Kidneys | The Massachusetts General Hospital Handbook of Neurology

Authors: Flaherty, Alice W.; Rost, Natalia S.

Title: Massachusetts General Hospital Handbook of Neurology, The, 2nd Edition

> Table of Contents > Medicine > Kidneys

Kidneys

A. H&P

Fluid intake, drugs (include NSAIDs), urine output, pain. Cardiac exam, kidney tenderness, palpable bladder, edema.

B. Neurological complications of kidney failure

Uremic encephalopathy:

H&P: Renal dz precipitating illness, with obtundation or agitation, myoclonus, asterixis, generalized seizures in 30%.

DDx: Malignant HTN, dialysis disequilibrium syndrome, stroke.

P.215

Table 57. Gram-negative susceptibilities (%). (MGH data 2005; courtesy of D. Hooper, MD.)

	Ampicillin	Piper-tazo	Cefazolin	Ceftriaxone	Cefepime	Aztreonam	Meropenem	Gentamicin	Amikacin	Ciprofloxacin	TMP-SMX	Chloramphen	Tetracycline	Nitrofurant
Acinetobacter	0	66	0	0	39	-	74	46	81	43	58	-	45	0
Aeromonas	0	90	0	93	100	100	100	100	100	97	97	-	-	-
Citro. freundii	0	85	0	83	99	84	99	93	99	86	85	-	79	99
Citro. keseri	0	99	91	97	100	95	100	99	100	96	98	-	100	95
Ent. aerogenes	0	84	0	93	100	91	100	98	100	91	98	-	88	38
Ent. cloacae	0	72	0	75	97	74	100	91	99	83	84	-	73	51
E. coli	59	97	92	99	99	99	100	93	100	88	76	-	73	99
H. influenzae	72	-	-	100	-	-	-	-	-	-	77	97	-	-
Klebs. pneumo.	0	85	81	84	84	84	100	87	94	80	79	-	78	54
Klebs. oxytoca	0	90	67	93	93	92	100	93	98	92	94	-	89	93
Mo. morganii	0	97	0	97	100	91	100	92	100	91	87	-	57	11
Pr. mirabilis	81	96	97	100	100	99	100	95	100	84	87	-	0	0
Pr. vulgaris	0	97	0	84	100	92	100	100	100	100	97	-	36	5
Ps. aeruginosa	-	91	-	-	86	70	86	72	77	66	-	-	-	-
Salmonella	90	97	-	98	100	98	100	-	-	100	98	-	91	-
Se. marcescens	0	94	0	94	98	94	100	95	99	93	94	-	15	-
Shigella	62	96	-	96	100	100	100	-	-	96	46	-	24	-

Table 58. Gram-positive susceptibilities (%). (MGH data 2005; courtesy D. Hooper, MD.)

	Penicillin	Oxacillin	Cephalothin c	Vancomycin	Clindamycin	Erythromycin	Tetracycline	Chloramphen	TMP-SMX	Levofloxacin	Rifampin	Linezolid	Nitrofurant.	Gentamicin
Staph. aureus	11	54	54	100	66	37	93	-	96	57	98	100	100	97
Coag-neg. Staph.	14	39	39	100	63	35	86	-	58	49	96	99	100	81
S. saprophyticus	-	-	-	100	89	48	86	-	97	99	100	100	100	100
S. lugdunensis	70	100	-	100	91	87	94	-	100	100	100	100	100	100
Strep. pneumo.	68	-	-	100	86	70	79	97	79	100	-	-	-	-
a-hemol. Strep.	62	-	-	100	85	56	62	-	-	93	-	-	-	-
Grp A b- Strep.	100-		100100		95	87	69	-	-	100	-	-	-	-
Grp B b- Strep.	100-		100100		86	73	13	-	-	100	-	-	-	-
Grp C, G b- Strep	100-		100100		94	76	44	-	-	100	-	-	-	-
S. anginosus	99	-	-	100	84	80	73	-	-	100	-	-	-	-
Enterococci	78	-	-	80	-	18	28	90	-	56	29	99	88	-
E. faecalis	100-		-	91	-	18	27	85	-	63	41	100	100	-
E. faecium	8	-	-	13	-	2	31	97	-	4	11	94	48	-

P.216

Rx: Treat renal failure; seizures. DPH and levetiracetam need renal dosing (see p. 163). Although phenobarbital is excreted by kidneys, levels are unaffected by renal failure unless GFR <10.

Dialysis disequilibrium syndrome: Acutely during or after dialysis, with headache, muscle cramps, confusion, seizures, or coma. Probably caused by cerebral edema.
Dialysis dementia syndrome: Subacute memory loss, personality change, apraxia, dysarthria, myoclonus, seizures. EEG shows bursts of slowing and spikes.

C. Hematuria workup

Stop anticoagulants, change bladder catheter, consider irrigation, renal ultrasound, cystoscopy, antineutrophil cytoplasmic Ab (ANCA), antiglomerular basement membrane antibody.

D. Causes of acute renal failure

Prerenal: Hypovolemia or hypotension from dehydration, sepsis, bleed, or heart failure; liver failure.
Renal:
- Acute tubular necrosis (ATN): From ischemia, toxins, radiocontrast agents, hemo- or myoglobinuria.
- Acute tubulointerstitial nephritis: From drug reaction, pyelonephritis, papillary necrosis.
- Intrarenal precipitation: Calcium, urates, myeloma protein.
- Other: Glomerulonephritis, DIC with cortical necrosis, arterial or venous obstruction.
Postrenal: Obstruction from prostatism, tumor, or stones.

E. Tests

Blood: BUN, creatinine, electrolytes, Ca, Mg, phos, CBC, CPK.
Urine: UA, sediment, culture, urine eosinophils, urine electrolytes after 6 h off diuretics (or test urine urea nitrogen if on diuretics).

FENa: Fractional excretion of sodium. Not helpful in nonoliguric acute tubular necrosis.

FENa = 100 (UNa SCr)/(SNa UCr); all in mg/dL.
Causes of low FENa: Dehydration, Na-avid renal failure, cirrhosis, nephrotic syndrome, CHF, glomerulonephritis, oliguric contrast-induced renal failure.
Causes of high FENa: Recent diuretics; renal failure.

Table 59. Prerenal kidney failure vs. acute tubular necrosis (ATN).

	Prerenal	ATN
BUN	Up	Up
Serum Cr	~nl	Up
BUN/S Cr	>20	nl
Urine Na	<20	>40
U Cr/S Cr	>40	<20
Urine osms	>500	<350
FeNa	<1	>2
IV fluid helps?	Yes	No

P.217

24-h urine for protein and creatinine in chronic renal failure.
- Creatinine clearance = [urine Cr (mg/dL)][vol (mL)]/[serum Cr (mg/dL)][time (min)]
- Estimated creatinine clearance: Inaccurate if Cr changing.
  - Male = (140 - age)(wt in kg)/(72 serum Cr)
  - Female = 0.85 male
Other tests: Consider renal ultrasound, renal scan, glomerulonephritis workup.

F. Orders

Renal diet (<60 g protein, 2 g Na, K) unless on dialysis, when need protein supplements. Strict I/O, bladder catheter, daily wts.

Stop nephrotoxins: Gentamicin, ACE-I, NSAIDs; renally dose cimetidine and Abx.
- NSAIDs can lower Na, increase K, cause proteinuria, acute interstitial nephritis.
- Gentamicin: Pts. on dialysis can have gentamicin; redose after each dialysis.
IV fluids: If dehydrated.
Diuretics: If oliguric. Furosemide IV; consider adding chlorothiazide or mannitol. Follow I/Os q1h. Hold diuretics if pt. has no response, or furosemide level will build up and cause ototoxicity.
Chronic renal failure: Nephrocaps or equivalent vitamin supplementation 1 qd; aluminum hydroxide Amphogel 30 cc qid (avoid Mg compounds), calcium acetate (PhosLo) 1 2 tabs. Consider erythropoietin, iron, calcium, vit D, bicarb (600 1,200 mg PO bid).