A 6-week-old breastfed male infant presents with nonbilious, nonbloody projectile emesis with progressive worsening and recent weight loss. He has been afebrile without diarrhea. He eats voraciously then vomits, only to want to eat again.
The most likely diagnosis is:
A. Gastroesophageal reflux disease (GERD).
B. Infantile hypertrophic pyloric stenosis (IHPS).
C. Malrotation with volvulus.
D. Vascular ring.
E. Formula intolerance.