Pyloric Stenosis

Pyloric Stenosis

Pyloric stenosis is a condition where milk cannot get out of the stomach because the 'exit' is extremely narrow.

Images showing how Pylorus stenosis affects the stomach

Key points to remember about pyloric stenosis

  • the pylorus is the passage that connects the lower part of the stomach to the rest of the bowel
  • all food leaving the stomach has to go through the pylorus
  • when a baby has pyloric stenosis, the muscles in the pylorus have become too thick to allow milk to pass through it
  • the first symptom is usually forceful, or projectile vomiting soon after feeds
  • if your baby has pyloric stenosis, it can be fixed by surgery
  • your baby's dehydration will need to be treated using intravenous fluids before they can have surgery

What is pyloric stenosis?

Pyloric stenosis (also called infantile hypertrophic pyloric stenosis or gastric outlet obstruction) is a narrowing of the pylorus – the passage leading from the stomach to the small intestine. When a baby has pyloric stenosis, the muscles in the pylorus have become too thick to allow milk to pass through it. This usually happens in the first 6 weeks after birth.

What causes pyloric stenosis?

Experts do not know exactly what causes the thickening and enlargement of the muscles in the pylorus.

What puts my child at risk of getting pyloric stenosis?

Pyloric stenosis affects far more boys than girls and tends to run in families.

What are the signs and symptoms of pyloric stenosis?


  • persistent vomiting of feeds, usually within 30 minutes of a feed
  • vomiting may be so forceful that the vomit can be projected 1 metre out of the mouth (projectile vomiting)
  • the vomit is usually yellow, the colour of curdled milk
  • occasionally, the vomit may have small brown specks of old blood in it
  • despite the vomiting, babies are usually keen to feed (because they are starving)

Being miserable

  • because they remain hungry
  • from stomach cramps which may be painful


  • dry mouth and tongue
  • fewer wet nappies or not passing as much wee as usual
  • unusual sleepiness, difficult to rouse (lethargic)
  • sunken eyes
  • the soft spot on the top of the head (fontanelle) is more sunken than normal


  • sometimes you can see ripples or waves move across the stomach (abdomen) after a feed – these are muscle contractions (peristalsis) as the stomach tries to empty into the small intestine

Failure to gain weight or weight loss and fewer, smaller stools are also symptoms to watch out for.

When should I seek help for my child with pyloric stenosis?

Pyloric stenosis needs prompt treatment.

If you think your child has pyloric stenosis symptoms, you should go to your doctor or after-hours medical centre straight away. Do not delay as young babies who are not able to feed normally can become more ill very quickly.

How is pyloric stenosis diagnosed?

Your doctor needs accurate information about your baby's symptoms, including:

  • patterns of feeding and vomiting
  • the colour of the vomit
  • any weight loss or failure to gain weight

Your doctor will also try to feel a mass or lump (which is the thickened pylorus) in your baby's stomach.

If the doctor can feel a lump, then your baby won't need an ultrasound scan or x-ray.

Investigations or tests, if necessary, may include the following:

A test feed

A doctor may give your child a small feed. This is to help your baby relax enough to allow the doctor to feel the lump in your child's tummy. If the doctor cannot feel a lump, but they still suspect your child has pyloric stenosis, your baby may need one of the tests or scans below.

An ultrasound of your baby's abdomen

An ultrasound may show the thickened pyloric muscle.

A barium meal

This is a special x-ray. Only a very small number of babies need it. A doctor or nurse will give your baby a small amount of chalky liquid (barium). Your baby will then have an x-ray of their abdomen, which will show the passage of the barium through the gut. Any blockage or narrowing will show on the x-ray.

Blood tests

In most cases, your child will need a blood test. If your child's vomiting has been severe and prolonged, dehydration and loss of electrolytes in the blood may have occurred.

What is the treatment for my child with pyloric stenosis?

The treatment for pyloric stenosis is an operation called a pyloromyotomy.

A team that usually includes a paediatric surgeon and a paediatric anaesthetist performs this using one of 3 techniques:

  1. 'key hole' surgery – the surgeon makes 3 three tiny cuts. This is the usual technique.
  2. open operation – a small cut is made directly over where the pylorus is
  3. umbilical approach – the cut is in the tummy button (umbilicus) itself

In all the operations, the surgeon then cuts through and spreads the thickened and enlarged muscles of the pylorus, which relieves the blockage (obstruction).

What happens to my child before the operation for pyloric stenosis?


Your child must not eat or drink anything before the operation.


Your child will need to have an intravenous drip put into their hand or arm before the operation. Children with pyloric stenosis usually have abnormal levels of several important substances in their blood. These levels must return to normal before any operation. This usually takes several hours and frequently can even take a day or two.

Talk with the surgical team

Your child's surgical team will discuss your child's operation with you, and any other treatment needed. You will have the opportunity to ask questions or make comments at this time.

What happens to my child after the operation for pyloric stenosis?

A nurse will take your baby back to the ward to recover. A doctor or nurse will give your child medicines through an intravenous drip to help relieve any pain.

For the first few hours, your baby will continue to have fluids through the drip. This will give the stomach time to start healing. Your child will be able to start feeding after about 12 hours. You will have to start with small amounts.

Your baby may still vomit some of the feed, but this won’t be forceful or projectile vomiting as before. The vomits or spills will decrease over several days. You will be able to take your baby home once they are feeding normally.

How can I care for my child at home after treatment for pyloric stenosis?

Continue to give your baby pain relief as advised by the doctor as their tummy may still be sore for a day or two.

Handle your child normally.

Usually, you can bath your child any time after the surgery. Check this with your surgeon.

Keep an eye on the wound. Take your child to your family doctor for urgent review if you notice any signs of infection:

  • increased redness around the wound
  • increased oozing or pus coming from the wound
  • a temperature
  • swelling around the wound
  • your baby stops feeding

You will need to take your baby back to the hospital for a check-up as an outpatient.

Are there any complications of treatment for pyloric stenosis?

All operations carry some degree of risk - bleeding during and after the surgery and the risks of anaesthesia. There is a small chance of damage to the delicate lining of the bowel, but this is usually recognised and fixed at the time of surgery. Pyloric stenosis can reoccur, but this is rare.

Images used with permission of Mayo Foundation for Medical Education and Research, all rights reserved.

This page last reviewed 20 November 2017.
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