Common causes of colon bleeding are hemorrhoids, colon polyps, colorectal cancer, ulcerative colitis and Crohn's disease, according to WebMD. Other causes of colon bleeding are diverticular disease, abnormalities in the blood vessels and ischemic colitis.
The inflammation and ulcers in the colon that cause ulcerative colitis lead to colon bleeding, says WebMD. Crohn's disease, a similar condition, causes rectal bleeding. Diverticula are pouches that form in the wall of the colon, says MedicineNet. They may bleed when they are inflamed or irritated.
Hemorrhoids are essentially enlarged veins in the colon, says WebMD. When they rupture, the resulting blood is bright red and can easily be seen in the stool or on toilet paper. Colon polyps are growths found in the lining of the large intestine. The two most common types are hyperplastic and inflammatory polyps and adenomas. Hyperplastic and inflammatory polyps are usually benign, though large ones on the right side of the colon need to be removed. Adenomas are considered precursors of colon cancer.
Abnormalities in the blood vessels in the colon also lead to bleeding, especially in older people. Ischemic colitis occurs when oxygen to the colon is cut off or reduced. This damages the cells that line the colon. The condition is also accompanied by bloody diarrhea.