FENa Calculator – Quick Tool for Calculating Fractional Sodium Excretion
Use this FENa Calculator to quickly calculate fractional excretion of sodium (FENa) — a valuable diagnostic tool in evaluating the cause of acute kidney injury (AKI). It helps distinguish prerenal azotemia from intrinsic renal damage, guiding your clinical approach effectively.
FeNa Calculator
Fractional Excretion of Sodium (FeNa) helps differentiate between prerenal and intrinsic renal causes of acute kidney injury (AKI).
Disclaimer: This calculator is intended for educational purposes only. It does not replace clinical judgment. Always consult a medical professional before making any decisions based on this tool.
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What is FENa?
FENa (Fractional Excretion of Sodium) measures the percentage of the sodium filtered by the kidney that is excreted in the urine. It helps determine whether the kidneys are retaining sodium appropriately in response to hypoperfusion (prerenal) or if tubular damage has impaired sodium reabsorption (intrinsic renal cause).
When to Use FENa Calculation?
You should consider using the FENa calculator when a patient presents with signs of acute kidney injury and you need to determine whether the cause is:
- Prerenal (e.g., hypovolemia, dehydration, heart failure)
- Intrinsic (e.g., acute tubular necrosis)
FENa Interpretation Guide
| FENa Value | Clinical Interpretation |
|---|---|
| < 1% | Suggests prerenal cause (volume depletion, hypoperfusion) |
| > 2% | Suggests intrinsic renal cause (e.g., ATN) |
| 1–2% | Indeterminate zone – consider clinical context |
How to Calculate FENa?
The formula used in our calculator is:
FENa (%) = [(Urine Na × Plasma Cr) / (Plasma Na × Urine Cr)] × 100
Rather than calculating manually, you can use the easy tool below to input your values and get instant results.
FAQs
FENa interpretation – What is the interpretation of FENa values?
FENa <1% suggests prerenal AKI, >2% suggests intrinsic renal cause, 1–2% is indeterminate.
FENa normal range – What is the normal range of FENa?
There’s no fixed “normal,” but FENa <1% is typical in prerenal states, >2% in intrinsic AKI.
FENa calculator mdcalc – What is the FENa calculator on MDCalc?
MDCalc offers an FENa calculator similar in function to this one for clinical use.
FENa prerenal – What does FENa indicate in prerenal conditions?
A FENa less than 1% typically indicates a prerenal cause of acute kidney injury.
FENa AKI – How is FENa used in AKI evaluation?
FENa helps differentiate between prerenal and intrinsic causes of AKI based on sodium handling.
FENa values – What are the clinical interpretations of different FENa values?
FENa values: <1% = prerenal, >2% = intrinsic, 1–2% = borderline or mixed.