Fractional Excretion of Sodium (FENa)

Name: Fractional Excretion of Sodium (FENa)
Creator: Daniel Diaz-Gil, MD
Keywords: nephrology, renal, sodium, FENa, fractional excretion, prerenal, intrinsic, AKI, acute kidney injury

Calculates fractional excretion of sodium to differentiate prerenal from intrinsic renal causes of acute kidney injury

The fractional excretion of sodium (FENa) calculation distinguishes prerenal acute kidney injury (FENa <1%) from intrinsic renal failure (FENa >2%) in pediatric patients by comparing urinary sodium excretion to filtered load, guiding fluid resuscitation decisions. This calculation requires spot urine and serum creatinine and sodium levels and helps clinicians rapidly assess renal perfusion status in undifferentiated acute kidney injury. FENa is less reliable in pre-renal states with significant proteinuria or in patients on diuretics.

Clinically Verified· 5 tests

For educational and informational purposes only. Verify all results before clinical application.

Serum Sodium *

mEq/L

Urine Sodium *

mEq/L

Serum Creatinine *

mg/dL

Urine Creatinine *

mg/dL

References

Espinel CH. The FENa test. Use in the differential diagnosis of acute renal failure. JAMA. 1976;236(6):579-581.[DOI]

Reviewed by Daniel Diaz-Gil, MD · Last updated March 2026

Medical disclaimer

This tool is for educational and informational purposes only. It is not a substitute for professional clinical judgment. Always independently verify results before making clinical decisions.

Professional Resources — Tools used by pediatricians for renal assessment

Pediatric Nephrology HandbookClinical reference for pediatric kidney disease and electrolytes~$80via Amazon Electrolyte Reference CardQuick-reference for pediatric electrolyte normal values and corrections~$10via Amazon