Acute renal failure: update.

Acute renal failure (ARF) is an abrupt decline in renal function, sufficient to result in the retention of nia'ogenous wastes, that is not immediately reversible by manipulation of extrarenal factors. Acute renal failure is not defined in terms of urine volume, and may be present both in oliguric and non-oliguric states. The obligatory daily osmolar load (urea, uric acid, ammonia, etc.) excreted is 400-500 mOsm. This represents the normal products of metabolic activity. When urine volume is less than 400 ml per 24 hours, normal osmolar clearance is impossible and nitrogenous wastes accumulate. Such a patient is in oliguric renal failure (ORF). Non-oliguric failure (NORF) occurs when the urine output is excessive for the physiologic state of the patient.