Most of the time, passing small amounts of bright red blood from the rectum at the end of bowel movements is due to benign rectal disorders, including hemorrhoids and anal fissures (both of these conditions are much more common in people who are chronically constipated). Occasionally, an abnormality known as diverticulosis can also cause rectal bleeding. However, polyps or cancers of the rectum and colon can also cause rectal bleeding.
I would recommend that you see an experienced gastroenterologist for further evaluation, including anoscopy and, if warranted, colonoscopy.
Sincerely,
Robert A. Wascher, MD, FACS