Melena is a medical term used to describe extremely black and “tarry”, and usually foul-smelling feces. This phenomenon is also known under the name melaena. Another similar phenomenon is known under the name hematochezia, and it is used to describe red or maroon colored feces. Melena is a serious symptom that should not be neglected, as it commonly indicates problems with gastrointestinal hemorrhage. Hemorrhaging is the loss of blood from the circulatory system. When it occurs in the gastrointestinal tract, it may indicate health problems in this body system. Sometimes, the gastrointestinal bleeding is only slight and relatively benign, but in some cases, the massive bleeding may result in decreased blood volume (hypovolemia), or shock. If this is the case, the patient’s life may be in danger.
Causes of melena
Melena generally occurs as a result of bleeding somewhere in the gastrointestinal tract. However, if the bleeding occurs in the lower gastrointestinal tract (in the rectum, for example) the feces is going to be colored in red or maroon. When the bleeding takes place anywhere in the upper gastrointestinal system (in the small intestines, for example) the stool appears dark and tarry, since there is enough time to allow for the enzymatic breakdown of blood, which results in darker color. Melena is therefore, associated with bleeding in the stomach or duodenum, and it usually appears as a symptom of peptic ulcers.
Peptic ulcers are the most common causes of melena. These are mucosal erosions of an area of the gastrointestinal tract. In most of the cases, peptic ulcers are caused by Helicobacter pylori, which is a bacterium that lives in the acidic atmosphere of the stomach. Bleeding from the peptic ulcer often results in tarry and foul-smelling stool, due to oxidized iron found in hemoglobin.
Sometimes, black stool indicates the presence of a tumor somewhere in the gastrointestinal tract, usually in the esophagus. Bleeding tumors are more common in the stomach and less common in the small intestines. Therefore, the bleeding caused by tumor usually causes red or maroon feces, and not the tarry black ones.
In some cases, the feces may appear black for some completely harmless reason. For example, if an individual eats black pudding or red beet vegetable or juice, the stool may appear dark because of the high content of iron in this food. False melena can also occur because of the iron supplements, blood swallowed because of the nose bleeding, etc.