PHYSICAL LAWS OF CHOLESTEROL GALLSTONE FRAGMENTATION

Efficient fragmentation is the most Important prerequisite for success ful treatment of gallstones by extracorporeally induced shock waves. N o data are available on the amount of energy necessary for stone disin tegration and on the threshold energy below which no further fragmenta tion occurs. We therefore performed an in vitro investigation on human cholesterol gallstones to elucidate physical laws governing shock-wav e lithotripsy. First, the focal pressure of the lithotripter was measu red to calculate the energy traversing a stone, Second, 96 gallstones from 16 gall bladders were analysed with respect to physicochemical co mposition, radiological features and ultrasound before fragmentation w as performed. Energy for stone disintegration was constant within each stone family but varied between 4.6 J mL(-1) and 36.8 J mL(-1) in dif ferent families. This energy correlated linearly with stone volume. No ne of the radiological and physicochemical factors revealed a clear-cu t correlation of the different energies necessary for similar stone di sintegration. The threshold energy differed between 0.26 mJ and 1.04 m J per pulse, In conclusion, stone volume was the best parameter predic ting stone fragmentation. However, in cholesterol stones with a simila r composition the required energy per volume varies considerably toget her with the threshold energy. Radiological and ultrasound parameters appear to be of minor importance in explaining these differences.