Residual risk in the >90% adequate bowel preparation rate cohort: a real-world large-scale study

Abstract Background In large real-world cohorts with >90% bowel preparation adequacy, residual risk factors for inadequate cleansing remain underexplored. Methods This retrospective study included 15,193 consecutive eligible patients undergoing colonoscopy at a tertiary academic referral endoscopy center between November 2022 and November 2023. Bowel preparation regimens included same-day 2 L polyethylene glycol (PEG), split-dose 3 L PEG, or a split-dose sodium picosulfate-based regimen. Univariable and multivariable logistic regression analyses were performed, and bowel preparation regimen was analyzed as a three-category variable using 2 L PEG as the reference. Results In the three-category multivariable model, the 3 L PEG regimen was independently associated with lower odds of inadequate bowel preparation compared with 2 L PEG (OR 0.54, 95% CI 0.46–0.63, p < 0.01), whereas the sodium picosulfate-based regimen did not differ significantly from 2 L PEG (OR 1.17, 95% CI 0.96–1.44, p = 0.12). Factors independently associated with higher odds of inadequate bowel preparation included age ≥ 57 years, prior gastrointestinal surgery, diabetes, constipation, tricyclic antidepressant use, and spinal cord injury. Diabetes remained associated with higher odds of inadequate bowel preparation among patients receiving 2 L PEG and 3 L PEG, but not among those receiving the sodium picosulfate-based regimen; no significant interaction by bowel preparation regimen was detected. Conclusions Older age, prior gastrointestinal surgery, diabetes, constipation, tricyclic antidepressant use, and spinal cord injury were associated with inadequate bowel preparation in this high-adequacy cohort. Compared with 2 L PEG, the 3 L PEG regimen was associated with lower odds of inadequate preparation, whereas the sodium picosulfate-based regimen showed no significant difference. These findings are confirmatory and hypothesis-generating, and diabetes and constipation remain clinically challenging factors that may require tailored strategies.