An imperforate anus is a defect that happens to an unborn baby while it is still growing inside its mother. The baby develops this defect or abnormality during the fifth to seventh weeks of the mother’s pregnancy. With these defects, the anus (opening at the end of the large intestine where stool passes) and the rectum (area of the large intestine just above the anus) do not develop properly.
Imperforate anus affects 1 in 5,000 babies and is a little more common in males.
The exact cause of imperforate anus is unknown. In some cases, environmental factors or drug use during pregnancy may play a role, but no one is completely sure. Although most babies who have imperforate anus are the only ones in their family to have it, there are some cases where other family members have had it as well.
Almost 50% of babies with imperforate anus have other abnormal defects along with the imperforate anus. These commonly include:
- Spinal abnormalities, such as hemivertebra, absent vertebra and tethered spinal cord
- Kidney and urinary tract malformations, such as horseshoe kidney and duplication of parts of the urinary tract
- Congenital heart defects
- Tracheal and esophageal defects and disorders
- Limb (particularly forearm) defects
- Down syndrome
- Hirschsprung’s disease
- Duodenal atresia
During a bowel movement, stool passes from the large intestine to the rectum and then to the anus. Nerves in the anus help us feel the need for a bowel movement and start muscle activity. Muscles in this area help control when we have a bowel movement.
With an imperforate anus, any of the following can happen:
- The anal opening may be narrow or misplaced in front of where it should be located
- A membrane (covering) may be present over the anal opening
- The rectum may not connect to the anus
- The rectum may connect to part of the urinary tract or the reproductive system though an opening called a fistula, and an anal opening is not present
A number of problems can happen depending on the type and how severe the imperforate anus is, including:
- When the anal opening is narrow or misplaced in front of the correct location, a child may have a hard time passing a bowel movement, causing constipation and discomfort.
- If there is a membrane covering the anal opening, the baby may be unable to have a bowel movement until the membrane is opened with surgery.
- If the rectum is not connected to the anus and no fistula (abnormal connection between the rectum and urinary tract or vagina) is present, there is no way for stool to leave the intestine. The baby will be unable to have a bowel movement. This will cause a bowel obstruction (stool becomes trapped inside the baby).
- When the rectum is not connected to the anus but a fistula is present, stool may pass through the fistula instead of the anus. This can cause urinary tract infection.
When a baby is born, the doctor will check the baby for any problems. While the doctor is checking the baby, he or she will check to make sure the baby’s anus is open and in the correct position. If an imperforate anus is found, a number of tests may be done to better understand the problem and to see if any other problems are present.
Treatment recommendations will depend on the type of imperforate anus, the presence and type of associated abnormalities and the child’s overall health. However, most infants with an imperforate anus will need surgery.
After surgery some infants may become constipated. To avoid this, a high-fiber diet is encouraged. Laxatives may be required prior to the age of potty training. In cases of severe constipation, a bowel management program may be developed according to the specific needs of the child. The program may include child and parent education in the use of laxatives, stool softeners, enemas, and bowel training technique.
Toilet training should be started at the usual age, usually when the child is around 3 years old. Children who have had imperforate anus generally gain bowel control more slowly, and depending on the type of malformation and the operations done to repair it, some children may not be able to gain good bowel control. Each child’s situation will be slightly different and will be determined with the help of your doctor.
Children who have had an imperforate anus that have a rectoperineal fistula are usually able to gain good control over their bowel movements after surgical repair. However, those with more difficult types of anorectal malformation may need to participate in a bowel management program to help them achieve control over their bowel movements and prevent constipation.