Definition: Anorectal infection (pararectal infection) refers to the infection located in the lower part of the anal canal and rectum and the surrounding tissues, and is generally divided into three stages: 1. anorectal saphenous stage. 2. anorectal abscess stage. 3.Anal fistula formation stage. Causes: When diarrhea is present, dilute stool can easily enter the anal saphenous fossa, and when stool is dry, it can easily cause the intestinal mucosa to tear, and intestinal bacteria can enter the anal. The glandular ducts and thus the anal glands, and through the tubular branches of the glands, spread to the perirectal spaces of the anal canal, forming abscesses in various parts. Due to the presence of primary foci of infection, abscesses often fail to heal on their own and form anal fistulas after self-rupture or incision and drainage of pus. The development of anal infection does not necessarily follow the three stages mentioned above, but is related to the strength of the body’s resistance, the size of bacterial virulence and the timeliness of diagnosis and treatment. If the resistance of the body is low, the virulence of the bacteria is strong, and the treatment is not timely, it is possible to develop according to the above three stages. However, the development of the disease can be controlled by paying attention to the characteristics of each stage of development, early diagnosis and treatment. If the disease is actively treated at the stage of anorectal fossa inflammation, it may not develop into perianorectal abscess, but if anorectal abscess is formed, it should be incised and drained early. Therefore, the lesion should be controlled at the early stage as much as possible to avoid the formation of abscess or anal fistula.