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Pyloric Stenosis

What Is Pyloric Stenosis?

Pyloric stenosis is a condition that can affect the gastrointestinal tract in babies. It can make a baby vomit forcefully and often, and can lead to other problems, such as dehydration. Pyloric stenosis needs immediate medical treatment.

What Happens in Pyloric Stenosis?

Food and other stomach contents pass through the pylorus, the lower part of the stomach, to enter the small intestine. Pyloric stenosis is a narrowing of the pylorus. When a baby has pyloric stenosis, this narrowing of the pyloric channel prevents food from emptying out of the stomach.

Pyloric stenosis (also called infantile hypertrophic pyloric stenosis) is a type of gastric outlet obstruction, which means a blockage from the stomach to the intestines.

Pyloric stenosis affects about 3 out of 1,000 babies in the United States. It's more likely to affect firstborn male infants and also runs in families — if a parent had pyloric stenosis, then a baby has up to a 20% risk of developing it. Most infants who have it develop symptoms 3 to 5 weeks after birth.

What Causes Pyloric Stenosis?

It's thought that babies who develop pyloric stenosis are not born with it, but have progressive thickening of the pylorus after birth. A baby will start to show symptoms when the pylorus is so thick that the stomach can't empty properly.

The cause of this thickening isn't clear. It might be a combination of several things; for example, use of erythromycin (an antibiotic) in babies in the first 2 weeks of life or antibiotics given to moms at the end of pregnancy or during breastfeeding can be associated with pyloric stenosis.

What Are the Signs of Pyloric Stenosis?

Symptoms of pyloric stenosis typically begin when a baby is around 3 weeks old. They include:

  • Vomiting. The first symptom is usually vomiting. At first it may seem that the baby is just spitting up often, but then it tends to become projectile vomiting, in which the breast milk or formula is ejected forcefully from the mouth, in an arc, sometimes over a distance of several feet. Projectile vomiting usually takes place soon after the end of a feeding, although in some cases it can happen hours later.

    The vomited milk might smell curdled because it has mixed with stomach acid. The vomit will not contain bile, a greenish fluid from the liver that mixes with digested food after it leaves the stomach.

    Despite vomiting, a baby with pyloric stenosis is usually hungry again soon after vomiting and will want to eat. It's important to know that even with the vomiting, the baby might not seem to be in great pain or at first look very ill.
  • Changes in stools. Babies with pyloric stenosis usually have fewer, smaller stools (poops) because little or no food is reaching the intestines. Constipation or poop with mucus also can happen.
  • Failure to gain weight or weight loss. Most babies with pyloric stenosis will fail to gain weight or will lose weight. As the condition gets worse, they might become dehydrated.

    Dehydrated infants are less active than usual, and they may develop a sunken "soft spot" on their heads and sunken eyes, and their skin may look wrinkled. Because less pee is made, they can go more than 4 to 6 hours between wet diapers.
  • Waves of peristalsis. After feeds, increased stomach contractions may make noticeable ripples, which move from left to right over the baby's belly as the stomach tries to empty itself against the thickened pylorus.

It's important to call your doctor if your baby has any of these symptoms.

Other conditions can cause similar problems. For instance:

  • gastroesophageal reflux (GER) usually begins before 8 weeks of age. GER involves lots of spitting up (reflux) after feedings, which can look like vomiting. But most babies with GER don't have projectile vomiting, and while they might have trouble gaining weight, they usually have normal poops.
  • a milk protein allergy also can make a baby spit up or vomit, and have diarrhea. But these babies don't have projectile vomiting.
  • gastroenteritis (inflammation in the digestive tract that can be caused by viral or bacterial infection) also can cause vomiting and dehydration. But babies with gastroenteritis usually also have diarrhea with loose, watery, or sometimes bloody stools. Diarrhea usually isn't seen with pyloric stenosis.

How Is Pyloric Stenosis Diagnosed?

The doctor will ask detailed questions about the baby's feeding and vomiting patterns, including what the vomit looks like. The baby will be examined, and any weight loss or failure to maintain growth since birth will be noted.

The doctor will check for a lump in the abdomen, which usually is firm and movable and feels like an olive. If the doctor feels this lump, it's a strong indication that a baby has pyloric stenosis.

When pyloric stenosis seems likely, an abdominal ultrasound usually is done. The enlarged, thickened pylorus can be seen on ultrasound images. The doctor may ask that the baby not be fed for several hours before an ultrasound.

Sometimes a barium swallow is done instead of an ultrasound. Babies swallow a small amount of a chalky liquid (barium), and then special X-rays are taken to view the pyloric area of the stomach to see if there is any narrowing or blockage.

The doctor also might order blood tests to check levels of electrolytes (minerals that help keep fluids balanced and vital organs working properly). An electrolyte imbalance often happens due to the ongoing vomiting of stomach acid and dehydration, and needs to be corrected.

How Is Pyloric Stenosis Treated?

When an infant is diagnosed with pyloric stenosis, either by ultrasound or barium swallow, the baby will be admitted to the hospital and prepared for surgery. Any dehydration or electrolyte problems in the blood will be corrected with intravenous (IV) fluids, usually within 24 hours.

A surgical procedure called pyloromyotomy, which involves cutting through the thickened muscles of the pylorus, will relieve the blockage. The pylorus is examined through a very small incision, and the muscles that are overgrown and thickened are spread and relaxed.

The surgery can also be done through laparoscopy. This is a technique that uses a tiny scope placed in an incision in the belly button, allowing the doctor to see the area of the pylorus. Using other small instruments placed in nearby incisions, the doctor can complete the surgery.

Most babies return to normal feedings fairly quickly, usually 3 to 4 hours after the surgery. Because of swelling at the surgery site, a baby may still vomit small amounts for a day or so. If there are no complications, most babies who have had pyloromyotomy can return to a normal feeding schedule and go home within 24 to 48 hours of the surgery.

If you're breastfeeding, you might worry about continuing while your baby is hospitalized. The hospital staff should be able to provide a breast pump and help you use it so that you can continue to express milk until your baby can feed regularly.

After a successful pyloromyotomy, your baby won't need to follow any special feeding schedules. Your doctor will probably want to examine your child at a follow-up appointment to make sure the surgical site is healing properly and that your baby is feeding well and maintaining or gaining weight.

Pyloric stenosis should not happen again after a pyloromyotomy. If your baby still has symptoms weeks after the surgery, there might be another medical problem, such as gastritis or GER, so let your doctor know right away.

When Should I Call the Doctor?

Pyloric stenosis is an urgent condition that needs immediate treatment. Call your doctor if your baby:

  • has lasting or projectile vomiting after feeding
  • is losing weight or not gaining weight as expected
  • is less active than usual or is very sleepy
  • has few or no stools (poops) over a period of 1 or 2 days
  • show signs of dehydration, such as more than 4 to 6 hours between wet diapers, a sunken "soft spot" on the head, or sunken eyes
Date reviewed: March 2017

Note: All information on KidsHealth® is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor.

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