Effect of Medical Management and Residual Fragments on Recurrent Stone Formation Following Shock Wave Lithotripsy

Minimal emphasis has been placed on the clinical sequelae of residual stone fragments following shock wave lithotripsy. Moreover, there are no studies investigating the role of medical therapy on the course of stone disease in patients with residual fragments. In this retrospective, nonrandomized review, we evaluated 80 patients who had undergone shock wave lithotripsy at various institutions in Texas and were referred to our mineral metabolism clinic for metabolic evaluation and medical management of the stone disease. Of the patients 31 were determined to be stone-free following lithotripsy, while 49 had residual stone fragments. All patients were contacted an average of 43.2 months (range 9 to 79) following shock wave lithotripsy and the radiographs were reviewed. Patients were placed into 4 groups after shock wave lithotripsy: stone-free or residual fragments on or off medical therapy. In the stone-free group (19 patients), medical treatment produced a significant decrease in stone formation from a median of 0.67 to 0.0 stones per patient per year (p <0.001). In 36 patients with residual fragments stone formation before shock wave lithotripsy was higher than in the stone-free group but there was also a significant decrease in the stone formation rate from a median of 2.47 to 0.00 stones per patient per year while on medical therapy (p <0.001). Of the 12 stone-free patients who did not remain on medical therapy there was a slight decrease in the stone formation rate from a mean of 0.83 to 0.40 stones per patient per year, although this decrease was not significant (p = 0.07). In 13 patients with residual fragments not on medical treatment there was only a minimal decrease in the stone formation rate from a median of 1.33 to 0.77 stones per patient per year (p = 0.06). We also assessed the significance of so-called clinically insignificant residual fragments (smaller than 5 mm.) following shock wave lithotripsy in 26 of the 36 patients with residual fragments. More than half of the 26 patients with clinically insignificant fragments in the group that did not continue on medical therapy demonstrated significant stone growth during followup, suggesting that these fragments were not insignificant. Moreover, only 16% of the patients with fragments smaller than 5 mm. demonstrated an increase in fragment size while on medical therapy, again suggesting that appropriate medical treatment can decrease the risk of recurrent stone formation or growth (p <0.05). Our findings suggest that appropriate medical therapy may control active stone formation in patients with or without residual stone fragments following shock wave lithotripsy. Moreover, residual fragments after shock wave lithotripsy place patients at higher risk for recurrent stone formation or growth.