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Quick Facts

Pyloric Stenosis


The Manual's Editorial Staff

Last full review/revision Dec 2019| Content last modified Dec 2019
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What is pyloric stenosis?

The pylorus is the muscle that closes the stomach off from the intestine and keeps food in the stomach. Stenosis means closed off. Pyloric stenosis is thickening of the pylorus muscle that partly or fully blocks food from passing out of the baby’s stomach into the intestine.

  • Babies with pyloric stenosis eat well but throw up forcefully soon after eating

  • Pyloric stenosis usually happens when a baby is 1 or 2 months old

  • Babies can become dehydrated (have too little fluid in their bodies) and not get enough nutrients

  • To tell if your baby has pyloric stenosis, doctors do an ultrasound

  • Doctors do surgery to cut and loosen the thickened muscle

There's a higher risk of pyloric stenosis in:

  • Male, first-born babies

  • Babies whose mothers smoked while pregnant

  • Babies given specific antibiotics

  • Babies with family members who had it

What are symptoms of pyloric stenosis?

Babies with pyloric stenosis are hungry, eat well, and then forcefully throw up (projectile vomiting) after eating. Unlike babies who throw up because they're sick, babies with pyloric stenosis want to eat and drink right away after they throw up.

Sometimes, babies throw up so much they:

  • Lose weight

Usually, babies are still able to absorb liquids enough that they don't become dehydrated. However, they may lose a lot of weight and look very thin before doctors figure out what's wrong.

How can doctors tell if my child has pyloric stenosis?

The doctor may be able to feel a small lump in your baby’s belly. Doctors do an ultrasound to be sure your baby has pyloric stenosis.

How do doctors treat pyloric stenosis?

Doctors will:

  • Give your baby fluids into the vein

  • Do surgery to cut the muscle that's blocking the stomach so formula or breast milk can move through

Your baby can usually return to eating normally the day after surgery.

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