GASTROINTESTINAL HEMORRHAGE (2): Melena. Melena, the passage of black, tarry stools, usually implies blood loss greater than 500 ml originating anywhere between the oropharynx and the right hemicolon. Melena occurs most often, Side by side comparison of Malignant Melanoma and Melanocytic nevi Download Scientific Diagram GASTROINTESTINAL HEMORRHAGE (2): Melena. Melena, the passage of black, tarry stools, usually implies blood loss greater than 500 ml originating anywhere between the oropharynx and the right hemicolon. Melena occurs most often, Melanocytic Lesions Basicmedical Key Recognition of Melanocytes in Immuno Neuroendocrinology and Circadian Rhythms: Beyond the Conventional Melanin Synthesis