What causes black stools? 17 possible conditions

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What Are Bloody or Tarry Stools?

Bloody or tarry stools refer to a stool sample that is either dark red or black in color. Bloody or tarry stools can indicate bleeding or other injuries in your gastrointestinal tract. You may also have dark, discolored bowel movements after eating dark-colored foods. Notify your doctor any time you have bloody or black-colored stool to rule out serious medical conditions.

Medical Causes of 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 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 include:

  • bowel ischemia: a reduction of blood flow to the intestines
  • vascular malformation: misshapen veins
  • varices: large protruding veins in the intestines

Medical Causes of Red, Bloody Stools

Red or bloody stools can also be caused by several different medical 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 blood 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 of Bloody- or Tarry-Looking Stools

The foods you eat can cause your stools to appear bloody or tarry. Eating red or black foods can give your feces a dark appearance without the existence of blood. Black licorice, blueberries, dark chocolate cookies, red-colored gelatin, beets, or red fruit punch are all examples of foods that can discolor your bowel movements.

What to Expect at the Doctor’s Office

Your doctor will take a medical history and perform a physical examination to determine the cause of your unusual stool color. Imaging tests such as MRIs, X-rays, and CT scans can help your doctor see the blood flow to your digestive system. These diagnostic tools will reveal any blockages that could be causing gastrointestinal (GI) bleeding.

Your doctor may schedule a colonoscopy to assess the condition of your colon. A colonoscopy is often performed under sedation. Your doctor will use a thin, flexible tube with a camera on the end to see the inside of your colon and look for the cause of your symptoms.

Treatment and Management of Bloody or Tarry Stools

Treatment of bloody or tarry stools varies according to the cause of the problem. According to the American Cancer Society, people that have hemorrhoids can ease the passage of stool and reduce bleeding by using stool softeners under a doctor’s direction (ACS). Sitz baths can also ease the pain of hemorrhoids and prevent bleeding.

Your doctor may prescribe acid-reducing medications to treat bleeding ulcers, or antibiotics and immunosuppressant drugs to calm inflammatory bowel disease and infections.

Vein abnormalities and blockages may require surgical repair if the bleeding does not stop on its own. If you have lost a lot of blood through your stool, you may be at risk for developing anemia. You may need a blood transfusion to replenish your supply of red blood cells.

Polyps on your colon that cause bloody stools can indicate precancerous conditions or cancer in some people. Your doctor will determine the appropriate treatment for these conditions. Removal of the polyps may be all that is needed in some cases. Others may require radiation therapy and chemotherapy if cancer is present.

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See a list of possible causes in order from the most common to the least.

1

Gastritis

Gastritis is acute or chronic inflammation of the protective lining of the stomach. It's often caused by the bacterium H. pylori, but can also be the result of excessive NSAID, alcohol, or cocaine consumption.

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2

Stomach Ulcer

Stomach ulcers are painful sores in the stomach lining or small intestine. They occur when the mucus that protects the stomach from digestive juices is reduced. They are curable but can become severe if not treated.

Read more »

3

Peptic Ulcer

Peptic ulcers are sores that develop in the lining of the stomach, esophagus, or rarely in small intestine. They are usually caused by H. pylori, excessive NSAID or alcohol usage, smoking, or stomach cancer.

Read more »

4

Diverticulitis

Diverticulitis occurs when the bulging sacs that usually appear in the lining of the large intestine get infected or inflamed. This usually causes abdominal tenderness on the lower left side, nausea, and diarrhea.

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5

Bleeding Esophageal Varices

This condition is considered a medical emergency. Urgent care may be required.

Bleeding esophageal varices occur when swollen veins in your lower esophagus rupture and bleed due to excess pressure. This condition is a medical emergency and must be dealt with promptly.

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6

Intussusception

This condition is considered a medical emergency. Urgent care may be required.

Most common in boys, intussusception occurs when a portion of the intestines become enfolded, causing a blockage. Symptoms include abdominal pain, vomiting, bloody stools, and others. It is potentially life-threatening.

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7

Crohn’s Disease

Crohn's disease is a chronic bowel disease that causes severe inflammation of the digestive tract. It is associated with abdominal pain, diarrhea, and may affect your quality of life. Crohn's disease is characterized b...

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8

Colitis

Colitis is inflammation of the colon, often causing discomfort and pain in the abdomen, as well as other gastrointestinal symptoms. Colitis has many possible causes, which determine the type.

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9

Alcoholic Liver Disease

Damage to the liver from excessive drinking can lead to ALD. Years of alcohol abuse cause the liver to become inflamed and swollen. This damage can also cause scarring known as cirrhosis. Cirrhosis is the final stage o...

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10

Stomach Cancer (Gastric Adenocarcinoma)

Gastric cancer, also known as gastric adenocarcinoma, is a cancer that forms inside of the stomach. It is the most common type of stomach cancer worldwide, and most commonly affects men over the age of 40.

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11

Acquired Platelet Function Disorder

Platelets are a type of blood cell. They play an important role in healing from injuries. Platelets help your body to form blood clots and stop bleeding. Some people's platelets don't function the way they should. Thi...

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12

Esophageal Cancer

The esophagus is a muscular tube that is responsible for moving food from the throat to the stomach. Esophageal cancer occurs when a malignant (cancerous) tumor forms in the esophagus lining. As it grows it can affec...

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13

Colonic (Colorectal) Polyps

Colonic polyps, also known as colorectal polyps, are growths that appear on the surface of your large intestine, or colon. You can have more than one polyp, and they may be flat or raised, benign or cancerous. Accordin...

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14

Colorectal (Colon) Cancer

Colorectal cancer is a cancer that originates in the rectum or colon. Both of these organs are located at the lower portion of your digestive system. The colon is at the end of the large intestine and the rectum is a...

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15

Enteritis

Enteritis is the inflammation of your small intestine. In some cases, the inflammation includes the stomach and large intestine.Ingesting food and water contaminated with bacteria is a leading cause of enteritis...

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16

Necrotizing Enterocolitis

This condition is considered a medical emergency. Urgent care may be required.

Necrotizing enterocolitis (NEC) is inflammation and death of intestinal tissue. It may involve just the lining of the intestine or the entire thickness of the intestine. In severe cases, the intestine may even perforat...

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17

Anthrax

This condition is considered a medical emergency. Urgent care may be required.

Anthrax is a serious illness caused by a microbe that lives in soil, called Bacillus anthracis. It became famous in 2001 when anthrax was used as a biological weapon and sent in the United States mail. The anthra...

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This feature is for informational purposes only and should not be used to diagnose.
Please consult a healthcare professional if you have health concerns.
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