Urinary Anion Gap

• Indications
  1. Non-Anion Gap Metabolic Acidosis
  2. Distinguishes renal from extra-renal causes

   

   

• Physiology: Measures unmeasured anions present in urine
  1. Sulfates
  2. Phosphates
  3. Bicarbonates
  4. Organic anions
     1. Lactate
     2. Citrate

   

   

• Calculation
  1. UAG = Urine Sodium + Urine Potassium - Urine Chloride

   

   

• Interpretation: Normal
  1. UAG = -10 to +10

   

   

• Interpretation
  1. Decreased Urine Anion Gap <-10
     1. Extrarenal non-Anion Gap Metabolic Acidosis
  2. Increased Urine Anion Gap >+10
     1. Renal non-Anion Gap Metabolic Acidosis