Colorectal neoplasms in melanosis coli: a survey in Japan and a worldwide meta-analysis

Purpose: The association between melanosis coli (MC) and colorectal neoplasms remains unclear. Thus, we primarily aimed to clarify the epidemiology of MC in the Japanese population, identify the relationship between the use of anthranoids and MC, and determine the prevalence of detected intestinal lesions in patients with MC. We subsequently conducted a meta-analysis of published data, including our results, to summarize the influence of MC on the prevalence of colonic neoplasms. Methods: We conducted a retrospective survey in Japan to investigate the effects of MC on intestinal disorders. The prevalence of colorectal neoplasms and ileal ulcers was evaluated by colonoscopy, and the clinical characteristics of the participants were investigated using an electronic database. Odds ratios for colorectal neoplasms were calculated. We also performed a meta-analysis using Review Manager to reveal the comprehensive relationship between MC and colorectal neoplasms. Results: We enrolled 690 Japanese participants in the primary study. The prevalence of regular anthranoid use was significantly higher in the MC group than in the control group (50.9% vs. 6.5%, p < 0.01). Hyperplastic/inflammatory polyps and adenomas were more frequently detected in the MC group than in the control group. In a meta-analysis of five studies, a significantly higher prevalence of hyperplastic/inflammatory polyps and adenomas was reported in the MC group than in the control group, while the incidence of adenocarcinoma was not significantly different between the two groups. Conclusion: Although hyperplastic polyps and adenomas were more frequently detected in MC patients, MC was not associated with an elevated risk of colorectal cancer.