FENa Calculator
Calculate Fractional Excretion of Sodium (FENa %) using serum sodium, urine sodium, serum creatinine, and urine creatinine. FENa can help support the evaluation of acute kidney injury (AKI).
Calculation Result
Formula
Interpretation
| FENa (%) | General Interpretation |
|---|---|
| <1% | Suggestive of Prerenal Acute Kidney Injury |
| 1–2% | Intermediate / Indeterminate |
| >2% | Suggestive of Intrinsic Renal Acute Kidney Injury |
Clinical Use
Fractional Excretion of Sodium (FENa) is a calculated laboratory parameter used as an adjunct in the evaluation of acute kidney injury. It may help distinguish reduced renal perfusion (prerenal causes) from intrinsic renal injury such as acute tubular injury.
FENa should not be interpreted in isolation. Clinical findings, urine studies, medications, volume status, and other laboratory results should also be considered.
Frequently Asked Questions
What is FENa?
FENa stands for Fractional Excretion of Sodium. It estimates the percentage of filtered sodium that is excreted in the urine.
What does a FENa below 1% suggest?
A FENa below 1% may be consistent with prerenal acute kidney injury, particularly when renal sodium conservation is present. Clinical correlation is required.
What does a FENa above 2% suggest?
A FENa above 2% may suggest intrinsic renal injury, including acute tubular injury. However, the result can be affected by several clinical factors.
Can FENa be used in patients receiving diuretics?
FENa may be less reliable in patients receiving diuretics because diuretics can increase urinary sodium excretion. In such situations, additional clinical assessment and alternative indices such as FEUrea may be considered.
Can FENa diagnose acute kidney injury?
No. FENa is an adjunctive laboratory calculation and should not be used as the sole basis for diagnosing acute kidney injury or determining its cause.
Clinical Applications
- Evaluation of acute kidney injury (AKI)
- Assessment of prerenal kidney dysfunction
- Evaluation of intrinsic renal injury
- Assessment of renal sodium handling
- Supportive evaluation of acute tubular injury
Disclaimer
This calculator is intended for educational and laboratory reference purposes only. It should not replace professional medical advice, diagnosis, treatment, or institutional protocols. FENa results should always be interpreted in the context of the complete clinical picture.
References
- KDIGO Clinical Practice Guideline for Acute Kidney Injury.
- Brenner & Rector's The Kidney.
- Tietz Fundamentals of Clinical Chemistry and Molecular Diagnostics.
