Urine Anion Gap Calculator

Urine Anion Gap Calculator — Clinical Acid-Base Analysis Tool

Calculate urine anion gap (UAG) for clinical assessment of metabolic acidosis. Evaluate acid-base disorders based on urine electrolyte measurements.

Step 1: Urine Electrolyte Values

Urine Sodium (Na⁺) Measured in mmol/L

Urine Potassium (K⁺) Measured in mmol/L

Urine Chloride (Cl⁻) Measured in mmol/L

Understanding Urine Electrolytes

Urine anion gap (UAG) = (Na⁺ + K⁺) – Cl⁻. UAG helps differentiate between types of metabolic acidosis. Negative UAG suggests renal tubular acidosis, while positive UAG suggests diarrhea or other causes.

Step 2: Analysis & Interpretation

Clinical Scenario

Show reference range comparison

Show clinical interpretation

Show electrolyte visualization

Clinical Significance

The urine anion gap is an indirect measure of urinary ammonium (NH₄⁺) excretion. It helps differentiate between normal anion gap metabolic acidosis causes, particularly renal tubular acidosis versus diarrhea.

Urine Anion Gap Results

Summary

Clinical Interpretation

Electrolyte Analysis

Calculated Urine Anion Gap

70 mmol/L

Based on Na⁺: 100, K⁺: 50, Cl⁻: 80 mmol/L

Urine Sodium (Na⁺)

100 mmol/L

Urine Potassium (K⁺)

50 mmol/L

Urine Chloride (Cl⁻)

80 mmol/L

UAG Interpretation

Positive UAG

Clinical Interpretation

Positive Urine Anion Gap (70 mmol/L)

A positive urine anion gap (>0 mmol/L) suggests:

Low urinary ammonium excretion – Indicates renal tubular acidosis (RTA)
Type 1 (Distal) RTA – Impaired distal tubule acidification
Type 4 (Hyperkalemic) RTA – Aldosterone deficiency/resistance
Possible causes: Autoimmune diseases, obstructive uropathy, sickle cell disease, medications (amphotericin B, lithium)

Clinical considerations: Evaluate serum electrolytes, arterial blood gas, and consider further testing for RTA if clinically indicated.

Comparison with Reference Ranges

Parameter	Your Value	Normal Range	Interpretation

Electrolyte Analysis

Urine Anion Gap Formula

UAG = (Na⁺ + K⁺) – Cl⁻

The urine anion gap is calculated by summing the urine sodium and potassium concentrations, then subtracting the urine chloride concentration. This indirect measure helps estimate urinary ammonium excretion, which is not routinely measured in clinical labs.

Interpretation guidelines:

Negative UAG (< 0 mmol/L): Suggests appropriate NH₄⁺ excretion (e.g., diarrhea, normal anion gap metabolic acidosis)
Positive UAG (> 0 mmol/L): Suggests impaired NH₄⁺ excretion (e.g., renal tubular acidosis)
Near zero: May be seen in various conditions; clinical correlation needed

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