The FENa test. Use in the differential diagnosis of acute renal failure

Abstract

The FENa test, a determination of the excreted fraction of the filtered Na, was performed in patients in the oliguric phase of acute renal failure. Patients with prerenal azotemia had an FENa of less than 1, and patients with acute tubular necrosis had an FENa of more than 3 (P < .001). This simple test clearly differentiates between these 2 conditions and, thus, is of considerable clinical value.