Risks associated with colonoscopy in a population-based colon screening program: an observational cohort study

BACKGROUND: The risks associated with colonoscopy performed through the British Columbia Colon Screening Program (BCCSP) are not known. We aimed to determine the rate of colonoscopy-related serious adverse events within this program. METHODS: For this prospective observational study, we used the BCCSP database to identify participants 50 to 74 years of age who had a positive result on fecal immunochemical testing (FIT) between Nov. 15, 2013, and Dec. 31, 2017, followed by colonoscopy. Unplanned medical events were recorded at the time of colonoscopy and 14 days later. We reviewed the unplanned events and defined them as serious adverse events if they resulted in death, hospital admission or intervention; we also classified them as probably, possibly or unlikely related to the colonoscopy. The primary outcome was the overall rate of serious adverse events; the secondary outcomes were 14-day post-colonoscopy rates of perforation, bleeding and death. RESULTS: During the study period, a total of 96 192 colonoscopies were performed by 308 physicians at 50 sites. The median age of patients was 62 (10th–90th percentile 52–71) years, and 56% were male. Of these, 78 831 patients were contacted after the colonoscopy. Serious adverse events were deemed to have occurred in 350 colonoscopies (44 per 10 000, 95% confidence interval [CI] 39–50 per 10 000), with a number needed to harm of 225. Of the 332 (94.9%) serious adverse events that were probably or possibly related to colonoscopy, perforation occurred in 6 (95% CI 5–8) per 10 000 colonoscopies, bleeding in 26 (95% CI 22–30) per 10 000 colonoscopies and death in 3 (95% CI 1–10) per 100 000 colonoscopies. INTERPRETATION: The rate of serious adverse events associated with colonoscopy in the BCCSP was in keeping with previous publications and met accepted benchmarks. The findings of this study inform stakeholders of the risks associated with colonoscopy in an FIT-based colon screening program.