A patient with proximal jejunal obstruction vomits large volumes of gastric contents repeatedly for several days. Which acid-base and electrolyte disturbance is most characteristic?

• A High anion gap metabolic acidosis with respiratory compensation
• B Hyperchloremic metabolic acidosis
• C Hypochloremic, hypokalemic metabolic alkalosis ✓
• D Hyperkalemic metabolic alkalosis

Explanation

Gastric juice contains high concentrations of hydrogen and chloride ions with modest potassium. Continued vomiting of proximal small bowel content depletes chloride and potassium, producing a hypochloremic, hypokalemic metabolic alkalosis, compounded by volume contraction that drives renal bicarbonate retention through aldosterone mediated hydrogen exchange. Diarrhoeal losses or distal colonic losses would instead generate hyperchloremic metabolic acidosis, and potassium falls rather than rises because of renal and gastric losses.

Reference: Ganong's Review of Medical Physiology, 26th ed.

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