Melena is a term that describes a particular appearance of blood in stools. This term describes stools that are black, tarry and often foul-smelling because of the presence of blood from the upper gastrointestinal tract.iagnostic tests that might be performed include blood tests, stool cultures and X-rays. Testing the stools is important because in certain specific situations, stools can take on the appearance of melena even if no bleeding is present.