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Bloody or tarry stools

  • Definition

    Bloody stools often are a sign of 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.

    Alternative Names

    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, and 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.

    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 as it passes through the intestines.

    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). However, sometimes massive or rapid bleeding in the stomach causes bright red stools.

    Eating 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.

    Bleeding in the esophagus or stomach (such as with peptic ulcer disease) can also cause you to vomit blood.

    Common Causes

    The upper part of the GI tract will usually cause black stools due to:

    • Abnormal blood vessels (vascular malformation)
    • A tear in the esophagus from violent vomiting (Mallory-Weiss tear)
    • Bleeding stomach or duodenal ulcer
    • Inflammation of the stomach lining (gastritis)
    • Lack of proper blood flow to the intestines (bowel ischemia)
    • Trauma or foreign body
    • Widened, overgrown veins (called varices) in the esophagus and stomach

    The lower part of the GI tract will usually cause maroon or bright red, bloody stools due to:

    • Anal fissures
    • Bowel ischemia (when blood supply is cut off to part of the intestines)
    • Colon polyps or colon cancer
    • Diverticulosis (abnormal pouches in the colon)
    • Hemorrhoids (common cause)
    • Inflammatory bowel disease (such as Crohn's disease or ulcerative colitis)
    • Intestinal infection (such as bacterial enterocolitis)
    • Small bowel tumor
    • Trauma or foreign body
    • Vascular malformation (abnormal collections of blood vessels called arteriovenous malformations or AVMs)