[Recurrence of stones after extracorporeal shock wave lithotripsy]

During the 11-year period from September 1984 through August 1995, extracorporeal shock wave lithotripsy (ESWL) was performed on 5,558 patients using a Dornier HM3 apparatus. A recurrence questionnaire was sent out to 2,379 of those who had had complete elimination of the calculi and for whom at least 3 years had passed since the ESWL. The last day of follow-up was defined as follows: the day of completion of the questionnaire in the recurrence-free group (n = 787), the day when recurrence of calculi was diagnosed in the recurrence group (n = 415) and the day of the last visit to the outpatient clinic in the miscellaneous group (n = 1,133). The cumulative recurrence rates were calculated by the Kaplan-Meier equation. The resultant data were analyzed for statistically significant differences by the log rank test and the generalized Wilcoxon test. Ap value of < or = 0.05 was considered to indicate significance. The recurrence rate was examined for differences in relation to the following risk factors: the patients' age and sex, the stone location, size and number, the presence or absence of past history of lithiasis, the composition of the stone (s), and the presence or absence of urinary tract complications. The cumulative recurrence rates for the total cases were 2.0% at one year, 13.1% at 3 years, 23.9% at 5 years, 30.7% at 7 years and 40.7% at 10 years. Significantly higher recurrence rates were found for patients under 60 years of age, those with multiple stones and those with a past history of disease.