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World J Gastrointest Endosc. 2016 Sep 16;8(17):616-22. doi: 10.4253/wjge.v8.i17.616.

Predictors of suboptimal bowel preparation in asymptomatic patients undergoing average-risk screening colonoscopy.

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Shail M Govani, Eric E Elliott, Stacy B Menees, Sameer D Saini, Annette L Urganus, Philip S Schoenfeld, Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48109, United States.



To identify risk factors for a suboptimal preparation among a population undergoing screening or surveillance colonoscopy.


Retrospective review of the University of Michigan and Veteran's Administration (VA) Hospital records from 2009 to identify patients age 50 and older who underwent screening or surveillance procedure and had resection of polyps less than 1 cm in size and no more than 2 polyps. Patients with inflammatory bowel disease or a family history of colorectal cancer were excluded. Suboptimal procedures were defined as procedure preparations categorized as fair, poor or inadequate by the endoscopist. Multivariable logistic regression was used to identify predictors of suboptimal preparation.


Of 4427 colonoscopies reviewed, 2401 met our inclusion criteria and were analyzed. Of our population, 16% had a suboptimal preparation. African Americans were 70% more likely to have a suboptimal preparation (95%CI: 1.2-2.4). Univariable analysis revealed that narcotic and tricyclic antidepressants (TCA) use, diabetes, prep type, site (VA vs non-VA), and presence of a gastroenterology (GI) fellow were associated with suboptimal prep quality. In a multivariable model controlling for gender, age, ethnicity, procedure site and presence of a GI fellow, diabetes [odds ratio (OR) = 2.3; 95%CI: 1.6-3.2], TCA use (OR = 2.5; 95%CI: 1.3-4.9), narcotic use (OR = 1.7; 95%CI: 1.2-2.5) and Miralax-Gatorade prep vs 4L polyethylene glycol 3350 (OR = 0.6; 95%CI: 0.4-0.9) were associated with a suboptimal prep quality.


Diabetes, narcotics use and TCA use were identified as predictors of poor preparation in screening colonoscopies while Miralax-Gatorade preps were associated with better bowel preparation.


Colonoscopy; Diabetes; Narcotics; Preparation; Quality

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