Hypertrophic pyloric stenosis is blockage of the passage out of the stomach due to overdevelopment (hypertrophy) of the muscle at the junction between the stomach and the intestines. It occurs in early infancy and causes vomiting after feeding, which may lead to severe dehydration and poor growth.

• For uncertain reasons, the passage that leads out of the stomach is blocked, preventing material from leaving the stomach.
• Infants feed well but vomit forcefully (projectile vomiting) shortly after eating.
• The diagnosis is based on results of an abdominal ultrasound.
• Typically the problem is corrected by fluids given intravenously and by minor surgery.

The pylorus is the muscular sphincter located where the stomach joins the first part of the small intestine (duodenum). Normally, the pylorus contracts to keep food in the stomach for digestion and relaxes to let the food out into the intestine. For reasons that doctors do not fully understand, the pylorus sometimes closes off, blocking material from leaving the stomach. This blockage usually occurs in the first month or two of life and is much more common among boys, especially first-born boys. Rarely, some older children have pyloric stenosis caused by peptic ulcers or an uncommon disorder similar to a food allergy (such as eosinophilic gastroenteritis).

Symptoms and Diagnosis

An infant with pyloric stenosis is hungry and feeds well but vomits forcefully (projectile vomiting) shortly after eating. Until dehydration is severe, or infants become significantly malnourished, they otherwise appear well, unlike those with vomiting caused by other disorders. After several days, the infant begins to become dehydrated and loses weight. A few infants have a yellowish discoloration of the skin and the whites of the eyes (jaundice).

The doctor may be able to feel a small lump (about the size of an olive) in the infant's abdomen (the enlarged pylorus). Most commonly, the doctor performs an abdominal ultrasound to confirm the diagnosis.

Treatment

Doctors give the infant intravenous fluids to treat the dehydration. Then, a surgeon cuts the thickened muscle to allow formula or breast milk to enter the small intestine more readily. This is relatively minor surgery, and most infants can eat within a day of the procedure.

Last full review/revision December 2007 by William J. Cochran, MD