Blood in stool

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at December 14, 2015
StartSymptomsBlood in stool

Bloody stools are a cause for concern. They may be black, maroon, or red in color and the possible causes of this type of bleeding are numerous. Getting a timely diagnosis of the location and cause for bloody stools is essential to prevent loss of blood volume. Learn the various causes of this condition and interventions that can be taken to prevent its occurrence.


Definition & Facts

Tarry or bloody stools refer to a sample of stool that is either black or dark red in color. These stools can be an indication of an injury in the gastrointestinal tract. Pain may not be present when blood is noted in the stool, however, other symptoms that may accompany this condition include diarrhea and abdominal cramps.

This condition is also referred to as rectal bleeding and is commonly evaluated and treated by gastroenterologists. A thorough history and physical exam is obtained to determine the origin of the bleeding. Other tests to determine the origin of rectal bleeding may include an anoscopy, flexible sigmoidoscopy, colonoscopy, and blood tests.


Blood in the stool can come from the stomach, duodenum, and occasionally the esophagus, which are all part of the upper gastrointestinal tract or the colon, rectum, or anus which are part of the lower gastrointestinal tract. The small intestine can also be the source of bleeding, however, this is typically infrequent.

Bleeding that occurs from the duodenum and stomach is frequently black and tarry. This type of stool is called melena and it typically occurs as a result of ulcers or a form of irritation in the esophagus or stomach. This is known as gastritis and can be the cause of bleeding. Certain medications may give stools a black appearance. These include iron supplements and bismuth-based medications.

At times, melena can result from a serious blood or circulation abnormality in the digestive system including:

When bloody stools are red in color they can be caused by several medical conditions. Bloody stools may be a result of bleeding in the lower digestive system, benign or cancerous polyps on the colon, and inflammatory bowel diseases such as ulcerative colitis, diverticulosis, and Crohn's disease. Commonly, the cause of bloody stools is the presence of hemorrhoids.

Hemorrhoids occur in the rectum or anus as a result of swollen veins and straining during a bowel movement can cause irritation and bleeding. There are also dietary causes for both red bloody stools and melena. Eating black or red foods can cause stools to have this appearance when no bleeding exists. Such foods include blueberries, dark chocolate cookies, black licorice, red-colored gelatin, red fruit punch, red wine, or beets.

When to see a doctor

As it is not normal for blood to be present in the stool, any occurrence should be reported to a healthcare professional. There are circumstances that may be considered an emergency and in the following situations medical care should be sought immediately:

  • Stools can also appear maroon colored which could indicate an upper gastrointestinal bleed or bleeding occurring in the small intestine requiring timely intervention.
  • When stools appear black and tarry this is a concern as the source of bleeding may be the stomach, esophagus, or duodenum. In patients with liver disease and/or portal hypertension who have esophageal varices, this is a serious concern as it could be a potentially life threatening situation.

Treatment & Therapy

The management and treatment of rectal bleeding includes the following:

  • Correcting low blood volume and anemia if present.
  • Diagnosing the location and cause of the bleeding.
  • Stopping active bleeding and preventing recurrence.
  • Assessing for other potential sources of bleeding to prevent future incidents.

If blood loss from rectal bleeding is moderate to severe, symptoms such as weakness, dizziness, fainting, low blood pressure, and shock may be seen. In these circumstances patients are typically hospitalized. If hospitalized, patients are treated quickly with intravenous fluids and/or blood transfusions in an effort to replace lost volume. This is done so diagnostic tests such as angiograms and colonoscopies can be safely performed to identify the location and cause of the bleeding.

Patients with chronic gastrointestinal blood loss may develop severe iron deficiency anemia. In this case, hospitalization may be necessary for blood transfusions followed by treatment with oral iron supplements. The cause of the chronic blood loss also needs to be identified so various tests will be performed as necessary.

Patients who present with mild anemia or mild rectal bleeding resulting from colon cancers, colon polyps, anal fissures, and hemorrhoids typically do not require hospitalization. This condition can be treated with oral iron supplements while various tests are performed to diagnose the cause for bloody stools.

Prevention & Prophylaxis

Some diseases that may cause rectal bleeding are preventable, however, often this is not possible. Interventions to keep the gastrointestinal tract healthy and at less risk for bleeding include monitoring food and drink intake to prevent Helicobacter pylori, a group of bacteria that may cause infections or ulcers.

These bacteria can be transmitted through contaminated food and water. Adequate hydration is necessary to prevent constipation which can lead to hemorrhoid development. Maintaining adequate fiber intake by consuming whole grains, wheat, vegetables, and fruits aids in the prevention of constipation, hemorrhoids, anal fissures, colon cancer and various other digestive problems that may cause bloody stools. Avoiding the unnecessary intake of nonsteroidal anti-inflammatory medications including naproxen, ibuprofen, meloxicam, and aspirin may aid in the prevention of ulcers and bleeding in the intestines and stomach.

Monitoring and controlling the intake of alcohol is important as excessive consumption can cause gastroesophageal reflux which can result in irritation or damage to the esophageal lining causing esophageal varices which may cause bloody stools. Also, it is beneficial to quit smoking, as smoking reduces the production of essential substances that neutralize stomach acids. This increases the acidity of the stomach which can lead to irritation and ulcers causing bloody stools.

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