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Pyloric Stenosis

What is Pyloric Stenosis?

Pyloric stenosis is the narrowing of the lower portion of the stomach (pylorus) that leads into the small intestine. The muscles in this part of the stomach thicken, narrowing the opening of the pylorus and preventing food from moving from the stomach to the intestine.

This problem typically occurs in infants between 2 and 8 weeks of age and affects one out of every 500 to 1,000 live births.

Reasons for Concern About Pyloric Stenosis

Since the stomach opening becomes blocked, food cannot move into the intestine. This causes a baby with pyloric stenosis to vomit forcefully after eating. As a result of this vomiting, several problems can arise.

The most serious problem is dehydration (excessive water loss from the body). A baby who vomits regularly will not get enough fluids to meet their nutritional needs.

Additionally, minerals that the body needs to stay healthy, such as potassium and sodium, are lost through vomiting. Not having the right amount of both water and minerals can cause infants to lose weight and become extremely sick very quickly.

Causes of Pyloric Stenosis

There is no clear cause identified for pyloric stenosis, though both genetic and environmental factors are thought to be involved. It is known, however, that there is nothing that can be done to prevent its occurrence.

Risk Factors for Pyloric Stenosis

Pyloric stenosis is considered a multifactorial trait, which means that many factors are involved. In many defects with multifactorial traits, one gender is affected more often than the other. For example, pyloric stenosis is four times more common in males than in females.

In families where one child has pyloric stenosis, there is an increased risk that a future brother or sister could also have this condition. Adults who have had pyloric stenosis when they were infants may pass the trait on to their children.

If a child with pyloric stenosis is female:

  • The likelihood of having a future son with pyloric stenosis is 1 in 5
  • The likelihood of having a future daughter with pyloric stenosis is 1 in 14

If a child with pyloric stenosis is male:

  • The likelihood of having a future son with pyloric stenosis is 1 in 20
  • The likelihood of having a future daughter with pyloric stenosis is 1 in 40

Other pyloric stenosis risk factors:

  • Caucasians seem to develop pyloric stenosis more often than babies of other races.
  • Due to the hereditary factor, several members of a family may have had this problem in infancy.

Signs and Symptoms of Pyloric Stenosis

The most common symptom of pyloric stenosis is forceful, projectile vomiting, which is quite different from a "wet burp" that a baby may have at the end of a feeding. The baby is usually quite hungry and eats or nurses eagerly.

Large amounts of breast milk or formula are then vomited and may go several feet across a room. The milk is sometimes curdled in appearance due to the fact that it remains in the stomach where it is exposed to acid.

Other symptoms include:

  • Weight loss
  • Dehydration
  • Lethargy (lack of energy)
  • Fewer bowel movements
  • Constipation
  • Mild jaundice (yellowish coloring in skin)

Diagnosis of Pyloric Stenosis

Careful physical examination generally reveals a firm mass, the size of an olive, in the mid-abdomen. Your physician may advise other diagnostic procedures to confirm the diagnosis and to eliminate conditions with symptoms similar to those seen in babies with pyloric stenosis. These procedures include:

  • Blood tests – done to evaluate dehydration and mineral imbalances
  • Abdominal ultrasound -- the gold standard for diagnosing pyloric stenosis. This is an imaging technique that uses high frequency sound waves and a computer to create images of blood vessels, tissues, and organs. It is used to find out the thickness and length of the pyloric muscle.
  • Barium swallow / upper GI series – looks at the organs making up the upper part of the digestive system (esophagus, stomach and the first section of the small intestine). A dense, chalky fluid called barium, used to coat the inside of organs so they will show up on an X-ray, is swallowed. X-rays are taken to evaluate the digestive organs. This test will also demonstrate a delayed emptying of the stomach content as well as the narrowing of the pylorus.

Treatment for Pyloric Stenosis

Pyloric stenosis is treated in two stages. First, fluids are given intravenously to treat dehydration and restore the body's normal chemistry.

Once this is done, an operation called a pyloromyotomy is performed. This opens up the tight muscle that has caused the narrowing in the stomach, allowing the passage of food from the stomach to the intestine.

This surgery is performed using either an open or laparoscopic surgical approach.

After Surgery


While in the operating room, your baby will receive a pain medicine injected into the incision. This should allow them to feel and appear comfortable for about six to eight hours after surgery. If necessary, you may give acetaminophen (medication such as Tylenol) to help ease discomfort.


Nothing should be given by mouth for the first two hours after surgery. Two hours after surgery, home feeds (breast milk or formula) are started. Feedings are continued even if the baby has two to three episodes of vomiting. If vomiting continues, all feedings should be held for two hours, and then restart feedings. The baby may be discharged when three consecutive goal feedings are tolerated. Goal feedings are usually 2 to 4 ounces every three hours and based on the amount advised by your primary care physician prior to surgery.


Although a baby often vomits for 24 to 48 hours after surgery, this usually disappears without any further treatment. Small amounts of the feeding being spit up is normal. If the baby vomits most or all of their feeding more than two times daily, contact your surgeon.


Your baby's incision should be kept clean and dry, and you should not bathe them in a tub for one week after surgery. The incision may be closed with tissue glue or Steri-Strips (bandage-like tape). If Steri-Strips are used, leave them in place and only remove them according to the instructions of your pediatric surgeon. They are generally left in place for seven to 10 days.

Call Your Child's Doctor If:

  • Your baby's temperature is above 101° F (38.6° C), even if it drops below this when acetaminophen is given.
  • There is an increase in redness, swelling or drainage at the incision site or if this site has drainage with a foul odor.
  • Pain is not relieved by medicine.
  • There are signs of dehydration such as fewer wet diapers each day, the absence of tears when crying, or a fontanel (soft spot on the head) appears sunken.
  • Vomiting occurs more than two times daily. Small spit-ups are normal.

Long-Term Outlook

There are no long-term effects of surgery, and there is less than a 1 percent chance that pyloric stenosis will recur.

Last Updated 11/2022

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