Right-side shift of metachronous colorectal adenomas after polypectomy

In our previous study, we showed that the development of adenomas in the right-side colon increased with aging in subjects with no colorectal neoplasms. The aim of the present study was to investigate the location of metachronous colorectal adenomas after endoscopic polypectomy.

The records of a colonoscopic follow-up study on 2900 subjects after polypectomy were analyzed. The location was classified as the right-side colon and left-side colon at the splenic flexure. Subjects were classified into three groups according to distribution of adenomas at the initial two colonoscopies: those with adenomas located only in the left side (LL), adenomas in both the left side and right side (LR), and adenomas only in the right side (RR). Distribution of initial and metachronous adenomas was evaluated according to age.

The annual incidence rates of colorectal adenomas in the left-side colon were estimated to be 8.56%, 11.2%, and 5.71% in the LL, LR, and RR groups, respectively. The rates in the right side were 5.91%, 15.5%, and 9.38%, respectively. The incidence rates in the left side in the age groups <40, 40-49, 50-59, and > or =60 years were 6.93%, 8.08%, 8.33%, and 8.48%/year, respectively. Those in the right side were 4.91%, 7.27%, 9.86%, and 12.41%/year, respectively.

Although there may be individual predilection for right-side or left-side location of colorectal adenomas, aging tends to increase the number of adenomas in the right-side colon, while only modestly affecting those in the left-side colon.