Sonographic patterns of radiolucent gall-bladder stones for predicting successful shock-wave lithotripsy

The aim of this study was to examine whether the sonographic patterns of gallstones are useful for predicting the outcome of piezoelectric shock-wave lithotripsy. Pretreatment analysis of gallstones based on our sonographic classification was conducted on 115 patients with radiolucent solitary stones of 10–30 mm in diameter, monitored for at least a year after the first lithotripsy. All stones were categorized as type I with gradual attenuation of echoes: type Ia, the stone echo appears as a full moon, usually accompanied by comet-tail artifacts beyond the stone itself (n= 55); type Ib, the stone echo showing the anterior half of the stone, seen as a half moon (n= 29); and type Ic, the stone echo seen as a crescent (n= 31). The most complete fragmentation, ‘pulverization', was achieved at a significantly higher rate for type Ia (51%) than for type Ib (14%, P < 0.005) and type Ic (7%, P < 0.0001) after significantly fewer shock-waves (vs type Ib, P < 0.01; vs type Ic, P < 0.0001). The rate of complete clearance at 12 months after lithotripsy was significantly greater for type Ia (91%) than for type Ib (62%, P < 0.01) and type Ic (45%, P < 0.0001). Comparison of the sonographic and computed tomography (CT) patterns of stones revealed a close relationship between the two: the vast majority (98%) of type Ia showed the iso- or hypo-dense, and the majority (90%) of type Ic the rimmed. We conclude that the sonographic patterns of radiolucent gallstones appear to provide another parameter for predicting fragmentation and clearance of the stones in lithotripsy treatment, and to be probably alternative to pretreatment CT.