Which symptom is most characteristic of pyloric stenosis?

• A. Abdominal tenderness
• B. Weight loss
• C. Projectile vomiting
• D. Jaundice

Answer: (C)

This question is about the classic presentation of infantile pyloric stenosis. The defining feature is nonbilious projectile vomiting after feeds due to gastric outlet obstruction from thickening of the pyloric muscle. That forceful vomiting occurs because the narrowed pylorus repeatedly ejects stomach contents, and since the obstruction is before the bile enters the GI tract, the vomit is nonbilious. Dehydration and weight loss commonly follow, and you may also notice visible stomach contractions and a palpable olive-sized mass in the upper abdomen. Abdominal tenderness isn’t a hallmark finding, and jaundice would point to a liver or biliary problem rather than pyloric obstruction.