Anal fissure, referred to as anal fissure for short, refers to a disease in which the skin of anal canal is ruptured or split in layers below the rectal tooth line, and it is a radial longitudinal ulcer (also described as spindle-shaped or oval) accompanied by chronic infection and periodic pain. The incidence of anal fissure in anorectal diseases is second only to hemorrhoids. Anorectal fistula is called anal fistula for short, commonly known as fistula, and it is also called anal leakage or sores in traditional Chinese medicine because there is liquid leaking from the anus to the outside. Anal fistula is a tube formed after the soft tissue around anus or rectum is infected and festered or artificially cut into perianal abscess. The fistula is one at the beginning, and with the development of the disease, there can be multiple pipes. It is a refractory disease in anorectal department. Anal fistula is essentially a sequela of perianal abscess. So its cause is the same as perianal abscess, that is, anal sinus infection.