A mother is alarmed because her 6-week-old boy has begun vomiting almost immediately after every feeding. In the past week, the vomiting has grown more forceful with the vomit projecting several feet from his mouth. He is always hungry again just after vomiting. At the physician’s office, the nurse holds the child and gives him a bottle of water. While he drinks, she notes an olive-size lump in his right abdomen. Which condition should the nurse suspect in this child?

Choice A reason: Gastroesophageal reflux in infants typically causes passive regurgitation, not projectile vomiting. It may lead to feeding difficulties and irritability but does not cause visible abdominal masses or persistent hunger after vomiting. Choice B reason: Pyloric stenosis is characterized by progressive, forceful (projectile) vomiting in infants, typically starting between 2–8 weeks of age. The olive-sized mass in the right upper quadrant is the hypertrophied pylorus. These infants remain hungry due to inability to retain feeds and may develop dehydration and metabolic alkalosis. This presentation is classic and warrants surgical intervention (pyloromyotomy). Choice C reason: Appendicitis is rare in infants and typically presents with fever, irritability, and abdominal distention. Vomiting may occur, but projectile vomiting and a palpable mass are not typical features. The location of the mass also does not correspond to appendiceal anatomy. Choice D reason: Peptic ulcer disease is extremely rare in infants and does not present with projectile vomiting or a palpable abdominal mass. It may cause hematemesis or melena but is not consistent with the described symptoms.