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.

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 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 caused by ibuprofen, naproxen, or aspirin are common causes of upper GI bleeding.

Maroon-colored stools or bright red blood usually suggest that the blood is coming from the lower part of the GI tract (large bowel or rectum). Hemorrhoids and diverticulitis (inflammation of an abnormal pouch in the colon) are the most common causes of 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):

• Bleeding stomach or duodenal ulcer
• Gastritis
• Esophageal varices
• Mallory-Weiss tear (a tear in the esophagus from violent vomiting)
• Trauma or foreign body
• Bowel ischemia (a lack of proper blood flow to the intestines)
• Vascular malformation

Lower GI tract (usually maroon or bright red, bloody stools):

• Hemorrhoids
• Anal fissures
• Diverticular bleeding
• Intestinal infection (such as bacterial enterocolitis)
• Vascular malformation
• Inflammatory bowel disease
• Tumor
• Colon polyps or colon cancer
• Trauma or foreign body
• Bowel ischemia (a lack of proper blood flow to the intestines)

Call your doctor 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 workup 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:

• Is there blood on the toilet paper only?
• What color is the stool?
• When did it develop?
• Have you had more than one episode of blood in your stool? Is every stool this way?
• Are you taking blood thinners or NSAIDs (ibuprofen, naproxen, aspirin)?
• Have you ingested black licorice, lead, Pepto-Bismol, or blueberries?
• Have you had any abdominal trauma or swallowed a foreign object accidentally?
• What other symptoms are also present -- abdominal pain, vomiting blood, bloating, excessive gas, diarrhea, or fever?
• Have you lost any weight recently?

Treatment depends on the cause and severity of the bleeding. For serious bleeding, you may be admitted to a hospital for monitoring and workup. 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:

• Blood studies, including a CBC and blood differential
• Colonoscopy
• Gastroscopy or EGD
• Bleeding scan
• Angiography
• Barium studies
• Stool culture
• X-rays of the abdomen
• Tests for the presence of Helicobacter pylori infection

• Eat vegetables and foods rich in natural fiber and low in saturated fat. These may reduce constipation, hemorrhoids, diverticulosis, and colon cancer.
• Avoid prolonged, excessive use of anti-inflammatory drugs like ibuprofen, naproxen, and aspirin. These can irritate the stomach and cause ulcers.
• If you drink alcohol, do so in moderation. Large amounts of alcohol can irritate the lining of the esophagus and stomach.
• DON'T smoke. It is linked to peptic ulcers and cancers of the GI tract.
• Try to avoid too much stress -- a possible factor in peptic ulcer disease.
• Your doctor may recommend antibiotics to prevent a future bleeding ulcer if you have been diagnosed with a helicobacter infection (often related to ulcers).

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:

• Fecal occult blood testing every year.
• Flexible sigmoidoscopy or barium enema every five years.
• Colonoscopy every 10 years.

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.

Green BT, Tendler DA. Ischemic Colitis: A Clinical Review. South Med J. 2005; 98 (2): 217-222.

Cappell MS. The role of sigmoidoscopy and colonoscopy in the diagnosis and management of lower gastrointestinal disorders: technique, indications, and contraindications. Med Clin North Am. 2002; 86(6): 1217-1252.