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URMC / Encyclopedia / Content

Pyloric Stenosis

What is pyloric stenosis?

Pyloric stenosis is a problem that causes forceful vomiting. It affects babies from birth to 6 months of age. Symptoms often start around 3 to 5 weeks of age. It can lead to dehydration. This condition is the second most common reason why newborns have surgery.

The pylorus is the lower part of the stomach that connects to the small intestine. In pyloric stenosis, the muscles in that part of the stomach get thick and large. This abnormal change causes the opening of the pylorus to get narrow. As a result, food stops moving from the stomach to the intestine.

What causes pyloric stenosis?

Pyloric stenosis is a birth defect. This means that your child is born with it.

This condition may run in some families. It’s a multifactorial trait. That means many things caused it. The factors are often both genetic and environmental.

Pyloric stenosis is 4 times more common in males than females.

Who is at risk for pyloric stenosis?

A child is more likely to have this condition if the child:

  • Takes certain medicines by mouth in the first 6 weeks of life. These medicines include antibiotics called azithromycin or erythromycin.

  • Bottle-feeds early

  • Has a family history of pyloric stenosis

  • Is a boy, especially firstborn

  • Is white

  • Has a mother who smokes

  • Is premature

  • Is born by cesarean section

What are the symptoms of pyloric stenosis?

The most common symptom is forceful, projectile vomiting. This kind of vomiting is different from spit-up or a wet burp. Large amounts of breastmilk or formula are vomited. It may go several feet across a room.

Your baby’s vomit may look curdled. This is because the milk stays in the stomach and doesn’t move to the small intestine. The stomach acid curdles it.

Other symptoms may include:

  • Weight loss

  • Being very hungry despite vomiting

  • Lack of energy

  • Fewer bowel movements

  • Constipation

  • Frequent stools that contain mucous

A baby with pyloric stenosis is often very hungry and wants to eat.

Some of these symptoms may be caused by other health problems. Make sure your child sees their healthcare provider for a diagnosis.

How is pyloric stenosis diagnosed?

Your child’s healthcare provider will check their health history. They will also give your child an exam. Your child may need tests to diagnose pyloric stenosis.

Blood tests

These tests check if your child is dehydrated or has mineral imbalances.

Abdominal ultrasound

This test uses sound waves to show images of your child’s internal organs and of blood flow through various vessels. And it may show if the pylorus muscles are thickened.

Abdominal X-rays

This test shows images of your child’s internal tissues, bones, and organs.

Upper gastrointestinal (GI) series

An upper GI series looks at the organs in the upper part of your child’s digestive system. These include the esophagus, stomach, and duodenum. The duodenum is the first section of the small intestine. For this test, your child will swallow barium. This is a metallic liquid that coats the inside of the organs. It helps them show up on an X-ray. Then your child’s healthcare provider will take an X-ray of these organs.

How is pyloric stenosis treated?

Treatment will depend on your child’s symptoms, age, and overall health. It will also depend on how severe the condition is.

Children with this condition must have surgery. But your child’s dehydration and mineral imbalances may need to be treated first. Water and minerals can be replaced through intravenous (IV) fluid.

Once your baby is no longer dehydrated, they will have surgery. Your child will need anesthesia. Their surgeon will make a small cut (incision) above your baby’s navel. Or they may make a few small cuts in your baby's belly. Then the surgeon will fix the pyloric muscle.

Your baby will stay in the hospital for 2 to 3 days. Most babies get better quickly after surgery. Your baby will likely be able to drink only clear liquids, such as an electrolyte drink, at first. But feedings are often started within 4 hours of the procedure.

Babies may still vomit for several days after surgery. This is because of swelling near the surgical site of the pyloric muscle. The swelling often goes away within a few days.

Most babies will be able to have normal feedings by the time they leave the hospital.

Babies who have surgery for this condition often have no long-term problems. Pyloric stenosis usually doesn’t reoccur.

What are possible complications of pyloric stenosis?

This condition can cause dehydration. When babies vomit often, they don’t get enough fluids to meet their nutritional needs. Minerals that the body needs are also lost through vomit. These include potassium and sodium. Babies who are dehydrated and don’t have enough minerals can get sick very quickly.

Pyloric stenosis can also cause weight loss. A baby who vomits most of or all their feedings won’t gain enough weight or absorb enough nutrients to stay healthy.

When should I call my child's healthcare provider?

Call your child’s healthcare provider right away if your baby has forceful, projectile vomiting.

Key points about pyloric stenosis

  • Pyloric stenosis is a problem that causes forceful vomiting in babies from birth to 6 months of age. It can lead to dehydration.

  • In pyloric stenosis, the muscles in the stomach that connect to the small intestine get thick and large. This abnormal change causes the opening of the pylorus to become narrow. As a result, food stops moving from the stomach to the intestine.

  • Babies with this condition must have surgery to fix the problem.

  • After surgery, most babies have no long-term problems from pyloric stenosis.

Next steps

Tips to help you get the most from a visit to your child’s healthcare provider:

  • Know the reason for the visit and what you want to happen.

  • Before your visit, write down questions you want answered.

  • At the visit, write down the name of a new diagnosis and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you for your child.

  • Know why a new medicine or treatment is prescribed and how it will help your child. Also know what the side effects are and when to report them to your child's provider.

  • Ask if your child’s condition can be treated in other ways.

  • Know why a test or procedure is recommended and what the results could mean.

  • Know what to expect if your child does not take the medicine or have the test or procedure.

  • If your child has a follow-up appointment, write down the date, time, and purpose for that visit.

  • Know how you can contact your child’s provider after office hours. This is important if your child becomes ill and you have questions or need advice.

Medical Reviewers:

  • Jen Lehrer MD
  • Rita Sather RN
  • Tara Novick BSN MSN