Benign growths or polyps of the colon are very common and are thought to be forerunners of cancer. These growths can cause either bright red blood or occult bleeding. Colorectal cancer is the second most frequent of all cancers in the United States and usually causes bleeding at some time. Inflammation from various causes can produce extensive bleeding from the colon. Different intestinal infections can cause inflammation and bloody diarrhea.
Ulcerative colitis can produce inflammation and extensive surface bleeding from tiny ulcerations.
Crohn's disease of the large intestine can also produce spotty bleeding. Finally, as one gets older, abnormalities may develop in the blood vessels of the large intestine, which may result in recurrent bleeding. The signs of bleeding in the digestive tract depend upon the site and severity of bleeding. If blood is coming from the rectum or the lower colon, bright red blood will coat or mix with the stool. The stool may be mixed with darker blood if the bleeding is higher up in the colon or at the far end of the small intestine.