Analyzing the Effect of Distance from Skin to Stone by Computed Tomography Scan on the Extracorporeal Shock Wave Lithotripsy Stone-Free Rate of Renal Stones

Abstract

PurposeTo determine whether the distance from skin to stone, as measured by computed tomography (CT) scans, could affect the stone-free rate achieved via extracorporeal shock wave lithotripsy (ESWL) in renal stone patients.Materials and MethodsWe retrospectively reviewed the records 573 patients who had undergone ESWL at our institution between January 2006 and January 2010 for urinary stones sized from about 5 mm to 20 mm and who had no evidence of stone movement. We excluded patients with ureteral catheters and percutaneous nephrostomy patients; ultimately, only 43 patients fulfilled our inclusion criteria. We classified the success group as those patients whose stones had disappeared on a CT scan or simple X-ray within 6 weeks after ESWL and the failure group as those patients in whom residual stone fragments remained on a CT scan or simple X-ray after 6 weeks. We analyzed the differences between the two groups in age, sex, size of stone, skin-to-stone distance (SSD), stone location, density (Hounsfield unit: HU), voltage (kV), and the number of shocks delivered.ResultsThe success group included 33 patients and the failure group included 10. In the univariate and multivariate analysis, age, sex, size of stone, stone location, HU, kV and the number of shocks delivered did not differ significantly between the two groups. Only SSD was a factor influencing success: the success group clearly had a shorter SSD (78.25±12.15 mm) than did the failure group (92.03±14.51 mm). The results of the multivariate logistic regression analysis showed SSD to be the only significant independent predictor of the ESWL stone-free rate.ConclusionsSSD can be readily measured by CT scan; the ESWL stone-free rate was inversely proportional to SSD in renal stone patients. SSD may therefore be a useful clinical predictive factor of the success of ESWL on renal stones.

Impact of body mass index on success, complications and failure of extracorporeal shock wave lithotripsy

“…The successful group was defined as individuals who are free from stone in CT scan or radiography for six weeks after ESWL and unsuccessful group was determined as remaining particles of stone after six weeks of ESWL. The results of this study showed that the SSD influenced the results of ESWL (14). These findings are similar to our study too.…”

Non-Contrast Computed Tomography Scan Based Parameters of Ureteric Stones Affecting the Outcome of Extracorporeal Shock Wave Lithotripsy

“…In some studies, however, no significant correlation was found between Hounsfield unit value and ESWL outcome [6, 11]. In our study, Hounsfield units of stone was a strong predictor of success of the procedure.…”

“…Park BH, et al described significant influence of SSD for ESWL in renal stones [6]. Müllhaupt, et al studied the effect of SSD on ureteral stone fragmentation and described its significance.…”

The effect of renal cortical thickness on the treatment outcomes of kidney stones treated with shockwave lithotripsy

“…The increased use of computed tomography (CT) to assess urinary calculi has provided information on some stone parameters, such as mean stone density (MSD) and stone volume (SV), that could be used to predict treatment outcomes after SWL [ 1 , 2 ]. Among the various stone parameters, skin-to-stone distance (SSD) is another factor that might be able to predict the results of treatment, although its role in the prediction of treatment outcomes is still controversial [ 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 ]. Because the shock wave (SW) path passes through various tissues with different compositions and densities, transmission of the SW along these different tissue planes may lead to energy loss and hence affect treatment outcome [ 12 , 13 ].…”