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Pyloric stenosis

Medically reviewed by Last updated on Dec 2, 2022.


Pyloric stenosis is an uncommon condition in infants that blocks food from entering the small intestine.

Typically, a muscular valve between the stomach and small intestine holds food in the stomach until it is ready for the next stage in the digestive process. This valve is called the pylorus valve. In pyloric stenosis, the pylorus muscles thicken and become abnormally large, blocking food from reaching the small intestine.

Pyloric stenosis can lead to forceful vomiting, dehydration and weight loss. Babies with pyloric stenosis may seem to be hungry all the time.

Surgery cures pyloric stenosis.


The pylorus is a muscular valve that holds food in the stomach until it is ready for the next stage in the digestive process.

Pyloric stenosis

In pyloric stenosis, the pylorus muscles thicken, blocking food from entering the baby's small intestine.


Symptoms of pyloric stenosis usually appear within 3 to 5 weeks after birth. Pyloric stenosis is rare in babies older than 3 months.

Symptoms include:

When to see a doctor

See your baby's doctor if your baby:


The causes of pyloric stenosis are unknown, but genetic and environmental factors might play a role. Pyloric stenosis usually isn't present at birth and probably develops afterward.

Risk factors

Risk factors for pyloric stenosis include:


Pyloric stenosis can lead to:


Your baby's health care provider will start with a physical examination. Sometimes, the provider can feel an olive-shaped lump when examining the baby's belly. This lump is the enlarged pylorus muscles. Wavelike contractions may sometimes be visible when examining the baby's belly, often before the baby starts vomiting.

Your provider also might recommend:


Surgery is needed to treat pyloric stenosis. The procedure, called a pyloromyotomy, is often scheduled on the same day as the diagnosis. If your baby is dehydrated or has an electrolyte imbalance, your baby receives fluids [fluid replacement] before surgery.

In pyloromyotomy, the surgeon cuts only through the outside layer of the thickened pylorus muscle, allowing the inner lining to bulge out. This opens a channel for food to pass through to the small intestine.

Pyloromyotomy is often done using minimally invasive surgery. A slender viewing instrument, called a laparoscope, is inserted through a small incision near the baby's navel. Recovery from a laparoscopic procedure is usually quicker than recovery from traditional surgery. This method also leaves a smaller scar.

After surgery:

Possible complications from pyloric stenosis surgery include bleeding and infection. However, complications aren't common, and the results of surgery are generally excellent.


In surgery to treat pyloric stenosis, called a pyloromyotomy, the surgeon makes an incision in the wall of the pylorus. The lining of the pylorus bulges through the incision, opening a channel from the stomach to the small intestine.

Preparing for an appointment

You may be referred to a health care provider who specializes in treating digestive disorders, called a gastroenterologist. Or you may be referred to a pediatric surgeon.

What you can do

Questions to ask your doctor

In addition to the questions that you've prepared, don't hesitate to ask other questions during your appointment.

What to expect from your doctor

Your provider is likely to ask you a few questions. Being ready to answer them may leave time to go over points you want to spend more time on. You may be asked:

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