The "mirroring" of gallstones: description of a novel silvering method to determine the surface area of an irregular object. In vitro demonstration that multiple gallstones from the same gallbladder dissolve in unsaturated "bile" at the same rate.

We describe a novel "silvering" method to determine the surface area of nonspherical objects and have applied this method to human cholesterol gallstones. A standard curve is first constructed, using data obtained from the dissolution rates of silver-coated plastic spheres of known dimensions in unstirred thiosulfate-ferricyanide solutions. Silver dissolution rates of silver-coated gallstones are then correlated with the standard curve so that the equivalent spherical surface area of the gallstones may be estimated. The technique has been applied to cholesterol dissolution rates of gallstones from the same patient and from different patients in unstirred bile salt (sodium chenodeoxycholate) solutions. The results demonstrate that cholesterol dissolution rates per unit surface area are identical for small stones as well as large ones, are identical for all stones from the same gallbladder, but are somewhat dissimilar for those originating from different gallbladders. The experimental results are in agreement with a priori theoretical predictions of mass transfer from spherical objects, and correlate satisfactorily with experimental dissolution rates of pure cholesterol monohydrate disks in unstirred bile salt solutions.