Melena an overview ScienceDirect Topics Foods That Cause Dark Stools and When to Be Concerned GoodRx Different stool colours can provide important clinical clues related to digestion, bleeding, liver disease, malabsorption, infection, or bowel inflammation. Disclaimer For educational purposes only. Not medical advice. Consult a qualified 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 vs hematochezia symptoms and differences Hematochezia vs melena: Comparing symptoms, causes, and treatment