FENa Calculator (Fractional Excretion of Sodium)
Pre-renal vs intrinsic AKI discrimination from paired serum/urine sodium and creatinine.
Espinel's classic discriminator: kidneys hungry for volume hoard sodium (<1%), damaged tubules can't (>2%). The famous traps — diuretics invalidate it (use FEUrea instead), and contrast nephropathy, rhabdo and early obstruction can read falsely 'pre-renal'. It refines a clinical picture; it never replaces one.
Formula
Reference aid for healthcare professionals only. Every result must be independently verified before clinical use. Never use this tool for self-medication or to replace clinical judgement.
Pre-renal vs intrinsic AKI discrimination from paired serum/urine sodium and creatinine. The FENa Calculator (Fractional Excretion of Sodium) is a free, private fena tool — every result computes instantly in your browser with no sign-up and no data upload.
About FENa Calculator (Fractional Excretion of Sodium)
Espinel's classic discriminator: kidneys hungry for volume hoard sodium (<1%), damaged tubules can't (>2%). It applies FENa = (UNa × SCr) ÷ (SNa × UCr) × 100. Use the FENa Calculator (Fractional Excretion of Sodium) to get an instant, clearly-explained result with the working shown step by step — free, private and with the source method cited.
How to use FENa Calculator (Fractional Excretion of Sodium)
- 1Enter your details in the FENa Calculator (Fractional Excretion of Sodium) input fields above.
- 2The result updates instantly with the working and reference bands shown.
- 3Adjust any value to explore how it changes the outcome — it's free and unlimited.
Why use FENa Calculator (Fractional Excretion of Sodium)?
- ✓Instant fena result that recomputes as you type — no waiting, no page reloads
- ✓100% client-side: your health data never leaves your browser
- ✓Shows the actual formula and your numbers substituted in, so you can see exactly how the result is reached
- ✓Based on published, citable sources (Espinel CH, JAMA 1976 — the FENa test)
- ✓Free forever with no sign-up, account or app install
Frequently asked questions
How does the FENa Calculator (Fractional Excretion of Sodium) work?+
Espinel's classic discriminator: kidneys hungry for volume hoard sodium (<1%), damaged tubules can't (>2%). The calculation uses the formula: FENa = (UNa × SCr) ÷ (SNa × UCr) × 100. Everything runs instantly in your browser as you type — your inputs are never uploaded.
Is the FENa Calculator (Fractional Excretion of Sodium) accurate, and what is it based on?+
The method is traceable to authoritative sources: Espinel CH, JAMA 1976 — the FENa test. Results are estimates — individual variation always applies, so treat the output as a well-grounded starting point.
Is the FENa Calculator (Fractional Excretion of Sodium) free and private?+
Yes. It's completely free with no sign-up, and all computation happens locally in your browser, so none of your health data ever leaves your device.
Can I use this for medical decisions?+
This is a reference aid for healthcare professionals and must be independently verified. It is not for self-diagnosis or self-medication.
What can I use the FENa Calculator (Fractional Excretion of Sodium) for?+
It's commonly used for fena, fractional excretion sodium, prerenal vs atn. Pre-renal vs intrinsic AKI discrimination from paired serum/urine sodium and creatinine.
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