An anal fissure is a tear in the lining of the lower rectum (anus) that causes pain during bowel movements. Anal fissures are caused by injury to the anal canal by passing a large or hard stool, repeated diarrhea, or childbirth. In some cases, anal fissures can be caused by Crohn's disease, an inflammatory bowel disease, and fistulas near the anus. Anal fissures can be accompanied by light bleeding or a yellow discharge and may itch. Anal fissures are typically treated at home. Follow the links below to find WebMD's comprehensive coverage about the cause of anal fissures, symptoms of anal fissures, treatment of anal fissures, and much more.