Recognition of Melanocytes in Immuno Neuroendocrinology and Circadian Rhythms: Beyond the Conventional Melanin Synthesis 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, Figure 2 from Smokers' melanosis in a Nigerian population: Having melena in stool makes it Melenic Stool NOT Melanotic stool MELENIC MELANOTIC #MedTwitter #IMbound #EMbound #MedEd #GITwitter Oral Melanotic Macule: Symptoms and Treatment Skinsight