Fractional Excretion of Sodium (FENa)

The Fractional Excretion of Sodium (FENa)
determines if renal failure is due to pre-renal, post-renal, or intrinsic renal pathology. But the FENa is only useful in acute renal failure, not chronic renal failure and cannot be used in patients on diuretics. You should always consider obstructive uropathy as a differential for acute renal failure, no matter what the FENa Score is.