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Pyloric stenosis

Pyloric stenosis affects around 2-4 in 1,000 newborn babies. It causes a blockage of food at the stomach outlet (pylorus). Persistently being sick (vomiting) is the main symptom. A small operation is needed, which cures the problem.

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What is pyloric stenosis?

pyloric stenosis

pyloric stenosis

The outlet of the stomach into the small intestine is called the pylorus. Stenosis means a narrowing. Pyloric stenosis means a narrowed outlet of the stomach. It occurs in some newborn babies.

Food and drink pass down the gullet (oesophagus) into the stomach. Here they mix with acid and are partially digested. The stomach then normally passes the food and drink into the small intestine to be fully digested and absorbed into the body.

A narrowed or blocked outlet from the stomach (pyloric stenosis) can lead to a serious illness unless it is treated.

What are the symptoms of pyloric stenosis?

Symptoms typically begin in a baby aged 2-4 weeks who is otherwise healthy. In some cases, first symptoms can take up to two months to start.

Being sick (vomiting) after a feed is the main symptom. The vomiting often starts like a 'normal' vomit and milk just dribbles down the front of the baby. Sometimes the vomiting is forceful and milk may be vomited quite a distance like a fountain. This is called projectile vomiting.

The baby remains hungry and will usually feed well - only to vomit the milk back soon after feeding. The vomiting tends to become worse and worse over several days. The milk in the stomach often curdles before the baby is sick.

Little food or drink passes through the narrowed pylorus which becomes narrower over time. This means that little or no food reaches the bowels, so babies often pass little poo (faeces). Affected babies do not gain weight and are in danger of quickly becoming lacking in body fluid (dehydrated) and seriously ill if the condition is not treated.

Note: it can be very common for newborn babies to vomit. The vast majority of babies who vomit do not have pyloric stenosis.

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What causes pyloric stenosis?

The muscle in the wall of the outlet of the stomach into the small intestine (pylorus) is abnormally thick. This causes the outlet from the stomach to become narrowed (stenosed). It is not known why this occurs.

Pyloric stenosis affects around 2-4 out of 1,000 babies. Boys are affected more commonly than girls. It can sometimes run in families.

Are any tests needed?

A doctor may examine the baby's tummy (abdomen) whilst they are feeding. A typical bulge next to the stomach can often be felt as the muscles in the stomach and stomach outlet (pylorus) contract.

An ultrasound scan may be done if there is doubt about the diagnosis. This painless test is very reliable at detecting the thickened pylorus.

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What is the treatment for pyloric stenosis?

A small operation, done under a general anaesthetic, normally cures the problem. A small cut is made in the skin over the the stomach outlet (pylorus). This operation is called a pyloromyotomy.

The pylorus is found and the muscle in the pylorus is then cut. This allows the pylorus to widen into a normal size. This means that food and milk can pass easily out of the stomach into the bowel.

This operation is usually done by keyhole surgery. This uses only a tiny cut to the skin to allow fine instruments into the tummy (abdomen) to cut the pylorus muscle.

The operation is usually totally successful. Normal feeds are started again shortly after the operation. Most babies recover quickly and have no further problems.

Further reading and references

  • Galea R, Said E; Infantile Hypertrophic Pyloric Stenosis: An Epidemiological Review. Neonatal Netw. 2018 Jul;37(4):197-204. doi: 10.1891/0730-0832.37.4.197. Epub 2018 Jul 1.
  • Garfield K, Sergent SR; Pyloric Stenosis. StatPearls, March 2020.

Article history

The information on this page is written and peer reviewed by qualified clinicians.

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