Pyloric Stenosis

(Infantile Hypertrophic Pyloric Stenosis)


Pyloric stenosis is narrowing of the opening from the stomach to the duodenum, the first part of the small intestine. Narrowing prevents food from passing freely between the 2 structures. Pyloric stenosis affects your baby's ability to get adequate nutrition and hydration. The sooner your baby is treated, the better the outcomes.
Pyloric Stenosis
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The narrowing is caused by an enlarged muscle surrounding the pylorus. The exact cause of the enlarged muscle is unknown. It is believed to be the result of several factors, which may include:
  • Genetics
  • Structural defects that occur during fetal development
  • Bacterial infection, such as Helicobacter pylori

Risk Factors

Pyloric stenosis is more common in male babies, especially if they are first born. Other factors that may increase your baby's chance of pyloric stenosis include:
  • Prematurity
  • Family history of pyloric stenosis
  • Bottle feeding
  • Ethnicity—more common in Caucasian than in Hispanic, Asian, or African-American babies


Pyloric stenosis is rarely present at birth. Symptoms generally appear when babies are 3-12 weeks old. The most common symptom is forceful, projectile vomiting. This is because of the build up of formula or milk in the stomach that cannot pass into the small intestine.Pyloric stenosis may also cause:
  • Your baby to act hungry most of the time
  • Weight loss
  • Signs of dehydration, such as less urination, dry mouth, and crying without tears
  • Fatigue
  • Fewer bowel movements
  • Blood-tinged vomit —occurs when repeated vomiting irritates the stomach, causing mild stomach bleeding

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