MELANOSIS COLI - A HARMLESS PIGMENTATION OR A PRECANCEROUS CONDITION

Melanosis coli has long been considered as a harmless pigmentation of the colorectum associated with the use of laxatives containing anthraq uinone. Recent experimental and clinical studies, however, have provid ed some evidence of a possible association between melanosis coli/laxa tive use and colorectal cancer. Methods: In 2.229 consecutive patients we retrospectively analysed the association of melanosis coli and lax ative use with colorectal neoplasia. All the patients had undergone to tal colonoscopy, and the colorectal neoplasias had been examined histo pathologically in accordance with the WHO classification. information concerning laxative use, bowel habits and family history of colorectal cancer was obtained from the medical records. The statistical analysi s tvas-done using the Mantel-Haenszel-test for linear association. Res ults: The presence of colorectal cancer was not associated with melano sis coli or laxative use. However, colorectal adenomas were found sign ificantly more frequently in patients with melanosis coli than in thos e without melanosis (p = 0.0002). But adenomas associated with. melano sis coli were significantly smaller than those not associated with mel anosis (p < 0.0001), and were located predominantly in the proximal co lon (p = 0.0002). In the patients with melanosis coli the relative ris k war significantly higher for tubular (1.80; 95% CI: 1.26-2.56) and t ubulovillous adenomas (2.03; 95% CI: 1.09-3.76), but not for villous a denomas. No significant differences were found in the grade of dysplas ia of adenomas in patients with, and those without, melanosis coli. Co nclusion: There appears to be no association between colorectal cancer and melanosis coli or laxative use. Colorectal adenomas are more freq uently found in patients with melanosis coli. Colorectal adenomas do n ot contain the melanin-like pigmentation. The association of adenomas with melanosis coli can be explained by the ease of detection of even tiny polyps as white spots within a dark-colored colonic mucosa.