Melena an overview ScienceDirect Topics Hematochezia vs melena: Comparing symptoms, causes, and treatment Dark Stools and Abdominal Pain: A Case Study of Mr. Arnold's Course Hero 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, 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, Melena and digestive system bleeding symptoms