Are Hounsfield densities of ureteral stones a predictive factor for effectiveness of extracorporeal shock wave lithotripsy?

Extracorporeal Shock Wave Lithotripsy (SWL) has long been used successfully to dissolve ureteral stones. We researched whether Hounsfield values of ureteral stones is a factor that affects the success of SWL. Methods: Data from 144 patients who had diagnoses of ureteral stones and underwent SWL, were retrospectively reviewed between January 2011 and December 2012. Urinary tomography of patients was processed and classified into 3 groups by Hounsfield units (Group 1, < 500 HU; Group 2, 500-1000 HU; and Group 3, > 1000 HU) and 2 groups by stone size (Group A; < 1 cm, Group B; > 1 cm). SWL success was analyzed for both of these group types. Failure was defined as any fragments of the stone that remained within the ureter. Results were analyzed by evaluating the predictive factors in both groups. Results: The study included 144 patients (100 men, 44 women) who fit the inclusion criteria. In Hounsfield unit Group 1 (12 women and 44 men), the mean age was 37.2 +/- 13.2, stone size was 8.5 +/- 2.5 mm, number of shocks was 3240 +/- 1414 (1200-7500) and number of treatments was 1.4 +/- 0.6. In Group 2 (26 women and 32 men), the mean age was 33.6 +/- 7.6, stone size was 9.6 +/- 3.1 mm, process number was 3375 +/- 2103 (1200-8750) and shock amount was 1.6 +/- 0.8. In Group 3 (6 women and 24 men), the mean age was 42.2 +/- 13.6, stone size was 11.7 +/- 3.0 mm, number of shocks was 4513 +/- 2458 (1300-8700) and number of treatments was 2.1 +/- 1.2. In size Group 1 (28 women and 74 men), the mean age was 35.8 +/- 10.6, stone size was 8.1 +/- 1.4 mm, process number was 3105 +/- 1604, shock amount was 1.4 +/- 0.5 and HU value was 580 +/- 297. In Group 2 (16 women and 26 men), the mean age was 39.9 +/- 14.2, stone size was 13.9 +/- 2.4 mm, number of shocks was 4722 +/- 2467, number of treatments was 2.3 +/- 1.1 and HU value was 912 +/- 270. Conclusion: Although stone density predicted the failure of SWL, size of the stone is more important criterion for successful lithotripsy of ureteral stones.