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Hypertrophic Pyloric Stenosis


William J. Cochran

, MD, Geisinger Clinic

Last full review/revision Aug 2021| Content last modified Aug 2021
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Hypertrophic pyloric stenosis is blockage of the passage out of the stomach due to thickening (hypertrophy) of the muscle at the junction between the stomach and the intestines.

  • The thickened muscle creates a partial blockage (obstruction) that interferes with the passage of stomach contents into the small intestine.

  • Infants feed well but vomit forcefully (projectile vomiting) shortly after eating and can become dehydrated and undernourished.

  • The diagnosis is based on results of an abdominal ultrasound.

  • Typically the problem is corrected by fluids given by vein (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 becomes thickened and sometimes closes off (called stenosis), blocking material from leaving the stomach. This blockage usually occurs in the first month or two of life.

Risk factors for pyloric stenosis

Risk factors include

  • Male sex (especially first-born boys)

  • Parents or siblings who had pyloric stenosis

  • Use of certain antibiotics (for example, erythromycin) during the first few weeks of life

  • Smoking during pregnancy

  • Bottle-feeding with formula

Rarely, some older children have pyloric obstruction caused by swelling due to peptic ulcers Peptic Ulcer in Children A peptic ulcer is a round or oval sore in the lining of the stomach or duodenum where it has been eroded by stomach acid and digestive enzymes. Sores form in the lining of the stomach or duodenum... read more or an uncommon disorder similar to a food allergy (such as eosinophilic gastroenteritis).

Symptoms of Hypertrophic Pyloric Stenosis

Infants with pyloric stenosis are hungry and feed well but vomit forcefully (projectile vomiting) shortly after eating. Some infants vomit so much that they become dehydrated and undernourished. Until dehydration is severe, or infants become significantly undernourished, they otherwise appear well. After several days to weeks, infants become progressively dehydrated and lose weight. Some infants have a yellowish discoloration of the skin and the whites of the eyes (jaundice) at this point.

Diagnosis of Hypertrophic Pyloric Stenosis

Treatment of Hypertrophic Pyloric Stenosis

  • Intravenous fluids

  • Surgical procedure

Doctors give infants fluids by vein (intravenously) to treat the dehydration and correct any electrolyte imbalance.

Then, a surgeon cuts the thickened muscle to relieve the blockage, allowing formula or breast milk to enter the small intestine more readily. This surgery (called pyloromyotomy) is relatively minor, and most infants can eat within a day of the procedure.

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Preventive Health Care Visits in Infants
Frequent doctor visits are recommended for all infants younger than 1 year of age. These visits, also called well-child visits, make it possible to check development, look for health problems, provide age-appropriate vaccinations, and educate parents. Which of the following is a condition that might affect some infants born very prematurely, with less than 32 weeks of development in the uterus?
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