A mass on the left side of the anus may be a sign of a perianal abscess. A perianal abscess is an inflammatory reaction of the skin around the anus caused by bacterial infection of the anal sinus inside the anus. It usually manifests itself as a mass around the anus, which has a painful pressure and an elevated skin temperature, and a significant fluctuating sensation can be felt during the pus-forming stage, and some patients also have symptoms such as fever and chills. In case of perianal abscess, it is not recommended to treat it with conservative treatment methods. Do not hope to treat it with topical or oral medication or intravenous drip antibiotics, which may delay the disease. During the treatment process, the scope of the lesion may expand, making the later surgery more difficult, and the recovery time after surgery will be extended accordingly. It is recommended to go to the hospital for surgical treatment as soon as possible, and the standardized use of antibiotics and professional drug exchange treatment after surgery is beneficial to the recovery of perianal abscess.