Blood in the Stool (Rectal Bleeding)

  • Medical Author:
    Jay W. Marks, MD

    Jay W. Marks, MD, is a board-certified internist and gastroenterologist. He graduated from Yale University School of Medicine and trained in internal medicine and gastroenterology at UCLA/Cedars-Sinai Medical Center in Los Angeles.

  • Medical Editor: Bhupinder S. Anand, MBBS, MD, DPHIL (OXON)
    Bhupinder S. Anand, MBBS, MD, DPHIL (OXON)

    Bhupinder S. Anand, MBBS, MD, DPHIL (OXON)

    Dr. Anand received MBBS degree from Medical College Amritsar, University of Punjab. He completed his Internal Medicine residency at the Postgraduate Institute of medical Education and Research, Chandigarh, India. He was trained in the field of Gastroenterology and obtained the DPhil degree. Dr. Anand is board-certified in Internal Medicine and Gastroenterology.

the human colon

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Diverticulitis

Diverticulosis is a condition in which the colon contains outpouchings (little sacks). Diverticula are present in a majority of people who reach the age of 50-60 years. The cause of colonic diverticula is not entirely known, but may be contributed by years of high pressure within the colon or a weakness in the wall of the colon. Diverticula are permanent, and no diet will cause them to disappear. The only way to rid a person of diverticula is to surgically remove the part of the colon that contains the diverticula. A person with diverticulosis typically has many diverticula scattered throughout the colon, but diverticula are most common in the sigmoid and descending colon.

Most people with diverticulosis have few or no symptoms. Diverticulosis is not a problem unless a diverticulum ruptures and an infection (abscess) results, a condition called diverticulitis. Diverticulitis causes abdominal pain, fever and tenderness usually in the left lower abdomen. Rarely, bleeding can occur from a diverticulum when a blood vessel inside the diverticulum is weakened by the infection and ruptures.

Bleeding from diverticulosis (diverticular bleeding) without the presence of diverticulitis is painless. Bleeding from diverticulosis is generally more severe and brisker than bleeding from anal fissures, hemorrhoids, and colon tumors. Diverticular bleeding is the most common cause of moderate to severe rectal bleeding that requires hospitalization and blood transfusions among the elderly population in the Western world.

When bleeding occurs in a diverticulum located in the sigmoid colon, the bleeding tends to be bright red. When bleeding occurs in a diverticulum located in the right or ascending colon, the bleeding may also be bright red if the bleeding is brisk and the transit through the colon is rapid; however, the color is more likely to be dark red, maroon, or, sometimes, even black (melena).

Bleeding from diverticulosis is usually brief (it stops on its own). However, diverticular bleeding tends to recur. For example, a patient may experience several episodes of rectal bleeding from diverticula during the same hospitalization. Even after discharge from the hospital, some patients who do not have the diverticula-containing part of their colon surgically removed will experience another episode of diverticular bleeding within 4-5 years.

Picture of diverticular disease (diverticulitis)
Picture of diverticular disease (diverticulitis)

Colon cancer and polyps

Tumors of the colon and rectum are growths (masses) arising from the wall of the large intestine. Benign tumors of the large intestine usually are called polyps because of their shape. Malignant tumors of the large intestine are cancers, and most are believed to have developed from polyps. Bleeding from colon polyps and cancers tends to be mild (the amount of blood loss is small), intermittent, and usually does not cause low blood pressure or shock.

Cancers and polyps of the colon and rectum can cause bright red rectal bleeding, maroon colored stools, and sometimes melena. The colon cancers and polyps located near the rectum and the sigmoid colon are more likely to cause mild intermittent bright red rectal bleeding, while colon cancers located in the right colon are more likely to cause occult bleeding that over time can lead to moderate or severe iron deficiency anemia.

Picture of the colon with colon cancer and colon polyps
Picture of the colon with colon cancer and colon polyps
Medically Reviewed by a Doctor on 5/4/2016

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