Which electrolyte abnormality is most commonly associated with diarrheal dehydration causing metabolic acidosis?

• A. Non-anion gap metabolic acidosis with bicarbonate loss and hyperchloremia
• B. Anion gap metabolic acidosis
• C. Metabolic alkalosis
• D. Respiratory alkalosis

Answer: (A)

Diarrheal dehydration causes bicarbonate to be lost in the stool, which lowers serum bicarbonate and creates metabolic acidosis. Because the base is lost rather than acid being added, the anion gap stays normal; the body compensates by retaining chloride, so serum chloride rises. This combination results in a non-anion gap (hyperchloremic) metabolic acidosis. That’s why the associated electrolyte abnormality is hyperchloremia with bicarbonate loss. In contrast, conditions with an elevated anion gap involve accumulation of unmeasured anions (like lactate or ketones), vomiting or diuretic use produce metabolic alkalosis, and respiratory alkalosis arises from hyperventilation rather than bicarbonate loss.