Pyloric stenosis in babies: symptoms, diagnosis and the operation

The pylorus is the muscular passage between the stomach and the first part of the small bowel (the duodenum). In pyloric stenosis the muscle becomes thicker than usual and closes up the inside of the passage. Great Ormond Street Hospital (GOSH) says this stops milk or food passing into the bowel to be digested.

It is a condition of the first months of life. Sheffield Children's describes it as a common condition, about 1 in 300 babies, usually affecting babies between 3 and 6 weeks, more often boys, and sometimes running in families. GOSH says we do not know exactly why it develops.

GOSH says that in most cases a baby begins by bringing up small amounts of milk after feeding. Over a few days this becomes worse until the baby can no longer keep any milk down. The vomiting may become so forceful that milk is projected several feet, which is called projectile vomiting.

Cambridge University Hospitals adds that a baby may want to feed again after vomiting and may not seem unwell at first. GOSH says the vomit can curdle and look yellow because it has been in stomach acid, and fewer dirty nappies are passed because little or no food reaches the bowel.

• Vomiting after feeds that becomes more frequent and forceful.

• Being hungry again straight after vomiting.

• Fewer wet nappies than normal.

• Lethargy, and a sunken soft spot (fontanelle) on top of the head.

• Poor weight gain or weight loss.

GOSH says that if the condition is not treated the baby will become dehydrated and not gain weight, and that the effects of dehydration can become serious quite quickly in children. Signs of dehydration include lethargy, wet nappies less frequently than normal and a sunken fontanelle.

If your baby is repeatedly vomiting forcefully after feeds, seems drowsy or is passing fewer wet nappies, contact your GP or NHS 111 the same day. Go to A&E or call 999 if your baby is very drowsy, floppy or hard to wake.

GOSH explains that the thickened muscle can sometimes be felt as a small, hard lump on the right side of the baby's stomach, especially during feeding. The doctor may examine the baby during a feed (a test feed) to watch for vomiting and feel for the lump.

Sheffield Children's says an ultrasound scan may be done to confirm the diagnosis if a lump cannot be felt. Cambridge adds that blood tests are often needed, which also show whether your baby is dehydrated and has lost salts.

It is treated with an operation. GOSH says it is usually done under general anaesthetic, lasts about 30 minutes, and is called a pyloromyotomy. Most are done by keyhole surgery (laparoscopically), occasionally by open surgery. The surgeon cuts through some of the thickened muscle so that the passage widens and milk can pass into the bowel.

Before the operation, babies who are dehydrated need fluids through a drip into a vein and blood tests to make sure the balance of salts and minerals is right. Cambridge says the operation only happens once blood tests are normal, which in some cases takes a few days. Your baby will not be allowed to feed meanwhile, and a nasogastric tube is passed through the nose into the stomach to drain its contents.

GOSH says all surgery carries a small risk of bleeding, and there is a rare chance of damage to the lining of the bowel, which would be stitched at the same operation. Sheffield Children's gives figures: in 3 to 5 of every 100 operations the muscle split is too deep and a hole is made in the stomach lining, and in 1 to 2 of every 100 babies the split is not enough, so vomiting continues and a further operation is needed. Infection and bleeding of the wound are also possible. Cambridge lists protrusion of tissue through the wound as rare.

Recovery is quick. Feeding usually restarts about six hours after the operation, in small amounts that are gradually increased (GOSH and Sheffield). Some babies keep vomiting for a few days or weeks, and Cambridge says this settles gradually. GOSH says most operations are successful, with the immediate effect of reducing or stopping vomiting after feeds.

Cambridge says your baby should be weighed weekly for at least six weeks, because weight is lost with the condition, and that most babies regain it within six weeks. A follow-up review is arranged roughly six to eight weeks after discharge.

GOSH says the tummy may feel sore for a while, loose clothes help, and regular pain relief such as paracetamol is needed for at least three days. Stitches dissolve on their own. Cambridge advises keeping the wound clean and dry, changing nappies as soon as they are wet, and sponge washes rather than baths for five days.

GOSH says to call your GP or the ward if your baby is in a lot of pain that pain relief does not ease, is not keeping fluids down or shows signs of dehydration, has a temperature of 37.5 degrees or higher that paracetamol does not bring down, has a red, hot or oozing wound, or continues to vomit.

Most baby vomiting is not pyloric stenosis. This table is a guide to the pattern that suggests it. A clinician makes the diagnosis.

On the NHS, a baby with suspected pyloric stenosis is usually seen urgently by a GP or at A&E, then transferred to a children's surgical unit. GOSH notes the baby is usually transferred from the local hospital. Because this is an urgent surgical condition in babies, it is almost always managed through NHS paediatric surgical services.