Abbreviation: UAG
The difference between the concentration of measured anions and the concentration of measured cations in the urine. Calculated as [Urine Na] + [Urine K+] - [Urine Cl-]. Normal range is -20 to -50 mEq/L. Positive urine anion gap is associated with decreased renal acid excretion (e.g., type 1 and type 4 renal tubular acidoses); negative urine anion gap is associated with loss of bicarbonate (e.g., diarrhea).