An imperforate anus is a malformation of the rectal area that may occur in several forms. The rectum may end in a blind pouch that does not connect with the colon. This means that from the outside, what appears to be an anus is evident, but it doesn’t go anywhere. Or it may have openings to the urethra, bladder, base of the penis or scrotum in boys, or the vagina in girls. A condition of narrowing of the anus or absence of the anus may be present. Typically, there are two types of imperforate anus:
The “high type” means that no opening is present on the outside of the child’s body, and the bowel ends above the muscles at the bottom of the pelvis.
The “low type” means that the bowel ends below the muscles of the pelvis and there is an opening present, but it is in an abnormal position or is covered by a layer of skin or other type of membrane.
The malformations are caused by abnormal development of the fetus, and many are associated with other birth defects. Imperforate anus is a relatively common congenital malformation that occurs in about one out of 5,000 infants. It is not the fault of the mother; the cause is unknown.
Symptoms may include the absence of an anal opening, or one in the wrong area, such as very close to the vaginal opening in females, and no stool within 24 to 48 hours after birth, or stool that comes out of the vagina, the base of the penis, urethra (where you urinate) or scrotum. Parents also may notice a swollen abdomen.
To diagnose this, the doctor may physically examine the child. He or she also may order a lower abdominal X-ray or enema to see whether fluid inserted into the anus is moving up into the small intestine.
The treatment is surgery. The “low type” may involve opening the thin membrane of skin or other tissue in surgery, repeated stretching of the opening, or surgical reconstruction.
The “high type” is treated by creating a temporary colostomy (re-routing the bowel out the abdominal wall). The baby then has bowel movements into a bag. At about six to 12 months, surgical rebuilding of an anal opening is completed, and any possible fistula is closed. The colostomy is removed a few weeks later.
Surgery usually is successful, but these children frequently are constipated. In these children, a bowel management program is recommended.
For an appointment with a Washington University pediatric surgeon, call (314) 454-6022, Monday-Friday, 8 a.m.-5 p.m.