A 3-week-old male infant presents with progressive projectile (forceful, non-bilious) vomiting after every feed for 5 days. He is hungry after vomiting and demands immediate re-feeding. Examination shows visible peristaltic waves from left to right across the epigastrium and an olive-shaped mass palpable in the right hypochondrium. Blood gas shows pH 7.55, HCO3 38 mEq/L, K 2.8 mEq/L, Cl 88 mEq/L. What is the correct sequence of management?

• A Immediate surgery without fluid correction as delay worsens obstruction
• B Nasogastric tube, IV omeprazole for 5 days to reduce pyloric spasm, then reassess
• C IV atropine infusion to relax the pyloric muscle
• D Emergency pyloromyotomy after IV fluids and electrolyte correction (correct the metabolic alkalosis first) ✓

Explanation

Pyloric stenosis causes hypochloraemic hypokalaemic metabolic alkalosis from loss of HCl and K in vomitus. IV pyloromyotomy (Ramstedt's operation) is the definitive treatment, but emergency surgery without correcting the metabolic derangement can cause post-operative apnoea from central respiratory depression (the brain relies on the alkalosis as a respiratory drive inhibitor, which normalises post-operatively). Preoperative correction with normal saline + KCl supplementation until pH, Cl, and K normalise is mandatory. Atropine has been used medically in some centres but surgery remains standard of care.

Reference: Ghai Essential Pediatrics, 10th ed.

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Written and medically reviewed by the StethoPrep medical team.