A 3-week-old infant has projectile non-bilious vomiting after feeds and a palpable “olive” mass in the abdomen. Most likely diagnosis is:

Correct option is B

Congenital hypertrophic pyloric stenosis presents with non-bilious projectile vomiting, visible peristalsis, and palpable pyloric “olive.”
Explanation of options: (a) ✘ Duodenal atresia → bilious vomiting + “double bubble” sign. (b) ✔ Correct; classic triad = projectile vomiting + non-bilious + olive mass. (c) ✘ GER causes regurgitation, not projectile vomiting with mass. (d) ✘ Intussusception → red currant jelly stool, colicky pain, not this presentation.