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 Hematochezia vs melena: Comparing symptoms, causes, and treatment Healthy Poop Chart: Is Your Poop Normal? Nikki Yelton RD Dark Stool Causes: Understanding Color Changes 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,