Melanosis Coli in Pigs Coincides With High Sulfate Content in Drinking Water.

Melanosis coli is a well-described condition in humans, characterized by the accumulation of lipofuscin-laden macrophages in the lamina propria of the colon, giving it a dark tone. An increased apoptosis rate of colonic epithelial cells appears to be the underlying pathogenesis. In pigs, oxidative damage has been proposed as one of the causes for melanosis coli. In this article, we report a series of cases of melanosis coli in pigs affecting several finishing units in the south of Spain. Large intestines had dark green to brown pigmentation of the mucosa. Histological, histochemical, and ultrastructural studies confirmed a high number of lipofuscin-laden macrophages in the lamina propria of the rectum and colon, which additionally stained positive for the apoptosis marker cleaved caspase-3. Of note, all affected finishing units utilized water supply with a high content of sulfates, which may be one of the causes for melanosis coli development in pigs.