Anal fistula is a common disease in anorectology. At the beginning, a hard node is often felt around the anus, which is red, swollen and painful, and in severe cases, it is accompanied by fever and other systemic symptoms. The development of anal fistula is divided into 4 main stages: 1. Inflammation of the anal fossa and flap. At the beginning, the inflammation is limited to localized inflammation, with localized redness, swelling and hardness, and hot and painful surface. 2. Inflammation starts from the local anal fossa and anal flap, and gradually spreads to form perianal proctitis. If the inflammation cannot be controlled, it may invade the perianal tissue gap with low resistance to disease causing the infection to expand. 3, because the perianorectal tissue gap of resistance to disease is reduced, it becomes the place where germs invade, spread, accumulate and multiply, resulting in the easy infection and inflammation of the tissue here, forming perianorectal abscess. If anorectal abscess can be handled properly in the early stage, the abscess can often be dissipated and cured without leaving sequelae; if the early treatment time is delayed or improperly handled, the tissue necrosis and pus can spread along its local gap, making the condition aggravated and complicated. 4, perianal abscess broke by itself or by incision and drainage after drug exchange treatment, although the abscess cavity gradually reduced, but the ulcerated sores are not closed for a long time, the cavity wall has formed a hard pipe wall of connective tissue hyperplasia, the gap left in the middle, which is the fistula, pus often flows out from the fistula, repeated infection, recurrent episodes, can not heal themselves, and become fistula. Anal fistulas do not heal naturally. The actual fact is that you can find a lot of people who are not able to get a good deal on a lot of things.