A 50-year-old man with a long history of dyspepsia presents with projectile vomiting of food eaten many hours earlier and visible peristaltic waves across the upper abdomen. A succession splash is present. Which acid-base abnormality is expected on arterial blood gas analysis?

• A Hyperchloremic metabolic acidosis with respiratory compensation
• B Normal anion gap metabolic acidosis with paradoxical aciduria
• C Metabolic alkalosis with hypochloremia and hypokalemia ✓
• D High anion gap metabolic acidosis with ketosis

Explanation

This is gastric outlet obstruction from chronic cicatrizing duodenal ulcer. Repeated loss of gastric hydrochloric acid produces hypochloremic hypokalemic metabolic alkalosis; potassium depletion worsens because aldosterone-driven renal potassium loss continues. In advanced volume depletion, sodium is preferentially reabsorbed in exchange for hydrogen ions, giving paradoxical aciduria despite systemic alkalemia. Hyperchloremic acidosis follows diarrheal bicarbonate loss or ureteric diversion, not gastric vomiting, and ketosis requires starvation diabetes physiology.

Reference: Bailey and Love's Short Practice of Surgery, 27th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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