Fate of residual fragments after successful extracorporeal shock wave lithotripsy

PURPOSE: The aim of the present study was to investigate the reason residual fragments from upper urinary tract calculi failed to clear after successful extracorporeal shock wave lithotripsy (ESWL). METHODS: Risk factors were analyzed in 161 patients with residual fragments (< or = 4 mm) that had remained for more than 3 months after ESWL. The factors examined in the present study were gender, a history of urolithiasis, the number, location and size of stones, hydronephrosis 3 months after ESWL and bacteriuria before ESWL. The mean follow-up period was 20.0 months (range 6-69 months). RESULTS: The overall stone-free rate was 14.3%. The stone-free rate in patients with multiple stones or hydronephrosis 3 months after ESWL was significantly lower than that in patients without these conditions (P < 0.05 and P < 0.01, respectively). The cumulative non-clearance rate in patients with hydronephrosis was significantly higher than in patients without this condition (P < 0.05). Results of Cox's proportional hazards model indicated that hydronephrosis was the most important and only significant factor for failure to clear of the seven factors investigated (P < 0.05). CONCLUSION: Hydronephrosis was most highly correlated with the fate of residual fragments after ESWL.