What is small bowel atresia

Small bowel atresia, also known as intestinal atresia, is a birth defect that affects a part of the small intestine, the tube that connects the stomach to the large intestine and helps digest food.

Depending on the extent of the blockage, the defect is classified as either atresia or stenosis.

• Atresia: A complete blockage (obstruction) or lack of continuity of the bowel.
• Stenosis: A partial obstruction that results in a narrowing or stricture of the bowel.

Types of small bowel atresia

Small bowel atresia is a type of intestinal atresia classified according to the location along the intestinal tract where the blockage or lack of continuity occurs. The opening between the stomach and the small intestine is called the pylorus. The small intestine is divided into three consecutive parts: the duodenum, jejunum and ileum.

• Pyloric atresia: The rarest type of congenital intestinal obstruction occurs in the pylorus, the opening between the stomach and the small intestine. Pyloric atresia occurs in approximately 1 in 1 million live births. Blockage of the pylorus due to a congenital atresia can be caused by a web or, in rare cases, the absence of the pylorus, resulting in a blind ending stomach and the lack of connection between the stomach and the duodenum.
• Duodenal atresia: Duodenal atresia occurs in approximately 1 in 6,000 to 1 in 10,000 live births and is the most common congenital small bowel obstruction diagnosed prenatally. This type of atresia occurs in the duodenum, the first part of small intestine that is connected to stomach.
• Jejunoileal atresia: The most common type of neonatal intestinal obstruction, jejunoileal atresia occurs in 1 in 1,000 to 1 in 3,000 live births. Two cases of jejunoileal atresia are reported for every one case of duodenal atresia. Jejunoileal atresia refers to a congenital bowel obstruction occurring in one of two different parts of the small bowel and thus may be further classified:
  • Jejunal atresia: Blockage in the jejunum, the second part of intestine that extends from the duodenum to ileum.
  • Ileal atresia: Blockage in the ileum, the lower part of the small intestine before the colon.

Evaluation and diagnosis

Prenatal diagnosis

Small bowel atresia is often diagnosed before birth by prenatal ultrasound or fetal MRI if available. Doctors may suspect a fetus has small bowel atresia or intestinal atresia if a pregnant woman has too much amniotic fluid (polyhydramnios).

Diagnosing fetal small bowel atresia is uncommon before 18 weeks gestation and difficult to detect up to 24 weeks. A prenatal diagnosis of intestinal atresia typically occurs during the third trimester when the bowel becomes easier to see on ultrasound.

Indicators of small bowel atresia

• Dilated bowel: An intestinal obstruction prevents bowel contents from passing through, causing a backup of fluid in the intestine that will make the bowel appear bigger than normal. Ultrasound will indicate dilated (expanded) bowel before the blockage.
• “Double bubble:” A classic sign of a proximal small bowel atresia (duodenal atresia) is the “double bubble,” when there is dilated bowel and fluid in the baby’s stomach and part of duodenum (first portion of intestine after contents leave stomach), but no fluid beyond that point.
• Polyhydramnios: Small bowel atresia is often associated with polyhydramnios, an increase in amniotic fluid that usually develops during the third trimester. Normally, the baby continuously swallows the amniotic fluid, it passes through the GI tract (bowel), and then the baby passes the fluid as urine. Because of the intestinal blockage, the baby can’t adequately swallow and process the fluid. As a result, the baby’s stomach and intestine dilate before the site of obstruction and the amniotic fluid accumulates within the uterine cavity.

Complications of fluid buildup

The extra fluid in the uterus can make it very uncomfortable for the mother, as well as increase the risk of preterm delivery related to the size and capacity of the uterus.

Polyhydramnios can be associated with all types of small bowel atresia, but is more frequently seen in cases where the obstruction occurs closer to the stomach. Polyhydramnios accompanies duodenal atresia in 53 percent of cases (30-65 percent according to Pediatric Surgery, 7th Edition), and jejunoileal atresia in 25 percent of cases.

Because of the high incidence of associated birth defects, a complete prenatal evaluation and amniocentesis are recommended for mothers carrying babies with small bowel atresia. Related conditions include cystic fibrosis, Trisomy 21 (Down syndrome), congenital heart disease, bowel rotational abnormality, annular pancreas, esophageal atresia, anorectal atresia and genitourinary conditions.

If your baby has been diagnosed with small bowel atresia before birth, we recommend a prenatal pediatric surgical consultation to help explain the details of your diagnosis, discuss delivery options, and answer any questions you have about the surgical procedures and plans for treating your baby after birth.

Postnatal diagnosis

Doctors may also diagnose a small bowel atresia on an abdominal ultrasound or X-ray after your baby is born. Newborns with intestinal atresia vomit frequently, which is also a sign that something is wrong.

Additional postnatal imaging tests can help to identify or confirm the diagnosis, as well as test for any related birth defects:

• Contrast study in lower GI to identify the exact area of the blockage
• Abdominal X-ray to take pictures of your baby’s belly
• Fetal echocardiogram to examine your baby’s heart for congenital heart defects

Here is an overview of the two more common types of small bowel atresia, including diagnostic indicators and associated conditions:

Duodenal Atresia

• 1 in 10,000 live births
• 53 percent polyhydramnios
• "Double bubble"
• 17-33 percent heart disease
• 30 percent Trisomy 21

Jejunoileal Atresia

• Most common: 1 in 3,000 live births
• 25 percent polyhydramnios
• Vascular disruption
• 10 percent cystic fibrosis

Treatment for small bowel atresia

There is currently no prenatal treatment option available for small bowel atresia. Close management and monitoring of the pregnancy plays an important role in the ability to offer highly specialized postnatal care and improve outcomes for your child.

Delivery of babies with small bowel atresia

Because of the risk of early delivery due to polyhydramnios and need for immediate surgical repair, babies prenatally diagnosed with small bowel atresia should be delivered in a tertiary care center with pediatric surgical and neonatal expertise readily available. If possible we recommend avoiding transport because of the associated physiological changes due to stress and fluid loss in infants with a congenital intestinal atresia.

At CHOP, babies with small bowel atresias have the option of being delivered in the Garbose Family Special Delivery Unit (SDU), allowing for the highest level of immediate care for your baby, as well as expert obstetric services — all within the same pediatric hospital. The world’s first birth facility designed exclusively for pregnancies complicated by birth defects, the SDU is a vital part of our team’s ability to provide comprehensive care. In the SDU, our delivery rooms feature adjacent neonatal stabilization rooms containing all of the equipment, medications and monitoring that your baby might need.

Stabilization

After delivery, your baby will be stabilized by a highly specialized team of pediatric surgeons, neonatologists, specially trained nurses and respiratory therapists, all with extensive experience in treating neonates with small bowel atresia.

If your baby is stable, we will bring her to you for a moment so that you can see her before she is passed through the access window that connects the delivery room to the stabilization room. This is where our multidisciplinary Neonatal Surgical Team will be waiting, ready to provide whatever care your baby needs.

This is what you can expect while your baby is being stabilized:

• A nasogastric tube (NG tube) will be placed in your baby’s nose. This will help to drain the contents from your baby’s stomach using a gentle suction. It is important to keep your baby’s stomach empty because the bowel may not be working properly.
• Intravenous lines will be placed in your baby’s umbilical artery and vein. This will allow us to give your baby nutrition through the veins, since she will not be able to eat.
• We will perform any additional imaging tests required to confirm the exact nature and location of the bowel defect. Tests may include an X-ray, ultrasound or others.
• Your baby’s blood will be drawn and sent for blood tests, such as red blood cell count, white blood cell count, hemoglobin and hematocrit. This is an important baseline assessment for us to have before your baby’s surgery.

Surgical repair of small bowel atresia

After your baby is stabilized in the SDU, she is brought down special elevators to the Newborn/Infant Intensive Care Unit (N/IICU), which is located directly below the SDU. From there, she will be prepared for the operating room. Our Neonatal Surgical Team can also perform surgery in the N/IICU, reducing risk of transport for high-risk neonates such as those with intestinal atresia.

Surgical repair of a bowel obstruction is usually performed in the first days of life, as soon as your baby is stabilized. Learn more about the procedure and what to expect after surgery to repair small bowel atresia.