Ann IM 2002;137:744; Nejm 1996;334:1448

Cause:Often multiple

• Shock, simple or that associated with: muscle breakdown/myoglobinuria, eg, traumatic crush injury (Nejm 1991;324:1417), exercise, or hypothermia; open heart surgery (1/3 get some, 3% get full ATN, correlates with pump time—Ann IM 1976;84:677), abdominal aneurysm repair with aortic cross-clamping, etc (Ann IM 1976;85:23)
• Nephrotoxins including heavy metals, CCl₄ and other organic solvents, drugs (eg, gentamicin, amphotericin), snake venom
• Intravascular hemolysis
• IVP or CT contrast material esp in elderly whose creatinine is >2 mg % (Nejm 1989;320:143), or patients with multiple myeloma

Pathophys:GFR decreases before tubular function decreases; fortunate, otherwise would dehydrate quickly. Tubular necrosis interstitial edema more oliguria due to increased extratubular pressure

Si:Oliguria usually, though nonoliguric form very common now with rapid fluid rx

Recovery in 10-30 d if maintain with dialysis; 30-40% will be left with a diminished GFR or concentrating ability

(Chronic Kidney Disease); CHF

r/o other causes of acute oliguria (Nejm 1998;338:671) like: obstructive disease; other intrinsic renal diseases like acute GN and interstitial nephritis, esp drug (NSAID)-induced type; and prerenal causes including hypovolemia and low cardiac output syndromes

Lab:

Path:Gross shows swollen kidney; congested medullary pyramids with pale cortex; microscopic shows tubular necrosis, esp proximally with poisons; interstitial edema; regenerating tubules by day 3

Urine:Smell absent, unlike prerenal azotemia (Nejm 1980;303:1125).

Urine osmoles <350-400 in contrast to prerenal azotemia where >500; osmole/plasma osmole ratio <1.7; Na >40 mEq/L unlike <20 in prerenal azotemia; urea nitrogen <3× plasma unlike >8 in prerenal azotemia; creatinine <20× plasma unlike >40 in prerenal azotemia; volume <400 cc/24 h, 50% false neg but that’s more benign type anyway

UA sediment shows tubular casts

Rx:

Avoid diuretics, which can worsen prognosis and don’t help (Jama 2002;288:2547)

Supportive with protein limitation to <30 gm/day; water to 400 cc plus urine output + insensibles; watch K⁺ by avoiding old blood if transfuse, and treat elevations with Na polystyrene (Kayexalate); peritoneal or hemodialysis, esp if muscle breakdown, peritoneal less good than hemo, at least if ATN caused by infection (Nejm 2002;347:895, 933)

Radiocontrast nephropathy-type (Nejm 2006;354:379; Jama 2006;295:2765):

• Occurs when contrast used in pt w creat >1.5 or creat clearance <50 cc/min, esp if other risk factors (AODM, age >75 yr, hypotension, CHF, anemia)
• Prevent by:
• d/c NSAIDs × 3-4 d, hold metformin × 2 d, stop diuretics
• 1 L normal (154 mEq/L) NaHCO₃ at 200 cc/h × 1 before procedure and 70 cc/h to follow (Jama 2004;291:2328, 2376) decr incidence to <2%, best choice; or normal saline as good (DBCT—Jama 2008;300:1038)
• Debatably w acetylcysteine 600 mg (3 cc of 20% soln) to 1200 mg, taken w soft drink po bid day before and day of; or 600-1200 mg iv before procedure decr incidence >5× (Nejm 2006:354; 2773; J Am Coll Cardiol 2003;41:2114; Jama 2003;289:553; Nejm 2000;343:180, 210); or 150 mg/kg in 500 NS over 30 min just before procedure; or
• NS at 1 cc/kg/h × 12 h just before and after angiography (Arch IM 2002;162:329); or
• Peri-procedure hemofiltraton (Nejm 2003;349:1333)
• Prophylactic dopamine infusion no help (Jama 2003;290:2284); mannitol and furosemide of equally doubtful help (Nejm 1994;331:1416)