A 3-week-old male infant presents with projectile non-bilious vomiting after every feed, with a palpable olive-shaped mass in the epigastrium. What is the investigation of choice and the definitive treatment?

• A Ultrasound abdomen showing pyloric muscle thickness >4mm and channel length >17mm; Ramstedt's pyloromyotomy after correction of electrolyte abnormalities ✓
• B Plain X-ray abdomen; nasogastric tube decompression
• C Upper GI contrast study; immediate surgical repair
• D Ultrasound abdomen; medical management with atropine

Explanation

Infantile hypertrophic pyloric stenosis (IHPS) presents classically at 3-6 weeks of life with projectile, non-bilious vomiting and a palpable 'olive' in the epigastrium. Ultrasound is the investigation of choice, with diagnostic criteria of pyloric muscle thickness ≥4mm (some use ≥3mm) and pyloric channel length ≥17mm. Before surgery (Ramstedt's pyloromyotomy), electrolyte abnormalities must be corrected — typically a hypochloraemic hypokalaemic metabolic alkalosis from HCl and K+ losses in vomit. Pyloromyotomy itself is curative with excellent outcomes. Atropine (medical pyloromyotomy) is used in some countries but surgery remains standard.

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

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Written and medically reviewed by the StethoPrep medical team.