Pyloric stenosis

About pyloric stenosis

The pylorus is the passage from the stomach into the small bowel. Pyloric stenosis is when the muscle in this area – called the pyloric sphincter – thickens, making the opening narrow. As a result of this narrowing, milk can't get out of the stomach to be digested.

Pyloric stenosis affects about one baby in every 400. The symptoms usually appear when your baby is around three weeks old, but can start any time between one and 18 weeks after birth.

Pyloric stenosis is more common in boys than in girls, particularly in firstborn babies.

Symptoms of pyloric stenosis

The first symptom you notice will probably be your baby vomiting small amounts of milk after feeding. At first, this may not be any more than usual, and may only occur after some feeds. However, the vomiting will become more severe and powerful, and start to happen after most feeds. This is called projectile vomiting and may be so forceful that it travels some distance out of your baby's mouth. The milk that your baby vomits may consist of curdled milk and, on occasion, may contain blood or have a similar colour and consistency to coffee grounds.

Other symptoms that your baby may have include:

  • being hungry all the time
  • constipation, with stools that look like ‘rabbit pellets’
  • dry nappies due to not urinating often
  • weight loss
  • lack of energy
  • yellowing of his or her skin (jaundice)

If your baby has these symptoms, see your GP. It's important that your baby receives treatment for pyloric stenosis, otherwise he or she may become seriously dehydrated. Your baby also won't be able to put on weight as he or she won't be absorbing any nutrients from the milk.

Causes of pyloric stenosis

Doctors don’t understand the exact reasons why some babies develop pyloric stenosis. However, there is evidence that the condition runs in families and is associated with conditions such as Turner’s Syndrome and disorders affecting the digestive system.

Diagnosis of pyloric stenosis

Your GP will ask about your baby's symptoms and examine him or her. During the examination, your doctor will feel to see if there is a small, hard lump on the right-hand side of your baby's stomach. This is called the 'olive test' because the thickened pylorus feels a bit like an olive.

Your GP may ask you to give your baby a ‘test feed’ so that he or she can feel your baby’s abdomen (tummy) and see any vomiting afterwards. During the feed, it may be possible to see the muscles around your baby's stomach moving from side to side as they try to push milk through the pylorus.

Your GP will want to rule out other conditions that could be causing your baby's symptoms, such as an infection, overfeeding or a milk allergy.

If your GP thinks your baby has pyloric stenosis, he or she will refer you to a specialist. The specialist may do more tests including:

  • blood tests
  • an ultrasound scan – this uses sound waves to produce an image of the inside of your baby's abdomen and will show the thickened pylorus muscle

Treatment of pyloric stenosis

Your baby will need to have an operation called a pyloromyotomy. This is sometimes referred to as a Ramstedt's pyloromyotomy or a Ramstedt operation. The surgeon will separate your baby's pylorus muscle and spread it open. This allows your baby's pylorus to widen so that milk can pass through.

Before the operation, your baby may be put on a drip for approximately 24 hours in order to rehydrate him or her.

The operation is carried out under general anaesthesia. This means that your baby will be asleep during the operation and will feel no pain. The operation takes about half an hour to an hour, depending on the type of operation used.

After the operation your baby will probably have to stay in hospital for a few days. Your baby’s surgeon will give you advice about feeding. He or she will probably tell you to wait a few hours before feeding to try to reduce the risk of vomiting, and then recommend small amounts of milk at first. Your baby may still vomit a bit to start, but this should improve within a week.

You will be able to take your baby home once he or she is feeding well and putting on weight. Almost all babies who have this operation recover well.


How do I tell whether my baby's vomiting is caused by pyloric stenosis?


The symptoms of pyloric stenosis are quite different to those caused by other conditions such as a stomach infection or overfeeding, as they get progressively worse with time.


If your baby has a stomach infection, he or she will probably not want to feed. This is different to pyloric stenosis when your baby is always hungry because he or she isn't getting any nourishment.

Overfeeding is when your baby gets more milk than he or she needs. It can cause spitting up (not as violent as vomiting) and diarrhoea.

With pyloric stenosis, your baby will vomit, but this will be much more forceful than usual. You may also notice that your baby's bowel movements are different from usual and that there are fewer wet or soiled nappies.

Is surgery the only way of treating pyloric stenosis?


Yes, at the moment if your baby develops pyloric stenosis, he or she will need to have an operation called a pyloromyotomy to treat the condition.


It's possible that in the future, new treatments may mean that pyloric stenosis can be treated without surgery. Recent studies suggest that it may be possible to treat pyloric stenosis with a medicine called atropine. Babies take the medicine through a tube into the nose for three weeks. More research is needed to find out if atropine is a suitable alternative treatment to surgery.

Are there any risks associated with the operation to treat pyloric stenosis?


All surgery carries an element of risk. However, pyloromyotomy is a successful operation and there are usually no long-term consequences, other than an incision scar.


There can be complications during or after any operation. These may include bleeding or the wound becoming infected afterwards. However, for most babies a pyloromyotomy is successful and they make a good recovery. Your baby's surgeon will either do an open or keyhole pyloromyotomy. There is no clear evidence as to which procedure is more effective, but if a keyhole operation is done, your baby's scar will probably be smaller.