A 3-week-old male infant presents with projectile non-bilious vomiting immediately after feeding for 10 days. Olive-shaped mass is palpable in the epigastrium. Ultrasound shows pyloric muscle thickness >4 mm and canal length >16 mm. Electrolytes reveal: Na 128 mEq/L, K 2.8 mEq/L, Cl 82 mEq/L, HCO3 32 mEq/L. What is the correct pre-operative management?

• A IV fluid resuscitation with 0.9% NaCl + KCl until electrolytes normalize, then surgery ✓
• B Emergency Ramstedt pyloromyotomy within 2 hours of diagnosis
• C NG tube insertion and H2-receptor antagonist to reduce acid production
• D Atropine infusion to relax the pyloric muscle as medical management

Explanation

Hypertrophic pyloric stenosis causes hypochloremic, hypokalemic metabolic alkalosis due to loss of HCl in vomitus. Surgery is NOT an emergency — it is urgent but must be preceded by IV fluid resuscitation and electrolyte correction. Standard protocol: 0.9% NaCl + KCl (20 mEq/L) IV until Cl >100 mEq/L, K >3.5 mEq/L, and HCO3 <30 mEq/L. Operating on uncorrected alkalosis risks post-operative apnea because metabolic alkalosis suppresses respiratory drive and anesthetic agents exacerbate this. Only after metabolic stabilization does Ramstedt pyloromyotomy (open or laparoscopic) proceed safely. Atropine is a medical alternative for poor surgical candidates but is not the standard approach.

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

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Written and medically reviewed by the StethoPrep medical team.