GROWTH-KINETICS, PHASE-TRANSITIONS, AND CRACKING IN CHOLESTEROL GALLSTONES

The growth kinetics of cholesterol gallstones have been studied by gro wing crystals from melted gallstones. The resulting microstructures ar e spherulitic which is essentially the same as the structures seen in natural gallstones prior to melting. The cholesterol crystals when obs erved in hot stage microscopy emerge from a unique nucleation center g rowing radially in the [001] direction with constant rate. The DSC the rmograph of a natural gallstone is initially similar to that of choles terol monohydrate. Upon melting, cholesterol monohydrate changes to an hydrous cholesterol; both forms are crystalline and exhibit polymorphi c transformations. Synthetic stones grown from cholesterol were anhydr ous and have a phase change at temperatures close to human body temper ature. Optical microscopy established that this phase transformation c racks the spherulitic crystals perpendicular to the fast growth direct ion. Thermal expansion measurements demonstrate that upon heating, the low density, low temperature phase is transformed to a high density p hase. This phase transformation and repeated cracking may prove to be useful in destroying natural gallstones, while suppressing this transf ormation and its associated cracking might aid in securing other solid cholesterol deposits within the human body.