After incision and drainage of a perianal abscess an anal fistula may form or heal depending on the location of the infection. Perianal abscess, also known as perirectal abscess, is an abscess formed by infection in the soft tissues around the rectum and anal canal or in the interstitial space around it. Common causes are anal gland infection, anal sinus infection, anorectal trauma, perianal skin infection, etc. Incision and drainage is the main method of treating perianal abscess. 1. Formation of anal fistula: for perianal abscess caused by sinus infection, anal gland infection, anorectal trauma, etc., due to the pus cavity and the anal canal or rectal connection, after the abscess incision and drainage can be narrowed to form a fistula, thus forming an anal fistula, the appearance of purulent secretion at the external mouth, perianal itching and other symptoms. 2. healed: for perianal skin infection and other causes of perianal abscess, due to the abscess of the pus cavity only in the perianal subcutaneous space, and the anus and rectum are not connected, the abscess will not form a fistula after incision and drainage, the inflammation can be cured after the dissipation of the postoperative period. Patients should actively cooperate with the doctor to carry out anti-infection treatment after the operation, such as the symptoms of anal fistula, should promptly go to the hospital for examination, the doctor according to the condition of the treatment.