FEUrea Calculator
Calculate Fractional Excretion of Urea for acute kidney injury cause differentiation
Calculate FEUrea
Normal: 0.7-1.3 mg/dL (62-115 μmol/L)
Normal: 8-20 mg/dL (2.9-7.1 mmol/L)
Normal: 15-25 mg/kg per 24h (varies widely)
Normal: 350-700 mg/dL (125-250 mmol/L)
FEUrea Reference Ranges
Prerenal
Decreased renal perfusion
Borderline
Mixed or early intrinsic
Intrinsic
Intrinsic kidney damage
Required Lab Tests
Blood Tests
Serum creatinine and urea/BUN
Urine Tests
Urine creatinine and urea
Random or 24-hour collection
FEUrea vs FENa
Use FEUrea when:
• Patient on diuretics
• Heart or liver failure
• Glucosuria present
• Contrast nephropathy
Use FENa when:
• No diuretics
• Simple AKI case
• Standard evaluation
Example Calculation
Sample Values
Serum Cr: 2.5 mg/dL
Serum Urea: 60 mg/dL
Urine Cr: 150 mg/dL
Urine Urea: 1200 mg/dL
Calculation
FEUrea = (1200 × 2.5) / (60 × 150) × 100
FEUrea = 3000 / 9000 × 100
FEUrea = 33.3%
Result: Prerenal cause
Understanding FEUrea (Fractional Excretion of Urea)
What is FEUrea?
FEUrea represents the percentage of filtered urea that is excreted in the urine. It's considered superior to FENa for differentiating the causes of acute kidney injury, especially in patients on diuretics or with complex medical conditions.
Why is FEUrea Important?
- •More reliable than FENa in many clinical scenarios
- •Unaffected by diuretic medications
- •Better performance in heart and liver failure
- •Helps guide appropriate treatment strategies
Formula Explanation
FEUrea = (Urine Urea × Serum Cr) / (Serum Urea × Urine Cr) × 100
- Urine Urea: Urea concentration in urine
- Serum Cr: Serum creatinine concentration
- Serum Urea: Serum urea/BUN concentration
- Urine Cr: Urine creatinine concentration
Clinical Context: In prerenal AKI, kidneys retain their ability to reabsorb urea, resulting in low FEUrea. In intrinsic AKI, this reabsorptive capacity is impaired, leading to higher FEUrea values.
Prerenal Causes
- • Hypovolemia (dehydration, bleeding)
- • Heart failure
- • Liver failure
- • Renal artery stenosis
- • Sepsis with hypotension
Intrinsic Causes
- • Acute tubular necrosis
- • Glomerulonephritis
- • Rhabdomyolysis
- • Nephrotoxic medications
- • Acute interstitial nephritis
Postrenal Causes
- • Urinary tract obstruction
- • Prostate hyperplasia
- • Kidney stones
- • Bladder cancer
- • Urethral stricture
⚠️ Important Medical Disclaimer
This calculator is for educational purposes only and should not replace professional medical advice.
- • Always consult with a qualified nephrologist or physician for AKI evaluation
- • FEUrea should be interpreted within the full clinical context
- • Consider other diagnostic tests and clinical findings
- • Use in conjunction with urinalysis, imaging, and patient history
- • Monitor patient response to treatment and adjust accordingly