Anal fistula is the sequelae of a perianal abscess that has broken down or been drained by incision. Perianal abscess is an acute infection, while fistula is a chronic infection. A fistula has a granulomatous external opening in the perianal skin and an internal opening in the rectum at the anal gland, with a fistula between the internal and external openings. The main symptoms of fistula are recurrent pus and painful swelling around the anus, and acute infection of the fistula due to fecal material entering the fistula at the internal opening. When the pressure in the fistula increases and the external opening breaks down, the pain subsides and continues to recur. The fistula will eventually need to be treated surgically in order to be completely cured.