Melena: What Is It, Causes, Symptoms, Bleeding, Treatment, and More Osmosis Oral Melanotic Macule: Symptoms and Treatment Skinsight Retroflexions.com The Rectal Bleeding Rainbow 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 Nevi and their Association with Melanoma Cancer