A 3-week-old male infant presents with non-bilious projectile vomiting immediately after feeding. He appears hungry after vomiting. A palpable 'olive-shaped' mass is felt in the right epigastrium. Electrolytes show hypochloraemic, hypokalaemic metabolic alkalosis. The appropriate pre-operative treatment before pyloromyotomy is:
- A Immediate laparoscopic Ramstedt pyloromyotomy
- B Nasogastric tube decompression alone and urgent surgery within 2 hours
- C Correction of fluid, electrolyte and acid-base derangements with IV 0.9% NaCl + KCl until metabolic alkalosis resolves ✓
- D Oral rehydration therapy for 24 hours then surgery
Correct answer: C. Correction of fluid, electrolyte and acid-base derangements with IV 0.9% NaCl + KCl until metabolic alkalosis resolves
Explanation
Hypertrophic pyloric stenosis causes hypochloraemic hypokalaemic metabolic alkalosis from persistent vomiting of HCl-rich gastric secretions. Surgery (Ramstedt's pyloromyotomy — laparoscopic or open) is NOT a surgical emergency; it is an electrolyte emergency. Pyloromyotomy performed in the setting of uncorrected metabolic alkalosis risks post-operative apnoea (alkalosis suppresses the respiratory drive). Rehydration with IV 0.9% NaCl + potassium chloride until serum bicarbonate <30 mEq/L, chloride >100 mEq/L, and urine output established is mandatory before surgery.
Reference: Bailey & Love's Short Practice of Surgery, 27th ed.
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Written and medically reviewed by the StethoPrep medical team.