Anal fistulas often have a history of perianal abscesses that have broken down on their own or have been incised to drain pus, after which the wound does not heal and becomes an external fistula. The main symptom is that a small amount of pus repeatedly flows from the external opening and contaminates the underwear; sometimes the pus irritates the perianal skin and causes itching. If the external opening is temporarily closed, the pus accumulates, the local area is red and swollen, there is swelling and pain, and the closed opening can be punctured again, or another new opening can be formed in the vicinity, and so on repeatedly, multiple openings can be formed and communicate with each other. If the fistula drains freely, there is no local pain and only slight swelling and discomfort, which the patient often does not mind. Wang Hao, Department of Anorectal Medicine, Guangdong Provincial Hospital