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, Retroflexions.com The Rectal Bleeding Rainbow Black or Tarry Stools UF Health What does your poop colour indicate? Pay attention. There's a lot to be learned by the colour and consistency of your stools, as well as the frequency and how easily passed Stool changes healthdirect Presence of melanotic stool in terminal ileum. Download Scientific Diagram