EDGE TARGETING REDUCES THE NUMBER OF SHOCK-WAVES REQUIRED FOR BILIARYESWL IN-VITRO

In vitro experiments were conducted to determine if differences in tar geting would effect stone fragmentation. Ten pairs of twin gallstones were used. The stones in each pair were identical in volume, diameter, radiolucency, and gross shape. One stone from each pair was subjected to shock waves focused at the center of the stone; the other was trea ted with shock waves targeted at the edge. Lithotripsy was terminated when all fragments were less than 5mm in diameter. The total number of shock waves used for each stone was recorded. In 7 of 10 pairs, fewer shock waves were required to fragment the edge targeted stone than th e center targeted stone. In two of the remaining three pairs, equal nu mbers of shock waves were required for complete fragmentation. The dif ference between edge targeting and center targeting was shown to bc st atistically significant using the nonparametric Wilcoxin Signed Rank T est. (1 tailed = p < 0.02, 2 tailed = p < 0.04). These findings sugges t that the outcome of biliary lithotripsy may be improved by targeting the edge of the stone.