Correct Answer: B. During palpation, over the epigastrium
In congenital hypertrophic pyloric stenosis (CHPS), the pyloric muscle undergoes progressive hypertrophy and hyperplasia, resulting in gastric outlet obstruction. The hallmark clinical finding is the "pyloric olive" — a firm, mobile, olive-shaped mass representing the hypertrophied pylorus. This mass is best detected by careful, deep palpation over the epigastrium, specifically in the right epigastric region just below the liver edge and to the right of the midline. This is the anatomically correct location of the pylorus, and skilled palpation in this region — ideally with the infant relaxed and the abdominal muscles soft — is the gold-standard clinical method for identifying the mass.
The pyloric olive is palpated in the epigastrium because the pylorus lies in the right upper quadrant, beneath the liver. When the examiner applies gentle, deep palpation in this region (often between feeds, when the stomach is not overly distended), the firm, mobile, sausage-shaped mass can be appreciated. This clinical sign, when present, is pathognomonic of CHPS and historically has been sufficient to proceed to surgical intervention (Ramstedt's pyloromyotomy) without further imaging. Ultrasound (pyloric muscle thickness >3 mm, channel length >14 mm) is used when the olive cannot be confidently palpated.
Why other options are wrong
- A. During feeding — While feeding may relax the infant and facilitate examination, the mass itself is a structural, permanently hypertrophied muscle — it is present at all times and is not "created" by feeding. The defining diagnostic act is palpation in the epigastrium, not the timing of feeding. Feeding is an adjunct to examination, not the defining criterion for mass detection.
- C. Soon after birth — CHPS does not manifest at birth. The pyloric hypertrophy develops progressively after delivery, with clinical presentation typically between 2–8 weeks of age (peak: 3–5 weeks). The pyloric muscle is essentially normal at birth, so no mass is detectable in the neonatal period.
- D. During palpation, over the left hypochondrium — The pylorus is anatomically located in the right upper quadrant/epigastrium, not the left hypochondrium. The left hypochondrium contains the stomach fundus and spleen. Palpating the left hypochondrium would entirely miss the pyloric olive.