25 - Adrenals
Authors: Macfarlane, Michael T.
Title: Urology, 4th Edition
Copyright 2006 Lippincott Williams & Wilkins
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Chapter 25
Adrenals
Anatomy
The adrenal glands are two small, triangular, retroperitoneal structures, weighing 3 to 5 grams, with a fascial covering provided by a superior extension of Gerota's fascia. The right adrenal blood supply comes mainly from the inferior adrenal artery off the right renal artery, the middle adrenal artery off the aorta, and the superior adrenal artery off the inferior phrenic artery. The left adrenal blood supply comes mainly from the middle adrenal artery arising from the aorta and smaller superior and inferior adrenal arteries. The very short right adrenal vein empties directly into the vena cava, whereas the left adrenal vein empties into the left renal vein, lateral to the aorta and medial to the gonadal artery. Lymphatic drainage of both glands is primarily to the lateral aortic lymph nodes just above the level of the renal arteries and anterior to the crura of the diaphragm.
Physiology
The outer cortical zona glomerulosa produces aldosterone under the influence of angiotensin II and the renin angiotensin system (see Renin angiotensin aldosterone System in Chapter 31). Aldosterone acts at the distal tubule to cause sodium retention and potassium secretion. Hyperkalemia is an important independent stimulus to aldosterone secretion.
The middle zona fasciculata and inner zona reticularis secrete primarily cortisol and dehydroepiandrosterone (DHEA) under the influence of pituitary adrenocorticotropic hormone (ACTH). Pituitary ACTH is under continuous feedback inhibition by cortisol. 17-Ketogenic steroids (17-KGSs) are metabolites of cortisol, whereas 17-ketosteroids (17-KSs) are metabolites of adrenal androgens (DHEA).
The adrenal medulla chromaffin cells function as a giant presynaptic sympathetic nerve ending secreting catecholamines, norepinephrine
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(20%), and epinephrine (80%). Vanillylmandelic acid (VMA) is a major catecholamine degradation product formed by the combined action of catechol-O-methyl transferase and monoamine oxidase.
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Pathology
Cushing's Syndrome
Cushing's syndrome is a clinical entity characterized by plethoric facies, bruising, truncal obesity, change in appearance, purplish cutaneous striae, hypertension, osteoporosis, hypokalemia, and poor wound healing as a result of hypersecretion of cortisol. A 24-hour urine sample demonstrating hyperexcretion of cortisol is the most reliable test.
Etiology
Cushing's Disease (75%)
Hypersecretion of ACTH by a pituitary adenoma unresponsive to cortisol negative feedback produces adrenal hyperplasia. Cortisol levels will be suppressed by a low-dose dexamethasone test (0.5 mg q6h for 2 days). Treatment is transsphenoidal hypophysectomy or bilateral adrenalectomy.
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Ectopic ACTH (<5%)
Extra-adrenal ACTH-producing tumors are unresponsive to cortisol negative feedback and arise from malignant carcinomas in lung, breast, ovary, gastrointestinal tract, and kidney. Most common are oat cell bronchogenic carcinomas, thymic tumors, or islet cell tumors of the pancreas. Treatment is surgical excision of the tumor.
Adrenal Adenoma (20%)
This condition presents with autonomous hypersecretion of cortisol and low serum ACTH levels. These are occasionally adenocarcinomas that are radioresistant and unresponsive to chemotherapy. Adrenal adenomas are generally from 2 to 5 cm, whereas adrenal carcinomas are usually larger than 6 cm. Treatment is radical adrenalectomy and lymphadenectomy.
Aldosteronoma (Conn's Syndrome)
Aldosterone hypersecretion owing to an adrenal adenoma or hyperplasia is characterized by hypertension, hypokalemic alkalosis, and low plasma renin activity (PRA). Aldosteronomas are small tumors, usually less than 3 cm, occurring between ages 30 and 60 years, and are more common in female than in male patients (2:1). Primary hyperaldosteronism accounts for fewer than 1% of all cases of hypertension.
Major Criteria for Diagnosis
Hypertension
Hypokalemia in absence of diuretics
High aldosterone output with high sodium intake
Suppressed plasma renin levels that fail to increase under conditions of upright position and restricted sodium intake
Localization
Localization of adenomas is made with computed tomography (CT) and magnetic resonance imaging (MRI).
Treatment
Surgical removal is indicated if a discrete tumor is identified or if medical management fails. If the tumor has not been identified preoperatively, explore the left adrenal first (tumors are found three times more often in the left adrenal). If no tumor is found, explore the right adrenal; if still no tumor is found, then a left adrenalectomy is appropriate with perhaps a partial or total right
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followed by cortisol-replacement therapy. Correct potassium deficits before surgery.
Adrenal Cysts
Adrenal cysts are rare, usually incidental, findings but may become large and symptomatic.
Classification
Pseudocyst (39%) formed from liquefaction of old blood clots secondary to hemorrhage
Endothelial cysts (45%) lined by smooth endothelium filled with lymphogenous fluid
Epithelial cysts (9%)
Parasitic cysts (7%) secondary to echinococcal disease
Diagnosis
Diagnosis is made with abdominal CT, MRI, and ultrasound [eggshell calcifications (15%) need not imply malignancy].
Treatment
Treatment is surgical excision if symptomatic.
Adrenal Carcinomas
Adrenal carcinomas are rare tumors occurring at any age and are usually larger than 6 cm when first discovered. Eighty percent are functioning tumors, and the most common clinical manifestations are Cushing's syndrome or virilization or both, usually in female patients. An aldosterone-producing carcinoma is occasionally found. Patients with adrenal cancer commonly excrete large amounts of adrenal androgens regardless of whether the tumor causes Cushing's syndrome or virilization. These are highly malignant neoplasms that metastasize to the lungs, liver, and lymph nodes. The 3-year survival rate is less than 25%.
Diagnosis
Diagnosis is made by finding high levels of plasma DHEA and urinary 17-KS or high urinary free cortisol levels.
Localization
Localization is determined by using abdominal CT and T2-weighted MRI.
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Treatment
Treatment is surgical excision if the tumor is functioning or larger than 6 cm. Glucocorticoid replacement is necessary in functioning adrenal carcinomas because the contralateral adrenal is usually suppressed. Radiotherapy and chemotherapy are largely useless. A 34% response rate can be seen with mitotane (ortho-para-DDD), but no survival increase has been observed.
Tumors Arising from Neural Crest Cells
Pheochromocytomas
Pheochromocytomas are rare, usually benign, tumors arising from chromaffin cells in the adrenal medulla, most commonly with a varied clinical presentation owing to hypersecretion of norepinephrine and epinephrine.
Pheochromocytomas are said to follow the rule of 10s 10% are malignant, 10% are multiple, 10% are bilateral, and 10% are extra-adrenal. The 10% extra-adrenal are most often found near the renal pedicles, occasionally in the organ of Zuckerkandl at the aortic bifurcation, and rarely in the thorax or wall of the bladder.
Presentation
Pheochromocytomas present in adults in the fifth and sixth decades with sustained (two thirds) and/or paroxysmal hypertension (sudden anxiety, diaphoresis, palpitation, and headaches accompanying sudden increases in blood pressure). Five percent are associated with familial syndromes such as (a) multiple endocrine adenomatosis (MEA) type II, with medullary carcinoma of the thyroid, (b) neurofibromatosis, and (c) von Hippel Lindau syndrome.
Diagnosis
Measure 24-hour urinary free catecholamines and catecholamine metabolites: VMA, normetanephrine, and metanephrine. Check plasma norepinephrine, epinephrine, and dopamine.
Localization
Most are larger than 2 cm and can be readily demonstrated with abdominal CT. The characteristically bright T2-weighted image on MRI scans can be effective in identifying pheochromocytomas. Selective venous sampling for catecholamines and arteriography is
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sometimes necessary. Meta-iodobenzylguanidine (MIBG) scan is useful in search of residual or multiple pheochromocytomas.
Note: Patients must be pretreated with -blockers before radiographic contrast studies, which have been known to cause release of catecholamines.
Treatment
Treatment is surgical excision. Volume expand the patient before surgery, and reduce the blood pressure with titration of an -blocker, such as oral phenoxybenzamine (20 40 mg/day initially). Complete excision of metastatic foci is recommended. The overall survival for malignant pheochromocytomas is 35% at 5 years.
Ganglioneuromas
Ganglioneuromas are benign tumors arising from mature neural crest cells of sympathetic ganglia or adrenal medulla in children. A distinct syndrome of weight loss, abdominal distention, hypertension, and chronic diarrhea is often found. Urinary free catecholamines and VMA may be elevated. Treatment is surgical excision.
Neuroblastomas
Neuroblastomas are malignant tumors that arise from immature neural crest tissue in the adrenal medulla or sympathetic ganglia. They are the most common solid tumor in children.
70% are first seen with metastases poor prognosis.
50% to 70% arise in the adrenal medulla.
50% are diagnosed during the first 2 years of life.
Clinical Presentation
Clinical presentation includes an abdominal mass, abdominal pain, weight loss, anemia, fever, and gastrointestinal disturbances. Metastases are to bone, liver, lungs, and brain ( 70% of bone marrow aspirates are positive), and the tumors are often calcified. Urinary catecholamine levels including dopamine, VMA, and homovanillic acid (HVA) are usually elevated.
Treatment
Treatment is complete surgical excision when possible, with use of preoperative and/or postoperative radiotherapy when needed.
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Workup of Adrenal Masses
How to deal with the increasing number of incidental adrenal masses found on CT, MRI, or ultrasound is problematic and controversial. All patients with solid adrenal masses should probably undergo some level of biochemical assessment (electrolytes and a 24-hour urine sample measuring cortisol, VMA, and 17-ketosteroids). Tumors larger than 5 cm should be removed. Functioning tumors 5 cm or smaller should be considered for surgical removal. Nonfunctioning tumors 5 cm or smaller should be monitored.
Differential Diagnosis
Metastatic carcinoma
Adrenal cysts
Functioning adrenal adenoma or carcinoma (tumors secreting cortisol or aldosterone and pheochromocytomas)
Nonfunctioning adrenal adenoma or carcinoma (myelolipomas and malignant adrenal cortical tumors)
History
Look for symptoms of a functioning tumor (e.g., cushingoid appearance, hypertension, or virilization).
Diagnostic Imaging
Abdominal CT with intravenous (IV) contrast
MRI with T2-weighted images
Ultrasound if cyst is suspected
Needle aspiration of equivocal cyst
24-Hour Urine Measurements
17-KGS: cortisol metabolites
17-KS: metabolites of adrenal androgens (increased levels suggest adrenal carcinoma)
Total free (unconjugated) catecholamines
Increased VMA in pheochromocytomas, ganglioneuromas, and neuroblastomas
Urinary cortisol levels
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Serum Measurements
Free cortisol and ACTH
Aldosterone and PRA
Potassium, sodium, CO2
Special Tests
Dexamethasone suppression test (to rule out Cushing's disease)
Adrenal venography (aids in localizing aldosteronomas)
Management of Adrenal Mass
Indications for Surgical Removal
Functioning adrenal mass
Mass larger than 5 cm on CT scan
Mass 3 to 5 cm on CT with high T2-weighted image on MRI
Growing adrenal cyst
Indications for Watchful Follow-up
Mass 5 cm or smaller on CT with low T2-weighted image on MRI
Stable adrenal cyst
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