracardinal system to develop
  Incidence:	0.07%; M:F = 3:1

• symptoms of right ureteral obstruction

• proximal right ureter swings medially over pedicle of L3-4, passes behind IVC, and emerges to right of aorta, returns to its normal position anterior to iliac vessels

• varying degrees of hydronephrosis + proximal hydroureteronephrosis

Cx:

recurrent urinary tract infections

Retroperitoneal Fibrosis

• = Ormond DISEASE = CHRONIC PERIAORTITIS

  Path:

  dense hard fibrous tissue enveloping the retroperitoneum with effects on ureter, lymphatics, great vessels

• Causes:

  • PRIMARY RETROPERITONEAL FIBROSIS (2/3)

    • Probably autoimmune disease with antibodies to ceroid (by-product of aortic plaque, which has penetrated into media) leading to systemic vasculitis;

    • Associated with fibrosis in other organ systems (in 8 15%):

      • mediastinal fibrosis, Riedel fibrosing thyroiditis, sclerosing cholangitis, fibrotic orbital pseudotumor

        Age:	31 60 years (in 70%); M:F = 2:1
        Rx:	responsive to corticoids

  • SECONDARY RETROPERITONEAL FIBROSIS (1/3)

    • Drugs (12%): methysergide, beta-blocker, phenacetin, hydralazine, ergotamine, methyldopa, amphetamines, LSD

    • Desmoplastic response to malignancy (8%): lymphoma, Hodgkin disease, carcinoid, retroperitoneal metastases (breast, lung, thyroid, GI tract, GU organs)

    • Retroperitoneal fluid collection: from trauma, surgery, infection

    • Aneurysm of aorta / iliac arteries (desmoplastic response)

    • Connective tissue disease: eg, polyarteritis nodosa

    • Radiation therapy

      Peak age:

      40 60 years; M:F = 2:1

• weight loss, nausea, malaise

• dull pain in flank, back, abdomen (90%)

• renal insufficiency (50 60%)

• hypertension

• leg edema, fever, hydrocele (10%)

• claudication (occasionally)

  Location:

  plaque typically begins around aortic bifurcation extending cephalad to renal hilum / surrounding kidney; rarely extends below pelvic rim, but may extend caudad to bladder + rectosigmoid

• IVP

  • Classic TRIAD:

    • ureterectasis above L4-5 (interference with peristalsis)

    • medial deviation of ureters in middle third, typically bilateral

    • gradual tapering of ureter (extrinsic compression)

  • usually mild pyelocaliectasis

• US:

  • hypoechoic homogeneous mass in paraaortic region / perinephric space

• CT:

  • periaortic mass of attenuation similar to muscle

  • may show contrast enhancement (active inflammation)

• MR:

  • low to medium homogeneous signal intensity on T1WI

  • heterogeneous high signal intensity on T2WI (with malignancy / associated inflammatory edema)

  • low signal intensity on T2WI (in dense fibrotic plaque)

• NUC:

  • gallium uptake during active inflammation

DDx:	lymphoma, retroperitoneal adenopathy
Rx:	(1) Withdrawal of possible causative agent
	(2) Interventional relief of obstruction
	(3) Corticosteroids

Retroperitoneal Leiomyosarcoma

Incidence:

2nd most common primary retroperitoneal malignancy (after liposarcoma)

• Origin:

  • retroperitoneal space without attachment to organs

  • wall of inferior vena cava

    Age:

    5th 6th decade; M:F = 1:6

• abdominal mass, pain, weight loss, nausea, vomiting

• abdominal distension, change in defecation habits, leg edema, back / radicular pain, frequency of urination

• hemoperitoneum, GI bleeding, dystocia, paraplegia

• Metastases:

  • frequently hematogenous, less commonly lymphatic dissemination

    • common sites: liver, lung, brain, peritoneum

    • rare sites: skin, soft tissue, bone, kidney, omentum

  • Distant metastases present at time of diagnosis in 40%

DDx:	(1) Liposarcoma (fat content)
	(2) Malignant fibrous histiocytoma (not as necrotic)
	(3) Lymphoma (nonnecrotic, tends to envelop IVC + aorta)
	(4) Primary adrenal tumor
	(5) IVC thrombus (no luminal enlargement, no neovascularity)
Rx:	(1) Complete excision (resectable in 10 75%)
	(2) Partial resection (reduction in tumor size)
	(3) Adjuvant chemotherapy / radiotherapy
Prognosis:	local recurrence in 40 70%; death within 5 years in 80 87% with extraluminal tumors

Extravascular Leiomyosarcoma (62%)

Path:

extraluminal (= completely extravascular) large tumor with extensive necrosis

• IVP:

  • large soft-tissue mass with

    P.971

    
    

    • displacement of kidney + ureter

    • gas-containing ascending / descending colon

  • well-defined fat plane between mass and kidney

  • obstruction of kidney (ureteral involvement)

  • usually not calcified

• US:

  • solid mass isoechoic to liver / rarely hyperechoic

  • complex mass with cystic spaces + irregular walls

• CT:

  • lobulated mass often >10 cm in size

  • large cystic areas of tumor necrosis in center of mass

  • areas of high attenuation with recent hemorrhage

• MR:

  • intermediate intensity on T1WI with low-intensity areas of necrosis

  • inhomogeneous intermediate to high signal intensity on T2WI (due to high water content of cystic areas)

• Angio:

  • hypervascular tumor with blood supply from lumbar, celiac, mesenteric, renal arteries

  • avascular center surrounded by thick hypervascular rind

Intravascular Leiomyosarcoma (5%)

Path:	intraluminal (= completely intravascular) polypoid mass firmly attached to vessel wall
Location:	between diaphragm + renal veins, may extend along entire length of IVC + into heart

• small solid mass within IVC

• gradually dilatation / obstruction of IVC

• intratumoral vascularity confirmed by Doppler

• irregular enhancement (CT bolus injection)

Cx:	(1) Budd-Chiari syndrome (extension into hepatic veins)
	(2) Nephrotic syndrome (extension into renal veins)
	(3) Edema of lower extremities (extension into lower IVC without adequate collateralization)
	(4) Tumor embolus to lung

Extra- & Intravascular Leiomyosarcoma (33%)

• solid / necrotic extraluminal mass not originating from a retroperitoneal organ with contiguous intravascular enhancing component (PATHOGNOMONIC)

Intramural Leiomyosarcoma (extremely rare)

Retroperitoneal Liposarcoma

• = slow-growing tumor that displaces rather than infiltrates surrounding tissue and rarely metastasizes

  Incidence:

  most common primary malignant retroperitoneal tumor, 95% of all fatty retroperitoneal tumors

• Histo:

  • lipogenic type:

    • radiodensity of fat

  • myxoid type (most common):

    • radiodensity between water + muscle

  • pleomorphic type (least common):

    • radiodensity of muscle

• Age: most commonly 40 60 years; M > F

• abdominal pain, weight loss, anemia, palpable mass

  Site:

  anterior to spine + psoas muscle > paraspinal + posterior pararenal space

• CT:

  • solid pattern: inhomogeneous poorly marginated infiltrating mass with contrast enhancement

  • mixed pattern: focal fatty areas ( 40 to 20 HU) + areas of higher density (+20 HU)

  • pseudocystic pattern: water-density mass (averaging of fatty + solid connective-tissue elements)

  • calcifications in up to 12%

• Angio:

  • hypovascular without vessel dilatation / capillary staining / laking

Prognosis:	most radiosensitive of soft-tissue sarcomas; 32% overall 5-year survival
DDx:	malignant fibrous histiocytoma, leiomyosarcoma, desmoid tumor

Rhabdoid Tumor of Kidney

• Most aggressive renal neoplasm of childhood!

  Frequency:	2% of pediatric renal tumors
  Mean age:	11 17 months; 6 12 months of age (25%), <1 year of age (60%), <2 years of age (80%); M:F = 1.5:1
  Origin:	renal sinus
  Histo:	monomorphic noncohesive large cells with prominent nucleoli + abundant eosinophilic cytoplasm (superficial resemblance to skeletal muscle, hence name); filamentous intracytoplasmic inclusions (CHARACTERISTIC)
  Associated with:	syn- / metachronous primary brain tumor of neuroectodermal origin (medulloblastoma, ependymoma, cerebellar / brainstem astrocytoma, PNET)
  Metastatic to:	lung, liver, brain

• paraneoplastic hypercalcemia (occasionally)

• centrally located heterogeneous renal mass:

  • indistinct borders with infiltration of medulla + sinus

  • PROMINENT peripheral crescent-shaped subcapsular fluid collection in 70% (subcapsular hematoma in 47% / necrotic cavity in 53%)

  • linear calcifications outlining tumor lobules

• midline posterior fossa mass

• metastases (in 80%) to lung, liver, abdomen, brain, lymph nodes, bone

Prognosis:	20% 18-month survival rate
DDx:	Wilms tumor, mesoblastic nephroma

Rhabdomyosarcoma, Genitourinary

Frequency:	4 8% of all malignant solid tumors in children <15 years of age (ranking 4th after CNS neoplasm, neuroblastoma, Wilms tumor); 10 25% of all sarcomas; annual incidence of 4.5:1,000,000 white + 1.3:1,000,000 black children
Age:	mean age of 7 years; white:black = 3:1; M:F = 6:4
Origin:	mesenchyme of the urogenital ridge
Path:	firm fleshy lobulated mass with infiltrative margin / well-defined pseudocapsule; composed of smooth grapelike clusters if intraluminal (= sarcoma botryoides)

• Histo (Horn & Enterline):

  • embryonal (56%)

  P.972

  
  

  • botryoid = grapelike (5%) = subtype of embryonal rhabdomyosarcoma

  • alveolar (20%): worst prognosis

  • pleomorphic (1%): mostly in adults

    DDx:	primitive neuroectodermal tumor, extraosseous Ewing sarcoma, synovial cell sarcoma, fibrosarcoma, alveolar soft part sarcoma, hemangiopericytoma, undifferentiated sarcoma, neuroblastoma
    Metastases:	lung, cortical bone, lymph nodes > bone marrow, liver

    • Metastases in 10 20% at time of diagnosis!

• nonspecific imaging features:

  • homogeneous echogenicity similar to muscle hypoechoic areas (hemorrhage / necrosis)

  • hyperemia with high diastolic flow component

  • bulky pelvic mass of heterogeneous attenuation

  • hypointense on T1WI + hyperintense on T2WI with heterogeneous enhancement

  • diffuse tumor vascularity on angio

• Prognosis:

  • (a) 14 35% 5-year survival with radical surgery

  • (b) 60 90% 3-year survival with chemotherapy added

  • Local recurrence is common!

Bladder-Prostate Rhabdomyosarcoma

• 5% of all rhabdomyosarcomas occur in genitourinary tract

• Most common bladder tumor in patients <10 years

  Age:	in first 3 years of life; M:F = 3:1
  Associated with:	congenital anomalies of the brain, neurofibromatosis, nephroblastoma
  Histo:	embryonal (90%), alveolar (10%)
  Location:	trigone of urinary bladder / prostate (tumor infiltrating both)

• abdominal pain + distension (from bladder outlet obstruction)

• urinary frequency + dysuria (from urinary tract infection) + retention

• palpable bladder

• hematuria (unusual late manifestation)

• strangury (= painful urge to void without success)

• polypoid intraluminal tumor mass

• elevation of bladder floor with obstruction of bladder neck + large postvoid residual

• invasion of periurethral / perivesical tissues

• retroperitoneal lymph node enlargement

• MR:

  • low signal intensity on T1WI + hyperintense on T2WI

  • heterogeneous enhancement

Rx:	chemotherpay prior to surgery
DDx:	polyp, hemangioma, ectopic ureterocele, hemorrhagic cystitis

Rhabdomyosarcoma of Female Genital Tract

Location:

vulva / vagina (infancy), cervix (reproductive years), uterine corpus (postmenopausal)

• vulvar / perineal / vaginal mass

• vaginal bleeding / discharge / protruding grapelike mass

DDx:	polyp, urethral prolapse, hydrometrocolpos, neoplasm
Prognosis:	91% 5-year survival rate for nonmetastatic rhabdomyosarcoma of genital tract

Vaginal Rhabdomyosarcoma

Age:	very young children (almost exclusively)
Histo:	commonly botryoid

• US:

  • large solid heterogeneous hypoechoic mass posterior to urinary bladder

Paratesticular Rhabdomyosarcoma

Age:	childhood, 2nd age peak in adolescence
Location:	spermatic cord, testis, penis, epididymis

• painless scrotal swelling

• palpable nontransilluminating intrascrotal tumor

• bulky abdominal (lymphadenopathy)

• displacement / compression / infiltration of adjacent testis

Prognosis:	73 89% 3-year survival rate
DDx:	hydrocele, epididymitis, testicular neoplasm

Schistosomiasis

• = BILHARZIASIS

  Organism:	trematodes of species:
  	S. haematobium (GU tract) >95%;
  	S. mansoni, S. japonicum (GI tract) <5%

• Life cycle:

  • female parasite discharges eggs into vesicular venules; eggs erode bladder mucosa, are excreted with urine + feces, and hatch in fresh water into larval miracidia; larvae invade snail (= intermediate host) of genus Bulinus, Biomphalaria, Oncomelania; resulting daughter sporocytes develop into cercariae and pass into surrounding body of water; penetrate human skin (usually foot) + pass into lymphatics; schistosoma settles in portal veins + migrates into pelvic venous plexus

    Incidence:

    8% of world's population; 25% in Africa (endemic in South Africa, Egypt, Nigeria, Tanzania, Zimbabwe); endemic in Puerto Rico

• @ Urinary tract

  • frequency, urgency, dysuria

  • hematuria, albuminuria (most common)

  • dull flank pain (from hydronephrosis)

  • index of infectious severity = urine egg count

    Location:

    lower ureters + bladder

  • bladder wall calcifications (in 4 56%): linear / coarse / floccular, beginning at base, parallel to upper aspect of pubic bone, involving all wall layers

  • vesical calculi (in 39%), distal ureteral calcification (in 34%), honeycombed calcification of seminal vesicles

  • striation of renal pelvis + proximal ureter in 21% (DDx: normal in 3%, other urinary tract infection, vesicoureteric reflux

  • ureterectasis (focal egg deposition leads to peristaltic disorganization)

  • ureteral strictures in distal third (in 8%, L > R), most commonly in intravesical portion with cobra-head configuration = pseudoureterocele); Makar stricture = focal stricture at L3

  • multiple inflammatory pseudopolyps in ureter secondary to granulomas (= bilharziomas)

  • ureteritis cystica

  • ureterolithiasis / ureteritis calcinosa (= punctate / linear calcifications)

  • vesicoureteral reflux

  P.973

  
  

  • polypoid filling defects + mucosal irregularities in urinary bladder (pseudotubercles, papillomas)

  • thick-walled fibrotic flat-topped bladder with high insertion of ureters

  • reduced bladder capacity with significant postvoid residual (fibrotic stage)

  • urethral stricture with perineal fistulas

    Cx:	Squamous cell carcinoma of bladder
    Age:	30 50 years (exposed early in childhood with 20 30-year latency period)
    Location:	posterior bladder wall, rarely trigone

    • irregular filling defect

    • discontinuous calcifications

• @ GI tract

  • portal hypertension (ova migrating into portal venous system incite fibrosing granulomatous reaction within presinusoidal portal veins)

  • esophageal varices (from portal hypertension)

  • polypoid calcifying bowel lesions (from eggs of S. mansoni trapped in bowel wall + inciting granulomatous reaction)

• @ Chest

  • enlargement of RV + pulmonary artery + azygos vein (from portal hypertension)

  • diffuse granulomatous lung lesions

Rx:

praziquantel

Scrotal Abscess

• Etiology:

  • Complication of epididymoorchitis (often in diabetics), missed testicular torsion, gangrenous tumor, infected hematoma, primary pyogenic orchitis

  • Systemic infection: mumps, smallpox, scarlet fever, influenza, typhoid, syphilis, TB

  • Septic dissemination from: sinusitis, osteomyelitis, cholecystitis, appendicitis

    Predisposed:

    diabetics

• NUC:

  • marked increase in perfusion, hot hemiscrotum with photon-deficient area representing the abscess on Tc-99m pertechnetate scan (DDx: chronic torsion)

  • increased scrotal uptake with leukocyte imaging

• US:

  • hypoechoic / complex fluid collection with low-level echoes (differentiation of intra- from extratesticular abscess location possible)

  • skin thickening

  • hydrocele

Cx:	(1) Pyocele
	(2) Fistulous tract to skin

Seminal Vesicle Cyst

• cystic mass posterior to urinary bladder (DDx: m llerian duct cyst)

• dilated ejaculatory duct

Acquired Seminal Vesicle Cyst

• Etiology:

  • Autosomal dominant polycystic kidney disease

    • bilateral seminal vesicle cysts

  • Invasive bladder tumor

  • Infection

  • Benign prostatic hypertrophy

  • Ejaculatory duct obstruction

Congenital Seminal Vesicle Cyst

Associated with:

anomalies of ipsilateral mesonephric duct:

• Etiology:

  • Ectopic insertion of ipsilateral ureter (92%) into bladder neck / posterior prostatic urethra / ejaculatory duct / seminal vesicle

  • Ipsilateral renal dysgenesis (80%)

  • Duplication of collecting system (8%)

  • Vas deferens agenesis

    Symptomatic age:

    21 41 years

• abdominal / flank / pelvic / perineal pain exacerbated by ejaculation

• dysuria, frequent urination

• epididymitis in prepubertal boy

• recurrent urinary tract infection

Sinus Lipomatosis

• = PERIPELVIC LIPOMATOSIS = PELVIC FIBROLIPOMATOSIS = PERIPELVIC FAT PROLIFERATION

• Etiology:

  • Normal increase with aging and obesity

  • Vicarious proliferation of sinus fat with destruction / atrophy of kidney (= replacement lipomatosis)

  • Extravasation of urine leading to proliferation of fatty granulation tissue

  • Normal variant

    Age:

    6th 7th decade

• kidney may be enlarged

• elongated spiderlike / trumpetlike pelvicaliceal system

• infundibula arranged in spoke-wheel pattern

• parenchymal thickness diminished with underlying disease

• occasionally focal fat deposit with localized deformity of collecting system

• Plain film:

  • diminished sinus density

• CT:

  • unequivocal fat values

• US:

  • echodense / patchy hypoechoic sinus complex

Replacement Lipomatosis

• = REPLACEMENT FIBROLIPOMATOSIS

• = extreme form of renal sinus lipomatosis

  Associated with:	infection, long-term hydronephrosis, calculi (70%)
  Path:	marked proliferation of hyperplastic sinus fat with extremely atrophied cortex + varying degrees of hydro- / pyonephrosis, acute / chronic pyelonephritis

• kidney enlarged by a fatty sinus mass and outlined by an extremely thin cortex:

  • fat characteristically distributed within renal sinus + perinephric space

• staghorn calculus inside an enlarged renal outline

• poorly functioning / nonfunctioning kidney

P.974

DDx:

xanthogranulomatous pyelonephritis, lipoma, angiomyolipoma, liposarcoma

Squamous Cell Carcinoma of Kidney

Incidence:	5 10% of all urothelial tumors; 1% of renal neoplasms; 2nd most common malignancy of pelvic urothelium after TCC
Age:	60 70 years; M:F = 2:1
Path:	flat ulcerating mass + extensive induration
Associated with:	chronic irritation of urothelium by renal infection + calculi (25 60%)

• painless hematuria

• flank pain (with ureteropelvic junction obstruction)

• infiltrating renal process

• nonfunctional kidney:

  • ureteropelvic junction obstruction (common)

• presence of faceted calculi (40 80%)

• IVP:

  • stricture that may simulate extrinsic cause

• Angio:

  • arterial encasement + occlusion + neovascularity

  • enlarged pelvic + ureteric arteries

  • occlusion of renal vein / branches (41%)

• CT:

  • thickening of pelvicaliceal wall (with superficial spread over large areas)

  • enlarged kidney maintaining reniform shape:

    • infiltrating growth into sinus + parenchyma

    • tumor mass infrequent

  • no contrast excretion (due to obstruction)

Prognosis:	worse than TCC due to early metastases; 33% 1-year survival rate
DDx:	xanthogranulomatous pyelonephritis (radiologically indistinguishable)

Supernumerary Kidney

• = aberrant division of nephrogenic cord into two metanephric tails (rare)

  Associated with:	horseshoe kidney, vaginal atresia, duplicated female urethra, duplicated penis
  Location:	most commonly on left side of abdomen caudal to normal kidney

• supernumerary ureter may insert into ipsilateral kidney / directly into bladder / ectopic site

Cx:

hydronephrosis, pyonephrosis, pyelonephritis, cysts, calculi, carcinoma, papillary cystadenoma, Wilms tumor

Testicular Infarction

Cause:

torsion, trauma, leukemia, embolus (eg, bacterial endocarditis), vasculitis (eg, polyarteritis nodosa, Henoch-Sch nlein purpura)

• diffusely hypoechoic small testis / focal mass

• hyperechoic regions (hemorrhage / fibrosis)

• decrease in size over time

• low signal intensity on T1WI + T2WI

DDx:

malignancy (difficult differentiation)

Testicular Microlithiasis

Etiology:	defect in phagocytotic activity of Sertoli cells leaving degenerated intratubular debris behind
Prevalence:	0.6%
May be associated with:	testicular germ cell tumor (40%), cryptorchidism, subfertility, infertility, Klinefelter syndrome, testicular infarcts, granulomas, male pseudohermaphroditism, Down syndrome, pulmonary alveolar microlithiasis
Histo:	laminated concretions within lumen of seminiferous tubules

• asymptomatic, uncommon incidental finding

• 1 2-mm hyperechoic nonshadowing foci (>5) scattered throughout the parenchyma of both testes (PATHOGNOMONIC):

  • may be asymmetrically distributed, unilateral, clustered in periphery

Cx:	concurrent germ cell tumor in up to 40% (21.6 risk)
Recommendation:	follow up in 6-month intervals to screen for testicular tumors (contested)
DDx:	postinflammatory changes, scars, granulomatous changes, benign adenomatoid tumor, hemorrhage with infarction, large-cell calcifying Sertoli cell tumor

Testicular Rupture

• Testicular rupture is indication for immediate surgical intervention!

  Cause:	scrotal trauma
  Salvageability:	80 90% if surgical repair occurs <72 hours after trauma; 30 55% if surgical repair occurs >72 hours after trauma

• areas of decreased / increased echogenicity (hemorrhage necrosis)

• loss of testicular outline

• thickened scrotal wall (= hematoma)

• visualization of fracture plane

• hematocele, may show thickening + calcification of tunica vaginalis if chronic

• uriniferous hydrocele from perforated bulbous urethra

• avascular region on color duplex

Cx:	torsion (due to stimulation of a forceful cremasteric contraction)
DDx:	laceration, contusion, hemorrhage

Testicular Torsion

• = SPERMATIC CORD TORSION

• Most common scrotal disorder in children, 20% of acute scrotal pathology

  Incidence:

  1:160, 10-fold risk in undescended testis compared with normal annual incidence of 1:4,000 males

• Etiology:

  • Bell and clapper deformity = high insertion of tunica vaginalis on spermatic cord

  • Abnormally loose mesorchium between testis + epididymis

  • Extravaginal torsion involving testis + tunica vaginalis due to loose attachment of testicular tunics to scrotum during in utero + perinatal period

    Peak age:	newborn period + puberty (13 16 years);
    	<20 years in 74 85%; >21 years in 26%;
    	>30 years in 9%

• sudden severe pain in 100% (frequently at night)

• negative urine analysis (98%)

P.975




• history of similar episode in same / contralateral testis (42%)

• nausea + vomiting (50%)

• scrotal swelling + tenderness (42%)

• leukocytosis (32%)

• low-grade fever (20%)

• history of trauma / extreme exertion (13%)

  Location:

  in 5% bilateral (anomalous suspension of contralateral testis found in 50 80%)

• Salvage rate:

  • versus time interval between onset of pain and surgery

    80 100%	<6 hours
    76%	6 12 hours
    20%	12 24 hours
    near 0%	>24 hours

  • Irreversible ischemic damage in only 3 6 hours!

  • Spontaneous detorsion in 7%

Cx:

testicular atrophy (in 33 45%)

Acute Testicular Torsion

• = symptoms present for <24 hours

• 70% of patients present within first 6 hours from onset of pain

• Brunzel sign = elevated horizontal lie of testis

• Ger sign = skin pitting at scrotal base

• US (80 90% sensitivity):

  • normal grey-scale appearance (within 6 hours)

  • diffusely hypoechoic echotexture (>6 hours)

  • testicular + epididymal enlargement with decreased echogenicity (within 8 24 hours)

  • visualization of twisted enlarged spermatic cord

  • scrotal skin thickening

  • hydrocele (occasionally)

• Color duplex (86% sensitive, 100% specific, 97% accurate):

  • loss of spermatic cord Doppler signal (sensitivity 44%, specificity 67%)

  • absence of testicular + epididymal flow (DDx: global testicular infarction)

    False-negative:

    torsion-detorsion sequence, incomplete torsion <360 degrees

• Degree of torsion and blood flow:

  • testis usually turns medially up to 1,080

  • diminished blood flow in <180 -torsion at 1 hour

  • absent blood flow in any degree of torsion >4 hours

  • hyperemia after spontaneous detorsion

• NUC (98% accuracy):

  Dose:	5 15 mCi Tc-99m pertechnetate
  Imaging:	at 2- to 5-second intervals for 1 minute (vascular phase); at 5-minute intervals for 20 minutes (tissue phase)

  • decreased perfusion / occasionally normal

  • nubbin sign = bump of activity extending medially from iliac artery denoting reactive increased blood flow in spermatic cord with abrupt termination

  • rounded cold area replacing testis (requires knowledge of side + location of painful testis)

Subacute Testicular Torsion

• = MISSED TESTICULAR TORSION

• = symptoms present for >24 hours + less than 10 days

• US:

  • enlarged / normal-sized testis with heterogeneous punctate / diffusely increased echotexture

  • increased peritesticular flow without parenchymal blood flow

• NUC:

  • normal NUC angiogram / nubbin sign

  • doughnut sign = decreased testicular activity with rim hyperemia of dartos perfusion

• MR:

  • enlarged spermatic cord without increase in vascularity

  • whirlpool pattern (twisting of spermatic cord)

  • torsion knot = low-signal-intensity focus at point of twist (displacement of free protons from epicenter of twist)

Chronic Testicular Torsion

• small atrophied homogeneously hypoechoic testis

• enlarged echogenic epididymis

Testicular Tumor

• Most common neoplasm in males between ages 20 and 34 years; 1 2% of all cancers in males; 4 6% of all male genitourinary tumors; 1.5% of all childhood malignancies; 4th most common cause of death from malignancy between ages 15 34 years (12%)

  Incidence per year:	4 6:100,000; 7,200 new cases in 2001 (100% increase since 1936)
  Peak age:	25 35 years and 71 90 years and infants up to 10 years: yolk sac tumor + teratoma;
  	White:Black = 4.5:1

• Risk factors:

  • Prior testicular cancer (20 risk = 2 5%)

  • Cryptorchidism (10 risk):

    • 5% for abdominal site, 1.25% for inguinal site

  • Family history of testicular cancer (6 risk for 1st-degree relative)

    • more prevalent in Caucasian race, Jewish religion

  • Infertility (0.4 1.1% prevalence of intratubular germ cell neoplasia)

  • Intersex syndrome: gonadal dysgenesis, true hermaphroditism, pseudohermaphroditism

• painless enlarging testis / mass (most common)

• heaviness / fullness in lower abdomen / scrotum

• acute scrotal pain (10%, from intratumoral hemorrhage)

• gynecomastia, virilization

  Location:	mostly unilateral; contralateral tumor develops eventually in 8%
  Metastases:	at presentation in 4 14%

  • lymphatic dissemination

    • along testicular lymphatic drainage to

      • interaortocaval chain at 2nd lumbar vertebra (for right testicular tumor)

        Age Group of Testicular Tumors

        Yolk sac tumor / teratoma	1st decade
        Choriocarcinoma	2nd + 3rd decade
        Embryonal cell carcinoma	3rd decade
        Seminoma	4th decade

      P.976

      
      

      • left paraaortic nodes between renal vein, aorta, ureter and inferior mesenteric artery

      • along thoracic duct

      • left supraclavicular nodes

      • lungs

  • hematogenous dissemination (usually late) to lung > liver, brain, bone

    • Choriocarcinoma has a proclivity for early hematogenous spread (especially to brain)!

  • direct extension through tunica albuginea to skin (rare and late) / epididymis resulting in spread to inguinal + iliac nodes

    Histo:

    may be different from that of primary tumor indicating totipotential nature of germ cells

• Tumor markers (elevated in 80% at time of diagnosis):

  -fetoprotein:	yolk sac tumors, mixed germ cell tumors with yolk sac elements
  -hCG:	seminoma, choriocarcinoma (tumors containing syncytiotrophoblasts)
  LDH:	correlates with bulk of disease (nonspecific as it is produced by multiple organs throughout the body)

• Color duplex:

  • tumor <1.5 cm is hypovascular in 86%, >1.6 cm hypervascular in 95% (DDx: orchitis associated with epididymal hyperemia)

  • distortion of vessels

• MR:

  • tumors isointense to testicular parenchyma on T1WI + T2WI

Prognosis:	>93% 5-year survival rate for stage I; 85 90% 5-year survival rate for stage II; complete remission under chemotherapy in 65 75%; relapse in 10 20% within 18 months
Rx:	inguinal orchiectomy (first-line treatment)

Germ Cell Tumors (95%)

Origin:

spermatogenic cells

• one histologic type in 65%

  • from unipotential gonadal line:

    • Seminoma

  • along a totipotential line forming nonseminomatous tumors:

    • Embryonal carcinoma (largely undifferentiated)

    • Teratoma (embryonic differentiation)

    • Yolk sac tumor (extraembryonic differentiation)

    • Choriocarcinoma (extraembryonic differentiation)

• mixed lesion in 35 40%

  • from totipotential cells developing along several pathways (embryonal carcinoma being the most common component of mixed lesions)

    • Teratocarcinoma (= teratoma + embryonal cell carcinoma)

      • 2nd most common after seminoma, may occasionally undergo spontaneous regression

    • Embryonal cell carcinoma + seminoma

    • Seminoma + teratoma

• Growing Teratoma Syndrome:

  • = evolution of mixed germ cell tumor into mature teratoma after chemotherapy (in 40%) followed by interval growth despite maintaining a benign histologic type

mnemonic:

YES CT

• Yolk sac tumor

• Embryonal cell carcinoma

• Seminoma

• Choriocarcinoma

• Teratoma

Seminoma (35 50%)

• Most common tumor in undescended testis!

• Most common pure germ cell tumor!

  Average age:	40.5 years (slightly older patient compared with other germ cell tumors)
  Histo:	uniform cellular morphology resembles primitive germ cells

  • Typical seminoma (85%)

  • Anaplastic seminoma (10%)

  • Spermatocytic seminoma (5%)

    Presentation:	in 75% limited to testis;
    	in 20% retroperitoneal lymphadenopathy;
    	in 5% extranodal metastases
    Associated with:	testicular microlithiasis

• serum -fetoprotein normal in pure seminomas

• -hCG elevation in 83%

  

  Classification of Testicular Cancer

P.977




• usually uniformly hypoechoic + confined within tunica albuginea:

  • lobulated / multiple confluent nodules

  • entire testis replaced (>50%)

  • cystic component (10%) fluid-debris level

• may be multifocal

• bilateral in 1 3%, almost always asynchronous

• MR:

  • homogeneously hypointense on T2WI

    Rx:	very sensitive to radiation chemotherapy
    Prognosis:	10-year survival rate of 75 85%;
    	19% develop pulmonary metastases

Nonseminomatous Tumor

Incidence:	50% of all germ cell tumors
Stem cell:	embryonal cell
Age:	20 30 years

• inhomogeneous texture (71%)

• cystic components (61%)

• irregular ill-defined margins (45%)

• echogenic foci (35%)

Embryonal Cell Carcinoma (20 25%)

• Second most common testicular tumor!

• Most common component of mixed germ cell tumors (embryonal cells present in 87%); often associated with teratoma

  Histo:	primitive anaplastic epithelial cells resembling early embryonic cells; in 3% as pure form
  Age:	25 35 years and <2 years
  Spread:	most aggressive testicular tumor, visceral metastases

• -fetoprotein elevation

• hypoechoic mass with heterogeneous areas:

  • ill-defined borders

  • areas of increased echogenicity (hemorrhage)

  • cystic areas (necrosis)

• may show invasion of tunica albuginea (common)

Rx:	less sensitive to radiation
Prognosis:	30 35% 5-year survival rate

Teratoma (4 10%)

• 2nd most common testicular tumor in young boys 5 years (75%)

  Prevalence:	1:1,000,000
  Histo:	consists of elements from more than one germ cell layer (keratin, muscle, bone, cartilage, hair, mucous glands, neural tissue); 2 3% as pure form (in adults)
  	(a) mature
  	(b) immature
  	(c) malignant areas

  Staging of Testicular Cancer

  I	limited to testis + spermatic cord
  II	metastases to lymph nodes below diaphragm
  II A	nonpalpable
  II B	bulky mass
  III	metastases to lymph nodes above diaphragm
  III A	confined to lymphatic system
  III B	extranodal metastases

  Age:

  within first 4 years of life; benign in children; may transform into malignancy in adulthood

• serum -fetoprotein usually normal

• well-circumscribed heterogeneous complex mass:

  • anechoic / complex cysts with variable echogenicity (serous, mucoid, keratinous fluid)

  • markedly echogenic components (cartilage, calcification, fibrosis, scar formation)

• Prognosis:

  • variable biologic behavior: benign in prepubertal testes BUT may metastasize in postpubertal testes with nonteratomatous germ cell elements; metastases to lymph nodes, bone, liver in 30% within 5 years

Epidermoid Cyst / Keratin Cyst of Testis (1%)

• = monodermal dermoid

• = benign teratoma with only ectodermal components / squamous metaplasia of surface mesothelium

  Age:	20 40 years; primarily in Whites
  Histo:	cyst contains keratin debris, wall com-posed of fibrous tissue + lined by kera-tinizing stratified squamous epithelium

• painless testicular nodule

• negative tumor marker status

• sharply circumscribed encapsulated round lesion of 1 3 (range 0.5 10.5) cm in diameter:

  • onion-skin / ringed appearance of alternating hypo- and hyperechogenicity (= alternating layers of compacted keratin + loosely arranged desquamated squamous cells):

    • hyperechoic fibrous cyst wall shadowing from calcifications / ossification

    • hypoechoic cyst contents (= laminated keratin debris)

      Staging of Testicular Cancer (American Joint Committee on Cancer)

      pTX	primary tumor not available (no orchiectomy)
      pT0	no primary tumor found
      pTis	intratubular germ cell tumor (carcinoma in situ)
      pT1	limited to testis + epididymis
      pT2	as pT1 + vascular / lymphatic invasion or involvement of tunica vaginalis
      pT3	invasion of spermatic cord
      pT4	invasion of scrotum
      pN0	negative lymph nodes
      pN1	node 20 mm; or 5 nodes involved all <20 mm
      pN2	node between 20 and 50 mm; or >5 nodes none >50 mm
      pN3	node mass >50 mm
      M0	no distant metastasis
      M1	distant metastasis
      S0	all markers normal
      S1	LDH <1.5 ULM + hCG <5,000mIU/mL + AFP <1,000 ng/mL
      S2	LDH <1.5 10 ULM hCG 5,000 50,000 mIU/mL AFP 1,000 10,000 ng/mL
      S3	LDH >10 ULM hCG >50,000 mIU/mL AFP >10,000 ng/mL
      ULM = upper limits of normal

    P.978

    
    

    • target / bull's eye appearance due to an echogenic center (secondary to compacted keratin / calcification)

    • confined by tunica albuginea

• diffuse testicular enlargement (10%)

• no blood flow on Doppler (avascular lesion)

• MR:

  • target appearance:

    • fibrous capsule of low signal intensity on T1WI + T2WI

    • cyst content (water and lipid) of high signal intensity on T1WI + T2WI

    • central calcification with center of low signal intensity

Prognosis:	no malignant potential
Rx:	enucleation + frozen section (to avoid orchiectomy)

Choriocarcinoma (1 3%)

Prevalence:	in 0.3% in pure form;in 8 16% in mixed germ cell tumors
Peak age:	20 30 years
Histo:	admixture of cytotrophoblastic + syncytiotrophoblastic cells
Spread:	may rapidly metastasize (lung, liver, GI tract, brain) without evidence of choriocarcinoma in primary lesion, pulmonary metastases develop in 81%

• symptoms of metastatic disease while primary not yet palpable

• serum -hCG always elevated (gynecomastia in 10%)

  N.B.:

  Choriocarcinoma has a proclivity for hemorrhage in primary site and metastases!

• often small tumor of mixed echotexture (hemorrhage, necrosis, calcifications)

• indistinct margins of pulmonary metastases (due to hemorrhage)

Prognosis:

death usually within 1 year of diagnosis; nearly 0 48% 5-year survival rate

Yolk Sac Tumor = Endodermal Sinus Tumor

• Equivalent to endodermal sinus tumor of ovary

• 80% of childhood testicular tumors!

• Present in 44% of mixed germ cell tumors of adults

  Age:

  2 years (80%)

• serum -fetoprotein elevated in >90% (exclusive to yolk sac elements)

• nonspecific imaging findings:

  • testicular enlargement without a mass

• pulmonary metastases (most common site of recurrent disease)

Sex Cord and Stromal Tumors = Interstitial Cell Tumors

Prevalence:

4% of all testicular tumors; 10 30% during childhood

• precocious virilism (children)

• gynecomastia (adults)

• loss of libido (adults)

• impotence (adults)

Rx:	orchiectomy; conservative resection under ultrasound guidance
Prognosis:	malignant in 10%

Leydig Cell Tumor

Prevalence:	1 3% of all testicular tumors
Origin:	interstitial cells forming the fibrovascular stroma
Age:	3 6 years; 20% in patients <10 years; 25% between ages 30 and 50 years; 25% in patients >50 years

• endocrinopathy (in 30%) with secretion of androgens or estrogens by the tumor:

  • precocious virilization

  • gynecomastia (in 30%)

  • decreased libido

• usually small hypoechoic nodule cystic areas (from hemorrhage / necrosis)

Prognosis:

benign:malignant = 9:1

Sertoli Cell Tumor

Prevalence:	<1% of all testicular tumors
Origin:	sex cords (derived from Sertoli cells of seminiferous tubules)
Peak age:	1st year of life

• may secrete estrogens (gynecomastia in 3%)

• usually well-circumscribed unilateral round / lobulated hypoechoic nodule

• multiple bilateral large areas of calcifications in large-cell calcifying Sertoli cell tumors (subtype of pediatric age group)

Associated with:	Peutz-Jegher syndrome, Carney syndrome
Prognosis:	benign:malignant = 9:1

Gonadoblastoma

• = primitive gonadal stroma tumor (exceedingly rare) containing sex cord-stromal elements + germ cells

• dysgenetic gonads

• abnormal karyotype in 80% (intersex status, phenotypically female)

Nonprimary Testicular Tumors

Metastases to Testis (in 0.7% of autopsies)

• in adults: prostate (35%) > lung (19%) > melanoma (9%), colon (9%) > kidney (7%), bladder, thyroid

  • More common than germ cell tumors in males >50 years of age!

• in children: neuroblastoma, Wilms tumor, rhabdomyosarcoma

• often multiple and bilateral

• mostly hypoechoic, occasionally echogenic masses

Lymphoma of Testis

• The most common bilateral testicular tumor!

  Incidence:

  5 6.7% of all testicular tumors; in <1% of patients with lymphoma; most common testicular tumor in men > age 60

• Presentation:

  • primary site of disease

  • initial manifestation of clinically occult disease

  • site of recurrent disease

    P.979

    
    

    Histo:	almost exclusively B-cell lymphoma (most commonly diffuse large cell lymphoma)
    Associated with:	extranodal involvement of skin, CNS, Waldeyer ring

• painless testicular enlargement

• weight loss, anorexia, fever, weakness (initial complaint in 25%)

  Location:

  bilateral in 38% (metachronous > synchronous)

• ill-defined diffuse infiltrative process

• focal hypoechoic mass / masses

• epididymis + spermatic cord commonly involved

Prognosis:

median survival of 13 months;12 35% 5-year survival

Leukemia of Testis

• Incidence:

  • 60 92% on autopsy;

  • 8 16% on clinical examination during therapy;

  • up to 41% on clinical examination after therapy

• Occult testicular tumor often found in patients in bone marrow remission (gonadal barrier = blood-testis barrier to chemotherapy)

• uni- / bilateral tumors:

  • diffuse / focal

  • hypo- or hyperechoic

Burned-out Tumor of Testis

• = Azzopardi TUMOR = REGRESSED GERM CELL TUMOR

• = widespread metastatic disease + spontaneous regression of testicular malignancy (teratocarcinoma)

  Histo:	minute amounts of residual tumor / dense deposit of collagen + scattered inflammatory cells
  Pathogenesis:	tumor with high metabolic rate outgrows its own blood supply

• small primary tumor:

  • hypoechoic lesion

  • highly echogenic focal lesion (= scarred tumor residue)

  • shadowing (= focal calcification)

• metastases to retroperitoneum, mediastinum, cervical / axillary / supraclavicular lymph nodes, lung, liver

Second Testicular Tumor

• Risk for second tumor in cryptorchidism:

  • 15% for inguinal, 30% for abdominal location

• Risk for second contralateral tumor:

  • 500 1,000 x; bilaterality in 1.1 4.4%;

• Development interval between 1st + 2nd tumor:

  • 4 months to 25 years

• Detected in 47% by 2 years; in 60% by 5 years,

  • in 75% by 10 years

• Synchronous contralateral tumor in 1 3%

• US: a testicular abnormality is malignant in only 50%!

Urothelial carcinoma

• = TRANSITIONAL CELL CARCINOMA

• Most common urinary tract cancer in USA + Europe!

  Prevalence:	85% of all urothelial tumors / primary renal pelvic tumors; 7% of all renal neoplasms
  Mean age:	68 years; M:F = 2.7:1; Whites > Blacks
  Pathogenesis:	chemical carcinogens act locally on epithelium (= field of change), action enhanced by length of contact time (eg, stasis / diverticulum)

• Risk factors:

  • tobacco (2 3 x)

  • aniline dye, benzidine, aromatic amines, azo dyes in textile, rubber, petroleum, printing, plastic manufacturing, arsenic in drinking water (lag time of 10 years)

  • cyclophosphamide therapy (lag time of 6.5 years)

  • analgesic abuse (8 increase): phenacetin

  • Balkan nephritis (= progressive renal failure + development of bilateral and multiple tumors)

  • recurrent / chronic urinary tract infection

• Classification:

  • papillary lesion (85%) with predominantly exophytic growth = frondlike structure with central fibrovascular core lined by epithelial layer

    • broad based

    • pedunculated

  • infiltrating: usually higher grade + less common

  • carcinoma in situ

    Grade:	usually correlates with stage
    	1 = cells slightly anaplastic
    	2 = intermediate features
    	3 = marked cellular pleomorphism
    Metastases:	regional lymph nodes, peritoneum, liver

• frank / microscopic painless hematuria (72%)

• dull flank pain (22%)

• acute renal colic (due to obstruction)

  Location:

  bladder 30 50 more common than upper urinary tract

• Propensity for multicentricity with synchronous and metachronous bladder + upper tract tumors!

Renal and Ureteral TCC

• @ Kidney

  Site:

  extrarenal part of renal pelvis > infundibulocaliceal region

  • IVP:

    • single / multiple sessile / pedunculated mulberry-like filling defects in renal pelvis (35%):

      • stipple sign = contrast material trapped in interstices (DDx: blood clot, fungus ball)

    • dilated calyx with filling defect (26%) due to partial / complete obstruction of infundibulum:

      • phantom calyx = failure to opacify from obstruction (DDx: TB stricture of infundibulum)

        Staging of Transitional Cell Cancer of the Kidney

        TNM	AJCC	Description
        Tis	0	in situ lesion
        Ta		noninvasive papillary carcinoma
        T1	I	invasion of subepithelial connective tissue
        T2	II	confined to muscularis layer
        T3	III	invasion of renal parenchyma / peripelvic soft tissues
        T4	IV	extension beyond renal capsule

      P.980

      
      

      • focal delayed increasingly dense nephrogram

      • oncocalyx = caliceal distension with tumor

    • caliceal amputation (19%)

    • absent / decreased excretion with renal atrophy (13%) due to long-standing obstruction of ureteropelvic junction

    • hydronephrosis with renal enlargement (6%) due to tumor obstruction of ureteropelvic junction

    • infiltrative invasion of renal parenchyma maintaining a bean-shaped kidney

  • US:

    • bulky hypoechoic (similar to renal parenchyma) / hyperechoic mass lesion

    • infiltrative without disruption of renal contour

    • splitting / separation of central renal sinus complex

    • caliectasis without pelviectasis

  • CT (52% accuracy due to overstaging):

    • sessile filling defect in opacified collecting system

    • thickening + induration of pelvicaliceal wall

    • central solid mass in renal pelvis expanding centrifugally

      • obliteration / compression of renal sinus fat

    • invasion of renal parenchyma (infiltrating growth pattern) with preservation of renal contour

    • coarse punctate calcific deposits (0.7 6.7%) may mimic urinary calculi

    • variable enhancement of tumor

• @ Ureter

  Site:

  lower 1/3 (70%), mid 1/3 (15%), upper 1/3 (15%)

• IVP:

  • nonfunctioning kidney in advanced tumor (46%)

  • hydronephrosis hydroureter (34%)

  • single / multiple ureteral filling defects (19%)

  • irregular narrowing of ureteral lumen

• Retrograde:

  • champagne glass / chalice / goblet sign

  • = focal expansion of ureter around + distal to mass (probably secondary to to-and-fro peristalsis of mass)

  • Bergman sign = catheter-coiling sign = coiling of catheter on retrograde catheterization below the mass

• CT:

  • intraluminal soft-tissue mass

  • eccentric / circumferential thickening of ureteral wall

Dx:	cytologic analysis of urine (selective lavage, ureteral urine collection, brush biopsy, ureteroscopy
DDx:	papilloma (benign lesion, fronds lined by normal epithelium)
Prognosis:	77 80% 5-year survival rate without invasion of muscularis mucosa; 5% 5-year survival rate with invasion of muscularis mucosa

Metachronous TCC in Upper Urinary Tract

• in 12% of pelvic + ureteral primaries (within 25 months)

• in 4% of bladder primaries (2/3 within 2 years, up to 20 years later)

Bladder TCC

Incidence:	63,210 new cases + 13,180 deaths in USA (2005); 5% of all new malignant neoplasms; most common tumor of genitourinary tract;
	2% of all cancer deaths in United States
Age:	usually in patients >65 years; 3.1% in patients <44 years; 8% in patients between 45 and 54 years; twice as frequent >80 years; M:F = 3 4:1

• Additional risk factors for bladder cancer:

  • bladder stones, bladder diverticulum (2 10% risk), chronic infection / irritation

    Staging accuracy:	50% clinically; 32 80% for CT; 72 96% for MR
    Overstaging due to:	edema following endoscopy / endoscopic resection, fibrosis from radiation therapy

  • Presentation:

    • Superficial papillary lesion (70%): papilloma, inverted papilloma, papillary urothelial neoplasm of low malignant potential (PUNLMP), low-grade and high-grade papillary urothelial carcinoma

      • in 20% progressing to invasive cancer

    • Aggressive invasive de novo tumor (20%)

    • Metastatic tumor (10%)

  • gross hematuria

  • frequency, dysuria, pelvic pain / pressure

    Location:	bladder base (80%); lateral wall of bladder, bladder diverticulum (in 0.8 10.8%); single (in 60%)
    Size:	<2.5 cm (in >50%)

  • intraluminal papillary / nodular mass

  • focal / diffuse wall thickening

  • ureteral obstruction indicates muscle invasion

  • IVP (70% accuracy rate):

    • irregular filling defect with broad base and fronds (DDx: rectal gas marginated by Simpson's white line)

    • <1% calcified

  • US:

    • papillary hypoechoic mass protruding into lumen

    • vascularity on Doppler imaging

      Staging of Bladder Cancer

      Jewett-Strong	TNM	Histopathologic Findings
      O	T0	no tumor
      	Tis	carcinoma in situ
      	Ta	papillary tumor confined to mucosa
      A	T1	invasion of lamina propria
      B1	T2a	of inner half of muscle
      B2	T2b	of outer half of muscle
      C	T3	of perivesical fat
      D1	T4a	of surrounding organs (seminal vesicles, prostate, rectum)
      	T4b	pelvic / abdominal wall
      	N1	metastasis to single node =2 cm
      	N2	metastasis to single node of 2-5 cm / in multiple nodes =5 cm
      	N3	metastasis to single node > 5 cm
      D2	N4	lymph node metastasis above bifurcation of common iliac arteries
      	M1	distant metastasis (lung, liver, bone)

  P.981

  
  

  • CT (delay for >7 days after instrumentation):

    • nodular/ arched tumoral calcifications (<5%) typically encrusting the surface

    • early tumor enhancement

    • increased attenuation of perivesical fat with invasion

  • MR (staging modality of choice):

    • tumor isointense to bladder muscle on T1WI + hyperintense on T2WI

    • T1WI optimal to detect invasion of perivesical fat, metastases to lymph nodes + bone

    • T2WI optimal to differentiate tumor from fibrosis + to evaluate tumor depth

    • enhancement differentiates between early enhancing mucosa, submucosa, tumor, nonenhancing muscle, edema + fibrosis

Prognosis:

40 70% recurrence rate

Multicentricity of Urothelial Cancers

• Additional bladder tumor (30 40%)

• Upper tract tumor (2.6 4.5%)

Metachronous TCC of Bladder

• in 23 40% of primary renal TCC after 15 48 months

• in 20 50% of primary ureteral TCC after 10 24 months

Synchronous TCC

• both renal pelves (in 1 2%)

• both ureters (in 2 9%)

• bladder

  • in 24% of primary renal pelvic involvement

  • in 39% of primary ureteral involvement

  • in 2% of primary bladder involvement

Prognosis:	overall 82% 5-year survival rate; after cystectomy 55 80% 5-year survival with tumor confined to lamina propria, 40% with invasion of muscularis propria, 20% with invasion of perivesical fat, 6% for metastatic cancer
Rx:	cystoscopic resection, intravesical mitomycin C, radical cystectomy with urinary diversion

Trauma to Kidney

Incidence:

10% of injuries in emergency department

• Indications for imaging:

  • Penetrating injury + hematuria

  • Blunt trauma + hematuria + hypotension <90 mm Hg

  • Microscopic hematuria + positive peritoneal lavage

  • Blunt trauma + known association with renal injury (contusion / hematoma of flank, fracture of lower ribs, fracture of transverse processes, fracture of thoracolumbar spine)

• Classification:

  • MINOR RENAL INJURY (75 85%)

    • no / limited perinephric hematoma

      DDx:

      respiratory motion artifact (low-attenuation area surrounding kidney)

    • no extravasation of urine (= no caliceal disruption)

      • Intrarenal hemorrhage / hematoma = renal contusion

        • hyperattenuating area of 40 70 HU (= acute clotted blood) on NECT

        • sharply / poorly defined round / ovoid area of decreased enhancement during CECT (DDx: renal infarction with no enhancement)

        • focal area of striation on delayed nephrogram

        • area of persistent contrast material staining on very delayed scan

      • Subcapsular hematoma

        • round / lenticular-shaped fluid collection + flattening of subjacent parenchyma

      • Perinephric hematoma without extension to collecting system / medulla

        • defects in periphery of renal parenchyma

        • limited perinephric hematoma with attenuation values of 45 90 HU

        • Subcapsular / perinephric hematoma usually proportional to extent of injury

      • Small subsegmental cortical infarct

        Cause:

        stretching + thrombotic occlusion of accessory renal artery / capsular artery / segmental artery

        • sharply demarcated wedge-shaped area of decreased contrast enhancement

          Rx:

          observation

  • II. MAJOR RENAL LACERATION (10%)

    • = complete cortical laceration / fracture extending to medulla collecting system

    • laceration connecting two cortical surfaces = renal fracture = separation of renal poles

    • devascularization of renal parenchyma

    • without involvement of collecting system:

      • nonenhancing deep parenchymal cleft filled with hematoma on CECT

      • perirenal hematoma from capsular disruption

    • with involvement of collecting system:

      • urine extravasation of contrast material on delayed images 3 5 minutes after injection

        Renal injury scale (American Association of Surgeons in Trauma)

        Grade 1	hematuria + normal imaging findings; renal contusion; nonexpanding subcapsular hematoma
        Grade 2	laceration of cortex (<1 cm deep); nonexpanding perirenal hematoma
        Grade 3	laceration of cortex + medulla (>1 cm deep)
        Grade 4	(a) parenchymal injury: laceration involving collecting system
        	(b) vessel injury: injury to renal artery / vein with contained hemorrhage; thrombosis of segmental artery
        Grade 5	(a) parenchymal injury: shattered kidney
        	(b) devascularizing injury: avulsion / in situ thrombosis of main renal artery

    P.982

    
    

    • active hemorrhage / pseudoaneurysm:

      • Hemodynamic decompensation may be imminent in 38%!

      • intense contrast enhancement within a laceration / hematoma during early phase:

        • linear / flamelike contrast extravasation of 80 370 HU or within 10 15 HU of aortic density

          Rx:

          variable (clinical judgement required)

  • III. CATASTROPHIC RENAL INJURY (5%)

    • extravasation of contrast material with patchy areas of 85 370 HU (= active bleeding)

      • Multiple renal lacerations = shattered kidney

        • multiple separate renal fragments

        • lack of enhancement of part of kidney (due to segmental renal arterial infarctions)

        • cortical rim nephrogram (= enhancement of renal periphery through intact capsular / collateral vessels)

          Rx:

          surgical exploration / nephrectomy

      • Vascular injury of renal pedicle

        • = occlusion of main renal artery by intimal flap; thrombosis / laceration of renal vein is RARE

        • hematuria may be absent

        • abrupt termination of main renal artery just beyond its origin

        • minimal hematoma around proximal renal a.

        • absence of perinephric hematoma (HALLMARK)

        • absent nephrogram on affected side

        • retrograde opacification of ipsilateral renal vein

        • cortical rim nephrogram (develops >8 hours after injury)

          Rx:

          revascularization procedure (in 14% return of renal function)

      • Avulsion of renal artery (rare)

        • = tearing of tunica muscularis + adventitia

        • absent contrast enhancement (= global infarct)

        • extensive medial perirenal hematoma

        • active arterial bleeding

          Prognosis:

          life-threatening

      • Thrombosis / laceration of renal vein (rare)

        • intraluminal thrombus in dilated renal vein

        • acute venous hypertension:

          • nephromegaly

          • diminished nephrogram

          • delayed nephrographic progression

          • decreased excretion

  • IV. INJURY OF THE UPJ (rare)

    • = laceration (= incomplete tear in 60%) / avulsion

      • (= complete transection) of ureter at UPJ

        

        Renal Trauma Grading System (American Association of Surgeons in Trauma)

        P.983

        
        

        Mechanism:	tension on renal pedicle by sudden deceleration
        Age:	usually young boys
        Associated with:	fracture of transverse process (30%)

      • gross / microscopic hematuria (53 60%)

        N.B.:

        delayed images to check for urine leak!

      • massive extravasation of contrast material medially in the region of UPJ

      • nonfilling of affected ureter (with avulsion)

      • circumferential perinephric urinoma

Cx:

posttraumatic renovascular hypertension

Blunt Trauma to Kidney

Incidence:	80 90% of all renal injuries
Cause:	motor vehicle accident, contact sports, falls, fights, assaults
Mechanism:	direct blow (>80%) often lacerated by lower ribs, acceleration-deceleration (renal artery tear)
Associated with:	other organ injury in 75%

• >95% hematuria (>5 RBCs per high-power field):

  N.B.:

  poor correlation between severity of hematuria + severity of renal injury

  • 25% of patients with gross hematuria have significant injuries!

  • 24% of patients with renal pedicle injury have no hematuria!

  • Normotensive patients with microscopic hematuria (<35 RBCs per high-power field) have a significant renal injury in <0.2%!

Location:	simultaneous upper + lower GU tract injury in <5%
Rx:	The only absolute indication for surgery is life-threatening active bleeding! Urine leaks will close spontaneously in 87%!

Penetrating Renal Trauma

Incidence:	10 20% of all renal trauma
Cause:	gunshot, shrapnel, stab wound
Associated with:	multiorgan injuries in 80%
Cx:	bullet colic , buckshot colic , birdshot calculus = ureteral obstruction 2 to migrating missiles

Blunt Trauma to Urinary Bladder

Associated with:

pelvic fracture in 70%

• Indications for urethrogram:

  • blood at urethral meatus

  • floating prostate

  • inability to pass Foley catheter

  • symphysis diastasis

• CT cystogram:

  • focal thickening of bladder wall = contusion

  • contrast extravasation

Bladder Contusion (most common injury)

• = intramural hematoma

• no extravasation

• lack of normal distensibility

• crescent-shaped filling defect in contrast-distended bladder

Interstitial Bladder Injury (uncommon)

• = bladder tear without serosal involvement

Bladder Rupture

Cystography:

diagnostic in >85%; false-negatives if tear sealed by hematoma / mesentery

Extraperitoneal Rupture of Bladder (80%)

Cause:	pelvic fracture (sharp bony spicule) or avulsion tear at fixation points of puboprostatic ligaments
Location:	usually close to base of bladder anterolaterally

• Plain film:

  • pear-shaped bladder

  • loss of obturator fat planes

  • paralytic ileus

  • upward displacement of ileal loops

• Contrast examination:

  • flame-shaped contrast extravasation into perivesical fat, best seen on postvoid films, may extend into thigh / anterior abdominal wall

• US:

  • bladder within a bladder = bladder surrounded by fluid collection

Intraperitoneal Rupture of Bladder (20 30%)

• Cause:

  • usually as a result of invasive procedure (cystoscopy), stab wound, surgery

  • blunt trauma with sudden rise in intravesical pressure (requires distended bladder)

    Location:

    usually at dome of bladder

• contrast extravasation into paracolic gutters

• contrast outlining small bowel loops

• uriniferous ascites

Combined Intra- and Extraperitoneal Rupture (5%)

 

Tuberculosis

• Urogenital tract is the second most common site after lung; almost always affects the kidney first as a hematogenous focus from lung / bone / GI tract

  Age:	usually before age 50; M > F
  Path:	organisms lodge in the periglomerular capillaries; breakdown in host immunity results in extensive necrosis + fibrosis (coalescing cortical granulomas); organisms spill down the nephrons and become trapped in the narrow segment of the loop of Henle forming ulcerocavernous papillary lesions, which erode into collecting system

• Spread:

  • (a) contiguous: from renal parenchyma along urothelium to infundibula, renal pelvis, ureter, bladder

  • (b) hematogenous (rare): epididymis, testis

  • It is unusual for genitourinary sites to be affected without involvement of kidney first!

• gross / microscopic hematuria

• sterile pyuria

• frequency, urgency, dysuria

P.984




• history of previous clinical TB (25%) with a lag time of 2 20 years

• IVP (abnormal in 85 90%)

Extrarenal Signs of TB on Abdominal Plain Film

• osseous / paraspinous changes of TB (diskitis + psoas abscess)

• calcified granulomas in liver, spleen, lymph nodes, adrenals

Renal Tuberculosis

• Renal TB in 5 10% of patients with pulmonary TB!

• Radiographic evidence of pulmonary TB in <50% of patients with renal TB (only 5% have active cavitary TB)!

  Location:

  unilateral renal involvement in 75%

• renal size: enlarged (early) / small (late) / normal (most common):

  • putty kidney = tuberculous pyonephrosis from ureteral stricture

  • autonephrectomy = small shrunken scarred nonfunctioning kidney dystrophic calcifications

  • cortical scars, often associated with parenchymal calcifications:

    • distortion of collecting system due to adjacent cortical scarring

• displacement of collecting system secondary to tuberculoma of low attenuation (initial infection)

• moth-eaten calyx = smudged papillae = irregular feathery appearance of surface of papilla due to erosion (earliest sign)

• cavities communicating with collecting system:

  • irregular tract formations from calyx into papilla

  • large irregular cavities with extensive destruction

  • blunted dilated calyces = papillary necrosis

• strictures of infundibula / renal pelvis:

  • dilated calices (hydrocalicosis) often with sharply defined circumferential narrowing (infundibular strictures) at one / several sites (most common finding)

  • caliceal truncation

  • phantom calyx / amputated calyx = incomplete visualization of calyx due to infundibular stenosis

  • reduced capacity of renal pelvis

  • Kerr kink = kinking of renal pelvis

  • mural thickening of collecting system

• dystrophic amorphous parenchymal calcifications in tuberculomas (in 25%): amorphous / granular / curvilinear / punctate / confluent ( toothpaste ) / involving entire kidney ( putty kidney ):

  • nephrolithiasis (in 10%)

• globally poor renal function

• infection may extend into peri- / pararenal space + psoas

Ureteral Tuberculosis

Incidence:	in 50% of genitourinary TB; always with evidence of renal involvement as it spreads from kidney
Location:	either end of ureter (most commonly distal 1/3), usually asymmetric, may be unilateral

• ureteral filling defects (due to mucosal granulomas)

• saw-tooth ureter = irregular jagged contour secondary to dilatation (from ureterovesical junction obstruction) + multiple small mucosal ulcerations + wall edema (early changes)

• strictures (late changes):

  beaded ureter	= alternating areas of strictures + dilatations
  corkscrew ureter	= marked tortuosity with strictures + dilatations
  pipestem ureter	= rigid aperistaltic foreshortened thick and straight ureter

• vesicoureteral reflux through fixed patulous orifice

• ureteral calcifications uncommon (usually in distal portion)

• CT:

  • thickening of ureteral wall with periureteric inflammation

Bladder Tuberculosis

• Infection from renal source causing interstitial cystitis

• thickened bladder wall (= muscle hypertrophy + inflammatory tuberculomas)

• filling defects (due to multiple granulomas)

• bladder wall ulcerations

• shrunken bladder = scarred bladder with diminished capacity

• thimble bladder = diminutive irregular bladder

• bladder wall calcifications (rare)

Cx:

fistula / sinus tract / vesicoureteral reflux (due to fibrosis of ureteral orifice)

Male Genital Tuberculosis

• calcifications in 10% (diabetes more common cause)

  • Tuberculous prostatitis / prostatic abscess:

    • hypoechoic irregular area in peripheral zone

    • hypoattenuating prostatic lesion

    • hypointense diffuse radiating streaky areas on T2WI (= watermelon sign )

    • peripheral enhancement

  • Tuberculous epididymitis

    • ascending / descending route of infection

  • Tuberculous orchitis

    • direct extension from epididymal infection, rarely from hematogenous spread

DDx:

brucellosis, fungal infections (identical picture)

Female Genital Tuberculosis

• Salpingitis (94%): mostly bilateral

• Tuboovarian abscess: extension into extraperitoneal compartment

Unicaliceal (Unipapillary) Kidney

Path:	oligomeganephronia = reduced number of nephrons and enlargement of glomeruli
Associated with:	absence of contralateral kidney, other anomalies

• hypertension

• proteinuria

• azotemia

Urachal anomalies

• urachus = median umbilical ligament = thick fibrous cord as the remnant of the allantois (= endodermal outgrowth from yolk sac into stalk), which regresses at 5th month of development

P.985

Cx:

infection (23%), intestinal obstruction, hemorrhage into cyst, peritonitis from rupture, malignant degeneration

Alternating Sinus

• = cystic dilatation of urachus periodically emptying into bladder / umbilicus

Patent Urachus

• = fistula between bladder and umbilicus

  Incidence:

  1:200,000 live births

• urine draining from umbilicus

Urachal Cyst (30%)

• = gradually enlarging cyst due to closure of both ends of urachus

  Incidence:

  1:5,000 (at autopsy)

• asymptomatic in children unless rupture occurs

• symptomatic in adults due to enlargement / infection

• cystic extraperitoneal mass

Urachal Diverticulum (3%)

• = urachus communicates only with bladder dome

Urachal Sinus

• = urachus patent only at umbilicus

  Associated with:

  urachal cyst

• umbilical mass / inflammation drainage

• thickened tubular structure with echogenic center

Urachal carcinoma

• = rare tumor arising from the urachus (vestigial remnant of cloaca + allantois) within space of Retzius

  Incidence:	0.01% of all adult cancers; 0.17 0.34% of all bladder cancers; 20 40% of all primary bladder adenocarcinomas
  Cause:	columnar epithelial metaplasia in urachal remnant

• Histo:

  • adenocarcinoma (84 90%), in 75% mucin producing

    • 34% of all bladder adenocarcinomas are urachal in origin

  • urothelial cancer (3%), sarcoma, squamous cell carcinoma

    • 75% of urachal neoplasms in patients <20 years of age are sarcomas!

  Age:

  40 70 years; M:F = 2:1 3:1

• suprapubic mass, abdominal pain

• hematuria (71%)

• discharge of blood, pus, mucus from umbilicus

• irritative voiding symptoms

• mucous micturition (25%)

  Location:	supravesical, midline, anterior (80%), extraperitoneally in space of Retzius (bounded by transversalis fascia ventrally + peritoneum dorsally)
  Site:	close to bladder (90%); along course of urachus / at umbilical end (10%)

• midline mass anterosuperior to vesical dome in the space of Retzius with predominantly muscular / extravesical involvement

• tumor bulk outside bladder + invasion of bladder dome (88%)

• mean tumor size of 6 cm

• low-attenuation mass in 60% (mucin)

  Stages of Urachal Carcinoma

  I	cancer limited to urachus
  II	invasion limited to urachus
  III A	local invasion of bladder
  III B	invasion of abdominal wall
  III C	invasion of peritoneum
  III D	invasion of other viscera
  IV A	metastases to local lymph nodes
  IV B	distant metastases (liver)

• often peripheral curvilinear / stippled psammomatous calcifications (50 72%) PATHOGNOMONIC for mucinous adenocarcinoma

• heterogeneous enhancement

• markedly increased signal intensity on T2WI (from mucin)

Cx:	pseudomyxoma peritonei (in peritoneal carcinomatosis)
Prognosis:	7 43% 5-year survival rate
Rx:	radical cystectomy
DDx:	infected benign urachal cyst, primary / secondary bladder tumor, desmoid tumor

Ureteral Duplication

• = RENAL DUPLICATION

Complete Duplication of Ureter

Cause:	second ureteral bud arising from mesonephric duct leading to complete ureteral duplication
Prevalence:	0.2% of live births; M:F = 1:2; in 15 40% bilateral
Risk of recurrence:	12% in 1st-degree relatives
Embryology:	ureters develop from separate ureteric buds originating from a single Wolffian duct

• renal enlargement

• tortuous dilated lower pole ureter

• US:

  • two separate echodense renal sinuses + pelves separated by parenchymal bridge

• IVP:

  • poor / nonvisualization of upper pole collecting system (delayed films):

    • drooping lily sign = hydronephrosis + decreased function of obstructed upper pole moiety causing downward displacement of lower pole calyces

  • lateral + downward displacement of lower pole collecting system + ureter:

    • nubbin sign = scarring, atrophy, and decreased function of lower pole moiety may simulate a renal mass

  • displacement of proximal orifice upward

• VCUG:

  • ureterocele

  • reflux into lower moiety (rare)

Cx:	(1) Vesicoureteral reflux (most commonly)
	(2) Ectopic ureteral insertion
	(3) Ectopic ureterocele
	(4) Ureteropelvic junction obstruction of lower pole

P.986

Weigert-Meyer Rule

• upper moiety ureter

  • remains with wolffian duct longer, passes through bladder wall + inserts ectopic inferior and medial to lower moiety ureter below the level of the trigone / into any wolffian duct derivative;

• lower moiety ureter

  • drains lower pole and interpolar portion; is incorporated into developing bladder first, ascends during bladder growth + enters bladder at trigone

Upper Moiety Ureter

• Subject to ureteral obstruction due to stenosis at ectopic ureteral insertion / ectopic ureterocele / aberrant artery crossing!

• The ectopic ureteral orifice is inferior + medial to orthotopic ureteral orifice!

  Associated with:

  significant renal dysplasia

• Site of insertion of ectopic ureter:

  • M: suprasphincteric insertion:

    • low in bladder, bladder neck, prostatic urethra, vas deferens, seminal vesicle (seminal vesical cyst), ejaculatory duct

      • NO ENURESIS in males as insertion is always above external sphincter

      • epididymitis / orchitis in preadolescent male

      • urge incontinence (insertion into posterior urethra)

  • F: infrasphincteric insertion:

    • distal urethra, vaginal vestibule, vagina, cervix, uterus, fallopian tube, rectum

      • WETTING in upright females if insertion is below external sphincter (common)

      • intermittent / constant dribbling

Cx:

upper pole obstructive hydronephrosis

Lower Moiety Ureter

• Subject to vesicoureteral reflux due to its shortened ureteral tunnel at bladder insertion!

  Cx:

  lower pole of duplex kidney may atrophy (in 50%) secondary to chronic pyelonephritis from reflux nephropathy (= reflux infection)

  • clubbed calyces underneath focal scars

Incomplete / Partial Duplication of Ureter

• = branching of single ureteral bud (common distal ureter + one ureteral orifice) before reaching metanephric blastema

  Prevalence:	in 0.6% of urograms
  Associated with:	ureteropelvic junction obstruction of lower renal pole

• bifid ureter (in early branching)

• bifid pelvis (in late branching)

• ureteroureteral reflux = yo-yo / saddle / seesaw peristalsis = urine moves down the cephalad ureter + refluxes up the lower pole ureter and vice versa

• asymmetric dilatation of one ureteral segment

• upper pole ureter may end blindly (seen on retrograde injection only)

Cx:

urinary tract infections

Ureterocele

• = cystic ectasia of subepithelial segment of intravesical ureter

  Prevalence:

  1:5,000 to 1:12,000 children

• IVP:

  • early filling of bulbous terminal ureter ( cobra head )

  • radiolucent halo (= ureteral wall + adjacent bladder urothelium)

• VCUG:

  • round / oval lucent defect near trigone

  • effacement with increased bladder distension

  • eversion during voiding

Simple Ureterocele

• = ORTHOTOPIC URETEROCELE

• = congenital prolapse of dilated distal ureter + orifice into bladder lumen at the usual location of the trigone, typically seen with single ureter

Presentation:	incidental finding in adults; M:F = 2:3; bilateral in 33%
Cx:	(1) Pyelocaliceal dilatation
	(2) Prolapse into bladder neck / urethra causing obstruction (rare)
	(3) Wall thickening secondary to edema from impacted stone / infection

Ectopic Ureterocele

• = ureteral bud arising in an abnormal cephalad position from the mesonephric duct and moving caudally resulting in an ureteral orifice distal to trigone within / outside bladder

Incidence:

in 10% bilateral

• in single nonduplicated system (20%)

  • M:F = 1:1

  • hypoplastic / absent ipsilateral trigone

  • poorly visualized / nonvisualized kidney

  • small / poorly functioning kidney

• in upper moiety ureter of duplex kidney (80%)

  • M:F = 1:4 1:8

Cx:	(1) Bladder outlet obstruction (from ectopic ureterocele prolapsing into bladder neck / urethra)
	(2) Contralateral ureteral obstruction (if ectopic ureterocele large)
	(3) Multicystic dysplastic kidney (the further the orifice from normal site of insertion, the more dysplastic the kidney!)

Pseudoureterocele

• = obstruction of an otherwise normal intramural ureter mimicking ureterocele

• Cause:

  • Tumor

    • bladder tumor (most common in adults), invasion by cervical cancer, pheochromocytoma of intravesical ureter

  • Edema

    • from impacted ureteral calculus (most common in children), radiation cystitis, following ureteral instrumentation, schistosomiasis

• thick, irregular halo in urinary bladder

• cobra head / spring onion appearance of distal ureter

P.987




• NO protrusion of ureter into bladder lumen (oblique views + cystoscopy normal)

Ureteropelvic Junction Obstruction

• Most common cause of fetal / neonatal hydronephrosis

  Age at discovery:

  <15 years (25%); >40 years (50%)

• Cause:

  • Primary UPJ obstruction

    • intrinsic cause

      • primarily functional (= adynamic segment) with impaired formation of urine bolus

        • replacement of UPJ muscle by excessive collagen

        • abnormal arrangement of junction muscles causing dysmotility (69%)

        • abnormal intercellular conduction

        • high ureteral insertion

        • mucosal folds in upper ureter

    • extrinsic cause

      • aberrant vessels to lower pole (in 25 39% of adult patients): anterior to UPJ (90 95%), posterior to UPJ (5 10%)

      • fixed kinks / angulation

      • adventitial bands

      • renal cyst

      • aortic aneurysm

  • Secondary UPJ obstruction

    • infection: eosinophilic ureteritis, XGP

    • stones

    • ischemia

    • iatrogenic injury

• Associated anomalies (27%):

  • vesicoureteral reflux, bilateral ureteral duplication, bilateral obstructed megaureter, contralateral multicystic dysplastic kidney, contralateral renal agenesis, meatal stenosis, hypospadia

• M:F = 5:1

• abdominal mass, abdominal pain, hematuria, UTI

  Location:

  left > right side; bilateral (10 20 40%)

• large dilated anechoic renal pelvis communicating with calyces, no dilatation of ureter

• IVP:

  • sharply defined narrowing at UPJ

  • pelvicaliectasis without ureterectasis

  • anterior rotation of pelvis

  • broad tangential sharply defined extrinsic compression (in arterial crossing)

  • longitudinal striae of redundant mucosa (in dehydrated state)

  • late changes: unilateral renal enlargement, diminished opacification, wasting of kidney substance

  • balloon-on-a-string sign:

    • caliceal crescents surrounding dilated collecting system

    • eccentric exit of ureter from dilated renal pelvis

• NUC: confirm obstruction at UPJ + determine function

• OB-US:

  • enlargement of renal pelvis + branching infundibula + calyces

  • anteroposterior diameter of renal pelvis 10 mm

  • large unilocular fluid collection (severely dilated collecting system)

    DDx:

    multicystic dysplastic kidney, perinephric urinoma

• ADDITIONAL TESTS:

  • Diuresis excretory urography (Whitfield): accurate in 85%

  • Diuresis renography (Iodine-131-iodohippurate sodium / Tc-99m-DTPA)

  • Pressure flow urodynamic study (Whitaker)

Rx:

early surgical correction may be needed to preserve renal function

Urethral diverticulum

Age:

26 74 years; 6 more common in black women

• urinary incontinence (9 32 70%)

• asymptomatic (3 20%)

Congenital Urethral Diverticulum

Cause:

ectopic cloacal epithelium

• M > F

Acquired Urethral Diverticulum

Prevalence:

0.6 6%; M < F

• Cause:

  • obstruction of paraurethral glands (of Skene) with subsequent infection + rupture into urethra

  • trauma: catheterization / childbirth

    May be associated with:	cloacal epithelium, wolffian / m llerian duct remnant
    Site:	posterolateral aspect of midurethra

• vague urinary tract symptoms mimicking chronic / interstitial cystitis, carcinoma in situ of the bladder, detrusor instability

• dyspareunia

• tender cystic swelling protruding from anterior wall of vagina + expulsion of purulent material

• dribbling after voiding

• frequency / urgency (67%), dysuria (45%)

• recurrent urinary tract infections (40%)

• Voiding cystourethrography (65% accurate):

  • rounded / elongated sac connected to urethra

• MR:

  • multiseptated cystic lesion surrounding urethra

  • heterogeneous hyperintense signal compared with urine on T1WI / fluid-fluid levels on T2WI if inflammation present

Cx:	(1) Infection
	(2) Stone formation (in up to 10%)
	(3) Malignant degeneration (5% of all urethral carcinomas)
DDx:	(1) Vaginal cyst (Gartner duct cyst, paramesonephric cyst, m llerian duct cyst, epithelial inclusion cyst)
	(2) Ectopic ureterocele
	(3) Endometrioma
	(4) Urethral tumor

Urethral Trauma

Incidence:	in 4 17% of pelvic fractures in males, in <1% of pelvic fractures in females
Associated with:	bladder injury in 20%

• Types:

  • I = separation of puboprostatic ligament with craniad displacement of prostate (least common)

    P.988

    
    

    • elongated narrowed urethra

    • elevation of bladder (displacement by hematoma)

  • II = urethral rupture at prostatomembranous junction above urogenital diaphragm

    • contrast extravasation into true pelvis

  • III = rupture of proximal bulbous urethra below the urogenital diaphragm (most common injury)

    • contrast extravasation into perineum scrotum

Cx:	(1) Urethral stricture (38 100%)
	(2) Impotence (in up to 40%)
	(3) Incontinence (30%)

Urinoma

• = uriniferous perirenal pseudocyst secondary to tear in collecting system with continuing renal function

• Etiology:

  • nonobstructive: blunt / penetrating trauma, surgery, infection, calculus erosion

  • obstructive:

    • ureteral obstruction (calculus, surgical ligature, neoplasm)

    • bladder outlet obstruction (posterior urethral valves)

  • Augmented by sudden diuretic load of urographic contrast material!

    Path:

    fibroblastic cavity (in 5 12 days), dense connective tissue encapsulation (in 3 6 weeks)

• malaise, nausea, fever

• hematuria (10 50%)

• fluctuant tender mass

• Location:

  • cystic mass in perirenal space = localized perirenal urinoma (most common)

  • cystic mass filling entire perirenal space = diffuse perirenal urinoma

  • sickle-shaped collection = subcapsular urinoma

  • encapsulated expanding intrarenal cystic mass separating renal tissue fragments = intrarenal urinoma

• Plain radiography:

  • soft-tissue mass obliterating retroperitoneal structures

  • superior + lateral displacement of kidney

• CT:

  • extravasation of contrast material

  • smooth thin-walled cavity ( 10 to +30 HU)

  • frequently associated with urine ascites

Cx:	retroperitoneal fibrosis, stricture of upper ureter, perinephric abscess
	Renal dysplasia of affected kidney in almost 100% when detected in utero!
Dx:	aspirated fluid with high urea concentration
DDx:	lymphocele, hematoma, abscess, renal cyst, pancreatic pseudocyst, ascites

Urolithiasis

• = NEPHROLITHIASIS

• Most common cause of calcification within the kidney:

  • 12% of population develop a renal stone by age 70

  • 2 3% of population experience an attack of acute renal colic during their lifetime

  • Patients with acute flank pain have ureteral calculi in 67 95%

    Annual incidence:	1 2:1,000; M:F = 4:1
    Age:	30 60 years

• Anderson-Carr-Randall theory of renal stone formation:

  • in the presence of abnormally high calcium excretion exceeding lymphatic capacity, microaggregates of calcium (present in the normal kidney) occur in medulla, increase in size, migrate toward caliceal epithelium, and rupture into calyces to form calculi

    • nucleation theory

      • = crystal / foreign body initiates formation in urine supersaturated with crystallizing salt

    • stone matrix theory

      • = organic matrix of urinary proteins + serum serves as framework for deposition of crystals

    • inhibitor theory

      • = little / no concentration of urinary stone inhibitors (citrate, pyrophosphate, glycosaminoglycan, nephrocalcin, Tamm-Horsfall protein) results in crystal formation

  • Composition:

    calcium oxalate	75%
    struvite	15%
    calcium phosphate	5%
    uric acid	5%
    cystine	1%

  • Cause:

    • genetics, diet, employment, geography, history of urinary tract infection

    • 70 80% of patients with first-time stones have a specific metabolic disorder (idiopathic hyperclaciuria, secondary hyperclaciuria (sarcoidosis, hyperparathyroidism), hyperuricosuria (gout, Lesch-Nyhan syndrome, hyperoxaluria, cystinuria)

  • 1. Hypercalciuria

    • with hypercalcemia (50%):

      • primary hyperparathyroidism, milk-alkali syndrome, hypervitaminosis D, malignant neoplasm, Paget disease, prolonged immobilization, sarcoidosis, adrenal insufficiency, hyper- and hypothyroidism, renal transplantation

    • with normocalcemia (30 60%):

      • obstruction, urinary tract infection, vesical diverticulum, horseshoe kidney, medullary sponge kidney, renal tubular acidosis, malignant neoplasm, Paget disease, Cushing syndrome, prolonged immobilization, idiopathic hypercalciuria, acetazolamide therapy, sarcoidosis

    • (a) absorptive hypercalciuria

      • = increased intestinal absorption of calcium

        Cause:

        increase in 1,25-dihydroxy-vitamin D levels (50%)

    • (b) renal hypercalciuria

      • = abnormal renal calcium leak

        Cause:

        diet high in sodium, urinary tract infection (33%)

    • (c) resorptive hypercalciuria

      • = increased bone demineralization secondary to subtle hyperparathyroidism

    • (d) idiopathic

      • attenuation of calcium stones >1,000 HU similar to bone cortex

        P.989

        
        

        Frequency and Radiographic opacity of urolithiasis

        Mineral Composition	Frequency (%)	Opacity
        A. Calcium stones	70-80	+++
        1. oxalate	20 30	+++
        (a) Calcium oxalate monohydrate (= whewellite) small highly opaque
        (b) Calcium oxalate dihydrate (= wedellite) may be spiculated / mamillated ( mulberry stone )
        2. Calcium oxalate-phosphate (calcium oxalate plus apatite)	30 40	+++
        3. Calcium phosphate (= apatite) rarely pure (= laminated), occasionally forms in infected alkaline urine	5 10	+++
        4. Calcium hydrogen phosphate (= brushite)		+++
        B. Struvite Stones	15 20	++
        1. Magnesium ammonium phosphate (= struvite) laminated, result of urea-splitting organisms (usually Proteus) most common constituent of staghorn calculus	1	++
        2. Struvite plus calcium phosphate associated with infection	15 20	++
        C. Cystine mildly opaque	1 3	+
        D. Uric acid radiolucent	5 10	-
        E. Xanthine nonopaque	extremely rare	-
        F. Matrix (mucoprotein / mucopolysaccharide) nonopaque	rare	-

  • Hyperoxaluria

  • Physiology:

    • 85% of urinary oxalate is produced endogenously in liver!

    • Oxalic acid is present in many foods but poorly absorbed in healthy individuals resulting in increase in urinary oxalate by only 2 3%!

  • Cause:

    • congenital = deficiency of an enzyme leading to accumulation of glycolate + oxylate

    • acquired = increased intake of oxalate / oxalate precursors, excess oxalate absorption from bowel in patients with ileal resection / inflammatory bowel disease

  • Hyperoxaluria has a stronger correlation to severity of stone disease than hypercalciuria!

• Hyperuricosuria

  • uric acid lithiasis (15 20%); stones form in acid urine

  • M > F; usually familial

  • multiple small hard smooth yellow / red-brown radiolucent stones

  • (a) with hyperuricemia:

    • gout (25 50%) from excessive intake of meat, fish, poultry, myeloproliferative diseases, antimitotic drugs, chemo- / radiation therapy, uricosuric agents, Lesch-Nyhan syndrome

  • (b) with normouricemia:

    • idiopathic; occurrence in concentrated acidic urine, which becomes supersaturated with undissociated uric acid (hot climate, ileostomy)

  • bright well-defined of medium-high attenuation (>150 HU [300 500 HU])

    Rx:

    raising urinary pH (potassium citrate / sodium bicarbonate)

• Cystinuria (stones form in acid urine)

  • = autosomal recessive disorder with tubular inability to reabsorb cystine, ornithine, lysine, arginine

    Age of onset:

    after 10 years (usually young girls)

  • multiple soft / hard, pink / yellow radiopaque stones

    Rx:	(1) decreased intake of methionine
    	(2) alkalinization of urine

• Xanthinuria

  • = inherited autosomal recessive deficiency of xanthine oxidase (failure of normal oxidation of purines)

• Urinary tract infection

  Cause:

  urea-splitting organisms (Proteus mirabilis, P. vulgaris, Haemophilus influenzae, S. aureus, Ureaplasma urealyticum) + alkaline environment (pH >7.19)

  • May lead to magnesium ammonium phosphate = struvite stones

    Predisposed:

    women (M:F = 1:2), neurogenic bladder, urinary diversion, indwelling catheter, lower-urinary-tract voiding dysfunction

  • often branching into staghorn calculi

  • most struvite stones are radiopaque, but poorly mineralized matrix stones are not

• Any condition causing nephrocalcinosis

• Idiopathic calcium urolithiasis

• Indinavir (protease inhibitor for treatment of HIV type 1) due to precipitation of drug crystals in renal tubule

  • rectangular brown puttylike nonradiopaque stones

  • detectable sonographically / IVP / CECT

• RADIOGRAPHIC SHAPE

  • spiculated stone = jack stone (child's toy jack)

    Composition:	calcium oxalate dihydrate
    Location:	urinary bladder > kidney

  P.990

  
  

  • mulberry stone = mamillated contour

    Composition:

    calcium oxalate dihydrate

  • seed calculi = small stones all of similar size with lapidary effect (like cut gems):

    • forming in small cavity (caliceal diverticulum, cyst, hydronephrosis)

  • milk of calcium (with urine-calcium level)

    • due to calcium carbonate:

    • forms in any epithelium-lined structure directly communicating with the collecting system (caliceal diverticulum, hydrocalyx, renal cyst)

  • staghorn calculus:

    • = branched calculus filling the entire bifid renal collecting system

      Composition:

      struvite (= mixture of calcium, magnesium, ammonium, phosphate) / cystine / uric acid stone

    • forms with recurrent urinary tract infections (the only stone more common in females)

Nonradiopaque Stones

mnemonic:

SMUX

• Struvite (rarely magnesium ammonium phosphate)

• Matrix stone (mucoprotein, mucopolysaccharide)

• Uric acid

• Xanthine

Calculi often Associated with Infection

mnemonic:

S and M

• Struvite (magnesium ammonium phosphate

• calcium phosphate)

• Matrix stone (mucoprotein, mucopolysaccharide)

Acute Obstruction by Ureteric Calculi

• = URETEROLITHIASIS

• see also ACUTE HYDRONEPHROSIS

• renal colic = acute severe spasmodic / steady continuous flank pain

• frequently radiating into pelvis / groin / scrotum / labia

• hematuria (85%): absent in completely obstructing stone

  Site:	at points of ureteral narrowing
  	(a) ureterovesical junction (UVJ) in 70%
  	(b) ureteropelvic junction (UPJ)
  	(c) iliac vessel crossing

• Plain radiography (45% sensitive, 77% specific):

  • Visualization:

    • 90% of urinary calculi are radiopaque

    • Confounding factors: small size of calculus, overlying bowel gas / fecal matter, osseous structures (transverse process, sacrum), abdominal calcifications (gallstone, calcific pancreatitis, mesenteric lymph node, arterial calcification, phlebolith)

  • 60% of calcifications along expected course of ureter on symptomatic side are ureteric stones!

  • Stones may be present in 30% of the time when KUB is negative!

• IVU (64 97% sensitive, 92 94% specific):

  • delayed opacification of collecting system: degree of obstruction displayed by time delay of appearance of contrast material (physiologic information)

  • persistent delayed nephrogram increasing in intensity with time

  • hydroureteronephrosis

  • column of contrast material proximal to obstructing calculus

  • Nonobstructing calculi may be difficult to detect

• US (37% sensitive):

  • highly echogenic focus + acoustic shadow within dilated ureter

  • unilateral hydronephrosis (11 35% false-negative, up to 10% false-positive rate)

  • resistive index >0.7 in symptomatic kidney (partial obstruction, NSAD, antecedent IVU may alter RI)

  • absent ureteral jet / continuous low-level flow on affected side (jet may be present with partially obstructing calculus)

  • direct visualization of prevesical calculus by transabdominal, transrectal, transvaginal US

• NECT (97% sensitive, 96% specific, 97% accurate):

  • Helical NECT is the most accurate technique for detecting urinary tract calculi!

  • Advantages:

    • visualization of all calculi

    • short exam time (3 5 minutes)

    • avoidance of IV contrast

    • detection of extraurinary causes of flank pain (in 16 45%)

  • calcified stone within ureter (PATHOGNOMONIC)

    DDx:

    phlebolith (no continuity with the ureter):

    • all stone compositions readily detectable (except unmineralized stone matrix + stones related to protease inhibitor indinavir [Crixivan ] for HIV treatment)

    • stone at ureterovesical junction

      DDx:

      stone passed into bladder (stone falls anteriorly in prone position)

  • soft-tissue rim sign (in 50 77%, 77% sensitive) = thickening of ureteral wall surrounding impacted small ureteric calculus due to edema within 4 24 hours after obstruction (92% specific):

    • in 90% of stones <4 mm

    • not seen in 33% of stones >5 mm as larger stones thin the ureteral wall

      DDx:

      gonadal vein phlebolith (in front of upper ureter, lateral to mid ureter); 2 8% of phleboliths have a soft-tissue rim sign

  • secondary signs of urinary tract obstruction (96%):

    • asymmetric stranding of perinephric fat (in 65%, 76% sensitive, 90% specific) with loss of well-defined fat-kidney interface due to

      • fluid within bridging septa of perinephric fat (due to increased lymphatic pressure)

        • A higher degree of perinephric edema means a higher degree of obstruction!

      • focal nonlinear fluid collection of extravasated urine as a result of forniceal rupture

    • periureteral edema (in 31%)

    • hydronephrosis (in 69%, 83% sensitive, 94% specific) = rounded fluid-filled calices and infundibula partially obliterating the renal sinus fat

      P.991

      
      

      DDx:

      extrarenal pelvis, parapelvic cysts

    • hydroureter above stone (87% sensitive, 90% specific) continuous with renal pelvis

    • unilateral renal enlargement (71% sensitive, 89% specific)

    • unilateral absence of white pyramid (= loss of the occasional incidental finding of high-attenuation medullary pyramids in normal kidneys)

  • False negatives (2 7%):

    • volume averaging (= stone small relative to collimation)

    • patients treated with indinacir

• NUC (DTPA, MAG3):

  • initially diminished uptake during renal perfusion phase

  • prolonged nephrographic phase

  • delayed excretion into collecting system

  • delayed transit of radiotracer with accumulation in obstructed collecting system

  • no clearing effect of IV furosemide injection

    Advantages:	quantitative assessment of renal function
    Cx:	xanthogranulomatous pyelonephritis
    Rx:	(1) hydration (within 3 hours after meal, during strenuous physical activity, at bedtime) maintaining urine output of 2 3 L/day
    	(2) diet: restrict amounts of protein, sodium, calcium
    	(3) drugs: thiazide diuretics (lowers urinary calcium), allopurinol (lowers urate + oxalate excretion)
    	(4) extracorporeal shock wave lithotripsy (ESWL)
    DDx:	(1) Recent passage of stone
    	(2) Phlebolith

    • comet-tail sign = extension of curvilinear soft-tissue band from stone representing the gonadal vein in 65%)

    • low-attenuation center (visible in 9%, detectable with profile analysis in 21%)

• Prognosis:

  • Spontaneous passage of ureteral calculi in 93%

    • stones <4 mm pass in 90%

    • stones 4 7 mm pass in 50%

    • stones >8 mm rarely pass

  • Without treatment stone recurrence is 10% at 1 year, 33% at 5 years, 50% at 10 years

Varicocele

• = abnormal dilatation + tortuosity of plexus pampiniformis secondary to retrograde flow into internal spermatic vein

• Components of pampiniform plexus:

  • internal spermatic vein (ventral location) draining testis

  • vein of vas deferens (mediodorsal location) draining epididymis

  • cremasteric vein (laterodorsal location) draining scrotal wall

• US:

  • multiple hypoechoic serpiginous tubular structures, initially superior and lateral, later posterior and inferior to testis

  • containing low-level echoes if flow slow

Idiopathic / Primary Varicocele

Cause:

incompetent / absent valve at level of left renal vein / IVC on right side

Grading of Varicocele

Grade	Relaxed State	During Valsalva
Normal	2.2mm	2.7mm
Small varicocele	2.5 4.0mm	by 1.0mm
Moderate varicocele	4.0 5.0mm	by 1.2 1.mm
Large varicocele	>5.0mm	by >1.5mm

• Incidence:

  • clinical varicocele: in 8 15% of adult males, in 21 39% of infertile men

  • subclinical varicocele: in 40 75% of infertile men

• Theoretical causes for infertility:

  • Increase in local temperature

  • Reflux of toxic substances from adrenal gland (countercurrent exchange of norepinephrine from refluxing renal venous blood into testicular arterial blood at the level of the pampiniform plexus)

  • Alteration in Leydig cell function

  • Hypoxia of germinative tissue due to venous reflux resulting in venous hypertension + stasis

• scrotal pain

• scrotal swelling with bag of worms quality

• abnormal spermatogram (impaired motility, immature sperm, oligospermia)

  Location:	left side (78%), bilateral (16%), right side (6%)
  	Reasons for left-sided prevalence:
  	(a) left testicular vein longer
  	(b) left testicular vein enters left renal vein at right angle
  	(c) compression of left renal vein by left testicular artery in some men
  	(d) compression of left testicular vein by descending colon distended with feces

• Bidirectional Doppler sonography (erect with quiet breathing):

  • SHUNT TYPE (86%): insufficient distal valves allow spontaneous + continuous reflux from internal spermatic vein (retrograde flow) into cremasteric vein + vein of vas deferens (where flow is orthograde) via collaterals

    • sperm quality diminished

    • clinically plexus type (grade II + III) = medium-sized + large varicoceles

    • continuous reflux during Valsalva maneuver

  • STOP TYPE / PRESSURE TYPE (14%): intact intrascrotal valves allow only brief period of reflux from spermatic vein into pampiniform plexus under Valsalva maneuver

    • sperm quality normal

    • clinically central type (grade 0 + I) = subclinical + small varicocele

    • short phase of initial retrograde flow

• US (almost 100% sensitive + specific):

  • diameter of dominant vein in upright position at inguinal canal

    Dx:	documentation of venous reflux
    Rx:	(1) Ivanissevitch procedure = surgery
    	(2) Transcatheter spermatic vein occlusion
    	Treatment improves sperm quality in up to 53%

P.992

Secondary Varicocele

• = compression of left renal vein by tumor, aberrant renal artery, obstructed renal vein, hydronephrosis, cirrhosis

• nondecompressible varicocele

• Check left renal vein!

Vesicoureteric Reflux

• A. CONGENITAL REFLUX = PRIMARY REFLUX

  • = incompetence of ureterovesical junction due to abnormal tunneling of distal ureter through bladder wall

    Prevalence:

    in 9 10% of normal Caucasian babies; in 1.4% of school girls; in 30% of children with a first episode of UTI

  • short submucosal ureteral tunnel (normally has a length/width ratio of 4:1)

  • large laterally located ureteral orifice

    Location:

    uni- / bilateral (frequently involves lower pole ureter in total ureteral duplication)

  • renal scars in 22 50%

    Prognosis:	disappears in 80%
    Cx:	reflux atrophy / nephropathy in 22 50%; end-stage renal disease in 5 15% of adults

• ACQUIRED REFLUX = SECONDARY REFLUX

  • Paraureteric diverticulum = Hutch diverticulum

  • Duplication with ureterocele

  • Cystitis (in 29 50%)

  • Urethral obstruction (urethral valves)

  • Neurogenic bladder

  • Absence of abdominal musculature (prune belly syndrome)

    Cx:

    renal scarring with UTI (30 60%)

• Radionuclide cystography:

  • Lower radiation dose to gonads than fluoroscopic cystography (5 mrad)!

• US (74% of kidneys with VUR may be normal by US):

  • intermittent hydroureteronephrosis = variable size of collecting system

  • redundant mucosa causing apparent thickening of renal pelvic wall

  • large thin-walled bladder

  • midline-to-orifice distance >7 9 mm has high probability of vesicoureteric reflux

    

    Grading of Vesicoureteral Reflux (International Reflux System)

    Grades of Vesicoureteral

    Grade I	reflex into ureter
    Grade II	reflex into pelvicaliceal system (without caliceal dilatation / blunting)
    Grade III	all of the above + mild dilatation of ureter and pelvicaliceal system
    	distinct forniceal angles + papillary impressions
    Grade IV	reflex into tortuous ureter + moderately dilated pelvicaliceal system
    	blunted forniceal angles
    	distinct papillary impressions
    Grade V	reflex into markedly dilated and tortuous ureter + markedly dilated pelvicaliceal system
    	obliteration of forniceal angles + papillary impressions

• Prognosis:

  • All grades of reflux can be outgrown:

    • 80% of grade I II and 46% of grade III outgrow reflux within 5 years

    • 50% of grade IV continue to have reflux 9 years after initial diagnosis

      Renal scarring:

      >20% chance for grade III V reflux; 2 3% chance for grade I II reflux

• Rx:

  • grade I III resolve with maturation of the ureterovesical junction

  • grade IV V require surgery to avoid renal scarring + renal impairment + hypertension (except in infants)

  • periureteral diverticulum requires surgery (grade of reflux not prognostic)

Wilms Tumor

• = NEPHROBLASTOMA

• Most common malignant abdominal neoplasm in children 1 8 years old (10%)!

• 3rd most common malignancy in childhood (after leukemia + brain tumors; neuroblastoma more common in infancy)!

• 3rd most common (87%) of all renal masses in childhood (after hydronephrosis + multicystic dysplastic kidney)!

  Incidence:	1:10,000 live births; 450 cases/year in USA; familial in 1 2%; multifocal in 10%; bilateral in 4 13% (with nephrogenic rests in 94 99%)
  Age:	peak age at 3 4 years (range of 3 months to 11 years); rare during first year; 50% before 3 years, 80% before 5 years; 90% before 8 years; rare in neonates (0.16% of cases) + adults; M:F = 1:1; more common in blacks
  Histo:	arises from undifferentiated metanephric blastema (= nephrogenic rests) with variable amounts of blastema, stroma, epithelium; occasionally mesodermal derivatives of striated / smooth muscle, fat, bone, cartilage = teratoid Wilms tumor

  • unfavorable histologic character (= presence of anaplasia) in 6.2%: localized / diffuse

  • favorable histologic character (90%)

    • Multilocular cystic nephroma, mesoblastic nephroma, nephroblastomatosis are related to the more favorable types of Wilms tumor!

  P.993

  
  

  Stage of Wilms Tumor (National Wilms' Tumor Study Group

  I	tumor limited to kidney (renal capsule intact)
  II	local extension beyond renal capsule into perirenal tissue / renal vessels outside kidney / lymph nodes
  III	not totally resectable (peritoneal implants, other than paraaortic nodes involved, invasion of vital structures)
  IV	hematogenous metastases (lung in 85%, liver in 7%, bone in 0.8%, brain [rare]) / lymph node metastases outside abdomen or pelvis
  V	bilateral renal involvement at diagnosis (4 13%)

  Genetics:

  multifactorial; abnormal WT1 gene on locus 11p13 with WAGR syndrome (Wilms tumor, aniridia, genitourinary abnormalities, mental retardation) or Drash syndrome; abnormal WT2 gene on locus 11p15 with Beckwith-Wiedemann syndrome or hemihypertrophy; familial Wilms tumor in 1%

• In 14% associated with:

  • Sporadic aniridia (= severe hypoplasia of iris)

    • 33% of patients with sporadic aniridia develop Wilms tumor!

  • Beckwith-Wiedemann syndrome = EMG syndrome (exomphalos, macroglossia, gigantism) + hepatomegaly, hyperglycemia from islet cell hyperplasia

    • 10 20% of patients with Beckwith-Wiedemann syndrome develop Wilms tumor!

  • Hemihypertrophy: total / segmental / crossed (2.5%);

    • Ipsilateral or contralateral kidney affected

    • Increased incidence of all embryonal tumors (adrenal cortical neoplasms, hepatoblastoma)

  • Genitourinary disorders (4.4%):

    • Drash syndrome (male pseudohermaphroditism, progressive glomerulonephritis)

    • Renal anomalies (horseshoe kidney, duplex / solitary / fused kidney)

    • Genital anomalies: cryptorchidism (2.8%), hypospadia (1.8%), ambiguous genitalia

• Screening recommendations (up to age 7 years):

  • CT at 6 months of age followed by US every 3 months

• asymptomatic palpable abdominal mass (90%)

• hypertension (in up to 25%) due to renin production by tumor / vascular compression by tumor

• abdominal pain (25%)

• low-grade fever (15%)

• gross hematuria (7 15%) with invasion of renal pelvis

• microscopic hematuria (15 25%)

• hemorrhage after minor trauma

• ascites due to venous obstruction

• varicocele from left-sided tumor

• RULE OF 10's:

  • 10% unfavorable histology

  • 10% bilateral

  • 10% vascular invasion

  • 10% calcifications

  • 10% pulmonary metastases at presentation

• large tumor (average size 12 cm)

• expansile growth:

  • sharply marginated with compression of renal tissue

    • = pseudocapsule

  • distorted clobbered / dilated calyces

  • displacement of major vessels, rather than encasement

• curvilinear / phlebolithic calcifications in 5% on plain film, in 15% on CT (DDx: regular stippled calcifications in 85% of neuroblastomas)

• tumor invasion of renal vein and IVC (4.1 10%); extension into right atrium (in 21% of cases with IVC invasion)

• tumor may cross midline

• poor / nonexcretion of IV contrast due to invasion or compression of hilar vessels + collecting system / extensive tumor infiltration of renal parenchyma

• US:

  • predominantly solid spherical mass:

    • heterogeneous echogenicity (frequent):

      • irregular anechoic areas due to central necrosis + hemorrhage + cyst formation

      • echogenic areas representing fat / calcium

    • fairly evenly echogenic (rare)

• CT (preferred modality):

  • well-circumscribed heterogeneous partially cystic mass due to focal hemorrhage and necrosis (71%), cyst formation, fat, calcification

  • beak / claw of renal tissue extends partially around mass

  • tumor less enhancing than renal parenchyma

• CECT:

  • nodal / hepatic metastases

  • tumor extension into renal vein / IVC

  • contralateral synchronous tumor/ nephrogenic rests

• MR:

  • hypointense on T1WI

  • high / variable intensity on T2WI

• NUC:

  • nonfunctioning kidney (10%)

  • hypo- / iso- / hyperperfusion on radionuclide angiogram

  • absent tracer accumulation on delayed static images

  • displacement of kidney + distortion of collecting system

• Angio:

  • hypervascular tumor: enlarged tortuous vessels, coarse neovascularity; small arterial aneurysms, vascular lakes

  • parasitization of vascular supply

Rx:	presurgical chemotherapy + nephrectomy + adjuvant chemotherapy radiation therapy
Prognosis:	survival rate depending on pathologic pattern, age at time of diagnosis, extent of disease; 4-year relapse-free survival: 91% for stage I; 88% for stage II; 79% for stage III; 78 84% for stage IV
DDx:	(1) Neuroblastoma (encasement / elevation of aorta, regular stippled calcifications)
	(2) Cystic partially differentiated nephroblastoma (largely cystic tumor)

Wolman Disease

• = PRIMARY FAMILIAL XANTHOMATOSIS

• = rare autosomal recessive lipidosis with accumulation of cholesterol esters and triglycerides in visceral foam cells + various tissues (liver, spleen, lymph nodes, adrenal cortex, small bowel)

  P.994

  
  

  Etiology:

  deficiency of lysosomal acid esterase / acid lipase

• malabsorption in neonatal period: failure to thrive, diarrhea, steatorrhea, vomiting

• delayed growth, diminished muscle mass, abdominal distension

• hepatosplenomegaly

• extensive bilateral punctate calcifications (calcification of fatty-acid soaps) throughout enlarged adrenals (maintaining their normal triangular shape) is DIAGNOSTIC

• enlarged fat-containing lymph nodes

• small bowel wall thickening (due to infiltration of mucosa of small bowel by lipid-filled histiocytes impairing absorption)

• generalized osteoporosis

CT & MR:	attenuation + signal intensities consistent with deposition of lipids
Dx:	assay of leukocytes / cultured skin fibroblasts
Prognosis:	death occurs within first 6 months of life

Zellweger Syndrome

• = CEREBROHEPATORENAL SYNDROME

• autosomal recessive

• muscular hypotonia

• hepatomegaly + jaundice

• craniofacial dysmorphism

• seizures, mental retardation

• brain dysgenesis (lissencephaly, macrogyria, polymicrogyria)

• renal cortical cysts

Prognosis:

death in early infancy