Snapshot An anxious young married couple presents to the ED with their 3-week-old firstborn. They report that the child was feeding well for the first two weeks after delivery but over the past few days he has taken less breast milk. Two days ago he experienced projectile vomiting after every meal. The mom and dad are concerned that he might have the stomach flu. Overview Introduction A congenital stenosis of the pyloric sphincter not present at birth but develops in 1st month deficiency in NO syntase results in inability to relax sphincter muscles May be aquired in adult cases with stricture following chronic ulcer disease Associated with the use of macrolides in newborns Presentation Symptoms projectile vomitting vomitus does not contain bile Physical exam palpable "olive" in epigastrium hyperperstalsis Evaluation Ultrasound is diagnostic Treatment Medical management IV fluid resuscitation electrolyte management/optimization pre-operatively (specifically Cl > 100) Surgical pyloromyotomy, open or laparoscopic