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What is pyloric stenosis?

Pyloric stenosis is a condition that prevents your baby’s stomach from emptying properly and usually results in your baby vomiting soon after a feed, before the food can pass through the stomach. Because most of the goodness from a feed is absorbed into the body after the food has passed through the stomach, your baby will become dehydrated and lose salts. This can be life-threatening and needs to be treated promptly.

Pyloric stenosis is caused by the valve muscle thickening. It is not known why this happens in some babies.

What are the benefits of surgery?

Your baby should be able to feed normally after about 2 days.

Illustration showing a thickened pyloric muscle.
A thickened pyloric muscle.

Are there any alternatives to surgery?

If your baby is dehydrated, your surgeon may recommend giving them fluid and salts through a drip in a vein but this will not treat pyloric stenosis.

What does the operation involve?

The operation is performed under a general anaesthetic and usually takes about an hour.

Your surgeon may place a tube (nasogastric or NG tube) into your baby’s nostrils and into their stomach to remove any fluid. Your surgeon will make a cut on the upper abdomen or just above the belly button so they can get to the pyloric muscle. They will split the pyloric muscle and spread it apart to open the passage into the intestines. The muscle will heal.

What complications can happen?

Some complications can be serious and can even cause death.

General complications of any operation

  • bleeding
  • infection of the surgical site (wound)
  • allergic reaction to the equipment, materials or medication

Specific complications of this operation

  • vomiting after the operation
  • making a hole in the mucosa (the lining of the stomach)
  • wound breakdown
  • developing a hernia in the wound

Consequences of this procedure

  • pain
  • unsightly scarring of the skin

How soon will my baby recover?

You will usually be able to take your baby home after 2 to 4 days.

Your baby should gradually return to normal feeding. If your baby continues to vomit, has a high temperature or shows any signs of dehydration such as not wetting nappies as often as usual and having a sunken fontanel (soft area at the top of their head), let your surgeon or GP know straight away.

Most babies make a good recovery and develop normally. However, pyloric stenosis can come back.


Pyloric stenosis causes your baby to vomit soon after a feed which prevents them from getting goodness from their food. If left untreated the condition can cause dehydration and loss of salts. This can be life-threatening and needs to be treated promptly.


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Last reviewed: September 2023

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