A hole next to the anus is first considered to be an anal fistula. An anal fistula is a sequelae of a perianal abscess that has broken down or been cut and drained. An anal fistula has an external opening around the anus, an internal opening in the anal saphenous, and a fistula between the internal and external openings. The external orifice of the fistula is mostly granulomatous and if it breaks down and drains pus during an acute attack, a small localized hole will form. The main symptom of anal fistula is recurrent pus and pain around the anus. When the external opening is closed, the fistula is locally infected with pus and the pressure will open the external opening and pus will flow. The fistula needs to be treated surgically to be completely cured. The fistula can be divided into a low anal fistula and a high anal fistula according to the location of the fistula, while a low anal fistula can be treated by fistulotomy or fistulotomy, and a high anal fistula requires stitching.