Predictors and colonoscopy outcomes of inadequate bowel cleansing: a 10-year experience in 28,725 patients

Background: Inadequate bowel preparation is still the main obstacle to a complete colonoscopy in many patients and necessitates many repeated procedures. We aimed to identify risk factors associated with inadequate bowel preparation and to better characterize these patients. Methods: This was a retrospective study that reviewed electronic reports of colonoscopy procedures over a 10-year period. Patients were divided into 2 groups: adequate vs. non-adequate bowel preparation. A multivariate analysis was performed to identify variables associated with inadequate bowel preparation, including age, sex, setting (inpatient/outpatient), preparation regimen and procedures' indications. We examined the effect of inadequate preparation on colonoscopy quality indicators. Results: Of the 28,725 patients included in the study, 6,702 (23.3%) had inadequate bowel preparation. In the multivariate analysis, advanced age (odds ratio [OR] 1.015, 95% confidence interval [CI] 1.013-1.017; P<0.01), male sex (OR 1.353, 95%CI 1.286-1.423; P<0.01) and a minority population (OR 1.635, 95%CI 1.531-1.746; P<0.01) were significantly associated with inadequate bowel preparation. The inpatient setting was among the most prominent factors associated with inadequate bowel preparation (OR 2.018, 95%CI 1.884-2.163; P<0.01). Adequate bowel preparation was associated with a higher polyp detection rate (26.8% vs. 23.6%; OR 1.22, 95%CI 1.109-1.347; P<0.01) and colorectal cancer (2.8% vs. 2.4%; OR 1.402, 95%CI 1.146-1.716; P<0.01), and higher frequencies of cecal (96.4% vs. 73.5%; OR 2.243, 95%CI 2.095-2.403; P<0.01) and terminal ileum intubation (8.1% vs. 5.4%; OR 1.243, 95%CI 1.088-1.434; P<0.01). Conclusion: We outlined various factors associated with inadequate bowel preparation and confirmed its adverse effect on colonoscopy quality indicators.