A colonoscopy, in which a flexible, lighted instrument is inserted into the colon via the anus, is performed under conscious sedation, a type of light anesthetic.
During surgery, the physician will assess the depth and extent of the fistula tract.
Most fistulas are treated with a fistulotomy, in which the skin and muscle over the tunnel are cut open, converting it into an open groove.
The type of surgery you need will depend on where the fistula is.
If the fistula is below or crosses the lower part of the sphincter muscles, your surgeon will cut it open to the skin and leave the wound open so that it can heal with healthy tissue.
In a small number of cases, the fistula can come back.