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.(ABSTRACT TRUNCATED AT 250 WORDS)