Risk factors for recurrent high-risk polyps after the removal of high-risk polyps at initial colonoscopy

Purpose: Colonoscopic polypectomy and surveillance are important to prevent colorectal cancer and identify additional relative risk factors for adequate surveillance. In this study, we evaluated risk factors related to recurrent high-risk polyps during the surveillance of patients with high-risk polyps. Materials and Methods: We included 434 patients who had high-risk polyps (adenoma ≥10 mm, ≥3 adenomas, villous histology, or high-grade dysplasia) on the baseline colonoscopy and underwent at least one surveillance colonoscopy from 2005 to 2011 at Severance Hospital. Data regarding patient characteristics, bowel preparation and polyp size, location, number, and pathological diagnosis were retrospectively collected from medical records. Patients with recurrent high-risk polyps were compared with patients with low-risk or no polyps during surveillance. Results: Patients were predominantly male (77.4%), with a mean age of 61.0±8.6 years and mean follow-up of 1.5±0.8 years. Highrisk polyps recurred during surveillance colonoscopy in 51 (11.8%) patients. Results of multivariate analysis showed that male gender, poor bowel preparation, and a larger number of adenomas were independent risk factors for recurrent high-risk polyps (p=0.047, 0.01, and <0.001, respectively). Compared with high-risk polyps found during initial colonoscopy, high-risk polyps on surveillance colonoscopy had higher proportions of small adenomas, low-risk pathology, and fewer adenomas overall, but there was no difference in location. Conclusion: Male patients and those with poor bowel preparation for colonoscopy or higher numbers of adenomas were more likely to experience recurrent high-risk polyps.