A 48-year-old man with a 20-year history of NSAID use for knee pain presents with projectile vomiting of food eaten the previous day, visible left-to-right peristaltic waves across the upper abdomen, and a succussion splash. Blood gas analysis is most likely to show which pattern?
- A Metabolic alkalosis with hypochloraemia and hypokalaemia ✓
- B Normal anion gap metabolic acidosis with hyperkalaemia
- C High anion gap metabolic acidosis with respiratory compensation
- D Respiratory alkalosis with normal electrolytes
Explanation
Benign gastric outlet obstruction from chronic peptic ulcer stricture produces repeated loss of gastric hydrochloric acid, generating a hypochloraemic, hypokalaemic metabolic alkalosis, sometimes with paradoxical aciduria. Projectile vomiting of stale food, visible gastric peristalsis, and a succussion splash are the classic bedside findings. High anion gap acidosis would fit lactic acidosis or ketoacidosis, and renal bicarbonate loss gives normal anion gap acidosis. Endoscopy after gastric lavage is required both to confirm the stricture and to exclude malignancy.
Reference: Sleisenger and Fordtran's Gastrointestinal and Liver Disease, 11th ed.
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