What is a pathognomonic physical exam finding for pyloric stenosis?

The pathognomonic physical exam finding for pyloric stenosis is the olive-shaped mass. In cases of pyloric stenosis, which is a condition that affects infants and leads to severe vomiting due to gastric outlet obstruction, a distinct palpable epigastric mass can often be felt during the physical examination. This mass is typically described as being firm, round, and resembling an olive in shape, located just to the right of the midline in the abdomen.

This finding is considered pathognomonic because when present, it strongly indicates the diagnosis of pyloric stenosis, particularly in conjunction with the clinical history of projectile non-bilious vomiting and failure to thrive in affected infants. Recognizing this specific mass is crucial for clinicians in forming a differential diagnosis and proceeding with appropriate management and potential surgical referral.