Pyloric stenosis (infantile hypertrophic pyloric stenosis) is a condition that causes severe vomiting in the first few months of life. Pyloric stenosis can occur any time between birth and 5 months of age. Pyloric stenosis is a narrowing of the pylorus, the lower part of the stomach through which food and other stomach contents pass to enter the small intestine. When an infant has pyloric stenosis, the muscles in the pylorus have become enlarged to the point where food is prevented from emptying out of the stomach. It affects about three out of 1,000 babies in the United States. Pyloric stenosis is about four times more likely to occur in firstborn male infants. It has also been shown to run in families - if a parent had pyloric stenosis, then an infant has up to a 20% risk of developing the condition.

Pyloric stenosis occurs more commonly in Caucasian infants than in babies of other ethnic backgrounds, and affected infants are more likely to have blood type B or O. The causes of pyloric stenosis are unknown, but genetic factors may play a role. 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. Most infants who develop pyloric stenosis are usually between 2 weeks and 2 months of age - symptoms usually appear during or after the third week of life. The first symptom of pyloric stenosis is usually vomiting. Some infants present with poor feeding and weight loss, but others demonstrate normal weight gain. Dehydrated infants are lethargic and less active than usual.

Pyloric stenosis is typically managed with surgery. Pyloric stenosis is typically treated with a surgical procedure known as pyloromyotomy. Before surgery, your baby may be given intravenous (IV) fluids to treat dehydration and restore electrolytes. Your baby may receive IV fluids for a few hours after surgery as well, until he or she can tolerate normal feedings. Pyloric stenosis must be repaired with an operation. However, physicians may need to treat your baby's dehydration and mineral imbalances first. Water and minerals can be replaced through intravenous (IV) fluid. Your baby's tolerance for specific medications, procedures, or therapies. Your opinion and preference. Complications from surgery (which may include infection at the incision site) are rare.