The Truth About Stool Color and Digestive Health 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, When is stool color concerning? Stool Colour Chart A quick clinical guide to interpret stool color changes and their possible causes. Stool appearance can give important clues about gastrointestinal healthbut always correlate with history, examination, and Melena, Causes, Signs and Symptoms, Diagnosis and Treatment YouTube