Risk factors for inadequate bowel preparation in patients using high- and low-volume cleansing products

Bowel preparation is crucial for colonoscopy completeness and lesions detection. Today, several cleansing products are equally recommended by guidelines, irrespective of patients' characteristics. Identification of preparation-specific risk factors for inadequate bowel preparation may lead to a personalized prescription of cleansing products to refine patients' tolerance and improve endoscopic outcomes.

We prospectively enrolled consecutive outpatients referred for colonoscopy using either a high-volume [HV: 4 l polyethylene glycol (PEG)] or a low-volume (LV: 2 l PEG + bisacodyl) preparation. Day-before regimen or split-dose regimen was used for morning or afternoon colonoscopies, respectively. Univariate and multivariate analyses were conducted to identify risk factors related to inadequate bowel preparation, according to the Boston bowel preparation scale for HV and LV preparations.

We enrolled 2040 patients, of which 1815 were included in the final analysis (average age 60.6 years, 50.2% men). Half of them (52%) used LV preparation. Adequate preparation was achieved by 87.6% without differences between the HV and LV groups (89.2% vs. 86.6%; P = 0.098). The use of day-before regimen and incomplete assumption of PEG were independent predictors of poor visibility for either HV or LV preparation. However, different specific risk factors for HV [diabetes: odds ratio (OR), 3.81; 95% confidence interval (CI), 1.91-7.58; low level of instruction: OR, 1.95; 95% CI, 1.11-3.44; and previous abdominal surgery: OR, 2.27; 95% CI, 1.20-4.30] and for LV (heart disease: OR, 2.06; 95% CI, 1.09-3.88; age > 65 years: OR, 1.51; 95% CI, 1.01-2.27) preparations were identified.

Day-before preparation and incomplete assumption of the purgative agents affect bowel visibility irrespective of the preparation volume. LV should be preferred to HV preparations in patients with diabetes, low level of instruction, and previous abdominal surgery, whereas an HV preparation should be preferred in patients with heart disease and in older patients.