Risk factors for inadequate bowel preparation: A retrospective study of 7931 paired colonoscopy cases with a predictive model

Abstract

BACKGROUND

Inadequate bowel preparation negatively impacts adenoma detection rates and overall colonoscopy quality; however, the associated risk factors have yet to be fully elucidated in large paired-cohort studies.

AIM

To identify independent risk factors associated with inadequate bowel preparation and to develop and validate a clinical prediction model for Chinese patients undergoing colonoscopy.

METHODS

A total of 7931 patients who underwent two or more colonoscopies were retrospectively enrolled in this study. Univariate and multivariate logistic regression analyses were performed to identify independent risk factors for inadequate bowel preparation. The predictive performance of the model was evaluated using 10-fold cross-validation, bootstrap resampling, temporal validation, and subgroup analyses.

RESULTS

The overall rate of inadequate bowel preparation was 13.67%. Independent risk factors included older age, male sex, afternoon colonoscopy, diabetes mellitus, constipation, and a history of inadequate bowel preparation (all P < 0.05), whereas inpatient status was identified as a protective factor (odds ratio = 0.391, P < 0.001). The prediction model demonstrated good discriminatory ability [area under the curve (AUC) = 0.699] and satisfactory calibration. In addition, the simplified scoring system yielded an AUC of 0.687 and exhibited a clear gradient of increasing risk across score categories.

CONCLUSION

A history of inadequate bowel preparation is the strongest predictor of subsequent preparation failure. Inpatient status is associated with significantly better bowel preparation quality than outpatient status. The simplified risk scoring system provides a practical tool for identifying patients at high risk of inadequate bowel preparation and facilitating personalized preparation strategies. To our knowledge, this is the first large-scale paired-colonoscopy study to quantify the recurrent nature of bowel preparation failure and to demonstrate the protective effect of inpatient status after adjustment for multiple potential confounders.

Keywords: Bowel preparation; Colonoscopy; Risk factors; Prediction model; Simplified scoring system; Inpatient status

Core Tip: Key findings of our study: In a large paired cohort of 7931 patients, prior inadequate bowel preparation was the strongest predictor of repeated inadequate preparation. Inpatient status was a significant protective factor, with substantially better bowel preparation quality than in outpatients. A simplified risk scoring system showed good discrimination and risk stratification, enabling rapid identification of high-risk patients in clinical practice.