What is pyloric stenosis?

Pyloric stenosis is an abnormal thickening and/or narrowing of the pylorus muscle. Normally, food and other stomach contents pass into the small intestine through the pylorus, which is the exit of the stomach. The thickened pyloric muscle causes a narrowing of the pyloric channel. As a result, liquid and/or food cannot pass out of the stomach into the small intestine.

How common is pyloric stenosis?

Pyloric stenosis affects 3 out of every 1,000 babies born. It is more likely to affect full-term, first-born male infants, and less likely to affect female infants. Pyloric stenosis is more common in Caucasian infants, especially those of European descent.

About 15% of infants born with pyloric stenosis have a family history of the condition. An infant is three times more likely to develop pyloric stenosis if the mother had the disease as an infant, as compared to the father

When does pyloric stenosis occur?

The symptoms of pyloric stenosis usually occur starting around the third week of life, but it could be up to age 5 months.

What are the symptoms of pyloric stenosis?

Because infants with pyloric stenosis are unable to tolerate their feedings, they may have the following symptoms:

  • Frequent episodes of projectile vomiting (forceful vomiting) within 30 to 60 minutes after feedings (could be after every feeding, or occasionally).
  • Small stools.
  • Dehydration.
  • Weight loss.
  • Irritability.
  • Hunger after feedings.
  • Abdominal pain.
  • Wave-like motion of the abdomen shortly after feeding and just before vomiting occurs.

Last reviewed by a Cleveland Clinic medical professional on 12/22/2016.


  • Aspelund G, Langer JC. Current management of hypertrophic pyloric stenosis. Sem Ped Surg 2007;16:27-33.
  • Merck Manual. Hypertrophic Pyloric stenosis. Accessed 1/31/2017.

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