A lump on the side of the anus is likely to be perianal disease, paranal disease and so on. 1. Perianal diseases: mainly seen in perianal abscess, thrombosed external hemorrhoids and so on. Perianal abscess is an acute suppurative infectious disease that occurs around the anus, anal canal and rectum, the main symptom is more severe pain in the perianal area, in the perianal area can be seen in the red and swollen mass, broken pus outflow, anal diagnosis can be touched with an abscess in the mouth; thrombosed hemorrhoid is manifested in the anus outside of the protruding dark red mass, the texture of the hardness, the pain is intense. 2. Para-anal diseases: boils and carbuncles are mostly seen in the skin. Boils and carbuncles are infectious diseases of skin follicles and their sebaceous glands, manifested as red and swollen lumps on the skin, accompanied by pain, and pus can be formed if the inflammation is not controlled in time. Para-anal infections progressing gradually towards the anus in the hidden hair sinus can also present as painful lumps on the side of the anus which can interfere with normal walking. Painful lumps on the side of the anus, it is recommended to go to the anorectal department of the hospital in time to find out the cause of the disease, and give reasonable treatment to avoid delaying the condition.