[Experience with extracorporeal shock wave lithotripsy for urinary stone. Factors for requiring more than two ESWL treatments and its result].

Extracorporeal shook wave lithotripsy (ESWL) was performed for the treatment of 1277 urolithiasis patients at Osaka City University Hospital from July, 1985 to December, 1988. A total of 1788 ESWL treatments were carried out using Dornier HM3 kidney lithotripter. 964 patients (75.5%) underwent only one ESWL treatment, while 313 patients (24.5%) more than two ESWL treatments. We retrospectively examined the factors for requiring more than two ESWL treatments. Not only stone number, size and location, but fragility were considered to be the main causes for requiring more than two ESWL treatments. According to component analysis of ureteral stones, which were hard and resistant to shock wave, calcium apatite content of these stones turned out to be high (p less than 0.001). As for fragility, the residual stones created by ESWL were more difficult to be disintegrated that the nontreated stones of the same size (p less than 0.05). "Fragility" of the stones before shock wave and residual stones after ESWL are considered to be a major problem in ESWL treatment of urinary stones to be solved in the years to come.