Food passes from the stomach to the small intestine. In pyloric stenosis, food cannot pass freely because the entrance between the stomach and the small intestine narrows. The narrowing is caused by the enlargement of the pylorus (the muscle at the entrance to the stomach). Almost all cases of pyloric stenosis happen in very young babies (usually 3-12 weeks old). This problem happens about 2-4 times out of every 1,000 births. It is much more common in males than in females. The sooner pyloric stenosis is treated, the fewer problems will result and the healthier your baby will be, so if you think your child has this condition, contact your doctor immediately.

Pyloric Stenosis
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Pyloric stenosis is rarely present at birth, but develops soon afterward. Its exact cause is unknown, but it is believed to be partly inherited, as cases of pyloric stenosis tend to run in families.