Bleeding from the GI tract does not necessarily cause black stools; some patients will pass bright red blood stools, depending on the location of the bleeding and how quickly it occurs. The GI tract is very long, from the stomach, duodenum, small intestine, colon, and rectum are all part of the GI tract, and bleeding anywhere will change when the patient has a bowel movement. If bleeding is caused in the stomach or duodenum or small intestine, most patients present with black stools, that is, black stools during defecation. If there is a small amount of bleeding from the colon and chronic blood loss, the patient passes black stools, and if there is more and faster bleeding from the colon, the patient passes bloody or soy sauce-colored bloody stools. If the rectum causes bleeding, such as rectal cancer causing bleeding, most patients have bloody stools that are bright red.