Urinary Anion Gap Calculator

Where:

• \( [\text{Na}^+] \): The concentration of sodium ions in the urine (mEq/L).
• \( [\text{K}^+] \): The concentration of potassium ions in the urine (mEq/L).
• \( [\text{Cl}^-] \): The concentration of chloride ions in the urine (mEq/L).

Description:

The Urinary Anion Gap (UAG) is used to assess the renal handling of acid-base balance and to differentiate between different types of metabolic acidosis. It is calculated by measuring the concentrations of sodium, potassium, and chloride ions in the urine. The UAG helps to identify the source of metabolic acidosis, particularly in distinguishing between renal and non-renal causes.

Formula Explanation:

The formula for calculating the Urinary Anion Gap (UAG) is based on the concentrations of sodium, potassium, and chloride in the urine. The UAG essentially reflects the ability of the kidneys to excrete unmeasured anions like ammonium. The formula can help differentiate between causes of metabolic acidosis:

• Positive UAG: A positive UAG typically indicates a renal cause of acidosis, such as renal tubular acidosis (RTA), where the kidneys are unable to excrete acid properly.
• Negative UAG: A negative UAG suggests a non-renal cause of acidosis, such as diarrhea, where there is a loss of bicarbonate in the gastrointestinal tract.

Interpretation:

• Normal UAG: A UAG close to zero may indicate normal renal acid handling and the absence of an underlying renal or non-renal cause of metabolic acidosis.
• Positive UAG (greater than +10): A positive UAG suggests a renal cause of acidosis, likely due to renal tubular acidosis or impaired ammonium excretion.
• Negative UAG (less than -10): A negative UAG points to a non-renal cause of acidosis, typically due to gastrointestinal loss of bicarbonate (e.g., diarrhea).

Usage:

The Urinary Anion Gap calculator is helpful in diagnosing the cause of metabolic acidosis, guiding clinical management, and determining the appropriate treatment for electrolyte and acid-base disorders.