Melanosis Coli El Atlas Gastrointestinal gastrointestinalatlas.com Dark stool vs black stool the difference can be serious. Dark brown stool is often food or iron related. Black, tarry stool may indicate internal bleeding and needs urgent medical attention. MALENA: Melena is the medical term for black, tarry stools caused by the presence of digested blood. It typically indicates bleeding in the upper gastrointestinal (GI) tract, such as the: Stomach Duodenum Constipation Knowledge @ AMBOSS