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What Causes Black Stool

What Causes Black Stool

What causes black stool? It may indicate presence of stomach ulcers, gastritis or intestinal issues such as Crohn's disease.
Nicks J
Did You Know?
Darkening of the stool, is pointing towards internal bleeding in the organs of upper gastrointestinal tract such as the stomach. However, in some cases, blood leaking from lower gastrointestinal tract can also cause stool to appear bright red or black.

Noticing black, tarry stools in the flush toilet bowl after defecation is a cause for concern as it is suggesting internal bleeding. When blood comes in contact with the stool, it is observed that stool color changes to black. Persistent abdominal discomfort, painful defecation, vomiting and change in bowel pattern (constipation or diarrhea) are some of the common symptoms associated with black bowel movement.
Black Stool Causes
Internal Bleeding
Internal bleeding may occur due to wide number of health issues that are often related to the stomach and the intestines. The most common causes of internal bleeding are given below:
Stomach Ulcers
As we all know ulcers are open wounds that bleed profusely when touched. Ulcers forming on the lining of the stomach or lower part of the small intestine may bleed. The blood then moves through the colon and eventually mixes with the stool, leading to black defecation.

Causes: Infection of H. pylori bacteria, indiscriminate use of anti-inflammatory medicines (ibuprofen, naproxen) and aspirin prescribed to prevent heart attacks can lead to ulceration in the stomach.
In this condition, the lining of the stomach is either inflamed or eroded. The stomach lining contain cells that secrete gastric acid to promote digestion. Hence, any damage to stomach lining is likely to cause indigestion.

Causes: Alcoholism, H. pylori infection and long term use of anti-inflammatory drugs are some of the factors that irritate the stomach lining, which may lead to gastritis.
Mallory-Weiss Tear
In this condition, the point of contact between the esophagus and the stomach is ruptured. The esophagus is the long passage that lies between the throat and the stomach. It is observed that the stomach and the esophagus are connected by a mucous membrane, which get damaged in people diagnosed with Mallory-Weiss tear.

Causes: Excessive coughing for long periods of time, violent vomiting and even retching are some of the most common causes of Mallory-Weiss tear.
Esophageal Varices
This condition is typically marked by swelling of the veins located in lower esophagus. Disturbance in blood circulation to the liver often causes the blood to move in opposite direction and accumulate in the veins of the esophagus. The veins may eventually break and leak blood that travels all the way down to the intestine and combines with the stool to give it a tarry appearance.

Causes: Liver diseases such as hepatitis or cirrhosis often due to drinking too much alcohol can disturb the blood flow to the liver and cause esophageal varices.
This is a term used to describe the inflammation of the diverticula. The large intestine is a long tubular structure where digestion takes place. Over time, sacs (pouches) protrude out of colonic wall. This abnormal bulging mass that is observed at different points on the intestinal wall is referred to as diverticula. When these diverticula are invaded by a bacterial infection, they become inflamed and may rupture. The rupturing of the diverticula eventually triggers bleeding from rectal area and causes defecation of black stools.

Causes: Although the exact cause is not identified, smoking, sedentary lifestyle, age over 40 and diet lacking in fiber increase the risk of diverticulitis.
Crohn's Disease:
Crohn's disease is typically marked by inflammation of the intestinal tract. Although any portion of the digestive system may get affected, it is usually the small or large intestine that gets swollen. Also, the inflammation is not superficial and penetrates deep into the intestinal tissues.

Causes: The exact cause is unclear but smokers and people with a family history of Crohn's disease are at increased risk of getting this inflammatory bowel condition.
Colon Cancer
Development of tumors in the colon that eventually become cancerous can also be one of the causes of black bowel movement. Tumors are nothing but abnormal protruding mass of tissue, resulting from indiscriminate division of cells. In most cases, tumors in the colon bleed and cause painful black bowel movement. Colon cancer is a serious issue and requires urgent treatment.

Causes: It is not known why people suffer from colon cancer but experts have pinned down certain risk factors, which include smoking, poor diet, lack of physical activity and chronic intestinal issues such as Crohn's disease and ulcerative colitis.
Anal Fissures
This is a painful condition associated with the anal canal. As we all know, the anal canal that lies between the anus and the rectum, has a length of 2.5 to 4 cm. The anal canal is a passage from where the stools are thrown out of the body. In this condition the lining of the anal canal gets damaged. To be more specific, it is torn and hence when hard stools pass through the anus, it causes further damage to the lining of the canal. This may lead to bleeding and is seen in the form of black stools.

Causes: Chronic constipation in which hard stools are defecated through the anal canal is the primary contributory factor in the development of anal fissures.
When the veins that are located inside the anal canal get swollen, the condition is referred to as hemorrhoids. In such cases, the inflamed veins may rupture during bowel evacuation. This bleeding in the rectal area ultimately leads to black bowel movement.

Causes: Strenuous bowel movement, pregnancy and spending a long time in the toilet are some of the common causes of hemorrhoids.
Pepto-Bismol that is prescribed for common digestion problems such as diarrhea, heartburn and nausea can also cause black bowel movement. This happens because an important constituent of this OTC drug is bismuth, which reacts with sulfur present in saliva and the intestine to produce bismuth sulfide, a black colored chemical compound. Bismuth eventually combines with stools formed in the large intestine to give them a tarry appearance. So, as long as you are taking Pepto-Bismol, there is a high probability of change in stool color.
Intake of Iron Rich Foods
Eating certain foodstuffs can also lead to black bowel movement. In such cases, change in stool color is not a cause for worry and doesn't require any visit to a doctor. Treatment generally involves minimizing the intake of these foods. Foods high in iron are the main culprits that make the stools black. People having too much intake of iron rich foods on a daily basis, produce black tarry stools. Some of the foods considered to be a good source of iron are given below:
  • Dark green leafy vegetables such as legumes and spinach
  • Fruits such as bananas, cherries, figs, blueberries and plums
  • Red meat, chicken and egg yolk
On the whole, correct diagnosis is the key to resolve the issue. X-ray of the abdominal area, colonoscopy, stool analysis and biopsy of the affected tissue are some of the diagnostic tests that may help to determine the underlying cause of black stool.
Disclaimer: The information provided in this article is solely for educating the reader. It is not intended to be a substitute for the advice of a medical expert.