Risk Factors Associated with Inadequate Bowel Preparation in Patients with Functional Constipation

Abstract

Background: Constipation is a common reason of poor bowel preparation, which negatively influences the quality of colonoscopy. Risk factors for inadequate bowel preparation in constipated patients remain unclear.

Aims: This study aimed to investigate the high-risk factors that might influence the quality of bowel preparation in patients with functional constipation.

Methods: Consecutive patients with functional constipation who underwent colonoscopy between June 2016 and April 2017 were enrolled. A standard split dose of 4 l polyethylene glycol was used for bowel preparation. Patient- and procedure-related parameters were recorded. The primary outcome was an adequate rate of bowel preparation. Risk factors for inadequate bowel preparation were screened by multivariate logistic regression analysis.

Results: A total of 199 patients were included. Adequate bowel preparation was found in 62.8% (125/199) of patients. At multivariate analysis, Bristol stool form scale (BSFS) 1 [odds ratio (OR) 2.73, 95% confidence interval (CI) 1.26-5.90; P = 0.011], rectal pain score during defecation < 2 (OR 4.14, 95% CI 1.22-13.97; P = 0.022), and starting-to-defecation interval ≥ 4 h (OR 3.83, 95% CI 1.34-10.91; P = 0.012) were risk factors for inadequate bowel preparation in patients with constipation. For patients with no, 1, 2, or 3 risk factors, the rates of inadequate bowel preparation were 11%, 23%, 49%, and 65%, respectively.

Conclusions: With the standard preparation regime, > 1/3 of patients with functional constipation had inadequate bowel cleansing. BSFS 1, rectal pain score during defecation < 2, and starting-to-defecation interval ≥ 4 h were identified as independent risk factors for inadequate bowel preparation in constipated patients.

Trial registration: ClinicalTrials.gov number NCT02842411.

Keywords: Bowel preparation; Colonoscopy; Functional constipation; Risk factor.