Anal Fissures, Fistula, and Abscesses The lower portion of the intestinal tract is the rectum and anal canal. Several conditions affect this area and may be confused with the more widely known problem in this area, hemorrhoids. Anal Fissure An anal fissure is a small tear that develops in the lining of the anus. Anal fissures most often develop due to straining during bowel movements, which.