title: The urine anion gap: a clinically useful index of ammonium excretion.
abstract: In patients with a normal plasma anion gap type of metabolic acidosis, knowledge of the rate of ammonium excretion can provide valuable information to determine if there is a renal cause for the disorder. Unfortunately, few hospital biochemistry laboratories offer routine determination of the urine ammonium concentration. Data are presented that demonstrate a direct linear relationship between the urine anion gap (Na+ + K+ - Cl-) and the urine ammonium concentration. In a 24-hour urine collection, the relationship is urine ammonium equals -0.8 (urine anion gap) +82 (r = 0.97 p less than 0.01). The applications of this index of ammonium excretion are discussed.
mesh_terms: D000136:Acid-Base Equilibrium; D000138:Acidosis / Q000175:diagnosis / Q000652:urine; D000141:Acidosis, Renal Tubular / Q000175:diagnosis / Q000652:urine; D000641:Ammonia / Q000652:urine*; D000643:Ammonium Chloride; D003937:Diagnosis, Differential; D004573:Electrolytes / Q000652:urine*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008433:Mathematics; D014556:Urine
chemical_list: D004573:Electrolytes; D000643:Ammonium Chloride; D000641:Ammonia