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Pyloric Stenosis

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Pyloric stenosis is a narrowing of the section of gut directly after the stomach, leading to obstruction of the gut and projectile vomiting. It occurs specifically in newborns between one and twelve weeks of age – most cases are between two and six weeks – and while it affects around 1 per 1,000 live newborns, it is much more common in boys than girls. The condition is not life-threatening but requires surgical treatment, following which the majority of infants are soon able to feed normally.


The condition is due to narrowing of the pylorus, the point where a sphincter separates the stomach from the small bowel. In pyloric stenosis, the muscle of the pylorus becomes thickened to the point that the exit from the stomach is obstructed. The reasons behind this are not entirely clear, but the condition is known to run in families and may have a genetic component. It is clear, though, that pyloric stenosis is not the fault of the parents.


Infants with pyloric stenosis can spread their stomach contents over distances of several metres, and this so-called 'projectile vomiting' can be very distressing for parents. The forcefulness of vomiting is in stark contrast to possetting, where infants bring up a little milk and wind after a feed, and reflux vomiting1, which is a lot gentler than projectile vomiting and may cause the infant to arch their back due to pain from heartburn. Pyloric stenosis may begin with gentle vomiting but soon progresses to the projectile form.

The vomit consists of yellowy curdled milk but is free from bile, a green substance that enters the bowel at a point beyond the pylorus. The infant is likely to become dehydrated and constipated due to lack of fluid intake, but will remain eager to feed despite the vomiting and may otherwise be perfectly well.


While pyloric stenosis isn't an emergency, it is a good idea to tell your health visitor or take your child to see a doctor if they have the above symptoms. Diagnosis is based on a history of the symptoms, examination looking for visible contraction of the gut and feeling for the pylorus during a feed, and investigations including a blood test for electrolyte levels2 and an abdominal ultrasound scan. Other scans can be used but are less useful.

Treatment involves the use of fluids via a drip in order to correct the dehydration and electrolyte levels, following which surgery can be performed. This involves Ramstedt's procedure, also known as pyloromyotomy, in which the pyloric muscle is cut without damaging the inner wall of the pylorus. The operation may be performed using keyhole surgery3. There are generally no alternatives to surgery.


Complications of surgery are rare and the prognosis is generally good – children with pyloric stenosis go on to lead normal lives. Some gentle vomiting may occur after treatment, but this is due to reflux rather than pyloric stenosis.

1This is where stomach contents is regurgitated due to a weakness of the sphincter at the entrance to the stomach.2Electrolytes are ions in the blood such as sodium, potassium and chloride. Due to the vomiting of stomach acid, infants with pyloric stenosis present with a high blood pH and a low level of potassium and chloride ions – chloride is lost in the vomiting, whereas potassium is lost via the kidneys while the body tries to bring down the blood pH.3This is where only small cuts are made into the abdomen, with special instruments and a camera being used through the holes.

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