Dissolution of cholesterol gallstones in vitro. Gallstone matrix content and diameter, not cholesterol content, predict gallstone dissolution in monooctanoin.

The goal of this study was to identify the structural and compositional features of human gallstones that influence in vitro gallstone dissolution in the cholesterol solvent monooctanoin. Gallstones were obtained from 86 consecutive patients who had at least three morphologically similar stones. One stone from each patient was dissolved in ethanol/ether to determine cholesterol and matrix composition. The remaining two matched stones were dissolved in either monooctanoin plus ethanol (n = 86) or monooctanoin plus 2-mercaptoethanol (n = 86). The thiol reducing agent 2-mercaptoethanol has been previously shown to solubilize the isolated gallstone matrix and to accelerate the dissolution of intact, small cholesterol stones. Stone matrix content and initial diameter had the most significant predictive value for stone dissolution (p less than 0.0001 for each), whereas cholesterol content had no predictive value (p = 0.558). Stones incubated in monooctanoin containing 2-mercaptoethanol dissolved more rapidly than those incubated in monooctanoin plus ethanol (16.7% of initial weight per day vs. 13.8% of initial weight per day, p less than 0.0001). Matrix content correlated significantly with the difference in dissolution rate between stones dissolved in monooctanoin plus ethanol or monooctanoin plus 2-mercaptoethanol (p less than 0.0001). These data indicate that the matrix content of human cholesterol gallstones significantly inhibits in vitro stone dissolution in the cholesterol solvent monooctanoin. This finding may be relevant to the clinical dissolution of gallstones.