Single-Center Experience With the Dual-Focus Storz Modulith SLX-F2 Lithotripter: A Retrospective Study

Abstract

Background: To calculate the modified efficiency quotient of the mobile Storz Modulith SLX-F2 lithotripter, to identify factors determining clinical succes rate and to identify complications and limitations with this device. Comparison of the results with reported data from other institutions for the same machine and other types in the peer review literature will be made. Methods: The study design is a retrospective chart review. Inclusion criteria include male and female and patients who were treated in the Texas Tech University Health Sciences Center for urinary calculi with the Storz Modulith SLX-F2 lithotripter between September 2006 and June 2011. During this period, 447 patients with single stones were treated, and 10 patients with radiolucent stones and 21 patients with incomplete follow-up were excluded. The patients were followed up with plain radiography and/or renal ultrasound to assess the clinical succes rate. Univariate and multivariate analyses were performed to identify the factors determining the clinical success rate. Results: Follow-up was complete for 416 patients. Mean age was 46.1 ± 14.4 years. The mean numbers of shock waves given were 2,457 and 2,838 for renal and ureteral stones, respectively. Mean stone sizes were 9.3 ± 4.5 mm and 9.7 ± 4.9 mm for renal and ureteral stones, respectively. Mean body mass index was 30.5 ± 7.04 kg/m 2 . The overall clinical success rate after one ESWL treatment was 84.6% (85.4% and 83.6% for renal and ureteral stones, respectively). The modified efficiency quotient was 0.69. On univariate analysis, clinical success rate was associated with smaller stone size ( < 10 mm, P = 0.016), and absence of a ureteral stent (31.7% vs. 10.5%; P = 0.0002). Presence of lower calyx stones (P = 0.04) was a negative predictor of clinical success. On multivariate analysis, lower calyx stones, smaller stone size and the absence of a ureteral stent continued to be significant determinants of clinical success status. All complications were minor with a complication rate of 4.3%. Conclusions: The mobile Storz Modulith SLX-F2 lithotripter is clinically effective in the management of solitary renal and ureteral stones. It has an adequate modified efficiency quotient combined with a favorable safety profile. Major advantages are the increased treatment depth in combination with exceptionally high weight limit and a dual-focus system. World J Nephrol Urol. 2014;3(1):7-17 doi: http://dx.doi.org/10.14740/wjnu111w