A bag on the side of the anus may be due to a perianal abscess. This condition mainly occurs around the anus, rectum and anal canal, and is an acute purulent infectious disease. In the early stage of abscess, pus pockets will form around the anus with pain, and the pain will gradually increase as the disease progresses. Patients may have difficulty sleeping and eating, and may even be reluctant to eat. The abscess will break down on its own when it grows to a certain extent, and the pain will be relieved after it breaks down, which may lead to generalized fever in the patient. Generally, the treatment of perianal abscess requires surgery to completely cure perianal abscess through surgical methods such as pus extraction and decompression, abscess incision and drainage, and bi-directional equal pressure drainage. And after the surgery, you need to change the medicine regularly and strengthen the antibiotic treatment to avoid the infection of the wound, which will not heal or even form an anal fistula. Most of the recovery time for perianal abscess surgery is between one month and one and a half months, and patients need to arrange their work life reasonably.