Reviewed by Rishi Desai, MD, MPH
Hypertrophic pyloric stenosis
Pyloric stenosis is narrowing of the opening from the stomach to the duodenum, due to hypertrophy of the muscle surrounding this opening, which spasms when the stomach empties. This condition causes severe projectile non-bilious vomiting. It most often occurs in the first few months of life. The thickened pylorus is felt classically as an olive-shaped mass in the middle upper part or right upper quadrant of the infant's abdomen. This condition typically develops in male babies in the first 2 to 6 weeks of life.