The pylorus is the opening between the stomach and the small intestine. Food passes out of the stomach through this opening. It acts like a valve controlling the passage of food from the stomach to the first part of the small intestine (duodenum). Pyloric stenosis is narrowing of this opening. This can block the passage of food out of the stomach.
The problem is often first seen in young babies. They are generally well at birth but start showing symptoms by the time they are 3 to 6 weeks of age. The baby may start vomiting after feeding. The vomiting may be very forceful (projectile vomiting). This may result in dehydration and weight loss.
The doctor takes a detailed medical history, including birth history, from the caregivers, performs a physical exam of the baby and may request certain tests, such as bloodwork, and ultrasound may be done. An ultrasound uses painless sound waves to create an image of the child's stomach and intestine. An X-ray of the abdomen may be needed in some cases.
If pyloric stenosis is found, it's usually treated with surgery. This makes the opening wider and corrects the problem.