Fractional Excretion of Sodium (FENa) Calculator
FENa Calculation
Formula
FENa = (Urine Na x Serum Cr) / (Serum Na x Urine Cr) x 100
Frequently Asked Questions
What is FENa?
FENa (Fractional Excretion of Sodium) measures the percentage of filtered sodium excreted in urine. It helps differentiate pre-renal from intrinsic causes of AKI.
What FENa indicates pre-renal failure?
FENa < 1% suggests pre-renal azotemia (kidneys are avidly retaining sodium). FENa > 2% suggests intrinsic renal damage (tubules cannot reabsorb sodium).
When is FENa unreliable?
FENa is unreliable with diuretic use, contrast exposure, CKD, or in early obstruction. Use FEUrea instead in patients on diuretics.
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