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Calculates the fractional excretion of uric acid (FEUA) to help distinguish prerenal azotemia from intrinsic renal injury in acute kidney injury, and to assess uric acid handling (e.g., SIADH, tumor lysis, Fanconi syndrome).
FEUA (%) = (Urine Uric Acid × Plasma Creatinine) ÷ (Serum Uric Acid × Urine Creatinine) × 100
~10% in euvolemic healthy adults (varies with volume status)
FEUA is the fractional excretion of urate across the proximal tubule. It is more stable than FENa in patients receiving diuretics and is used both in AKI differential diagnosis and in disorders of urate handling.
Specialty
Internal MedicineCategory
NephrologyDifficulty
Basic
Estimated Time
30 seconds
Version
1.0
Last Updated
2026-08-16
Formula
Keywords
Normal Range
~10% in euvolemic healthy adults (varies with volume status)
| Classification | Range |
|---|---|
Prerenal pattern (AKI) acute kidney injury | <12% |
Indeterminate acute kidney injury | 12–20% |
Intrinsic renal injury (ATN) pattern acute kidney injury | >20% |
Quantifies the fractional excretion of uric acid (FEUA) to help distinguish prerenal azotemia from intrinsic renal injury in acute kidney injury, and to assess urate handling in conditions such as SIADH, tumor lysis syndrome, and Fanconi syndrome.
In AKI, FEUA < 12% supports a prerenal pattern, 12–20% is indeterminate, and > 20% is more consistent with intrinsic renal injury such as ATN. In hyponatremia evaluation, a FEUA above 12% has been proposed as supporting SIADH. Thresholds overlap substantially and should not be used in isolation.
FEUA is less affected by diuretics than FENa, making it a useful complementary index in the AKI differential and in disorders of urate excretion such as SIADH and tumor lysis syndrome.
A 45-year-old man with early AKI has a urine uric acid of 20 mg/dL, serum uric acid 6 mg/dL, urine creatinine 80 mg/dL, and plasma creatinine 1.2 mg/dL.
Inputs:
FEUA = (20 × 1.2) ÷ (6 × 80) × 100 = 5.0%. This value below 12% supports a prerenal pattern.
FENa is inflated by diuretics and saline resuscitation, which makes it unreliable in many AKI patients. FEUA is less affected by diuretics and can complement FENa and FEUrea.
In AKI, a FEUA persistently > 20% is more consistent with intrinsic renal injury (e.g., ATN), whereas a low FEUA supports a prerenal pattern. Overlap is common.
Disclaimer: This calculator is intended for educational and clinical decision support purposes only. FEUA must be interpreted with the clinical context and alongside other urinary indices.