Surreptitious laxative ingestion. Delayed recognition of a serious condition: a case report

A 46-year-old man with chronic diarrhea underwent exhaustive investigations, including laparotomy, but a definitive diagnosis could not be made. It was not until a colonoscopic biopsy demonstrated the pigment of melanosis coli that the surreptitious use of laxatives was considered seriously. This diagnosis was confirmed by simple chemical tests that demonstrated phenolphthalein in the feces and urine.