Foods That Cause Dark Stools and When to Be Concerned GoodRx Hematochezia vs. melena: What's the difference? UT MD Anderson 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, Black, tarry stools are NOT normal. They could be a sign of Melena upper gastrointestinal bleeding that requires urgent medical attention. Learn the difference between Melena vs Hematochezia, common The Scoop On Poop Access Health Care Physicians Melena an overview ScienceDirect Topics