Topic Overview

What is pyloric stenosis?
Pyloric stenosis is a condition in which a baby's pylorus gradually swells and thickens, which interferes with food entering the intestine. The pylorus is the connection between the stomach and the first part of the small intestine (duodenum).

Pyloric stenosis can occur any time between birth and 5 months of age. However, it most commonly develops about 3 weeks after birth. The onset of symptoms may be delayed if your baby was premature.

See an illustration of pyloric stenosis.

What causes pyloric stenosis?
While the exact cause is unknown, the development of pyloric stenosis may be related to several factors, including genetic conditions, a family history of pyloric stenosis, and the use of antibiotics such as erythromycin within the first 2 weeks of life. However, the vast majority of pyloric stenosis cases are not related to taking antibiotics.

In the past, pyloric stenosis was considered a birth defect. Now there is some evidence that it develops after birth.

What are the symptoms?
Vomiting all or most of feedings is the main symptom of pyloric stenosis. Vomiting usually starts gradually, but as the pylorus becomes tighter over time, your baby's vomiting becomes more forceful (projectile vomiting).

A baby with pyloric stenosis acts irritable and hungry, even immediately after being fed. You also may notice that your baby has fewer wet diapers and fewer, harder stools. If the vomiting continues, your baby can become dehydrated.

A baby with pyloric stenosis:
Vomits formula or breast milk shortly after a feeding.
Has a full (distended) upper abdomen after feedings.
Acts irritable and hungry.
Has fewer and harder stools (constipation) than normal.
Passes smaller amounts of urine than normal.
As the vomiting continues, your baby will:

Lose weight.
Develop symptoms of not getting enough fluids (dehydration).
Be sleepier than normal and very fussy when awake.

How is pyloric stenosis diagnosed?
Your baby's health professional can diagnose pyloric stenosis by a physical examination and by reviewing your baby's symptoms. An upper gastrointestinal (UGI) series or an abdominal ultrasound can be used to diagnose the condition. Blood tests also may be done to see whether your baby is dehydrated.

How is pyloric stenosis treated?
Pyloric stenosis is corrected by surgery. Most likely, your baby will recover completely.