What is "pyloric stenosis"

n. (context pathology English) A narrowing of the pylorus, which prevents the normal passage of food from the stomach to the small intestine.

n. narrowing of the pyloric sphincter that blocks the passage of food from the stomach into the duodenum

Pyloric stenosis or pylorostenosis is narrowing ( stenosis) of the opening from the stomach to the first part of the small intestine known as the duodenum, due to enlargement ( hypertrophy) of the muscle surrounding this opening (the pylorus, meaning "gate"), 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, when it may thus be more specifically labeled as infantile hypertrophic pyloric stenosis. 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. In pyloric stenosis, it is uncertain whether there is a true congenital anatomic narrowing or whether there is merely a functional hypertrophy of the pyloric sphincter muscle. This condition typically develops in male babies in the first 2 to 6 weeks of life.

Pyloric stenosis also occurs in adults, where the cause is usually a narrowed pylorus due to scarring from chronic peptic ulceration. This is a different condition from the infantile form.