Advancement flap for coverage of an anorectal fistula

This is a schematic diagram of creating an advancement mucosal flap. A probe is inserted from the external opening of the fistula to the internal opening. The fistulous tract is curetted and debrided. The flap includes mucosa, submucosa, and a portion of the sphincter muscle fibers and is advanced to cover the internal primary opening. The lateral view shows the fistulous tract and the components of the advancement flap.