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Urinary Anion Gap
Aka: Urinary Anion Gap, Urine Anion Gap
- Indications
- Non-Anion Gap Metabolic Acidosis
- Distinguishes renal from extra-renal causes
- Physiology: Measures unmeasured anions present in urine
- Ammonium (not excreted in Renal Tubular Acidosis)
- Sulfates
- Phosphates
- Bicarbonates
- Organic anions
- Lactate
- Citrate
- Calculation
- UAG = Urine Sodium + Urine Potassium - Urine Chloride
- Interpretation: Normal
- UAG = -10 to +10
- Interpretation
- Decreased Urine Anion Gap <-10
- Extrarenal Non-Anion Gap Metabolic Acidosis (e.g. gastrointestinal bicarbonate losses)
- Increased Urine Anion Gap >+10
- Renal Non-Anion Gap Metabolic Acidosis (Urine pH will also be >6.0)
- Causes
- Type 1 Renal Tubular Acidosis
- Type 4 Renal Tubular Acidosis (Hypoaldosteronism)
- Renal Failure