Severe grade of melanosis coli is associated with a higher detection rate of colorectal adenoma.

The severity and distribution of melanosis coli differ among individuals, and the related factors remain unknown. Additionally, their clinical implications have not been sufficiently demon-strated. Thus, we aimed to detect clinical factors related to the severity and range of melanosis coli and elucidate the associations between the grade, location, and detection rate of colorectal neoplasms. Colonoscopy cases performed at our institution from January 2011 to February 2021 were included. Melanosis coli was classified into mild and severe grades. Clinical characteristics and neoplasm detection rates were compared between the mild and severe MC groups and between the right-sided and whole-colon melanosis coli groups. Overall, 236 MC (mild,  = 143; severe,  = 93) cases, of which 50 were right-sided, 5 were left-sided, and 181 were whole-colon melanosis coli cases, were enrolled. The proportion of anthranoid users was higher in the severe melanosis coli group than in the mild melanosis coli group. The adenoma detection rate was higher in the severe melanosis coli and whole-colon melanosis coli groups. The prevalence of neoplasms measuring 5-9 mm and >9 mm was higher in the severe melanosis coli group (<0.01 and  = 0.04). Severe melanosis coli due to anthranoid usage is associated with colorectal adenoma development.