Five RCTs (n=521: 322 for UDCA and 199 for placebo) were included. All studies were classed as high quality (scores ranged from 3 to the maximum of 5). Only two studies had complete follow-up for all patients; the rest had missing data for between 17.2% and 31.7% of patients.
Gallstone formation (five trials): UCDA resulted in a significantly reduced risk of gallstone formation after surgery compared with placebo in both the available case analysis (RR 0.40, 95% CI 0.22 to 0.74, with substantial heterogeneity I2=58.9%) and the intention-to-treat analysis (RR 0.43, 95% CI 0.22 to 0.83, with substantial heterogeneity I2=61.9%). The trial with the greatest loss to follow-up and the worst patient compliance with treatment was the cause of most of the observed heterogeneity, but conclusions about UCDA remained the same when this trial was excluded.
Adverse effects: Two trials reported on adverse effects. One found comparable mild to moderate side effects between UCDA and placebo; the other reported that several patients dropped out because of vomiting or skin rashes, but that numbers were similar between treatment groups.