Fractional Excretion of Sodium (FENa %) & Renal Azotemia Reference Calculator

Compute FENa% = 100 × (U_Na × P_Cr) / (P_Na × U_Cr) for nephrology reference.

Fractional Excretion of Sodium (FENa)
0.19 %
Urine-to-Plasma Creatinine (U/P Cr) 52.38 ratio
Renal Failure Index (U_Na / (U_Cr/P_Cr)) 0.27 index
Urine-to-Plasma Sodium Ratio 0.1 ratio
Inputs
mEq/L
Serum Sodium (P_Na) in mEq/L.
mg/dL
Serum Creatinine (P_Cr) in mg/dL.
mEq/L
Spot Urine Sodium (U_Na) in mEq/L.
mg/dL
Spot Urine Creatinine (U_Cr) in mg/dL.
Results & Graph
Fractional Excretion of Sodium (FENa)
0.19 %
Urine-to-Plasma Creatinine (U/P Cr)
52.38 ratio
Renal Failure Index (U_Na / (U_Cr/P_Cr))
0.27 index
Urine-to-Plasma Sodium Ratio
0.1 ratio

Fractional Excretion of Sodium (FENa)

Graph 1 • Serum Sodium Meq L Sensitivity Recalculates the domain equation across 50% to 150% of the primary input while holding other parameters constant.
0 % 0.5 % 1.1 % 50%: 0.39 % 0.4 50% 75%: 0.26 % 0.3 75% 100%: 0.19 % 0.2 100% 125%: 0.15 % 0.1 125% 150%: 0.13 % 0.1 150%
Graph 2 • Primary & Supporting Metric Comparison Compares the primary output alongside supporting domain benchmarks.
Fractional Excretion of Sodium (FENa) 0.19 % Urine-to-Plasma Creatinine (U/P Cr) 52.38 ratio Renal Failure Index (U_Na / (U_Cr/P_Cr)) 0.27 index Urine-to-Plasma Sodium Ratio 0.1 ratio
Graph 3 • Exact Output Table & Units Displays each calculated output in its exact domain unit.
Fractional Excretion of Sodium (FENa)0.19 %Urine-to-Plasma Creatinine (U/P Cr)52.38 ratioRenal Failure Index (U_Na / (U_Cr/P_Cr))0.27 indexUrine-to-Plasma Sodium Ratio0.1 ratio
Summary: FENa is 0.19% (Pre-Renal Pattern (<1%)) with a urine-to-plasma creatinine ratio of 52.4.
Summary: FENa is 0.19% (Pre-Renal Pattern (<1%)) with a urine-to-plasma creatinine ratio of 52.4.
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Formula & Mathematical Methodology: FENa % Renal Reference Reference Equation

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: Laboratory and clinical equations retain full floating-point precision and round displayed results to 2 decimal places.

Worked Example: Reference Calculation: FENa % Renal Reference

Compute FENa% = 100 × (U_Na × P_Cr) / (P_Na × U_Cr) for nephrology reference.

  1. Enter the reagent concentrations, assay readings, or clinical laboratory parameters.
  2. Compute the standard formula: FENa% = [ (Urine_Na × Serum_Cr) / (Serum_Na × Urine_Cr) ] × 100.
  3. Review the primary result, supporting reference intervals, and 3 SVG visualizations.
Result: Evaluates FENa % Renal Reference via FENa% = [ (Urine_Na × Serum_Cr) / (Serum_Na × Urine_Cr) ] × 100.

Frequently Asked Questions

What formula is used by the Fractional Excretion of Sodium (FENa %) & Renal Azotemia Reference Calculator?

It computes FENa% = [ (Urine_Na × Serum_Cr) / (Serum_Na × Urine_Cr) ] × 100 and plots three custom SVG graphs showing parameter sensitivity and component breakdowns.

Can I compare different reagent dilutions or lab scenarios side by side?

Yes. Use the "Compare (0/3)" button to pin up to 3 scenarios side by side.

Are entered values stored on any server?

No. Every calculation runs 100% locally in your browser.

Health & Fitness · Clinical Diagnostics & Scoring

Fractional Excretion of Sodium (FENa %) & Renal Azotemia Reference Calculator: inputs, method, and how to read the result

Compute FENa% = 100 × (U_Na × P_Cr) / (P_Na × U_Cr) for nephrology reference.

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

What the calculation includes

With the default values shown, Fractional Excretion of Sodium (FENa) is 0.19 %. The calculation follows FENa % Renal Reference Reference Equation; 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 0.19 % to 0.18 %. This is a comparison inside the calculator's stated model, not a prediction.

Where to use caution

  • Uses standard IUPAC atomic weights, 25°C (298.15 K) reference thermodynamics, and published clinical literature equations.
  • Educational and laboratory reference tool only; clinical scoring calculators do not replace professional medical judgment or institutional protocols.

Scope: IUPAC / NIH Laboratory & Clinical Reference Standard Check the assumptions and limitations against your situation before relying on the estimate.

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