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Causes of Rectal Bleeding in Men

author image Dr. C. Richard Patterson
C. Richard Patterson is a retired surgeon and chief medical officer with special interest and experience in gastrointestinal, breast, cancer and trauma surgery. He is the author or co-author of 17 scientific publications, including textbook chapters.
Causes of Rectal Bleeding in Men
Doctor speaking with older man. Photo Credit: Comstock Images/Stockbyte/Getty Images

Rectal bleeding in men is caused by diseases of the rectum or other parts of the digestive tract. Rectal bleeding should be evaluated by a doctor to determine the cause. Some conditions that cause rectal bleeding are life threatening. Early diagnosis may simplify treatment and increase the chance of cure.

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Benign Diseases of the Anus and Rectum

The anus and rectum comprise the last 6 to 8 inches of the intestinal tract. Hemorrhoids are enlarged blood vessels under the lining of the anal canal. These blood vessels can cause bright red rectal bleeding. You may notice drops of blood in the toilet water or on tissue following a bowel movement. Bleeding from hemorrhoids is usually not painful and, while typically occurring in small amounts, can cause significant loss of blood. An anal fissure is a tear in the lining of the anal canal and causes bright red blood to streak the stool or appear much like hemorrhoidal bleeding. Unlike hemorrhoids, a fissure typically causes an intense pain immediately following a bowel movement.

Noncancerous Colon Disease

Diverticulosis is the development of small sacs in the wall of the colon, consisting of the lining poking through weak spots in the muscle wall of the bowel. Each sac is near a blood vessel, and hard fecal matter trapped there can erode the vessel and cause voluminous bleeding. Arteriovenous malformations are abnormalities of the colon blood vessels themselves. The involved vessels can burst and also cause substantial bleeding. Poor blood supply to the colon may also lead to rectal bleeding, as can ulcerative colitis.

Colon and Rectum Cancer

Cancer of the large intestine and rectum begins to appear in males in the teenage years and becomes more common with increasing age. After age 20, men are more likely to develop these cancerous tumors than women are. The bleeding associated with colorectal cancer may mimic that of hemorrhoids, or it may be more massive and include the passage of clots.

Anal Cancer

Anal cancer occurs in men as early as age 20, and the risk increases with age until approximately age 65. The bleeding is usually spotty, like that of hemorrhoids, and painless until the tumor advances into the surrounding tissues. Men exposed to human papilloma virus, or HPV, are at increased risk for developing anal cancer.

Bleeding From the Small Intestine

Rectal bleeding in men is very rarely caused by disease in the small bowel, such as Crohn disease, diverticulosis, poor blood supply and tumors. Your doctor will eliminate the more common causes of rectal bleeding before evaluating your small intestine.

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