Hematochezia is the passage of bright red blood from the rectum, with or without feces. It is commonly associated with lower gastrointestinal bleeding , most often due to either hemorrhoids or diverticulosis; however, it can be related to colon cancer, which is a potentially fatal illness. Hematochezia is rarely due to upper gastrointestinal bleeding, as the blood from upper bleeding is usually chemically modified by action of acid and enzymes, resulting in melena. However, since blood is a cathartic, sufficiently brisk bleeding from an upper source can be seen as hematochezia.