FENa (Fractional Excretion of Sodium) Pre-Renal vs. ATN Kidney Calculator

Compute FENa = (U_Na × P_Cr) / (P_Na × U_Cr) × 100 for AKI evaluation.

Fractional Excretion of Sodium (FENa)
0.2 %
Renal Failure Index (RFI) 0.28 index
Urine-to-Plasma Creatinine Ratio 50 : 1
Spot Urine Sodium 14 mEq/L
Inputs
⚡ Scenarios:
mEq/L
Serum Sodium concentration (P_Na) in mEq/L.
mg/dL
Serum Creatinine concentration (P_Cr) in mg/dL.
mEq/L
Spot Urine Sodium concentration (U_Na) in mEq/L.
mg/dL
Spot Urine Creatinine concentration (U_Cr) in mg/dL.
Results & Graph
Fractional Excretion of Sodium (FENa)
0.2 %
Renal Failure Index (RFI)
0.28 index
Urine-to-Plasma Creatinine Ratio
50 : 1
Spot Urine Sodium
14 mEq/L

Fractional Excretion of Sodium (FENa)

Graph 1 • FENa Kidney Fraction • Domain Architecture & Live Telemetry Maps Serum Sodium Meq L, Serum Creatinine Mg Dl, Urine Sodium Meq L through FENa Kidney Fraction Formula.
FENa Kidney Fraction • Clinical & Physiological Reference Scale Low / Baseline Target / Reference Elevated / Watch High / Action Fractional Excretion of Sodium (FENa): 0.2 % Renal Failure Index (RFI) 0.28 index Urine-to-Plasma Creatinine 50 : 1 Spot Urine Sodium 14 mEq/L
Graph 2 • Fractional Excretion of Sodium (FENa) Across Serum Sodium Meq L Sweep (40% → 160%) Evaluates FENa (%) = [ (Urine_Na × Serum_Cr) / (Serum_Na × Urine_Cr) ] × 100 across 7 operating points (current input highlighted).
0 % 0.550 % 1.10 % 0.510 55.20mEq/L 0.340 82.80mEq/L 0.250 110.4mEq/L 0.200 138mEq/L 0.170 165.6mEq/L 0.140 193.2mEq/L 0.130 220.8mEq/L
Graph 3 • Joint Sensitivity: Serum Sodium Meq L × Serum Creatinine Mg Dl Compares Fractional Excretion of Sodium (FENa) when Serum Creatinine Mg Dl is shifted +25% (solid) vs. −25% (dashed).
0 % 0.550 % 1.10 % --- Serum Creatinine Mg Dl @ 75% 0.360 -30% 0.300 -15% 0.250 +0% 0.220 +15% 0.200 +30%
Summary: FENa is 0.2% (Pre-Renal Azotemia (<1.0%)) with a Renal Failure Index (RFI) of 0.28.
Summary: FENa is 0.2% (Pre-Renal Azotemia (<1.0%)) with a Renal Failure Index (RFI) of 0.28.
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Formula & Mathematical Methodology: FENa Kidney Fraction Formula

FENa (%) = [ UrineNa × SerumCrSerumNa × UrineCr ] × 100
FENa (%) = [ (Urine_Na × Serum_Cr) / (Serum_Na × Urine_Cr) ] × 100
  • serumSodiumMeqL: Serum Sodium Meq L (mEq/L)
  • serumCreatinineMgDl: Serum Creatinine Mg Dl (mg/dL)
  • urineSodiumMeqL: Urine Sodium Meq L (mEq/L)
  • urineCreatinineMgDl: Urine Creatinine Mg Dl (mg/dL)

Rounding: Clinical scores round to statutory integer or decimal precision; physiological metrics round to 2 decimal places.

Worked Example: Clinical / Physiology Scenario: FENa Kidney Fraction

Compute FENa = (U_Na × P_Cr) / (P_Na × U_Cr) × 100 for AKI evaluation.

  1. Enter lab values, anthropometric measurements, or performance test metrics.
  2. Evaluate the reference equation: FENa (%) = [ (Urine_Na × Serum_Cr) / (Serum_Na × Urine_Cr) ] × 100.
  3. Inspect the primary classification, supporting indices, and 3 SVG charts.
Result: Computes FENa Kidney Fraction via FENa (%) = [ (Urine_Na × Serum_Cr) / (Serum_Na × Urine_Cr) ] × 100.

Frequently Asked Questions

How does the FENa (Fractional Excretion of Sodium) Pre-Renal vs. ATN Kidney Calculator compute its result?

It evaluates FENa (%) = [ (Urine_Na × Serum_Cr) / (Serum_Na × Urine_Cr) ] × 100 directly in your browser and updates three custom SVG visualizations in real time.

Can I use Goal Seek to solve backwards for a target lab value or pace?

Yes. Click "🎯 Goal Seek" in the results toolbar to solve backwards for any numeric input parameter.

Are my health and biometric inputs kept private?

Yes. All calculations run 100% locally on your device with zero external transmission.

Health & Fitness · Clinical Nephrology & Electrolytes

FENa (Fractional Excretion of Sodium) Pre-Renal vs. ATN Kidney Calculator: inputs, method, and how to read the result

Compute FENa = (U_Na × P_Cr) / (P_Na × U_Cr) × 100 for AKI evaluation.

Choose inputs for the case you are checking

The defaults are illustrative. Replace them with values for your case and keep the units shown beside each field.

  • Serum Sodium Meq L: Serum Sodium concentration (P_Na) in mEq/L.
  • Serum Creatinine Mg Dl: Serum Creatinine concentration (P_Cr) in mg/dL.
  • Urine Sodium Meq L: Spot Urine Sodium concentration (U_Na) in mEq/L.
  • Urine Creatinine Mg Dl: Spot Urine Creatinine concentration (U_Cr) in mg/dL.

What the calculation includes

With the default values shown, Fractional Excretion of Sodium (FENa) is 0.2 %. The calculation follows FENa Kidney Fraction Formula; the formula and variable definitions above show how the inputs combine.

One-input check: With the other defaults held constant, changing Serum Sodium Meq L from 138 mEq/L to 152 mEq/L changes Fractional Excretion of Sodium (FENa) from 0.2 % to 0.18 %. This is a comparison inside the calculator's stated model, not a prediction.

Where to use caution

  • Uses peer-reviewed clinical and sports physiology formulas.
  • For educational and informational reference only; clinical scores do not replace physician judgment or laboratory reference ranges.

Scope: Global Clinical & Sports Science Consensus Check the assumptions and limitations against your situation before relying on the estimate.

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