What does the color of the blood say?
A distinction is made between two different types of blood in the stool: Based on these criteria, it is already possible to make an assumption about the location of the gastrointestinal bleeding source: If it is fresh blood, the source of bleeding is in the lower gastrointestinal tract, in any case behind the stomach. In the case of a tar stool, the blood has already been digested in the stomach by the aggressive gastric acid to form the so-called haematin and then decomposed by bacteria living in the intestine, giving it its dark, black colour and making it no longer liquid and light. In this case one speaks of an upper gastrointestinal bleeding.
In an upper gastrointestinal haemorrhage, the source of bleeding can be in the oesophagus, stomach and duodenum. Upper bleeding is significantly more frequent than bleeding in the lower part of the gastrointestinal tract. However, if the stomach contents are rapidly emptied into the intestine or if the acidity of the stomach acid is reduced by medication, blood from an upper gastrointestinal bleeding does not necessarily have to manifest itself as tarry stools. If blood is found in the stool, this should always be clarified by a doctor. – liquid, light (fresh) blood (haematochecia)
- Very dark, sticky and shiny stool (tarry stool/melena)
What is occult blood?
The term “occult” comes from Latin and means “hidden”. In medical terms, it means something that is not visible to the naked eye alone. Blood admixtures in the stool can also be occult.
Even if the blood is not visible, there may still be small particles of blood in the intestine, which can be detected in the stool using immunological tests. Most affected people do not visit a doctor until visible amounts of blood are found in the stool. However, intestinal cancer in particular can cause minimal bleeding, which can be detected in bowel cancer screening. From the age of 50 onwards, such a laboratory test for occult blood in the stool is recommended for all people, as the probability of bowel cancer increases at this age. However, the test results can be distorted, for example, by the consumption of bloody meat, which in the laboratory turns out to be occult blood.
What is tarry stools?
The so-called “tarry stool” is also known as “melena” in technical terminology. As the name suggests, this is a pitch-black stool with a tar-like consistency. The stool also has a similar shine to fresh tar and often has a nasty smell.
Bleeding in the digestive tract is also responsible here. Bleeding in tar stools usually occurs in the stomach, for example due to an ulcer disease. The blood is decomposed by stomach acid in such a way that the product “hematin” is formed, which is responsible for the colour and consistency.
An ulcer of the stomach is often very painful and can be caused by infections, eating habits or stress. More rarely, such black coloration of the stool can also be caused by medication or foods such as blueberries. These rather harmless causes should not be confused with an acute bleeding of the stomach.
