Imperforate anus repair is surgery to correct birth defects involving malformation of the rectum and anus.

Normally, the large intestine (colon) empties into a pouch-like portion of bowel (rectum). Through complex nerve and muscle structures, the rectum releases stool through the anus out of the body.

Infants with imperforate anus defect, however, have malformations of the rectum and anus in which abnormal development leads to growth of skin over the anus and incomplete development of the rectum.

As a result, these infants have either no opening through which stool can pass, or a very small opening that allows only a small amount of stool to pass out of the rectum. This very small opening is often accompanied by fistulas, which are abnormal channels that connect skin to bowel.

Variations of the defect include:

• Complete absence of an anal opening
• A small tube-like opening (fistula) from the bowel to the skin, vagina, or urethra
• Rectum ends above the pelvic nerve and muscle structures (high-type imperforate anus)
• Rectum extends completely or partially through the pelvic nerve and muscle structures (low-type imperforate anus)

Surgical repair involves creating an opening for the passage of stool. Complete absence of an anal opening requires emergency surgery for the newborn.

Surgical repairs are performed while the baby is under general anesthesia.

Surgery for a high-type imperforate anus defect usually involves creation of a temporary opening of the large intestine (colon) onto the abdomen to allow passage of stool. This is called a colostomy. The baby is allowed to grow for several months before attempting the more complex anal repair.

The anal repair involves an abdominal incision, which loosens the colon from its attachments in the abdomen to allow it to be repositioned. Through an anal incision, the rectal pouch is pulled down into place, and the anal opening is completed. The colostomy may be closed during this stage or may be left in place for a few more months while the tissues heal, and closed at a later stage.

Surgery for the low-type imperforate anus (which frequently includes a fistula) involves closure of the fistula, creation of an anal opening, and repositioning the rectal pouch into the anal opening.

A major challenge for either type of defect and repair is finding, using, or creating adequate nerve and muscle structures around the rectum and anus to provide the child with the capacity to move the bowels normally.

This surgery is recommended to repair cases of imperforate anus and other anorectal malformations.