New concepts in acute renal failure.

The clinical patterns of acute renal failure have changed in the past 10 to 15 years. Nonoliguric acute tubular necrosis has become more common, as has nephrotoxic acute tubular necrosis. Other syndromes that have increased in incidence are acute tubular necrosis secondary to rhabdomyolysis and acute renal failure secondary to nonsteroidal anti-inflammatory drugs. Calculation of the fractional sodium excretion or the renal failure index helps distinguish between prerenal azotemia and acute tubular necrosis. In a significant number of patients with acute renal failure, a kidney biopsy may be necessary to establish the correct diagnosis and initiate the appropriate therapy.