Frontiers Review on melanosis coli and anthraquinone containing traditional Chinese herbs that cause melanosis coli Melena, Causes, Signs and Symptoms, Diagnosis and Treatment YouTube The patient with constipation or diarrhea 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. 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