Chemical composition of gallstones resistant to dissolution therapy with chenodeoxycholic acid.

The gallstones of 14 patients, who had been treated unsuccessfully with chenodeoxycholic acid (15 mg/kg/day) for at lest six months, were obtained at cholecystectomy. The stones were then analysed for their cholesterol and calcium content. Two patients' stones were black in colour and low in cholesterol content, and were classified as pigment stones. Of the remaining 12 patients' stones, which all contained more than 70% cholesterol, 10 contained at lest 1% calcium on the stone surface. In two patients, the surface contained sufficient calcium to form a radio-opaque layer, although the stones had been radiolucent at the start of dissolution therapy. Overall, the results suggest that deposition of calcium salts inhibits the dissolution treatment of gallstones with chenodeoxycholic acid, irrespective of the radiolucency of the stones.