The uric acid-whewellite association in human kidney stones.

Human kidney stones, composed almost exclusively of uric acid and whewellite, were studied using x-ray (powder and single-crystal) as well as scanning electron-diffraction techniques. Whewellite--showing as a concentric aggregate characteristically marked by radial striations--is enclosed within a mass of uric acid, the crystallites of which grow with their b axis parallel to the radial direction of the striations. That axis corresponds to b (2 X 7.294 A) and tends to systematically superimpose over its uric acid counterpart (b = 7.40 A). Nonetheless no other such dimensional match was found for the other set of periodicities that characterize the uric acid whewellite interfaces, raising questions that a systematic epitaxial interaction could there take place. Selected uric acid-whewellite contacts and the crucial role of the "matrix" were also investigated.