Surgery is necessary to cure an anal fistula. Although fistula surgery is usually relatively straightforward, the potential for complication exists, and is preferably performed by a specialist in colon and rectal surgery. It may be performed at the same time as the abscess surgery, although fistulae often develop four to six weeks after an abscess is drained sometimes even months or years later. Fistula surgery usually involves cutting a small portion of the anal sphincter muscle to open the tunnel, joining the external and internal opening and converting the tunnel into a groove that will then heal from within outward. Most of the time, fistula surgery can be performed on an outpatient basis – or with a short hospital stay.