Right-Sided Colonic Adenomas Are Much More Prevalent Than Left-Sided Adenomas

Abstract

Introduction: Colon cancer prevalence has been reduced since the implementation of colon cancer screening in the United States. However, there is a disproportionate risk reduction between right-sided and left-sided colon cancer after using colonoscopy as the primary tool for screening. The risk reduction after screening colonoscopy has a lesser impact for right-sided colon cancer than for left-sided colon cancer. The data analysis from our cohort population over the past 3 years suggests that the prevalence of adenomas is much higher on the right-side than on the left-side of the colon. Failure to detect and remove right-sided adenomas during routine screening colonoscopy may be the reason behind the higher incidence of right-sided colon cancer and inability to reduce the right colon cancer risk. Methods: From January 2012 to December 2014, our group collected data on 5894 colonoscopies, of which 3630 found adenoma(s). Right-sided adenomas and left-sided adenomas were recorded separately. A right-sided adenoma was defined as an adenoma found above the splenic flexure; specifically, an adenoma from the transverse colon, ascending colon, or cecum. A left-sided adenoma was defined as an adenoma found in the descending colon, sigmoid colon, or rectum. The pathology of each entry was confirmed by our staff pathologist. The types of adenomas included tubular adenomas, tubular-villous adenomas, villous adenomas, and sessile serrated adenomas. Results: Please see Table 1 and Figure 1.Figure 1Table 1: The Prevalence of Right-Sided vs. Left-Sided Colonic AdenomasConclusion: Colonoscopy is a good tool for detecting and removing colonic adenomas. The risk of colon cancer is reduced when the adenomas are found and removed. Failure to detect and remove right-sided colonic adenomas may be the reason for a higher incidence of right-sided versus left-sided colon cancer after screening colonoscopy. According to our data set, right-sided adenomas are twice as common as left-sided adenomas. More importantly, the number of adenomas are nearly three-times higher in the right colon. The average size of the largest adenoma is equivalent between the right and left colon. Therefore, it is important to pay more attention and to spend more time on detecting and removing right-sided adenomas during colonoscopy exams in order to reduce the risk of right-sided colon cancer.