Melanosis Coli

Abstract

A 59-year-old man taking an oral Aloe vera supplement and with a history of colonic polyps 6 years prior, presented for a surveillance colonoscopy. From the anal verge to the ileocecal valve the colonic mucosa was diffusely darkly pigmented, consistent with marked melanosis coli. Melanosis coli is a benign condition in which macrophages in the colonic lamina propria are stained by lipofuscin pigment as a result of phagocytosis of apoptotic epithelial cells caused by exposure to plant-based anthraquinone laxatives, usually over a period of at least 2–3 months. Senna, cascara, aloe, and rhubarb supplements are some of the most common sources of anthraquinones. Neither the small bowel nor colonic polyps are stained as a result of anthraquinone exposure, as can be seen in photographs of the ileocecal valve (Figure A) and polyps (Figures B and C). The sharp contrast produced by the lack of color change in neoplastic polyp tissue can render otherwise subtle polyps more readily visible. In this patient the presence of melanosis coli aided in the detection and removal of a 10-mm flat cecal tubular adenoma and 10 additional small sessile tubular adenomas.