A prospective analysis of the value of urinary diagnostic indices in ascertaining the cause of acute renal failure was undertaken. Our results show that in the setting of acute oliguria a diagnosis of potentially reversible prerenal azotemia is likely with urine osmolality >500 mosm/kg H2O, urine sodium concentration <20 meq/liter, urine/plasma urea nitrogen ratio >8, and urine/plasma creatinine ratio >40. Conversely, a urine osmolality <350 mosm/kg, urine sodium concentration >40 meq/liter, urine/plasma urea nitrogen ratio <3, and urine/plasma creatinine ratio <20 suggest acute tubular necrosis. A significant number of oliguric patients will not have urinary indices that fall within these guidelines. In this setting, urine sodium concentration divided by the urine-to-plasma creatinine ratio (the renal failure index) and the fractional excretion of filtered sodium provide a reliable means of differentiating reversible prerenal azotemia from acute tubular necrosis.
ASJC Scopus subject areas
- Internal Medicine