The pylorus is a muscular valve located between the stomach and the small intestine. It’s the exit point of the stomach and the gateway to the duodenum of the small intestine. It helps the stomach hold food, liquids, acids, and other matter until they are ready to move on to the small intestine and be further digested and then absorbed.

For reasons that aren’t entirely understood, the pylorus can sometimes thicken and cause luminal narrowing. This is called pyloric stenosis. This thickening can become so large that it blocks the flow of food from the stomach to the small intestine.

Pyloric stenosis is most likely to affect young babies. It’s found in 2 to 3 out of every 1,000 babies. It most often appears in the first 2 to 8 weeks of life, although it can occur in babies up to 6 months of age. The condition interferes with feedings, so it can affect growth and hydration. That’s why early diagnosis and treatment are important.

Gastrointestinal issues are the main symptoms of pyloric stenosis. Most babies with this condition appear fine at birth. Symptoms typically begin and become progressively worse during the first few months of life. Symptoms may include:

  • Forceful vomiting after a feeding that differs from normal spit up. As the pylorus valve thickens over time, the vomiting becomes more frequent and explosive. It may be projectile vomit, meaning that it travels several feet from the baby’s mouth.
  • Dehydration. The thickened pylorus not only blocks the passage of solid food, but also that of liquids. A baby who is dehydrated may cry without tears, have fewer wet diapers, and become listless.
  • Hunger. A baby with pyloric stenosis may want to constantly feed or be fussy because of hunger.
  • Constipation. Without adequate food and liquid reaching the intestines, the condition can cause constipation.
  • Stomach cramps. Some parents notice “wave-like” contractions that move across their baby’s abdomen after a feeding. This occurs as the stomach muscles strain to try to move the food through the narrowed pylorus lumen and pyloric sphincter.

Unlike with a stomach bug, babies with pyloric stenosis generally don’t seem as sick in between feedings.

Pyloric stenosis is not common. Certain babies are more prone to it than others. Things that put a baby at risk are:

  • Sex. Male babies, especially first-born males, are more at risk than females.
  • Family history. Roughly 15 percent of babies with the condition have a family history of the disorder. A baby born to a woman who had the condition as an infant is three times more likely to have pyloric stenosis.
  • Race. The condition is most likely to affect Caucasians of Northern European descent. It’s less common in African-Americans and Asians.
  • Smoking tobacco. Smoking during pregnancy almost doubles the chance of giving birth to a baby with pyloric stenosis.
  • Bottle feeding. In a 2012 study, infants who were bottle fed had a higher risk for pyloric stenosis, being at least four times as likely to develop the condition than those who weren’t bottle fed. Experts in this study could not determine exactly if the higher risk was because of the feeding mechanism itself, or if breast milk versus formula during the feedings also contributed to the increased risk.
  • Antibiotic use. The use of certain antibiotics early in life can increase a baby’s risk of pyloric stenosis. One study suggests that infants given antibiotics in the first two weeks of life had the greatest risk.

When pyloric stenosis is suspected, your baby’s doctor will take a thorough history and perform a physical exam of your child’s abdomen. If the doctor can feel a thickened pylorus muscle, which may feel like an olive, no further tests may be needed.

If the doctor cannot feel the pylorus, they may order an abdominal ultrasound to examine the abdominal tissue in order to see the pylorus. The doctor may also want X-ray imaging taken after your baby drinks a contrasting liquid to help improve clarity of the images. This oral contrasted X-ray can show how the liquid travels from the stomach to the small intestine and show if there is a blockage.

Pyloric stenosis needs to be treated. It won’t improve on its own.

Your child will need surgery called pyloromyotomy. During this surgery, which can be done laparoscopically, a surgeon will cut through part of the thickened muscle in order to restore a pathway for food and liquid to pass through.

If your baby is dehydrated because of frequent and forceful vomiting, they may need to be hospitalized and given fluid through an intravenous needle inserted into a vein (IV fluid) before surgery. Once properly hydrated, your baby will have to refrain from feedings for several hours to reduce the risk of vomiting while under anesthesia.

The surgery itself usually takes less than hour, but your baby will likely stay in the hospital for 24 to 36 hours. Most babies do fine after surgery. Feedings are gradually resumed, and pain is generally managed with over-the-counter pain relievers. It’s normal for babies to vomit a little in the first few hours and days after the surgery as the stomach settles down.

This condition can affect your child’s nutritional and hydration needs, so it’s important to seek medical help whenever your baby has feeding difficulties. The condition can be successfully corrected with surgery, and most infants will go on to grow and thrive just like other babies.


Can this condition develop in adults, or is it only seen in babies?

Anonymous patient


Yes, according to the literature, pyloric stenosis very rarely occurs in adults. It may develop due to an attributable cause, such as an adjacent ulcer, cancer, or adhesions after an abdominal surgery. It can also be idiopathic, where there is no underlying cause found. The idiopathic form is much less common and tends to occur more in middle-aged men. When the symptoms become severe, and gastrointestinal form and function cannot properly occur, surgery is required. Depending on the degree of pyloric stenosis present, corrective surgery in an adult may be more extensive than that performed in a baby.

Stacy Sampson, DOAnswers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.
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