Background: Melanosis coli (MC) is a colonoscopic finding in which the colonic mucosa appears darkly pigmented than usual and generally caused by extended anthranoid laxative use.
Methods: We performed a retrospective study at Zhuhai Hospital to investigate the risk of MC for CR neoplasm development. A total of 12,776 patients who underwent colonoscopy from 2013 to 2016 including 250 diagnosed with MC and 500 controls were included in this study. Odds ratios (OR) and 95% confidence intervals (95%CI) for associations of MC with CR neoplasm detection were estimated using univariate and multivariable multinomial logistic analyses for known risk factors.
Results: The presence of MC was associated with a significant increase in the CR neoplasm detection rate compared with controls (OR = 1.701, 95% CI = 1.252-2.31; P = 0.001). The effect was also observed in different tumor sites, age group, gender, and lifestyle. Using univariate multinomial analysis, patients with MC were significantly associated with both hyperplastic polyp (OR = 2.069, 95% CI = 1.253-3.415; P = 0.005) and low-grade (LG) adenoma (OR = 1.585, 95% CI = 1.115-2.254; P = 0.010). However, there was no significant difference with adenocarcinoma (OR = 1.701, 95% CI = 0.990-2.924; P = 0.055). Using multivariate multinomial analysis, MC patients remained associated with increased hyperplastic polyp (OR = 1.870, 95% CI = 1.119-3.125; P = 0.017) and LG adenoma (OR = 1.474, 95% CI = 1.027-2.114; P = 0.035), but not adenocarcinoma (OR = 1.620, 95% CI = 0.914-2.871; P = 0.098). A significant increase in CR neoplasm rate was observed with drinker, smoker, and elderly patients but not with gender.
Conclusion: Patients with MC were more likely to have both hyperplastic polyp and LG adenoma. If confirmed, such findings could suggest the discontinuation of anthranoid laxative use particularly in the elderly.
Keywords: Colonoscopy; Colorectal adenoma; Colorectal carcinoma; Colorectal neoplasm; Melanosis coli.