Blood In Stool

Blood in stool is not a true disease; it is just a symptom accompanying a number of pathologic conditions. Usually blood in stool is not serious but it shall never be underestimated.


It is essential to distinguish finding of red bright blood from black blood. Red bright blood found in stool is called enterorrhagia and tarry black smelly blood is called melena. Blood in stool unnoticeable by naked eye is called occult bleeding.


Bright red blood is not digested and it comes from the lower part of the digestive tract. Melena is digested blood, because it comes from higher parts of the digestive tracts from anywhere between mouth and upper two-thirds of small intestine. Bleeding from lower third of the small intestine, colon and rectum causes bright red blood occurrence.


Esophageal disorders

Bleeding from the esophagus may manifest either by vomiting blood or by melena after blood passage through stomach and intestines. Bleeding can accompany serious cases of gastroesophageal reflux disease, mucous membrane tearing by Mallory-Weiss syndrome and esophageal cancer. Quite special and dangerous causes of bleeding are so-called esophageal varices. These dilated veins most often accompany liver diseases, especially liver cirrhosis complicated by portal hypertension.

Peptic ulcers

Peptic ulcers can cause long-term minor blood loss into stool that is not visible by naked, but sometimes it can cause a sudden greater bleeding. In this case, blood in stool is visible as black melena. There are often other symptoms such as abdominal pain.

Autoimmune diseases

This group consists of Crohn's disease, celiac disease and ulcerative colitis. Crohn's disease and ulcerative colitis are also known as inflammatory bowel diseases (IBDs). IBDs are usually accompanied by diarrhea, fever, abdominal pain and sometimes by mucus in stool (especially by ulcerative colitis).

Bowel infections

Blood in stool may be found especially in bacterial infections such as salmonellosis, dysentery and campylobacteriosis. Elevated body temperature, profuse diarrhea and mucus in stool are usually present.

Ischemic colitis

This is an inflammation of intestine that is caused by lack of oxygen and nutrients coming into the intestinal wall.


Diverticula are pouches protruding from intestine, they typically occur in distal colon as so-called diverticulosis. They are caused by unhealthy diet with lack of fiber. They can bleed or cause inflammation knows as diverticulitis. There is also a special type of diverticulum known as Meckel's diverticulum. It is a congenital defect of digestive tube located in the small intestine.

Radiation colitis

Radiation colitis is a chronic inflammation of the intestinal wall that is caused by radiation damage. It is usual after radiation therapy of pelvic area malignant diseases.

Colon Cancer

Colon cancer is a complex issue and really an important cause of blood in stool (usually bright red blood). The cancer is usually preceded by long period of an intestinal polyp that causes occult blood in stools. When such polyp is found during a colonoscopy, it can be easily removed. Other warning symptoms of a colon cancer include anemia, weight loss and alternating diarrhea and constipation.


These are probably the most common cause of finding blood in stool. Blood is bright red, occurs on the surface of stool and it is also present on toilet paper. If you have these symptoms, do not panic, it is probably connected to hemorrhoids.

Anal fissure

Especially acute case of anal fissure causes blood in stool and anal pain. Usually this condition accompanies constipation.

Causes outside digestive tract

We should especially mention blood clotting disorders that are either congenital (hemophilia, Von Willebrand disease) or more often obtained. Disruption of the blood clotting system is often due to the influence of anticoagulant drugs. Increased bleeding from the digestive tract can also cause non-steroidal anti-inflammatory drugs. Bleeding can occur anywhere in digestive tract.

Food-colored stool

Food can cause red or black discoloration of stool, for example blueberries and beets. Similarly, iron supplements color stool into dark-green.

Diagnostic approach

Blood in stool is usually not serious, but medical examination is advised*. Medical history should be focused on other symptoms, current medication and family history. Digital rectal examination should be always performed. Blood test can inform us about signs of anemia. Our examination should be, of course, focused of stool examination. Occult blood in stool invisible to naked eye can be detected by so-called fecal occult blood test. If there is a suspicion of upper GI bleeding, upper GI endoscopy is performed. Colon is examinable by colonoscopy. Small intestine is difficult to examine, it is possible by capsule endoscopy or double-balloon enteroscopy.


* You should be especially cautious when other symptoms accompany blood in stool. These symptoms are for example:

Jiri Stefanek, MD  Author of texts: Jiri Stefanek, MD
 Sources: basic text sources