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Bloody stools often indicate an injury or disorder in the digestive tract. Your doctor may use the term "melena" to describe black, tarry, and foul-smelling stools or "hematochezia" to describe red- or maroon-colored stools.
Stools - bloody; Hematochezia; Melena; Stools - black or tarry
Blood in the stool may come from anywhere along your digestive tract, from mouth to anus. It may be present in such small amounts that you cannot actually see it, but it is only detectable by a fecal occult blood test. When there IS enough blood to change the appearance of your stools, the doctor will want to know the exact color to help find the site of bleeding. To make a diagnosis, your doctor may use endoscopy or special x-ray studies.
A black stool usually means that the blood is coming from the upper part of the gastrointestinal (GI) tract. This includes the esophagus, stomach, and the first part of the small intestine. Blood will typically look like tar after it has been exposed to the body's digestive juices. Stomach ulcers or inflammation caused by ibuprofen, naproxen, or aspirin are common causes of upper GI bleeding.
Maroon-colored stools or bright red blood usually suggests that the blood is coming from the lower part of the GI tract (large bowel, rectum, or anus). Hemorrhoids and diverticulosis (an abnormal pouch in the colon) are the most common causes of lower GI bleeding. Abnormal collections of blood vessels called arteriovenous malformations (AVMs) and tumors in the intestine may also cause lower GI bleeding. However, sometimes massive or rapid bleeding in the stomach causes bright red stools.
Consuming black licorice, lead, iron pills, bismuth medicines like Pepto-Bismol, or blueberries can also cause black stools. Beets and tomatoes can sometimes make stools appear reddish. In these cases, your doctor can test the stool with a chemical to rule out the presence of blood.
Brisk bleeding in the esophagus or stomach (such as with peptic ulcer disease), can also cause you to vomit blood.
Upper GI tract (usually black stools):
Lower GI tract (usually maroon or bright red, bloody stools):
Call your doctor immediately if you notice blood or changes in the color of your stool. Even if you think that hemorrhoids are causing blood in your stool, your doctor should examine you in order to make sure that there is no other, more serious cause present at the same time.
In children, a small amount of blood in the stool is usually not serious. The most common causes are constipation and milk allergies. But it is still worth reporting to your doctor, even if no evaluation is necessary.
Your doctor will take a medical history and perform a physical examination, focusing on your abdomen and rectum.
The following questions may be included in the history to better understand the possible causes of your bloody or dark stools:
Treatment depends on the cause and severity of the bleeding. For serious bleeding, you may be admitted to a hospital for monitoring and evaluation. If there is massive bleeding, you will be monitored in an intensive care unit. Emergency treatment may include a blood transfusion.
The following diagnostic tests may be performed:
The earlier you detect colon cancer, the more likely that treatment will be successful. The American Cancer Society recommends one or more of the following screening tests after age 50 for early detection of colon cancer and pre-cancer:
Screening tests should be started earlier if you have a family history of colon cancer or polyps. Tests should also be performed more often if you have had polyps, colon cancer, or inflammatory bowel disease.
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Overton DT. Gastrointestinal bleeding. In: Tintinally JE, Kelen GD, Stapczynski JS, Ma OJ, Cline DM, eds. Emergency Medicine: A Comprehensive Study Guide. 6th ed. Columbus, OH:McGraw-Hill;2006:chap 74.