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, Your Poop Is Talking .. Are You Listening? Your stool is your gut's daily report card. The shape, color, and texture tell you exactly what's going on inside. Here's a quick doctor style Hematochezia vs. melena: What's the difference? UT MD Anderson Hematochezia vs melena: Comparing symptoms, causes, and treatment A Quick Guide to Stool Color and What They May Mean NaturWarriors