A 58-year-old man with a long history of epigastric pain now presents with projectile vomiting of food ingested many hours earlier. Examination shows a succussion splash and visible gastric peristalsis. Serum electrolytes: sodium 138 mEq/L, potassium 2.9 mEq/L, chloride 88 mEq/L, bicarbonate 36 mEq/L. Which acid-base disturbance is expected?
- A Hyperchloremic metabolic acidosis
- B Mixed metabolic and respiratory acidosis
- C Respiratory alkalosis with compensatory aciduria
- D Hypochloremic hypokalemic metabolic alkalosis ✓
Explanation
The clinical picture is gastric outlet obstruction, classically from chronic duodenal ulcer scarring. Repeated loss of gastric hydrochloric acid produces hypochloremia and metabolic alkalosis, while volume depletion drives secondary hyperaldosteronism causing potassium wasting and paradoxical aciduria. Hyperchloremic metabolic acidosis follows diarrheal bicarbonate loss or renal tubular acidosis, not gastric vomiting. Respiratory alkalosis accompanies hyperventilation states such as salicylate toxicity or anxiety, neither of which fits the obstructive findings here.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
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