What is Anorectal Abscess? An anorectal abscess is a collection of pus in the anal or rectal region. What are the causes of anorectal abscess? Infection of an anal fissure, sexually transmitted infections, and blocked anal glands are common causes of anorectal abscesses. Deep rectal abscesses may be caused by certain intestinal disorders. What are the following factors, which increase your risk for an anorectal abscess? Diabetes, A weakened immune system, engaging in anal sex, inflammatory bowel disease (Crohn's disease and ulcerative colitis) What is the treatment? Commonly done surgeries are Incision and drainage of perianal abscess, Incision and drainage of ischiorectal abscess.