Blood in the stool - these are the causes!


If you notice blood in your stool when you go to the toilet, many people are often afraid. Often one of the first thoughts goes in the direction of cancer of the bowel. What they forget is that blood in the stool can be caused by numerous other common causes.

If there is blood in the stool, attention should be paid to the color of the blood. Dark blood is more likely to indicate a disorder in the upper part of the gastrointestinal tract, whereas light blood is more likely to indicate a disorder of the lower part. In any case, it is certain that the occurrence of blood in the stool should be clarified by a doctor in order to clarify a cause which in some cases is malignant.

Causes of blood in the stool

These causes can exist

  • hemorrhoids

  • Inflammatory bowel disease

  • Infections of the intestines

  • Stomach ulcer or duodenal ulcer

  • Inflammation of the esophagus

  • Stomach cancer

  • Colon cancer

  • Diverticula or polyps

  • Medication


Hemorrhoids in the area of ​​the anus can, depending on their location and size, lead to blood in the stool. These are usually bright red because the blood is relatively fresh. The cause of the bloody additions is a direct mechanical irritation of the hemorrhoid surface during bowel movements. Haemorrhoids should be examined by a doctor in the event of long-term occurrence, as they represent a risk factor for colon cancer.

If you would like more information on this topic, we recommend our website: hemorrhoids


As a symptom, diarrhea can be caused by various diseases in combination with blood in the stool. An example of this can be antibiotics that change the surface of the mucous membrane of the intestine, which allows other pathogens to lodge. Another possibility are long-term effects in the context of colon cancer.

Result of antibiotics / pseudomembranous colitis

If antibiotics are taken for a long time, as is the case with pronounced pneumonia, for example, the intestinal mucosa is damaged. This is mainly used by the clostridial pathogens to establish themselves in the intestine. Characteristic symptoms of this infection are so-called pseudomembranous diarrhea, which can also be bloody.

Gastric ulcer / duodenal ulcer

With an ulcer of the stomach or duodenum, so-called ulcerative changes in the mucous membrane occur. This means that there is a defect in the surface, which means that it can no longer fulfill its normal function. This condition is also known as an ulcer. Often there is pain in the upper abdomen at first, but it can also lead to blood in the stool. This is mostly caused by the Helicobacter pylori bacterium, but in less common cases also by medication or stress. The treatment focuses on reducing the acid production of the stomach through medication.

Further information on this topic can be found at: Gastric ulcer

Inflammation in the esophagus

Inflammation of the esophagus (Esophagitis) usually occurs in the context of gastroesophageal reflux disease. Rising stomach acid causes inflammation of the mucous membrane in the esophagus. This often manifests itself as heartburn, which occurs mainly at night and often in combination with a feeling of pressure and belching. However, it can also lead to blood in the stool, which is usually dark in color. Acute esophagitis can be treated with drugs by inhibiting gastric acid secretion.

For more information, please also read: Esophagitis

Mallory-White Syndrome

Mallory-Weiss syndrome is an increasing number of cracks in the mucous membrane at the transition area between the esophagus and the stomach. This typically induces vomiting at first. Later on there are upper abdominal pain, bloody vomiting and bloody stools. Mallory-Weiss syndrome can usually be treated well by gastroscopy with hemostasis, usually without complications.

Further information on this topic can be found at: Mallory-White Syndrome

Liver disease with portal hypertension

Chronic liver disease causes high pressures in the venous portal vein system so that, in the long run, venous outflow from the intestine into the liver becomes increasingly difficult. It can happen that the venous blood - due to the high pressure - flows from the portal vein in the direction of the intestine, i.e. changes direction. This leads to overstressing of the vessels in some places, which are not aligned for this high pressure. These spots are mainly in the esophagus and anal canal. Depending on the location, this can lead to dark or light-colored blood in the stool.

Crohn's disease

Crohn's disease is one of the most common forms of inflammatory bowel disease (IBD for short). The entire gastrointestinal (= gastrointestinal tract) area is affected, which is usually not continuous. The disease often manifests itself through unwanted weight loss, lower abdominal pain, usually one-sided on the right side and through very frequent diarrhea. The latter symptom in particular causes severe irritation of the intestinal mucosa, which can lead to small tears with blood in the stool as a result.

For more information, also read: Crohn's disease

Ulcerative colitis

Alongside Crohn's disease, ulcerative colitis is one of the most common chronic inflammatory bowel diseases (IBD for short). This leads to an inflammation of the intestinal wall due to an unexplained cause, in some cases antibodies can also be detected. The clinical picture typically manifests itself as diarrhea, which is mainly bloody and slimy and often occurs in combination with abdominal pain and fever. Furthermore, severe pain can occur when there is an urge to defecate.

For more information, see: Ulcerative colitis

Intestinal polyps

Colon polyps are bulges in the lining of the bowel. These are very common in the elderly and can remain completely symptom-free and may not be detected. As a possible symptom, stool may appear slimy and bloody. Other changes in stool behavior can also occur. Constipation or diarrhea can occur. If colon polyps are discovered during a colon mirror, they should be removed due to the risk of degeneration into malignant tumor tissue.

Read more on this topic at: These are the symptoms that help you recognize colon polyps


Diverticula in the intestine are protrusions from layers of intestines into the lumen of the intestine. Since this remains symptom-free for a long time, the first sign is often a stool of blood that is caused by severe irritation of the diverticula. If there are frequent diverticula in the intestine, this is called diverticulosis - the chronic form of diverticula. If the diverticula are inflamed, one speaks of diverticulitis, which may have to be treated surgically, depending on the complication rate.

For more information, see: Diverticulosis

Stomach cancer

There are many different symptoms that can occur with cancer of the stomach. The symptoms are often only noticeable in later stages, as in the early stages there are often only unspecific abdominal pain, a feeling of fullness and a possible aversion to meat. Vomiting and dark blood in the stool occur in later stages. Therapeutically, stomach cancer is treated surgically or with chemotherapy, depending on the stage.

If you are interested in more information on this topic, we also recommend: Stomach cancer

Small bowel cancer

Small bowel cancer is a very rare type of cancer and therefore not a common cause of blood in the stool. If there are tumorous changes in the small intestine, these can lead to various disorders in the gastrointestinal tract-related area. These include constipation, diarrhea, abdominal pain, and stool with blood that usually appears as a dark additive. Tumorous changes in the rear section of the small intestine lead to more blood in the stool than in the front section.

Further information on this topic can be found at: Small bowel cancer

Mesenteric infarction

Mesenteric infarction is a highly acute and life-threatening clinical picture with rupture of an important abdominal vessel. This manifests itself in the first six hours as cramp-like abdominal pain, vomiting and diarrhea. Later there is the appearance of blood in the stool and a decrease in the previously increased bowel movements. If surgery is not taken at this stage at the latest, this means that sections of the intestine will die off, which can be life-threatening for the person concerned.

Causes of blood in the stool without pain

If blood appears in the stool without additional pain, this should always be clarified by a doctor. Most often, pain associated with blood in the stool is an expression of inflammation or irritation of a section of the gastrointestinal tract.

Painless admixture of blood, on the other hand, can be an expression of a malignant change in the intestinal mucosa with a tendency to develop colon cancer. However, it can also be a question of diverticula, which depending on the location, like intestinal polyps, do not necessarily have to trigger pain in the abdominal area. To clarify this, if blood appears in the stool without the associated pain, it should be documented exactly what the stool and blood look like and how much blood is with each stool. This should be passed on to the doctor as important information for the search for the cause.

Causes of bright red blood

If there is light red blood in the stool, it is usually a sign of a cause that is in the lower part of the digestive tract. Hemorrhoids are often responsible for the bright red fresh blood deposits. However, deep-seated intestinal polyps or diverticula or a chronic inflammatory bowel disease are also possible causes.