II. Indications
- Non-Anion Gap Metabolic Acidosis
- Distinguishes renal from extra-renal causes
III. Physiology: Measures unmeasured anions present in urine
- Ammonia (not excreted in Renal Tubular Acidosis)
- Sulfates
- Phosphates
- Bicarbonates
- Organic anions
- Lactate
- Citrate
IV. Labs
- Urine Anion Gap (obtain urine Electrolytes)
- Urine Anion Gap = Urine Sodium + Urine Potassium - Urine Chloride
V. Interpretation
- Normal: UAG = -10 to +10
- Decreased Urine Anion Gap <-10
- Extrarenal (e.g. Diarrhea, TPN) Non-Anion Gap Metabolic Acidosis
- Gastrointestinal bicarbonate losses (e.g. Diarrhea, TPN)
- Appropriate renal ammonia excretion
- Increased Urine Anion Gap >+10
- Renal Non-Anion Gap Metabolic Acidosis
- Impaired renal ammonia excretion
- See Renal Tubular Acidosis
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| Concepts | Laboratory Procedure (T059) |
| English | urine anion gap measurement (lab test), urine anion gap measurement |
