PHYSICOCHEMICAL DETERMINANTS OF INVITRO SHOCK-WAVE BILIARY LITHOTRIPSY

Human gallstones were studied by visual inspection, computerized tomographic imaging, and chemical analysis to assess physicochemical characteristics that may determine the outcome of in vitro shockwave fragmentation. Eighty-five stones (mean diameter: 13.2 ± 5 mm) were each collected from different patients. Fifty-five (65%) calculi were angular and 30 (35%) round or oval-shaped. Three easily obtained measures were derived from each stone's optimal computerized tomographic image including the mean stone density, a measure corresponding to the standard deviation of the mean stone density value which we termed the stone density distribution index and which may reflect the physicochemical heterogeneity of a given gallstone, as well as the density range. After the administration of 2500 shock waves using an electrohydraulic generator, fragmentation was noted in 68 calculi (80%) and was satisfactory in 27 (32%) (where the largest resulting fragment diameters were all ≤5 mm). Strong determinants of satisfactory fragmentation on mullivariale analysis included a stone diameter of ≤15 mm, the presence of an angular stone shape, and a stone density distribution index of ≥60 Hounsfield units. The other parameters did not independently determine satisfactory fragmentation. Prospective clinical trials are needed to assess whether these findings result in a better prediction of the success of extracorporeal biliary lithotripsy and a broadening of its indications. © 1991 by the American Gastroenterological Association.