Review Question - QID 108429

This presentation is most consistent with a diagnosis of pyloric stenosis, which is caused by hypertrophy of the longitudinal and circular smooth muscle segments surrounding the pylorus resulting in development of non-bilious projectile vomiting between 2-6 weeks of age.

Vomiting in the neonatal period usually indicates a congenital gastrointestinal disorder. These disorders can be distinguished based on whether the vomit contains bile (suggests obstruction distal to the common bile duct), whether the disorder is present at birth (GI discontinuities will present within the first 48 hours), and whether the site of obstruction can be visualized (usually determined by ultrasound or radiography). In this case, the non-bilious emesis indicates a site of obstruction proximal to the bile duct; the presentation around 1 month suggests a stricture rather than a discontinuity; the palpable “olive” epigastric mass is the classic physical exam finding in pyloric stenosis. Risk factors for this disorder include being the first born male and exposure to macrolides, both of which are seen in this case. The mechanism of pyloric stenosis is hypertrophy of the pyloric musculature causing failure of pyloric relaxation.

Incorrect Answers:
Answer 1: A defect in luminal recanalization is the mechanism behind duodenal atresia. This disorder presents with bilious vomiting in the first few days of life and is associated with Down syndrome. The classic finding in duodenal atresia is the double bubble sign from dilation of the stomach and the proximal duodenum.

Answer 3: Intestinal vascular accidents would cause “apple peel” atresia of the jejunum or the ileum. The mechanism involves disruption of mesenteric blood flow followed by ischemic necrosis of the affected part of bowel. It also presents with bilious vomiting with an apple peel sign on radiography.

Answer 4: Neural crest cell migration is responsible for supplying the Auerbach and Meissner plexuses of the distal colon. Failure of their migration can lead to Hirschsprung disease, which presents with failure to pass meconium at birth. The classic finding is dilated loops of bowel with no stool in the rectal vault.

Answer 5: Abnormal fusion of the ventral pancreatic bud can lead to development of an annular pancreas. This structure encircles the duodenum and can lead to non-bilious vomiting. This disease is not associated with a palpable epigastric mass.

Bullet Summary:
Pyloric stenosis often presents with non-bilious vomiting in first born males around 1 month of age. It is caused by pyloric smooth muscle hypertrophy and can be felt as an olive-sized mass in the epigastrium.