Pain in the caudal vertebrae with anal swelling and discomfort. The most common cause of this condition is perianal abscess. The infection is caused by the perianal area and causes compression of the surrounding tissues. This can cause pain in the caudal vertebrae and discomfort around the anus. After a perianal abscess breaks down, pus flows out and can cause an anal fistula. The treatment of perianal abscess is mainly based on surgery. Surgery to cut open the abscess, release the pus, and find the internal opening to hang a wire is beneficial to treatment and to reduce the recurrence in the future.