Rectal bleeding refers to the presence of bright red blood on or in a bowel movement, on the toilet tissue after wiping, or in the toilet bowl water. It is a common problem for people of all ages.
There are many causes of rectal bleeding. The two most common causes are anal fissures and hemorrhoids. Both of these problems can be caused by constipation.
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Anal fissures are tiny tears, usually less than 1/2 inch long, in the skin of the anus. The anus is the opening through which bowel movements pass. Fissures are most often caused by hard bowel movements that tear the skin as they pass through the anus.
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Hemorrhoids are swollen veins in the lower rectum and anus. They may be external, which means they can be seen outside the anus. Or they may be internal, which means they are up inside the rectum and can't be seen without special instruments.
Diverticula in the colon are a fairly common cause of rectal bleeding in middle-aged and older adults. Diverticula are fingerlike pouches at weak points in the wall of the colon.
Other possible causes of rectal bleeding are:
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Infection in the intestines. In this case the bloody diarrhea lasts for 1 to 3 days and then is gone.
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Inflammatory bowel disease. This irritation of the lining of the colon causes abdominal pain, diarrhea, and mucus in your bowel movements as well as bleeding.
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Cancer of the rectum or colon.
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Bleeding in the upper digestive system. However, when this happens the bleeding is usually heavy and constant and is a medical emergency.
The first symptom is bright red blood on the bowel movement, the toilet tissue, or in the toilet water. You may or may not have some pain with passing the bowel movement. If you have external hemorrhoids, you may have pain when you sit.
If you have diverticula, you may have no symptoms or you may have bouts of abdominal pain.
Sometimes you may have bouts of pain with fever for a day or two if the diverticula are inflamed or infected.
When colon cancer is causing rectal bleeding, you may have diarrhea some of the time and constipation some of the time, as well as abdominal pain, weight loss, loss of appetite, and tiredness. You may have blood in your bowel movements, but it's not possible to see it. Special tests are done to detect the blood.

Often rectal bleeding is discovered with a routine screening test that can find even very small amounts of blood in a sample of bowel movement. When the sample is checked in the lab, the test may find blood that you might not have noticed otherwise.
If you have rectal bleeding, your health care provider will ask about your medical history to learn what other symptoms you may have. You will have a rectal exam to look for anal fissures, external hemorrhoids, and cancerlike masses. A sample of bowel movement may be checked for blood. Your provider may insert a small plastic tool called an anoscope an inch or two into the rectum to look for internal hemorrhoids or other causes of bleeding in the rectum.
If these exams do not find a cause for the bleeding, and especially if you are at risk for colon cancer because of your age or family history, you may have a special exam called a sigmoidoscopy or a colonoscopy. This exam with a long flexible tube and tiny camera can also be used to look for other problems such as diverticula in the colon. A special type of x-ray called a barium enema is another way to look for cancers and diverticula.
You may also have some blood tests.
The treatment for rectal bleeding depends on the cause. For simple problems such as fissures and hemorrhoids, you may need to increase the fiber in your diet and make other lifestyle changes to prevent constipation. Your health care provider will discuss with you other possible treatments if something else is causing rectal bleeding.
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When you have bleeding, see your health care provider to make sure it is not a symptom of serious disease. Rectal bleeding is not normal. If your bleeding is nonstop or in large amounts, you should seek emergency care.
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Follow your provider's instructions carefully.
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If you are not getting better, let your provider know.
Try to keep the lower intestine as healthy as possible. Eat a healthy diet with lots of high-fiber foods, such as whole grains, fresh fruits and vegetables, and drink lots of fluids. A high-fiber diet, lots of fluids, and regular exercise help the intestines work better. They help prevent constipation, hemorrhoids, diverticula, and colon cancer.