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. But it most commonly develops about 3 weeks after birth. If your baby was premature, symptoms may be delayed.

See a picture of pyloric stenosis.

What causes pyloric stenosis?

The exact cause of pyloric stenosis is not known. The condition likely develops for more than one reason. In some cases, pyloric stenosis may be passed down through families (inherited), or a baby may have the problem as part of another genetic condition. Antibiotics, such as erythromycin, given to a baby within the first 2 weeks of life may slightly increase his or her chances for developing pyloric stenosis. But it is very unlikely that taking antibiotics would by itself cause pyloric stenosis.

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). If your baby's vomit is yellow or green, it may suggest a more serious problem than pyloric stenosis.

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.

How is pyloric stenosis diagnosed?

Your baby's doctor 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 it treated?

Pyloric stenosis is corrected by surgery. Almost all babies recover completely.

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