Positive urine anion gap 2024-07-21T06:42:37Z The urine anion gap (UAG), calculated as [(Na+ + K+) - (Cl-)] has been used to roughly estimate whether urine ammonium is increased or decreased in the evaluation of hyperchloremic metabolic acidosis. The more ammonium in the urine, the lower the UAG is, which achieves negative values within a wide range (0 to -200 mEq/L) during hyperchloremic metabolic acidosis. In patients with distal renal tubular acidosis (RTA) of several etiologies, the UAG is positive, despite the prevailing metabolic acidosis, and this is a useful bedside diagnostic index of impaired ammonium excretion. Abnormal urine pH