Recurrent projectile nonbilious vomiting, typically in a 3- to-6-week-old infant (usually male), but may occur on older infants.
Features may include a history of feeding intolerance with multiple formula changes.
Failure to thrive/weight loss may progress to increasing volume depletion. An olive-shaped mass may be palpable in the right upper abdomen.
Ultrasound shows pyloric channel length >17 mm and pyloric muscle thickness >4 mm.
Treatment is with intravenous fluid and electrolyte replacement, followed by pyloromyotomy (open or laparascopic).
Complications of treatment surgery include wound infection, gastric or duodenal mucosal perforation, or incomplete myotomy.
In infantile hypertrophic pyloric stenosis (HPS), hypertrophy of the pyloric sphincter results in narrowing of the pyloric canal. It is the most common cause of gastric outlet obstruction in the 2- to 12-week-old age group.  Pyloric stenosis leads to progressive and projectile vomiting.
Assistant Professor of Pediatric Surgery
Ann and Robert H. Lurie Children’s Hospital of Chicago
CJH declares that she has no competing interests.
Dr Catherine Hunter would like to gratefully acknowledge Dr Jeffrey S. Upperman, Dr Yigit S. Guner, and Dr Arturo Aranda, previous contributors to this monograph. JSU, YSG, and AA declare that they have no competing interests.
Assistant Professor of Surgery
Department of Surgery
Division of Pediatric Surgery
NYU Medical Center
EN declares that he has no competing interests.
Emeritus Nuffield Professor of Paediatric Surgery
Institute of Child Health
LS declares that he has no competing interests.
Consultant in Paediatric and Neonatal Surgery
Royal Alexandra Children's Hospital
RH declares that she has no competing interests.
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