In pediatric hypertrophic pyloric stenosis, which biochemical abnormality must be corrected before surgical pyloromyotomy?

• A Hypochloremic hypokalemic metabolic alkalosis ✓
• B Hyperchloremic metabolic acidosis
• C Hyponatremic dehydration with metabolic acidosis
• D Hyperkalemic metabolic acidosis

Explanation

Hypertrophic pyloric stenosis causes persistent projectile vomiting of gastric contents (HCl-rich) leading to hypochloremic, hypokalemic metabolic alkalosis (also called paradoxical aciduria—the kidney excretes H+ to conserve sodium despite alkalosis, with urinary pH paradoxically acidic in late stages). Surgery is NOT an emergency—hydration and electrolyte correction must precede anesthesia to avoid apnea and laryngospasm. Pyloromyotomy (Ramstedt's procedure) is definitive. The condition does NOT cause metabolic acidosis.

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

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