Sonographic gallstone patterns are of value in predicting the outcome of biliary lithotripsy

The purpose of our study was to determine whether the qualitative features of gallstones, as expressed by their sonographic image, are related to the degree of fragmentation by shock-wave lithotripsy and the rate of stone clearance. The sonographic stone images of 73 patients with 1-3 uncalcified gallstones, followed for at least 1 yr after extracorporeal shock-wave lithotripsy, were analyzed and categorized by three independent observers into two distinct groups: type I--crescent to disc shape with gradual attenuation of echoes, and type II--rim-shape with abrupt shadowing. The degree of fragmentation and rate of stone clearance were significantly greater for type I stones than for type II stones. For all subjects, 1 yr after lithotripsy, 56% (27/48) of type I stones and 12% (3/25) of type II stones had cleared completely (p less than 0.0005). The clearance rate for solitary type I stones was 63% (20/32) versus 14% (2/14) for type II stones (p less than 0.005). Our observations suggest that sonographic analysis of stone patterns might help in predicting success, and contribute to greater cost-effectiveness of biliary extracorporeal shock-wave lithotripsy.