The sequential deposition of crystalline material in gallstones: evidence for changing gallbladder bile composition during the growth of some stones.

Determination of the sequential deposition of crystalline compounds in a representative collection of gallstones from 578 patients has shown that a change in composition of gallstones containing both cholesterol and calcium salt(s) has frequently occurred during growth. Generally a central stone area composed of one of these types of compound is surrounded by outer layers formed of a mixture of both, or vice versa. In a few stones, however, there is a change from one type of compound to the other occurring in successive layers. Both in stones containing cholesterol and calcium salt(s) and in those consisting entirely of calcium salt, there is often also a change in the type of calcium salt present. Such changes provide indirect evidence of changes in gallbladder bile composition during growth of stones, the origin and mechanism of which are not understood.