A 4-week-old male infant presents with progressive non-bilious projectile vomiting after every feed for the past week. The baby appears hungry after vomiting. Examination reveals visible gastric peristalsis from left to right and an olive-shaped mass in the epigastrium. What is the INVESTIGATION OF CHOICE to confirm the diagnosis?

• A Upper GI contrast study (barium meal)
• B Plain X-ray abdomen
• C Endoscopy
• D Abdominal ultrasound ✓

Explanation

This is the classic presentation of hypertrophic pyloric stenosis, the most common cause of surgical obstruction in infancy, presenting at 3-6 weeks of age (peak 4-6 weeks) predominantly in first-born males. Ultrasound is the investigation of choice, demonstrating increased pyloric muscle thickness (>4 mm) and pyloric channel length (>16 mm). The metabolic consequence is hypochloremic hypokalemic metabolic alkalosis from loss of HCl with vomiting. Treatment is Ramstedt's pyloromyotomy after correcting electrolyte imbalance.

Reference: Ghai Essential Pediatrics, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.