Rectal Bleeding

June 26th, 2013 by Eduardo Krajewski, MD, FACS, FASCRS

Bleeding from intestinal sources can present itself in many different ways. For example, if you pass very dark, tarry stools this is usually due to an upper source of bleeding like from the stomach or small intestine. However, if you see maroon or bright red blood or blood clots, then the source is probably from the lower intestines.

There are some exceptions to this rule. For example, with massive upper GI bleeding there can be bright red blood passed from the anus. In this article, we will learn about lower GI sources of bleeding.

Categories of Rectal Bleeding

In general, rectal bleeding can be divided into four main categories. These are:

  • Anatomic: A change in the intestinal structure that leads to bleeding, such as seen in diverticular bleeding
  • Vascular: Blood supply related problems
  • Inflammatory: Inflammatory bowel disease and infections
  • Cancers

Causes of Rectal Bleeding

The causes of rectal bleeding can vary with age. For example, in persons under 50 years of age the most common cause is hemorrhoids. The bleeding from hemorrhoids is almost always minor, although it can be startling to see a bright splash of blood in the toilet bowel or upon wiping.

Another common cause of bleeding from the rectum is diverticulosis. Diverticula are pouches that form in the colon perhaps due to the lack of fiber in the diet. If a diverticulum forms in the area of an artery, the artery becomes stretched and may even rupture. The resultant bleeding can often be very severe, even life threatening. It is not uncommon for persons to require blood transfusions to treat diverticular bleeding.

Ischemia can also cause lower gastrointestinal bleeding. This occurs when an artery gets blocked and blood flow is interrupted.

Angiodysplasia is when there is a malformation of the blood vessels. When this occurs in the colon, the malformation might be fragile and eventually break down leading to rectal bleeding.

Inflammatory bowel disease (ulcerative colitis, Crohn’s disease) can cause bleeding from the bowels as well. The inflammation and ulceration of the lining of the colon causes bleeding in these cases.

Any type of colitis, in fact, can cause lower GI bleeding. Radiation colitis, for example, is a side effect of radiation therapy where the colon was exposed to high levels of x-rays. There are also infectious causes of colitis, like salmonella poisoning. Additionally, colitis can be caused by medications such as antibiotics which can then result in rectal bleeding.

Colon Cancer and Other Miscellaneous Causes of Rectal Bleeding

It is well known that colon cancer can cause rectal bleeding. Even though this might be the thing we worry about the most, only about ten percent of all rectal bleeding is due to colon cancer. The bleeding from colon cancer tends to be of low volume, and it also tends to be recurrent.

Finally, some other causes of rectal bleeding are anal fissures and rectal ulcers. In some rare cases, ovarian cancer in women can actually be complicated by rectal bleeding symptoms. Also, any time a procedure or biopsy is taken of the large intestine, there can be post-biopsy bleeding.


As we can see, rectal bleeding can come from a large variety of sources. Some are quite harmless and other can be life threatening. In any case, if you see blood in your stool or when you wipe, you should consult with a doctor right away.

Take a look around The H Doctor website. Here you will find the most current information about hemorrhoid treatment and other digestive health topics.

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