Most anal fistulas are formed when an anorectal abscess breaks down or is incised to drain the pus. The abscess gradually shrinks, but the intestinal contents continue to enter the abscess cavity, in the process of healing and shrinking, often forming tortuous cavities, poor drainage is not easy to heal, after a long time there are many scar tissue around the cavity, forming a chronic infectious pipeline. In Chinese medicine, this disease is called “hanging carbuncle”, “sitting horse carbuncle”, “dirty poison”, etc. It is mostly caused by the rupture of perianal abscesses around the rectum and the formation of granulomatous canals around the anus that do not heal over time. It occurs mostly in men aged 20-40. Anal fistulas generally consist of a primary internal opening, a fistula arm, and a secondary external opening. Most of the internal openings are located near the dentition line, mostly one, and the external openings are located on the skin around the anus and can be one or more. The main symptom is pus, the amount of pus is related to the length of the fistula, how much, the new fistula flow more pus, secretions irritate the skin and itching discomfort, when the outer mouth is blocked or false healing, pus accumulation in the fistula, local swelling and pain, and even fever, later closed fistula break, the symptoms only disappear. The main symptom is a small amount of purulent, bloody, or mucus discharge from the external orifice of the fistula. In larger high anal fistulas, because the fistula is located outside the sphincter, it is not controlled by the sphincter and often has fecal and gas discharge. Due to the stimulation of the discharge, the anal area is moist and itchy, and sometimes eczema is formed. When the external opening is healed and an abscess is formed in the fistula, it can be painful and accompanied by fever, chills, malaise and other symptoms of systemic infection. The symptoms are relieved. The recurrence of the above symptoms is the clinical characteristic of fistula. 2. Pain: When the fistula is open and there is no inflammation, there is often no pain, only localized swelling and discomfort, which increases when walking. When the fistula is swollen and inflamed due to infection or poor drainage of pus, it can cause pain. In the case of internal fistula, you often feel burning discomfort in the lower part of the rectum and the anus, and pain when defecating. 3, itching: because the pus constantly stimulates the perianal skin, often feel itching, perianal dampness and discomfort, skin discoloration, epidermal peeling, fibrous tissue proliferation and thickening, and sometimes the formation of eczema. 4, poor defecation: complex anal fistula mouth for a long time, can cause the formation of large fibrotic scar or ring-shaped strips around the anorectum, affecting the anal diastole and closure, feel difficult when defecating, with the feeling of incomplete stool. 5, systemic symptoms: in the acute inflammatory phase and repeated attacks of complex anal fistula, fever of different degrees, or with long-term chronic wasting symptoms such as emaciation, anemia and weakness may appear. Most anal fistulas are caused by perirectal abscesses, so the internal opening is mostly at the sinus on the dentate line, and the external opening is formed at the place where the abscess breaks down or is cut and drained, and is located on the perianal skin. Due to the faster growth of the external opening. The abscess often heals pseudo-chemically, resulting in recurrent abscesses breaking or incising, forming multiple fistulas and external openings. It makes simple anal fistulae into complex anal fistulae. The pruritic canal is surrounded by dense fibrous tissue, with inflammatory granulation tissue near the lumen, and the lumen may become epithelialized in later stages. Atopic inflammatory conditions such as tuberculosis, ulcerative colitis, clonorchiasis, malignant tumors, and traumatic anal canal infections can also cause anal fistulae, but are less common.