Non-Anion Gap Metabolic Acidosis: A Clinical Approach to Evaluation

Abstract

Acid-base disturbances can result from kidney or nonkidney disorders. We present a case of high-volume ileostomy output causing large bicarbonate losses and resulting in a non-anion gap metabolic acidosis. Non-anion gap metabolic acidosis can present as a form of either acute or chronic metabolic acidosis. A complete clinical history and physical examination are critical initial steps to begin the evaluation process, followed by measuring serum electrolytes with a focus on potassium level, blood gas, urine pH, and either direct or indirect urine ammonium concentration. The present case was selected to highlight the differential diagnosis of a non-anion gap metabolic acidosis and illustrate a systematic approach to this problem.

Keywords: Non–anion gap metabolic acidosis; acid-base; high volume ileostomy output; renal acidification; urinary ammonium; urine anion gap; urine osmolal gap.