Effect of Chronic Ursocholic Acid Administration on Bile Lipid Composition and Bile Acid Pool Size in Gallstone Patients

We assessed the effect of chronic (4–6 weeks) administration of ursocholic acid (UCA) (15 mg/kg/day), a natural bile acid with poor detergent capacity, on biliary lipid composition of gallbladder bile (n = 26) and bile acid pool size (n = 5) in gallstone patients. During treatment the biliary molar percentage UCA increased from trace values to 28% (p < 0.001). This effect was accompanied by an increase in molar percentage deoxycholic acid from 16% to 33% (p< 0.001). Total bile acid pool size remained unchanged during UCA administration; cholic acid and chenodeoxycholic acid pool sizes decreased from 1.0 to 0.6mmol (p < 0.05) and from 1.6 to 0.9 mmol (p < 0.05), respectively. The molar percentage cholesterol of gallbladder bile decreased from 9.8% to 7.0% (p < 0.001) during UCA, but bile remained supersaturated with cholesterol in 21 patients. The weak effect on biliary lipid composition and the increase of potentially toxic deoxycholic acid in bile suggest that UCA is unlikely to replace ursodeoxycholic a...