Sacramento State Medic Module 6 Practice Test

Pyloric stenosis most often presents as a gastric outlet obstruction in a young infant, causing projectile, nonbilious vomiting after feeds. Because the obstruction is at the pylorus and lies before the bile ducts join the intestine, the vomit does not contain bile. This pattern—forceful vomiting shortly after feeding—is the hallmark. You may also see dehydration, weight loss, and sometimes a palpable olive-shaped mass in the abdomen with visible peristaltic waves.

The other findings don’t fit as well: bilious emesis would indicate an obstruction distal to where bile enters the duodenum, not at the pylorus; bright-red blood in stools suggests GI bleeding rather than a gastric outlet obstruction; and respiratory distress is not a typical presenting sign of pyloric stenosis.