The Facts

Pyloric stenosis describes a condition in newborn babies. Specifically, pyloric stenosis occurs when the muscle (pyloric muscle or pylorus) that allows food to move from the stomach into the small intestines thickens.  Thickening of this muscle narrows the opening and prevents food from moving easily from the stomach into the small intestine.

A baby with pyloric stenosis experiences gradually increased vomiting, which may eventually become projectile and lead to dehydration. Since the food the baby eats does not enter the small intestines there may not be enough nourishment for the developing infant.

Although the condition affects both boys and girls, boys are 4 times more likely to have this problem. The condition often begins around the second or third week of life but may start any time up to the age of 6 months. Frequent spitting up after feedings is the first clue to the condition. Later, spitting up develops into projectile vomiting: vomiting that is sudden and vigorous, and projects several feet away from the body.


No one knows exactly what causes pyloric stenosis.

Factors that seem to play a role in whether or not a baby develops this condition include:

  • family history of the condition
  • gender of the baby
  • genetic abnormalities
  • use of certain medications shortly after birth (although most infants with the condition were not given antibiotics early in life)
  • maternal smoking

Symptoms and Complications

Spitting up with increasing frequency and projectile vomiting are both signs that point towards pyloric stenosis. A checkup by the family doctor can help rule out other possible causes such as acid reflux, infection, abnormal anatomy, allergy, or rare metabolic disorders (e.g., galactosemia).

Spitting up is normal for many newborn babies. It becomes more worrisome for parents if the spitting up happens after every feeding or increases in frequency over a period of time. Also, if spitting up gradually becomes projectile vomiting, you should check with your doctor.

Pyloric stenosis can contribute to:

malnutrition: food does not move into the small intestine where it would normally be digested and used by the body

dehydration: a baby with this condition is at an increased risk for dehydration due to frequent vomiting

Other symptoms that may show your child has pyloric stenosis include:

  • continuous hunger.
  • decreased or infrequent bowel movements or harder stools.
  • decreased weight.
  • overly fussy behaviour and later lethargy (listlessness and excessive tiredness).

See your doctor if you suspect your baby has pyloric stenosis.

Making the Diagnosis

Frequent vomiting with poor hydration may indicate that the baby has pyloric stenosis. The doctor will first examine the abdomen for any bowel sounds or hard lumps.

A doctor who examines the baby may request certain tests. These tests include an abdominal ultrasound and blood tests. An abdominal ultrasound is a painless procedure that allows the doctor to see the pyloric muscle at the bottom of the stomach where it joins the small intestines. If it is thickened, this likely indicates pyloric stenosis.

Sometimes, a special X-ray called a barium swallow is ordered. The baby drinks breast milk or formula with barium added to it, and then a series of X-rays are done to watch how the liquid passes through the stomach. This test is sometimes referred to as an "upper GI series." With pyloric stenosis, a "string sign" may be seen, where the outlet from the stomach has become so narrow from the thickened pyloric muscle that the barium flowing though it looks like a string.

Checking that the baby is well hydrated is also important and both a physical examination and blood tests can help determine this. The blood tests also detect chemical abnormalities that can be associated with advanced cases of pyloric stenosis.

Treatment and Prevention

If pyloric stenosis is diagnosed the baby will require minor surgery.

Doctors use surgery to cut into and spread apart the enlarged pylorus muscle. This widens the opening from the stomach into the small intestines and allows food and liquids to move more easily.

Parents should see a decrease in spitting up and vomiting after the surgery as well as increased weight gain as food begins to nourish the infant's developing body.

The 2 main surgical options to correct pyloric stenosis include:

laparoscopic surgery: A doctor uses a thin tube that passes through an incision in the infant's belly-button. This tube helps guide the doctor to the pyloric muscle.

open surgery: Open surgery requires the doctor to make an incision in the baby's abdomen to reach the pyloric muscle.

Treating the condition with surgery is very effective and the baby can usually go home within a day or two. In rare cases, spitting up after the surgery may be a sign that the pyloric muscle was not cut enough to widen the opening from the stomach into the small intestines.

In developed countries, surgery is the way pyloric stenosis is treated because it is so effective. If you are in an area with no pediatric surgeon or anesthesiologist, medical treatment with atropine* may be recommended. Atropine is a less effective treatment, and so it is not recommended if surgery is possible.

Preventing pyloric stenosis is not possible. However, knowing the signs and symptoms of the condition and recognizing them in your child may help you get the care your baby needs as early as possible. In turn, you may prevent complications such as dehydration, weight loss, and poor nutrition.

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