The gastrointestinal bleeding as cause

Black diarrhea can be caused by bleeding in the mucous membrane of the gastrointestinal tract. The location of the bleeding is most likely to be in the upper part of the gastrointestinal tract, because the blood coagulates on its way through the gastrointestinal tract and then causes the black coloration and the change in consistency of the stool due to the iron it contains. Because of these two factors it is also called tar stool.

The diagnosis is usually a mirror image of the stomach and the upper duodenum. The contraceptive pill interferes with the female hormone cycle to prevent pregnancy. Depending on the preparation and the hormone it contains, ovulation or the build-up of the lining of the womb is inhibited.

However, the hormone balance also affects other organs of the body, including the gastrointestinal tract.It can therefore happen that an already existing irritable bowel – i.e. recurrent diarrhea and constipation – is made worse by taking the pill. However, these diarrhea are usually not black. So if the color of the diarrhea differs from the color of the stool, other causes should be looked for.

Certain painkillers can also cause black diarrhea: The so-called non-steroidal antirhematics, which include Diclofenac and Aspirin®, can damage the stomach lining and cause bleeding, which turns the stool black, i.e. causes tarry stools. This is done by inhibiting a certain enzyme that is partly responsible for building up the protective mucous layer in the stomach. Without this functioning protective layer, the aggressive stomach acid can reach the surface of the mucous membrane and damage the tissue. For this reason, the additional administration of a proton pump inhibitor, such as omeprazole or pantoprazole, should be used if such drugs are taken regularly over a long period of time. These ensure a less aggressive stomach acid, which makes the mucosal defects less dangerous.

The accompanying symptoms

A persistent black diarrhea should be clarified in any case, since a bleeding and an associated defect of the gastrointestinal mucosa can be the cause. This bleeding can be assumed to be in the upper part of the gastrointestinal tract, as this is the only way to give the blood enough time to clot before it is excreted. Bleeding in the upper gastrointestinal tract is therefore different from bleeding in the lower gastrointestinal tract, as the latter is more likely to have a red, bloody coloration of the stool.

For this reason, a diagnosis will usually include a mirror image of this area, specifically the esophagus, stomach and the adjacent duodenum. All this can be done together, so there is no need for several mirror images. In addition, a detailed survey should be carried out on foods consumed, especially those that can cause black diarrhoea, and on the intake of food supplements and medication.