Review of the Diagnostic Evaluation of Normal Anion Gap Metabolic Acidosis.

Background: Normal anion gap metabolic acidosis is a common but often misdiagnosed clinical condition associated with diarrhea and renal tubular acidosis (RTA). Early identification of RTA remains challenging for inexperienced physicians, and diagnosis and treatment are often delayed.

Summary: The presence of RTA should be considered in any patient with a high chloride level when the CL/Na ratio is above 0.79, if the patient does not have diarrhea. In patients with significant hyperkalemia one should evaluate for RTA type 4, especially in diabetic patients, with a relatively conserved renal function. A still growing list of medications can produce RTA.

Key Messages: This review highlights practical aspects concerning normal anion gap metabolic acidosis.