Pyloric Stenosis and Pyloric Atresia


Pyloric atresia and pyloric stenosis are conditions involving an obstruction (blockage) in the lower part of the baby’s stomach, known as the pylorus, that connects to the small intestine.

The blockage prevents food and other contents of the baby’s stomach from passing into the small intestine.

Because this outlet from the stomach is blocked, babies with pyloric atresia and pyloric stenosis experience severe, forceful vomiting that can lead to serious complications, including dehydration and a loss of electrolytes needed for the body to function properly.

Surgery is required to repair these defects.

Pyloric atresia and stenosis are part of a group of defects known as gastric outlet obstructions or

While the two conditions have similar symptoms, they involve different types of obstructions and require different surgical treatments.

About Pyloric Stenosis

Pyloric stenosis is a blockage caused by narrowing of the pylorus, the lower part of the stomach that connects to the small intestines. The narrowing occurs when the muscles in this area are abnormally enlarged and thickened, blocking food and other contents from leaving the stomach.

Pyloric stenosis is one of the most common reasons for surgery in newborns. The condition occurs more frequently in males than females. Often there is a family history. The cause is unknown.

In most cases pyloric stenosis is an isolated defect, meaning there are no other abnormalities present, and the prognosis is good.

The condition is also called infantile hypertrophic pyloric stenosis. Hypertrophy means enlargement of an organ or tissues.

Symptoms of Pyloric Stenosis

Signs and symptoms of pyloric stenosis typically appear within a few weeks of birth and may include:

  • Vomiting that is severe and increasingly forceful (projectile vomiting); the vomit will be nonbilious, meaning it will not contain bile (greenish fluid) as it is unable to leave the stomach
  • Fussiness
  • Hungry between feedings
  • Lethargic
  • Swollen belly
  • Weight loss or inability to gain weight (“failure to thrive”)
  • Dehydration, including fewer wet diapers and less tears when crying
  • Constipation or fewer, smaller stools
  • Waves of stomach contractions as the muscles try and push food through the narrowed pylorus into the small intestine

Because many of these symptoms are common to other conditions, accurate diagnosis is vital to proper treatment.

Diagnosing Pyloric Stenosis

Pyloric stenosis is diagnosed after birth. Testing may include:

  • A physical exam, checking the baby’s abdomen for a small, firm, immobile lump (described as olive shaped), which is the enlarged pylorus
  • Blood tests to check for dehydration and electrolyte levels (mineral imbalances)
  • An ultrasound of the abdomen
  • X-rays, if needed, that use a chalky white liquid (barium) swallowed by the infant to better view the stomach and small intestine (known as contrast imaging). Barium x-rays can help reveal the dilated stomach, which appears as a large single bubble, and the narrowing of the pylorus, distinguishing the blockage from other intestinal obstructions.

Treatment of Pyloric Stenosis

Babies with pyloric stenosis require surgery to remove the obstruction. Surgery is typically performed shortly after diagnosis.

During the procedure, known as a pyloromyotomy, the surgeon cuts along the enlarged, thickened muscle to split the muscle and allow the contents of the stomach to pass through. The surgery may be performed through a small open incision on the abdomen, or laparoscopically, a minimally invasive approach that uses a tiny scope and instruments inserted through very small incisions in and near the belly button.

Prior to surgery, if your baby has dehydration or electrolyte needs (mineral imbalance) caused by severe vomiting he or she will be treated with intravenous (IV) fluids.

About Pyloric Atresia

Unlike pyloric stenosis, pyloric atresia is a very rare form of gastro outlet obstruction, affecting an estimated 1 out of every 100,000 live births. In some cases there may be a family history.

Pyloric atresia is a congenital defect, meaning it is present at birth. The defect occurs when the stomach doesn’t form correctly during fetal development. The exact cause is unknown.

There are three types of pyloric atresia, based on whether the blockage is caused by:

  • a pyloric membrane or “web”
  • a solid cord of tissue that formed instead of an open passage
  • a complete separation or gap between the stomach and duodenum (the upper portion of the small intestine)

Pyloric atresia is typically an isolated condition, meaning there are no other abnormalities present. In rare cases, the defect may occur with other gastrointestinal abnormalities or it may be associated with a severe and often fatal skin condition known as epidermolysis bullosa (EB).

Pyloric atresia is sometimes referred to as congenital pyloric atresia, or CPA. 

Symptoms of Pyloric Atresia

Signs and symptoms of pyloric atresia typically appear within a few weeks of birth and may include:

  • Forceful (projectile) vomiting after feeding, caused when the stomach is full and the contents can’t pass to the small intestine; the vomit will be nonbilious, meaning no bile (greenish fluid) will be in it
  • A distended (swollen) abdomen
  • The absence of stool
  • Dehydration, including fewer wet diapers and less tears when crying
  • Weight loss or inability to gain weight (“failure to thrive”)
  • Respiratory distress due to pulmonary aspiration

Diagnosing Pyloric Atresia

During Pregnancy

Pyloric atresia may be diagnosed or suspected during pregnancy following a routine ultrasound that detects a combination of:  

  • polyhydramnios, a build-up of amniotic fluid in the womb that occurs when the fetus is unable to swallow and digest amniotic fluid; and
  • a dilated or extended (swollen) stomach.

A diagnosis during pregnancy enables your family and your healthcare team to plan ahead for the special treatment needs your baby will have at birth, for the best possible outcomes.

After Birth

After birth, pyloric atresia may be diagnosed or confirmed through testing that includes an abdominal ultrasound and in some cases x-rays of the upper digestive system.

The imaging will show air in the baby’s dilated stomach (which appears as a large single bubble), but no air in the intestinal tract beyond the stomach obstruction. In cases where some air is able to pass into the small intestine, the condition may resemble pyloric stenosis (narrowing of the pylorus caused by enlarged muscles).

X-ray testing may include the use of barium, a chalky white liquid swallowed by the infant to better visualize the stomach and small intestine and help distinguish the blockage from other intestinal obstructions. This approach is known as contrast imaging or an upper GI study.

Accurate, timely diagnosis is vital, ensuring proper treatment and helping prevent life-threatening complications including pulmonary aspiration or gastric perforation, for example.

Treatment of Pyloric Atresia

Babies with pyloric atresia require surgery after birth to remove or bypass the obstruction. The type of surgical procedure will depend on the type of pyloric atresia your baby has. Surgery is typically performed shortly after diagnosis.

Prior to surgery, your baby may be treated with intravenous (IV) fluids if he or she is dehydrated or has electrolyte needs (mineral imbalance) caused by severe vomiting. The baby’s swollen stomach may also be “decompressed” using a special tube through the nose (nasogastric or NG tube) to remove any air and fluids.

Babies with associated abnormalities may require additional treatment for those conditions.

Specialized Evaluation and Prenatal Care

If pyloric atresia or pyloric stenosis are diagnosed or suspected during pregnancy, you may be referred to a fetal center for further evaluation.

At Texas Children’s Fetal Center, we arrange for you to visit for a comprehensive assessment by a team of specialists experienced in the diagnosis and treatment of gastric outlet obstructions, including maternal-fetal medicine physicians (OB/GYNs specializing in high-risk pregnancies), fetal imaging experts, pediatric surgeons and anesthesiologists, genetic counselors and neonatologists.

Additional testing will be performed using state-of-the-art imaging technologies and techniques that provide detailed views of your baby’s condition, for the most accurate diagnosis and treatment planning. Our specialists will then meet with you about the results, discuss treatment recommendations and answer any questions you have.

You and your baby will be more closely monitored throughout pregnancy to assess the baby’s growth and watch for signs of complications such as polyhydramnios, which can pose risks to the pregnancy and fetus.

Because surgical intervention may be necessary shortly after birth, we recommend delivery at a center with pediatric surgeons experienced in the treatment of gastric outlet obstructions and the highest level of neonatal intensive care (NICU), if needed.

Postnatal Care

Depending on your baby’s condition, his or her postnatal care team may include:

A unique and distinct advantage for mothers delivering at Texas Children’s Pavilion for Women is our location inside Texas Children’s Hospital, ranked one of the best children’s hospitals in the nation by U.S. News & World Report, for seamless access to the specialists your child may need.

Our Fetal Center team works closely with Texas Children’s Gastroenterology, Hepatology and Nutrition service, ranked #2 in the nation in gastroenterology and GI surgery, carefully planning and coordinating your baby’s postnatal care. This means the pediatric experts responsible for treating your child after delivery have been an integral part of their care team since before birth.

Why Texas Children’s Fetal Center?

  • A single location for expert maternal, fetal and pediatric care. At Texas Children’s Hospital, mother and baby receive the specialized care required for the diagnosis and treatment of pyloric atresia and stenosis all in one location, for highly coordinated care and treatment planning, including immediate access to our level IV NICU, if needed.
  • A skilled, experienced team with proven outcomes. We have a dedicated team of maternal-fetal medicine specialists, fetal imaging experts, neonatologists, pediatric surgeons, anesthesiologists, genetic counselors and others who work in concert to care for you and your baby, using proven protocols we’ve developed over the years. With their combined expertise and unified approach, this team offers the best possible care for pregnancies involving gastric outlet obstructions.
  • We care for your child’s needs at every stage of life. Our comprehensive approach starts with your first prenatal visit and continues through delivery, postnatal care, childhood and beyond, as needed, thanks to one of the nation’s leading teams of fetal and pediatric specialists for the care and treatment of gastrointestinal birth defects.


Additional Resources

For more information or to schedule an appointment,

call Texas Children’s Fetal Center at 832-822-2229 or 1-877-FetalRx (338-2579) toll-free.

Our phones are answered 24/7. Immediate appointments are often available.