🫘 Fractional Excretion of Urea (FEUrea)
Differentiate pre-renal AKI from ATN with the fractional excretion of urea (FEUrea).
Clinical takeaway
More reliable than FENa when diuretics have been given.
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When to use
Assess acute kidney injury, especially after diuretics.
How it works
FEUrea = (urine urea × serum creatinine) / (serum urea × urine creatinine) × 100. < 35% pre-renal; > 50% intrinsic.
Key points
- More reliable than FENa when diuretics have been given.
- Urea handling is less affected by diuretics.
- Interpret with clinical context and urine microscopy.
References
Decision support for licensed clinicians only; not a substitute for clinical judgement, diagnosis or local protocols.
Worked calculation
The values below come from this tool's own example placeholders and are computed server-side with the formula shown on this page, so the arithmetic can be checked quickly. It demonstrates how to substitute values only — it is not clinical advice and not a real case.
| Urine urea | 300 mg/dL |
|---|---|
| Serum urea (BUN) | 30 mg/dL |
| Urine creatinine | 100 mg/dL |
| Serum creatinine | 2.0 mg/dL |
→FEUrea20.0%
- Interpretation：< 35% — suggests pre-renal
- Formula：(Uurea × SCr)/(Surea × UCr) × 100
Frequently asked questions
- What is Fractional Excretion of Urea (FEUrea)?
- Differentiate pre-renal AKI from ATN with the fractional excretion of urea (FEUrea).
- How is Fractional Excretion of Urea (FEUrea) calculated? What is the core formula?
- FEUrea = (urine urea × serum creatinine) / (serum urea × urine creatinine) × 100. < 35% pre-renal; > 50% intrinsic.
- When is Fractional Excretion of Urea (FEUrea) used?
- Assess acute kidney injury, especially after diuretics.
- What are the key clinical points for Fractional Excretion of Urea (FEUrea)?
- More reliable than FENa when diuretics have been given. Urea handling is less affected by diuretics. Interpret with clinical context and urine microscopy.
- What are the limits and cautions when using Fractional Excretion of Urea (FEUrea)?
- For licensed clinicians and clinical researchers. Interpret results with history, investigations and local protocols; not a diagnosis or prescription, and not a substitute for multidisciplinary decision-making or local guidelines.
- How is Fractional Excretion of Urea (FEUrea) calculated in practice? Can you show a worked example?
- Inputs: Urine urea 300 mg/dL, Serum urea (BUN) 30 mg/dL, Urine creatinine 100 mg/dL, Serum creatinine 2.0 mg/dL → Result: FEUrea 20.0 %（Interpretation: < 35% — suggests pre-renal, Formula: (Uurea × SCr)/(Surea × UCr) × 100）