SONOGRAPHIC PATTERNS OF RADIOLUCENT GALLBLADDER STONES FOR PREDICTINGSUCCESSFUL 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 s hock-wave lithotripsy. Pretreatment analysis of gallstones based on ou r sonographic classification was conducted on 115 patients with radiol ucent solitary stones of 10-30 mm in diameter, monitored for at least a year after the first lithotripsy. All stones were categorized as typ e I with gradual attenuation of echoes: type Ia, the stone echo appear s as a full moon, usually accompanied by comet-tail artifacts beyond t he 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 sto ne 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 rb (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 li thotripsy 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 sono graphic and computed tomography (CT) patterns of stones revealed a clo se relationship between the two: the vast majority (98%) of type Ia sh owed the iso- or hypo-dense, and the majority (90%) of type Ic the rim med. We conclude that the sonographic patterns of radiolucent gallston es appear to provide another parameter for predicting fragmentation an d clearance of the stones in lithotripsy treatment, and to be probably alternative to pretreatment CT.