Introduction: Infantile hypertrophic pyloric stenosis (IHPS) is a common cause of infant vomiting. Emergency department (ED) diagnosis is usually made by pyloric ultrasound and treated by pyloromyotomy.

Case Report: An eight-week-old boy with a history of IHPS about six weeks status post pyloromyotomy presented to the ED with vomiting and failure to thrive, and a critically narrowed pylorus was identified by ultrasound. An upper gastrointestinal series confirmed recurrent pyloric stenosis, necessitating another pyloromyotomy.

Conclusion: Prolonged vomiting after pyloromyotomy should be concerning for recurrent IHPS. Upper gastrointestinal series should augment ultrasound to diagnose recurrent IHPS and determine whether a second pyloromyotomy is warranted.