What is the role of diarrhea in the etiology of hyperchloremic acidosis?

Updated: Oct 18, 2018
  • Author: Sai-Ching Jim Yeung, MD, PhD, FACP; Chief Editor: Romesh Khardori, MD, PhD, FACP  more...
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Diarrhea is the most common cause of external loss of alkali resulting in metabolic acidosis. Biliary, pancreatic, and duodenal secretions are alkaline and are capable of neutralizing the acidity of gastric secretions. In normal situations, a luminal Na+/H+ exchanger in the jejunal mucosa effectively results in sodium bicarbonate (NaHCO3) reabsorption, and, therefore, normally the 100 mL of stool excreted daily has very small amounts of bicarbonate.

The development of diarrheal states and increased stool volume (potentially several L/d) may cause a daily loss of several hundred millimoles of bicarbonate. Some of this loss may not occur as bicarbonate loss itself; instead, intestinal flora produces organic acids that titrate bicarbonate, resulting in loss of organic anions in the stool stoichiometrically equivalent to the titrated bicarbonate. Because diarrheal stools have a higher bicarbonate concentration than plasma, the net result is a metabolic acidosis with volume depletion. Diarrhea may also be caused by external pancreatic, biliary, or small bowel drainage; an ileus; a ureterosigmoidostomy; a jejunal loop; or an ileal loop, resulting in hyperchloremic metabolic acidosis.

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