Stage 1: Inflammation of the anal fossa and anal flap. This is limited to local inflammation, and if the infection is not treated in time, the inflammation can spread to the perianal area. Stage 2: Inflammation begins locally in the anal fossa and flap and gradually spreads to form perianal proctitis. If the inflammation is not controlled, it may invade into the tissue interstices with low resistance to disease. Stage 3: As the disease resistance of the perianorectal tissue gap decreases, it will become a place for germs to invade, spread and accumulate and multiply over time, resulting in easy infection and inflammation of the tissues here and the formation of perianorectal abscess. If anorectal abscess can be handled properly in the early stage, it can often make the abscess dissipate and cure without leaving sequelae; if the early treatment time is delayed or improperly handled, the tissue necrosis and pus can spread along its local gap, which will aggravate and complicate the disease, so the surgery should be performed as early as possible to open and drain the abscess, so that the pus can be drained and the development of inflammation can be controlled. The fourth stage: perianorectal abscesses break down on their own or after the incision and drainage of the change of treatment, although the abscess cavity gradually shrinks, but the ulcerated sores do not close the mouth 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 a fistula.