📋 Clinical Utility: FENa helps distinguish prerenal azotemia (< 1%) from ATN (> 2%) in oliguric acute kidney injury.
Best interpreted in the context of clinical presentation and other laboratory findings.

👤 Patient Information (Optional)

Age

years

Sex

🧪 Serum Values *

Serum Sodium (Na) *

mEq/L

Normal range: 136-145 mEq/L

Serum Creatinine *

mg/dL

Normal range: 0.7-1.3 mg/dL (adults)

💧 Urine Values *

Urine Sodium (Na) *

mEq/L

Prerenal: usually < 10-20 mEq/L
ATN: usually > 40 mEq/L

Urine Creatinine *

mg/dL

Spot urine creatinine concentration

🩺 Clinical Context (Optional)

Oliguria (UO < 400 mL/day) Hypotension/Sepsis Recent Nephrotoxins Recent Diuretics Pre-existing CKD

These contextual factors can affect FENa interpretation .

📖 FENa Formula:
FENa = (Urine Na / Serum Na) / (Urine Cr / Serum Cr) × 100%
Interpretation:
• < 1%: Prerenal azotemia (high sodium avidity)
• 1-2%: Borderline (consider clinical context)
• > 2%: ATN (impaired sodium reabsorption)
Limitations: Diuretics, CKD, glycosuria, recent contrast, or acute GN can alter FENa. Consider FEurea or clinical context .

🧪 Fractional Excretion of Sodium (FENa)

📊 FENa Results