Evaluation of computed tomography findings for success prediction after extracorporeal shock wave lithotripsy for urinary tract stone disease.

Abstract

Currently, the most widely used method of treatment of urinary tract stones is extracorporeal shock wave lithotripsy (SWL). Patient and stone characteristics are important for SWL success. We evaluated noncontrast computed tomography (NCCT) characteristics of urinary tract stones for the prediction of SWL success. Records of patients who underwent NCCT before SWL treatment between January 2008 and June 2012 were retrospectively evaluated. Demographic data were recruited from patient files. Hounsfield units (HU), stone size and skin-to-stone distance (SSD) were measured on NCCT. After serial measurements of the highest HU value (HUmax) and lowest HU value (HUmin), HU value was calculated as the average of these two values (HUave). These parameters were compared between successful [stone-free (SF) group] and unsuccessful [residual fragment (RF) group] cases after SWL. A total of 254 patients, 113 kidney stones and 141 ureteral stones, were evaluated. Mean age was 51.0±14.6 (18-87) years, and mean stone size was 10.9±3.7 mm. Stone diameter, HUmax, HUmin and HUave were significantly lower in SF group when compared with RF group for both kidney and ureteral stones (p<0.05). We also found that SSD for kidney stones was predictive for SWL success. We suggest that HUmax, HUmin and HUave values are significant predictors of SWL success for both kidney and ureteral stones. They might be used in daily clinical practice for patient counselling.