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Causes of Black Stool

Black stool isn't always due to a big problem. There are many reasons stool could appear black, and iron supplements or even coffee could be to blame. This is especially true for people who have had ostomy surgery or a colectomy, because food is not being digested as fully as it is in people who have not had any abdominal surgery. However, if you have had gastrointestinal bleeding in the past, there is a foul smell, or the problem goes on for longer than a few days, that's a good enough reason to see your doctor.

Causes

Black, Tarry Stools

Bleeding in the upper portion of your digestive system can cause black, tarry stools. Ulcers or another form of irritation in your esophagus or stomach known as gastritis can often cause bleeding. When the blood mixes with digestive fluids, it takes on the appearance of tar. Certain medications can also lead to black-colored stools. Iron supplements and bismuth-based medications, for example, can darken your stools. Sometimes, serious blood and circulation abnormalities in your digestive system can cause black, tarry stools. These can include the following:

  • Bowel ischemia is a reduction of blood flow to the intestines.
  • Vascular malformation is misshapen veins.
  • Varices are large, protruding veins in the intestines.

Red, Bloody Stools

Red or bloody stools can also be due to several different conditions. Your stools may be bloody due to bleeding in the lower half of your digestive system. Cancerous or benign polyps on your colon can produce gastrointestinal bleeding in some cases. Inflammatory bowel diseases such as diverticulosis, ulcerative colitis, and Crohn’s disease may cause you to expel bright red or maroon-colored blood in your stool. A common cause of bloody stools is the presence of hemorrhoids. Hemorrhoids are swollen veins located in your rectum or anus. Straining to produce a bowel movement can cause bleeding. Blockages at any point in your digestive tract can cause black, tarry, or bloody stools.

Dietary Causes

The foods you eat can cause your stools to appear bloody, black or tarry. Eating red or black foods can give your feces a dark color without the existence of blood. The following can discolor your bowel movements:

  • black licorice
  • blueberries
  • dark chocolate cookies
  • beets
  • red fruit punch

Symptoms

Black stools are a worrisome symptom because it may be due to a large amount of bleeding into the GI tract, most often from the upper GI tract including the esophagus, stomach, and duodenum. Red blood cells are broken down by digestive enzymes in the intestine and turn the stool black. These stools tend to be tarry (sticky), and very bad smelling. This can be a medical emergency and black tarry stools should not be ignored. Blood from nosebleeds or from dental procedures or mouth injuries can be swallowed and may be the cause of black stool.

Treatment

The treatment of bloody, black or tarry stools varies according to the cause of the problem. According to the American Cancer Society, people with cancer who have hemorrhoids can ease the passage of stool and reduce bleeding by using stool softeners under a doctor’s direction. Sitz baths can also ease the pain of hemorrhoids and prevent bleeding. Your doctor may prescribe acid-reducing medications to treat bleeding ulcers. Antibiotics and immunosuppressant drugs can also calm inflammatory bowel disease and infections. Vein abnormalities and blockages may require surgical repair if the bleeding doesn’t stop on its own. If you’ve lost a lot of blood through your stool, you may be at risk of developing anemia. You may need a blood transfusion to replenish your supply of red blood cells.

Consult your doctor if you're concerned about your stool color. If your stool is bright red or black, which may indicate the presence of blood, seek prompt medical attention.