Intestinal atresia is a broad term used to describe a complete blockage or obstruction anywhere in the intestine. Stenosis refers to a partial obstruction that results in a narrowing of the opening (lumen) of the intestine. Though these conditions may involve any portion of the gastrointestinal tract, the small bowel is the most commonly affected portion.
The frequencies, symptoms and methods of diagnosis differ depending on the site of intestinal involvement.
Types of intestinal atresia include:
- Pyloric atresia – Pyloric atresia involves an obstruction at the pylorus, which is the passage linking the stomach and the first portion of the small intestine (duodenum). This is quite rare, and tends to run in families. Children vomit stomach contents, and due to the accumulation of intestinal contents and gas, develop a swollen (distended) upper abdomen. Abdominal X-rays reveal an air-filled stomach but no air in the remaining intestinal tract.
- Duodenal atresia – The duodenum is the first portion of the small intestine that receives contents emptied from the stomach. Duodenal atresia occurs in 1 out of every 2,500 live births. Half of the infants with this condition are born prematurely and approximately two-thirds have associated abnormalities of the heart, genitourinary, or intestinal tract. Nearly 40% have Down syndrome. Infants with duodenal atresia usually vomit within hours after birth, and may develop a distended abdomen. Abdominal X-rays show a large dilated stomach and duodenum without gas in the remaining intestinal tract.
- Jejunoileal atresia – Jejunoileal atresia involves an obstruction of the middle region (jejunum) or lower region (ileum) of the small intestine. The segment of intestine just before the obstruction becomes massively enlarged (dilated), thus hindering its ability to absorb nutrients and propel its contents through the digestive tract. In 10 to 15% of infants with jejunoileal atresia, part of the intestine dies during fetal development. A significant percentage of infants with this condition also have abnormalities of intestinal rotation and fixation. Cystic fibrosis is also an associated disorder and may seriously complicate the management of jejunoileal atresia. Infants with jejunoileal atresia should be screened for cystic fibrosis.Infants with jejunoileal atresia, regardless of the subtype, usually vomit green bile within the first 24 hours of life. However, those with obstructions farther down in the intestine may not vomit until two to three days later. Infants often develop a swollen (distended) abdomen and may not have a bowel movement (as is normally expected) during the first day of life. Given the age of the patient and the symptoms, an abdominal X-ray is usually sufficient to establish a diagnosis.There are four subtypes of jejunoileal atresia:
- Atresia type I — The blockage is created by a membrane (web) present on the inner aspect of the intestine. The intestine usually develops to a normal length.
- Atresia type II — The dilated intestine terminates as a blind end. It is connected to a smaller caliber segment of the intestine by a fibrous scar. The intestine develops to a normal length.
- Atresia types IIIa and IIIb — The blind ends of intestine are separated by a defect in the intestinal blood supply. This often leads to a significantly shortened intestinal length that may result in long-term nutritional deficiencies or the short gut syndrome.
- Atresia type IV — Multiple regions of obstruction exist. This may result in a very short length of useful intestine.
- Colonic atresia – This rare form of intestinal atresia accounts for less than 15% of all intestinal atresias. The bowel becomes massively enlarged (dilated), and patients develop signs and symptoms similar to those associated with jejunoileal atresia. Colonic atresia may occur in conjunction with small bowel atresia, Hirschsprung’s disease or gastroschisis. The diagnosis is confirmed by an abdominal X-ray along with an X-ray contrast enema.
Intestinal obstructions are increasingly being identified through prenatal ultrasounds.
Children with intestinal atresia and stenosis require an operation, and the exact type of operation differs depending on the location of the obstruction.
Prior to the operation, all babies must be stabilized. The excess intestinal contents and gas that contribute to abdominal swelling is removed through a tube that is placed into the stomach through the mouth or nose. Removing air and fluid from the intestinal tract can prevent vomiting and aspiration, and reduce the risk of bowel perforation. It also provides babies with some comfort as abdominal swelling is relieved. Intravenous fluids are given to replace vital electrolytes (minerals and salts in the bloodstream and body) and fluid that has been lost through vomiting. Once the baby is stabilized, surgery is performed to repair the obstruction.
Children who undergo surgery for intestinal atresia require regular follow-up to ensure adequate growth and development, and to avoid nutritional deficiencies that may occur as a result of the loss of intestine.
How babies progress depends to a large extent on whether there is an associated abnormality and whether or not the baby is left with an adequate length of intestine. In general, however, most babies do well. Complications after surgery are rare, but may occur. In the immediate to early postoperative period, intestinal contents may leak at the suture line where the ends of the bowel were sewn together. This may cause an infection within the abdominal cavity and require additional surgery. Complications that may later occur include malabsorption syndromes, functional obstruction due to an enlarged and paralyzed segment of intestine, or short gut syndrome.