The Obese Patient: Effects of Split-dose Preparation During Colonoscopy on Adenoma Detection Rate

Abstract

Introduction: Obesity is associated with an increased risk of colorectal cancer. A study by Grewal, et al showed that adenoma detection rate (ADR) is higher among overweight and obese males compared to their normal weight counterparts, suggesting a higher prevalence of precancerous adenomas in this population. ADR, however, is not a direct measure of adenoma prevalence because of its dependence on colonoscopy quality, including the quality of the bowel prep. Obesity is an independent risk factor for suboptimal bowel prep, suggesting that ADR may significantly underestimate adenoma prevalence in this group. Because split-dose bowel prep is associated with improved bowel prep scores, our aim was to determine if split-dose bowel prep is also associated with higher ADR among obese patients. Methods: This study utilized prospectively collected data at point-of-care using Qualoscopy (Docbot, Inc). Inclusion criteria was all obese patients, defined as a BMI ≥30, who had colonoscopies performed for any indication at our outpatient facilities from June, 2012 to April, 2017. Statistical analysis was performed using chi-square and two-sample t-test. For reference, the same measures were analyzed in normal/underweight (< 25) and overweight BMIs (25-29.9). Results: Of 1419 colonoscopies performed among obese patients, 856 (60.3%) received split-dose bowel prep and 563 (39.7%) received single-dose prep. The split-dose group was weighted towards female patients, but there were no significant differences in BMI, gender, or primary indication (table 1). ADR was significantly higher among those who received split-dose (50.7% vs 38.4%, p < 0.001). Similarly, adequate bowel prep (defined as a Boston Bowel Prep Score ≥8) was significantly more frequent in the splitdose compared to single-dose groups (72% vs 60%, p < 0.001). The degree of benefit of split-dose prep, as measured by % improvement in ADR and % improvement in fraction of adequate preps, was highest in obese patients compared to those who were normal/underweight or overweight (table 2).Table: Table. Patient DemographicsTable: Table. Outcomes Based on BMI and Bowel Preparation UsedConclusion: Our data shows that split-dose bowel prep in obese patients is associated with significantly higher ADR and percentage of patients with adequate prep. Furthermore, these benefits of split-dose prep were most pronounced among the obese population. Based on compelling evidence that higher ADRs are associated with lower interval cancer rates, our data supports widespread use of split-dose prep in this high-risk population.