Melaena

Melena
Classification and external resources
Specialty	General surgery, gastroenterology
ICD-10	K92.1
ICD-9-CM	578.1
MedlinePlus	003130
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In medicine, melena or melæna refers to the black "tarry" feces that are associated with upper gastrointestinal bleeding. The black color is caused by the hemoglobin in the blood being altered by digestive chemicals and intestinal bacteria.

Iron supplements may cause a grayish-black stool that should be distinguished from the black, tarlike stool that occurs from bleeding ulcer.

The origin of melena is dated to the early 19th century via modern Latin, via Greek melaina (feminine of melas, black).

The most common cause of melena is peptic ulcer disease. Any other cause of bleeding from the upper gastrointestinal tract or even the ascending colon can also cause melena. Melena may also be a sign of drug overdose if a patient is taking anticoagulants, such as warfarin. It is also caused by tumors, especially malignant tumors affecting the esophagus, more commonly the stomach and less commonly the small intestine due to their bleeding surface. However, the most prominent and helpful sign in these cases of malignant tumors is haematemesis. It may also accompany hemorrhagic blood diseases (e.g. purpura and hemophilia). Other medical causes of melena include bleeding ulcers, gastritis, esophageal varices, Meckel's diverticulum and Mallory-Weiss syndrome.

Causes of "false" melena include iron supplements, Pepto-Bismol, Maalox, and lead, blood swallowed as a result of a nose bleed (epistaxis), and blood ingested as part of the diet, as with consumption of black pudding (blood sausage), or with the traditional African Maasai diet, which includes much blood drained from cattle.

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