The parents of a 6-week-old infant boy come to the clinic for evaluation because the infant has been vomiting, and it is becoming more forceful and increasing over the last week. A diagnosis of hypertrophic pyloric stenosis is suspected. When performing the physical exam, what would the nurse most likely find?

Choice A reason: Tenderness over McBurney’s point suggests appendicitis, not hypertrophic pyloric stenosis, which involves pyloric muscle hypertrophy causing gastric outlet obstruction. This condition presents with vomiting and a palpable mass, not right lower quadrant tenderness, making this an incorrect finding for the diagnosis. Choice B reason: The FACES scale assesses pain, but hypertrophic pyloric stenosis typically causes discomfort from vomiting, not localized epigastric/umbilical pain rated at 6. Infants may show fussiness, not specific pain scores, making this an incorrect and non-specific finding for the suspected condition. Choice C reason: A sausage-shaped mass is associated with intussusception, not hypertrophic pyloric stenosis. The latter causes a firm, olive-shaped mass in the upper right quadrant due to pyloric hypertrophy, making this finding incorrect for the suspected diagnosis in a 6-week-old with forceful vomiting. Choice D reason: A firm, olive-shaped mass in the upper right quadrant is a hallmark of hypertrophic pyloric stenosis, caused by thickened pyloric muscle obstructing gastric outflow. Palpable during exam, it correlates with the forceful vomiting described, making this the most likely and correct physical finding.