Fractional Excretion Of Sodium Calculator

Fractional Excretion of Sodium Equation:

\[ FENa = \frac{(Sodium_{urinary} \times Creatinine_{plasma})}{(Sodium_{plasma} \times Creatinine_{urinary})} \times 100 \]

Urine Sodium Concentration:

mmol/L

Creatinine Concentration in Plasma:

μmol/L

Sodium Concentration in Plasma:

mmol/L

Creatinine Concentration in Urine:

μmol/L

Fractional Excretion of Sodium (FENa):

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1. What is Fractional Excretion of Sodium?

Fractional Excretion of Sodium (FENa) is the percentage of the sodium filtered by the kidney which is excreted in the urine. It's a useful diagnostic tool to differentiate between prerenal azotemia and acute tubular necrosis.

2. How Does the Calculator Work?

The calculator uses the FENa equation:

\[ FENa = \frac{(Sodium_{urinary} \times Creatinine_{plasma})}{(Sodium_{plasma} \times Creatinine_{urinary})} \times 100 \]

Where:

\( Sodium_{urinary} \) — Urine sodium concentration (mmol/L)
\( Creatinine_{plasma} \) — Plasma creatinine concentration (μmol/L)
\( Sodium_{plasma} \) — Plasma sodium concentration (mmol/L)
\( Creatinine_{urinary} \) — Urine creatinine concentration (μmol/L)

Explanation: The formula calculates what percentage of filtered sodium is being excreted, which helps determine if the kidneys are appropriately conserving sodium.

3. Importance of FENa Calculation

Details: FENa is crucial for differentiating between prerenal azotemia (FENa < 1%) and acute tubular necrosis (FENa > 2%). It helps guide appropriate treatment in patients with acute kidney injury.

4. Using the Calculator

Tips: Enter all four required values in the appropriate units. All values must be positive numbers. The calculator will compute the FENa percentage.

5. Frequently Asked Questions (FAQ)

Q1: What is a normal FENa value?
A: Normally, FENa is less than 1%, indicating appropriate sodium conservation by the kidneys.

Q2: When is FENa most useful?
A: FENa is most valuable in the evaluation of acute kidney injury to differentiate between prerenal and intrinsic renal causes.

Q3: Are there limitations to FENa interpretation?
A: Yes, FENa may be less reliable in patients on diuretics, with chronic kidney disease, or with certain electrolyte disorders.

Q4: What does FENa > 2% indicate?
A: FENa greater than 2% typically suggests acute tubular necrosis or other intrinsic renal disease.

Q5: Can FENa be used in children?
A: Yes, but interpretation may differ slightly, and age-specific reference ranges should be considered.