Nephrology

Fractional Excretion of Sodium (FeNa)

Differentiates prerenal disease from acute tubular necrosis (ATN).

Parameters

mEq/L
mg/dL
mEq/L
mg/dL

Fractional Excretion of Sodium (FeNa) Result

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FormulaFeNa (%) = (Urine Na × Serum Cr) / (Serum Na × Urine Cr) × 100

Clinical Pearls

A cornerstone diagnostic calculation in the workup of oliguric Acute Kidney Injury.

Limitations

Not accurate if the patient is taking diuretics (which artificially increase urine sodium). In such cases, the Fractional Excretion of Urea (FeUrea) is preferred.