Digestive Tract Defects
A birth defect can occur anywhere along the length of the digestive tract--in the esophagus, stomach, small intestine, large intestine, rectum, or anus. In many cases, an organ is not fully developed or is abnormally positioned, which often causes narrowing or blockage (obstruction). The internal or external muscles surrounding the abdominal cavity may weaken or develop holes. The nerves to the intestines may also fail to develop (Hirschsprung disease, or congenital megacolon).
Blockages (obstructions) that develop in the intestines, rectum, or anus can cause rhythmic, crampy abdominal pain, abdominal swelling, and vomiting.
Most digestive tract defects require surgery. Generally, obstructions are surgically opened. Weakenings or holes in the muscles surrounding the abdominal cavity are sewn shut.
Esophageal Atresia and Tracheoesophageal Fistula
Normally, the esophagus, a long tubelike organ, connects the mouth to the stomach. In esophageal atresia, the esophagus narrows or comes to a blind end; food is delayed or prevented from going from the esophagus to the stomach. Most newborns with esophageal atresia also have a tracheoesophageal fistula, an abnormal connection between the esophagus (below the narrowing) and the trachea. Swallowed food and saliva travel through the fistula to the lungs, leading to coughing, choking, difficulty breathing, and possibly pneumonia. Food or fluid in the lungs may impair oxygenation of blood, leading to a bluish discoloration of the skin (cyanosis). Characteristically, a newborn with esophageal atresia coughs and drools after attempting to swallow. Many children with esophageal atresia and tracheoesophageal fistula have other abnormalities, such as heart defects.
 See the figure Atresia and Fistula: Defects in the Esophagus.
To detect a blockage, x-rays are taken as a tube is passed down the esophagus.
The first steps in treatment are withholding oral feedings and placing a tube in the upper esophagus to continuously suction out saliva before it can reach the lungs. The infant is fed intravenously. Surgery needs to be performed soon to establish a normal connection between the esophagus and stomach and to close the connection between the esophagus and the trachea.
Anal Atresia
Anal atresia is narrowing or blockage of the anus. Most infants with anal atresia develop some type of abnormal connection (fistula) between the anus and either the urethra, the area between the urethra and anus (the perineum), the vagina, or the bladder.
Infants with anal atresia fail to defecate normally after birth. Eventually, intestinal obstruction develops. However, doctors often detect the abnormality by looking at the anus when they first examine the baby after birth, before symptoms develop.
Using x-rays, a radiologist can see the path of a fistula. Anal atresia usually requires immediate surgery to open a passage for feces and to close the fistula. Sometimes, a temporary colostomy (making a hole in the abdomen and connecting it to the colon to allow stool to flow into a plastic bag on the abdominal wall) may be necessary.
Intestinal Malrotation
Intestinal malrotation (abnormal rotation of the intestines) is a potentially life-threatening defect in which the intestines develop incompletely or abnormally. Malrotation can cause the intestines to later twist (volvulus), cutting off their blood supply. Infants with intestinal malrotation can suddenly develop symptoms of vomiting, diarrhea, and abdominal swelling; these symptoms can also come and go. If the blood supply to the middle of the intestine is completely cut off (mid-gut volvulus), sudden, severe pain and vomiting develop. Bile, a substance formed in the liver, may be vomited and appear yellow, green, or rust-colored. Eventually, the abdomen swells. X-rays may help the doctor determine the diagnosis. However, the volvulus can be seen only on x-rays taken after placing barium, a substance visible on the x-ray, in the rectum (barium enema).
Treatment, including intravenous fluids and usually emergency surgery, must begin within hours. If not treated rapidly, the defect can result in loss of intestinal tissue or death.
Biliary Atresia
Bile, a fluid secreted by the liver, carries away the liver's waste products and helps digest fats in the small intestine. Bile ducts within the liver collect the bile and carry it to the intestine. In biliary atresia, the bile ducts are destroyed--either partially or completely--so bile cannot reach the intestine. Eventually, the bile accumulates in the liver and then escapes into the blood, causing a yellowish discoloration of the skin (jaundice). Progressive, irreversible scarring of the liver, called biliary cirrhosis, starts by the age of 2 months if the defect is not treated.
In infants with biliary atresia, the urine becomes dark, the stools become pale, and the skin becomes increasingly jaundiced. These symptoms and an enlarged, firm liver are usually first noticed about 2 weeks after birth. By the time the infant is 2 to 3 months old, he may have stunted growth, be itchy and irritable, and have large veins visible on his abdomen, as well as a large spleen.
To prevent biliary cirrhosis, the diagnosis of biliary atresia must be made before the age of 2 months. To make the diagnosis, a doctor performs a series of blood tests. Ultrasound may be helpful. If the defect is still suspected after these tests, surgery (which consists of examination of the liver and bile ducts and a liver biopsy) is performed to diagnose the defect.
Surgery is needed to create a path for bile to drain from the liver. Constructing replacement bile ducts that flow into the intestine is best, and this kind of operation is possible in 40 to 50% of infants. Most of the infants with replacement bile ducts can lead normal lives. Infants who cannot have replacement bile ducts constructed usually require liver transplantation by age 2 years.
Diaphragmatic Hernia
A diaphragmatic hernia is a hole or weakening in the diaphragm that allows some of the abdominal organs to protrude into the chest. Diaphragmatic hernias occur on the left side of the body 90% of the time. The stomach, loops of intestine, and even the liver and spleen can protrude through the hernia. If the hernia is large, the lung on the affected side is usually incompletely developed. Many children with diaphragmatic hernias also have heart defects.
After delivery, as the newborn cries and breathes, the loops of intestine quickly fill with air. This rapidly enlarging structure pushes against the heart, compressing the other lung and causing severe difficulty breathing, often right after birth. A chest x-ray usually shows the defect. The defect can also be detected before birth using ultrasound. Diagnosis before birth allows the doctor to prepare for treatment of the defect. Surgery is required to repair the diaphragm. Measures to deliver oxygen, such as a breathing tube and ventilator, may be needed.
Hirschsprung Disease
The large intestine depends on a network of nerves within its wall to synchronize rhythmic contractions and move digested material toward the anus, where the material is expelled as feces. In Hirschsprung disease (congenital megacolon), a section of the large intestine is missing the nerve network that controls the intestine's rhythmic contractions.
Children with Hirschsprung disease can have symptoms that suggest intestinal obstruction--bile-stained vomit, a swollen abdomen, and refusal to eat. If only a small section of the intestine is affected, a child may have milder symptoms and may not be diagnosed until later in childhood. These children may have ribbonlike stools and a swollen abdomen; they often fail to gain weight. In rare cases, constipation is the only symptom. Delayed passage of stool (meconium) by a newborn raises the suspicion of Hirschsprung disease.
Hirschsprung disease can also lead to life-threatening toxic enterocolitis, which produces sudden fever, a swollen abdomen, and explosive and, at times, bloody diarrhea.
A barium enema is often performed. Rectal biopsy and measurement of the pressure inside the rectum (manometry) are the only tests that can reliably be used to diagnose Hirschsprung disease.
Severe Hirschsprung disease must be treated quickly to prevent toxic enterocolitis. Hirschsprung disease is usually treated with surgery to remove the abnormal section of intestine and to connect the normal intestine to the rectum and anus. In some cases, for example, if the child is quite ill, the surgeon connects the lower end of the normal part of the intestine to an opening made in the abdominal wall (colostomy). Stool can thus pass through the opening into a collection bag, restoring normal movement of food through the intestines. The abnormal section of intestine is left disconnected from the rest of the intestine. The normal part of the intestine can be reconnected to the rectum and anus when the child is older.
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