The FeNa Test

Abstract

The Fe_Natest, a determination of the excreted fraction of the filtered sodium, was performed in patients in the oliguric phase of acute renal failure. Patients with prerenal azotemia had an Fe_Naof less than 1, and patients with acute tubular necrosis had an Fe_Naof more than 3 (P<.001). This simple test clearly differentiates between these two conditions and, thus, is of considerable clinical value. (JAMA236:579-581, 1976)