Pyloric Stenosis

Hypertrophic Pyloric Stenosis or HPS, is a condition in which there is a thickening of the muscle in the wall of the intestine, just beyond the stomach.

What causes this condition?

The cause of HPS is essentially unknown, however, there are a number of theories that have been suggested. Many of these theories suggest an absence, or a deficiency of particular proteins or chemical message receptors in the muscle of the gut which is affected. The part of the gut that is affected is approximately 2cm long and is called the pylorus.

Who Develops HPS?

HPS occurs in approximately 1 in every 350 babies and occurs most commonly between the ages of 2 and 10 weeks. It occurs more commonly in boys than girls, and in children of parents who had HPS when they were babies. First born boys, are more likely than others to develop HPS. This suggests an hereditary or genetic susceptibility, which is in fact greater if the mother had HPS rather than the father.

How do children with pyloric stenosis present?

The child with HPS will present with increasing numbers of large milky vomits, and will vomit within half an hour of every single feed. Immediately after vomiting, the baby will be hungry again.

HPS is not a painful condition, however, it is potentially a life threatening one, as the babies can become dehydrated very quickly.

A baby that is developing HPS may not thrive and may in fact lose weight. A baby who is becoming dehydrated will have fewer and fewer wet nappies and as no food/milk is going through the gut, the baby will have less and less soiling of its nappies.

With increasing dehydration, the baby will become irritable and then will eventually become quiet and listless, with sunken fontanelles, dry mouth and lips and reduced elasticity of the skin.

How is the diagnosis made?

When a Paediatric Surgeon examines a baby with HPS, he may see waves of stomach contractions.

When he feels the abdomen after the baby is given a feed, he should be able to feel the thickened muscle in the upper part of the abdomen.

An ultrasound of the pylorus is the most accurate and safest test that can be performed to confirm the diagnosis.

How is this condition managed?

Having made the diagnosis, it is important that the Paediatric Surgeon resuscitate the baby before an operation is performed. The babies with HPS usually require an intravenous drip to give them fluids in order to reverse their dehydration. They are also given sugar in the drip to provide energy for the brain as well as salts to prevent changes in the rhythm of the heart.

This intravenous resuscitation may take up to 3 days before the baby is stable enough for an operation. During this time, a drainage tube is left in the stomach via the nose to prevent a build up of saliva and secretions within the stomach.

What operation is performed?

The standard operation for HPS is called a Pyloromyotomy, which is performed via a small cut in the abdomen usually at the level of the belly button.

The aim of the operation is to cut the muscle of the pylorus and to stretch it far enough apart, so that it no longer causes an obstruction to the drainage of milk from the stomach.

A pyloromyotomy can be performed laparoscopically with or without a balloon placed on the inside of the gut to stretch open the pylorus from within. There has been no significant advantage demonstrated performing this operation laparoscopically with or without the use of a balloon within the bowel.

If the diagnosis of HPS is delayed, the baby will become increasingly sick and may die from the complications of dehydration.

What is the prognosis?

The prognosis following the operation for HPS is excellent and the baby is usually feeding normally within two days.

Sometimes, after the operation the baby will continue to vomit intermittently. This is usually due to reflux of milk, or in other words gastro-oesophageal reflux, which will have been present even before the pyloric stenosis developed.

There is less than 1% chance of the baby requiring a further operation for the same condition.

The best investigation if necessary to demonstrate that the operation has been successful, is an x-ray in which the baby swallows fluid mixed with contrast material, which should show normal emptying from the stomach into the rest of the bowel.