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Fractional Excretion of Sodium & Urea Calculator (FeNa & FeUrea)

Nephrology and intensive care audit. Fractional Excretion of Sodium (FeNa) and Urea (FeUrea) is the diagnostic standard to differentiate hypovolemia/dehydration (Prerenal) from intrinsic acute tubular necrosis (ATN).

Input Parameters

Serum Sodium (Na+ in blood) (mEq/L)

Urine Sodium (Na+ in urine) (mEq/L)

Serum Creatinine (Cr in blood) (mg/dL)

Urine Creatinine (Cr in urine) (mg/dL)

Instant Calculation Result

Estimated Output

Active in Real-Time

Adjust values on the left to calculate live results.

Formula: FeNa Formula: FeNa (%) = (Urine Na × Serum Cr) / (Serum Na × Urine Cr) × 100. Tiers: FeNa < 1% Prerenal, FeNa > 2% Acute Tubular Necrosis (ATN). If patient is on loop diuretics, use FeUrea (< 35% Prerenal).

In-Depth Guide & Mathematical Methodology

🩸 AKI Diagnostic Thresholds (FeNa vs FeUrea)

FeNa < 1.0%: Prerenal Azotemia (Dehydration, hypovolemia, heart failure). Reabsorption intact.

FeNa > 2.0%: Intrinsic Acute Tubular Necrosis (ATN). Tubular reabsorption impaired.

Diuretic Confounding: Loop diuretics force sodium excretion. If patient received diuretics, calculate FeUrea (FeUrea < 35% confirms Prerenal etiology).

Frequently Asked Questions (FAQ)

What is the Fractional Excretion of Sodium & Urea Calculator (FeNa & FeUrea) and how does it work?

How do I use this Fractional Excretion of Sodium & Urea Calculator (FeNa & FeUrea)?

Enter Serum Sodium (Na in mEq/L). Enter Urine Sodium (Na in mEq/L). Enter Serum Creatinine (Cr in mg/dL). Enter Urine Creatinine (Cr in mg/dL). View calculated FeNa (%) percentage and etiology of Acute Kidney Injury.

What mathematical formula is used in this calculation?

FeNa Formula: FeNa (%) = (Urine Na × Serum Cr) / (Serum Na × Urine Cr) × 100. Tiers: FeNa < 1% Prerenal, FeNa > 2% Acute Tubular Necrosis (ATN). If patient is on loop diuretics, use FeUrea (< 35% Prerenal).

Is the Fractional Excretion of Sodium & Urea Calculator (FeNa & FeUrea) on FindCalculator free to use?

Yes, all 330+ interactive tools on FindCalculator.online are 100% free, run directly in your browser without registration, and do not store your private calculation data.

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