RESUMO
BACKGROUND: Screening by means of biennial fecal occult blood test has provided a reduction in overall colorectal cancer mortality. Notwithstanding, we should not underestimate the harms that it can produce. AIM: The aim of this article is to identify the independent risk factors of complications after a screening colonoscopy. METHODS: A six-year, nested case-control study was conducted. Mortality/complications within 30 days after colonoscopy were registered and its predictors identified through logistic regression. RESULTS: After 39,254 colonoscopies, the complication rate was 1.0%. Independent predictors were sex (OR 1.68 for men; CI 95% 1.18-2.39), ASA physical status classification system (OR 1.73 for ASA II-III; CI 95% 1.53-3.69), history of abdominal surgery (OR 2.37; CI 95% 1.72-4.08), diverticulosis (OR 2.89; CI 95% 1.94-4.30), inadequate cleansing (OR 29.35; CI 95% 6.52-132.17), detection of advanced neoplasia (AN) (OR 4.92; CI 95% 3.29-7.36), detection of stage I adenocarcinoma (OR 9.44; CI 95% 4.46-20.0), polyps in right colon OR 2.27 CI 95% 1.38-3.74) and complex polypectomy (OR 2.00; CI 95% 1.25-3.20). The logistic model explained 82% of the complications (CI 95% 0.798-0.854, p < 0.001). CONCLUSIONS: Colonoscopy, with or without removal of a lesion, is an invasive procedure with a non-deniable risk of major complications. Factors like inadequate cleansing or detection of AN are determinants. Therefore, it is vital to know which aspects predict their appearance to implement countermeasures.