Risk factors for adverse events related to polypectomy in the English Bowel Cancer Screening Programme

Background and study aims: The English National Health Service Bowel Cancer Screening Programme (NHSBCSP) is one of the world's largest organized screening programs. Minimizing adverse events is essential for any screening program. Study aims were to determine rates and to examine risk factors for adverse events. Patients and methods: Bleeding and perforations in NHSBCSP colonoscopies between August 2006 and January 2012 were examined. Logistic regression was used to examine risk factors for adverse events, including age, gender, polyp size, morphology, and location. For accurate attribution of adverse events, procedures with resection of only one polyp (single-polypectomy) were analyzed in detail. Results: 130831 colonoscopies (167208 polypectomies) were analyzed, including 30881 single-polypectomies. Overall bleeding rate was 0.65%, rate of bleeding requiring transfusion was 0.04% and perforation rate was 0.06%. Polypectomy increased bleeding risk 11.14-fold and perforation risk 2.97-fold. Cecal location (but not elsewhere in the proximal colon) and increasing polyp size were the two most important risk factors for bleeding and perforation. After adjustment for polyp size, the odds ratio (OR) relative to the distal colon for bleeding requiring transfusion after cecal snare polypectomy was 13.5 (95%CI 3.9-46.4) and for perforation after cecal nonpedunculated polypectomy it was 12.2 (95%CI 1.2-119.5). Conclusion: This is the largest study focusing on polyp-specific risk factors. We have confirmed that the greatest risk factor for both post-polypectomy bleeding and perforation is polyp size. This is the first demonstration of substantial and significantly increased risk for both noteworthy bleeding (requiring transfusion) and perforation from cecal polypectomy for a given polyp size, compared with elsewhere in the colon.