Twelve studies were included (1,162 participants). Six studies were randomised controlled trials, five were retrospective cohort studies, and one was a case-control study.
The diagnostic yield (OR 1.81, 95% CI 1.25 to 2.63; 5 studies) and proportion of patients with adequate or excellent/good small bowel visualisation quality (OR 2.11, 95% CI 1.25 to 3.57; 7 studies) were greater in patients who received a purgative preparation compared with those who received a clear-liquids diet, prior to VCE. There was little heterogeneity (p=0.127, I2=39.6) among studies assessing diagnostic yield but strong evidence for those assessing small bowel visualisation quality (p=0.011, I2=59.6%). Sensitivity analysis for these studies showed that significant differences between the two comparison groups remained when the analysis was restricted to RCTs (p=0.022), full paper publications (p=0.008), and sodium phosphate purgative use (p=0.046).
There was no difference between the two treatment groups in VCE completion rates (10 studies), VCE gastric transit times (7 studies), or small bowel transit times (8 studies). None of the included studies reported any clinically significant complications.
There was no statistically significant evidence of publication bias for any of the outcomes assessed (p>0.05).