Pyloric stenosis is a condition that causes severe vomiting in the first few months of life. There is narrowing (stenosis

Stenosis

A stenosis is an abnormal narrowing in a blood vessel or other tubular organ or structure.It is also sometimes called a stricture ....

) of the opening from the stomach to the intestines, due to enlargement (hypertrophy

Hypertrophy

Hypertrophy is the increase in the volume of an organ or tissue due to the enlargement of its component cells. It should be distinguished from hyperplasia, in which the cells remain approximately the same size but increase in number...

) of the muscle surrounding this opening (the pylorus

Pylorus

The pylorus is the region of the stomach that connects to the duodenum . It is divided into two parts:* the pyloric antrum, which connects to the body of the stomach.* the pyloric canal, which connects to the duodenum....

, meaning "gate"), which spasms when the stomach empties. It is uncertain whether there is a real congenital narrowing or whether there is a functional hypertrophy of the muscle which develops in the first few weeks of life.

Pyloric stenosis also occurs in adults where the cause is usually a narrowed pylorus due to scarring from chronic peptic ulceration.