Melena is characterized by which of the following?

Melena is characterized specifically by the presence of black, tarry stools. This condition arises from the digestion of blood as it passes through the gastrointestinal tract, leading to the characteristic dark coloration. The black, tarry appearance is typically a result of the blood being exposed to digestive enzymes and bacteria, which alters its color due to chemical changes.

Fresh, red blood in stool is usually indicative of bleeding in the lower gastrointestinal tract and does not correlate with the term melena. Diarrhea with mucus signifies various conditions related to intestinal inflammation or infection, which do not directly pertain to the presence of digested blood. Lastly, the formation of blood clots relates to coagulation issues and does not provide any indication of melena or upper gastrointestinal bleeding.

The definition of melena highlights its association with upper gastrointestinal bleeding, commonly resulting from conditions such as peptic ulcers or varices, thereby supporting why black, tarry stools is the correct characterization.