In diarrhea-induced metabolic acidosis, what is the typical anion gap?

• A. Normal
• B. Elevated
• C. Decreased
• D. Variable

Answer: (A)

In diarrhea-induced metabolic acidosis, bicarbonate is lost in the stool, lowering the serum HCO3-. To keep electrical neutrality, chloride is retained, increasing Cl- and offsetting the bicarbonate loss. Because the anion gap is calculated as Na minus (Cl plus HCO3), this shift keeps the gap within the normal range. Clinically this is known as a normal (non‑anion gap) metabolic acidosis, or hyperchloremic metabolic acidosis. Elevated anion gap would point to extra unmeasured anions from conditions like lactic acidosis or ketoacidosis, while decreased or highly variable gaps are not typical for this scenario.