February 2011

Document Type


Degree Name



Dept. of Public Health and Preventive Medicine


Oregon Health & Science University


Background and Aims: Colorectal cancer is the third most common cancer and the second most common cause of cancer death among Americans. Colonoscopic screening holds the potential to significantly reduce the amount of colorectal cancer death; however, the procedure is invasive and carries the risk of complications. This study aims to evaluate various patient characteristics that might predict both clinically significant findings and complications from colonoscopy. Methods: A cohort study following over 20,000 patients estimated the risk of serious complications within 30 days of colonoscopy. The present study utilizes those from that cohort with indication of screening or surveillance colonoscopy. Multivariate logistic regression models were constructed for two outcomes: (1) serious complication related to colonoscopy and (2) neoplasia (polyp or other mass) greater than 9 mm. The number needed to endoscope (NNE) in order to observe one instance of each outcome was estimated based on results from the multivariate logistic regression models. Results: Data from 21,302 participants were included in the present analysis. Sixty-eight participants experienced serious adverse events (0.31%), while 1866 had one or more polyps or other masses of size greater than 9 mm found on their exam (8.76%). Peri-procedural anticoagulation therapy was a significant risk factor for complication. Statistically significant predictors for neoplasia over 9 mm included male gender, increased patient age, ASA class of II or greater, and prior positive screening test as indication for exam. Among adults under 65, it would require an estimated 509 colonoscopies among males 607 among females before expecting to see 1 serious complication, compared to 332 for males older than 74 and 396 for similarly aged females. Use of anticoagulants appears to markedly increase risk of complication without any increase in yield of the procedure. Increased ASA class may increase likelihood of complication, but has a corresponding increased yield of neoplasia. Regular use of aspirin and NSAIDs appears to protect against large neoplasia. Conclusions: Male gender, increased age, and increased ASA class may be risk factors for complication from colonoscopy, though the present study is under-powered to detect moderate effects. Anticoagulation therapy is a risk factor for increased risk of complication, though it is not associated with clinically significant neoplasia. Screening may lose its benefit as procedure yield may plateau at older ages while risk of complication may continue to increase. Screening in females has lower yield, but may be somewhat safer.




School of Medicine



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