Digestion

Black Stools in Adults – Causes of Black Stools in Adults

Black stool in elderly people is always taken seriously in most of cases. But it may also be a temporary occurrence, resulting from consumption of certain medicines, nutrition supplements or dyed foods. Black stool is not always alarming in adults unless it is found persisting over a few days. Black, tarry, smelly stools are called melena. Melena is the result of an internal bleeding in the upper portion of the digestive tract (esophagus, stomach or small intestine). So common terms, black stool in adults can be considered as an indicator of an injury or disorder within the digestive tract.

Where does blood come from?

  • Blood can flow from any part of the digestive system. Staring from mouth to anus, any injury in any of the part can result in excretion of bloody stools.
  • Blood may be present in our stool most of the time, but its minute quantity is often invisible to the eyes. But when the presence of blood increases in the stool, it becomes in the form of bloody, black, red or maroon, green or clay colored stools.
  • The amount of blood in the stool increases with the amount of bleeding.
  • Fecal occult blood test can be done to detect presence of blood even in minute quantities in the stool.
  • Endoscopic tests or special X-ray tests are done to diagnose the exact size, cause and location of the bleeding.
  • In case of black stools, it is believed that that the blood flows from the upper part of the GI tract.

Why does the blood appear black?

  • The blood is often reddish in color, but the appearance of black colored stool due to the presence of blood in it is not convincible.
  • The blood appears black when the blood is retained within the body for a longer period before excretion.
  • Sometimes, the iron present in the hemoglobin of the blood gets oxidized while passing through the ileum. This can also blacken the blood.
  • The tarry appearance of the stool is due to the exposure and mixing of several digestive juices with the blood.

Common causes of Black Stool in Adults

Foods –

  • Consuming black licorice, blueberries can often turn the color of the stool.
  • Medicines containing lead or bismuth compounds (like Pepto-Bismol) can also make the stool black in adults.

Bleeding causing black stools in adults –

  • Bleeding ulcers in the stomach or duodenal ulcer
  • Gastritis
  • Esophageal varices
  • Mallory-Weiss tear (violent vomiting may cause tear in the esophagus)
  • Trauma or foreign body
  • Bowel ischemia (improper supply of blood to the intestines)
  • Vascular malformation

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