2 month old male infant with regurgitation and projectile, nonbilious vomiting after feeding. A firm, ovoid, 1-2 cm abdominal mass was palpable. Abnormal left to right hyperperistalsis was evident during feeding.
The stomach is grossly distended. There is circumferential thickening (hyperplasia / hypertrophy) of the pyloric muscularis propria with narrowing of the gastric outlet tract.