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| Factors Determining Stone-free Rate in Shock Wave Lithotripsy Using Standard Focus of Storz Modulith SLX-F2 Lithotripter |
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Elkoushy MA, Hassan JA, Morehouse DD, Anidjar M, Andonian S Department of Surgery, McGill University, Montreal, Quebec, Canada
AbstractAbstractOBJECTIVES: To calculate the efficiency quotient (EQ) of the latest mobile Storz Modulith SLX-F2 lithotripter and to identify the factors determining the stone-free rate. METHODS: A retrospective review of a prospectively collected database of the first consecutive 533 patients undergoing shock wave lithotripsy (SWL) from June 2009 to February 2010 was performed. A total of 16 patients with radiolucent stones and 43 patients with incomplete follow-up were excluded. The patients were followed up with plain radiography to assess the stone-free status. Univariate and multivariate analyses were performed to identify the factors determining the stone-free rates. RESULTS: Follow-up was complete for 474 patients, with a mean age of 54.2 ± 14.5 years. The success rate after a single SWL session was 82.7% (renal 82.2% and ureteral 83.3%; P = .81). The retreatment rate was 14.7% (renal 15.2% and ureteral 14.2%; P = .79). The stone-free rate was 77% (renal 74.1% and ureteral 80.9%; P = .10). Of the 474 patients, 43 had pre-SWL ureteral stents, and 13 required post-SWL ureteral stenting; 35 patients required post-SWL curative procedures. The EQ was 0.66, and the modified EQ was 0.62. On multivariate analysis, the stone-free patients had a smaller stone size (9.5 vs 10.3 mm, P = .02), younger age (53.1 vs 58.0 years, P = .002), right-sided stones (83.6% vs 71.0% P = .001), and the absence of a ureteral stent (78.7% vs 64.3%; P = .001). CONCLUSIONS: The mobile Storz Modulith SLX-F2 lithotripter has an acceptable EQ of 0.66. In the present study, smaller stones (<10 mm), younger age, right-sided stones, and the absence of ureteral stents were associated with significantly greater stone-free rates. Copyright © 2011 Elsevier Inc. All rights reserved. PMID: 21550641 [PubMed - in process] CommentCommentA good paper that may stimulate thinking. The 0.66 EQ of the MODULITH SLX-F2 was similar to the EQ of 0.64-0.67 of the HM3 lithotripter reported in the literature. In a recently reivewed publication by Zehnder et al. (A Prospective Randomised Trial Comparing the Modified HM3 with the MODULITH SLX-F2 Lithotripter. Europ Urol 59 (2011) 637 – 644) the overall EQs for the modified HM3 and MODULITH1 SLX-F2 lithotripters were 67% and 58%, respectively. The stone-free rates for the proximal, mid-, and distal ureteral locations were 76.8%, 84.6%, and 86.1%, respectively, which is not as good as the stone-free rate of 96.1%, 97.8%,and 97.9% reported by Tiselius (Tiselius HG. How efficient is extracorporeal shock wave lithotripsy with modern lithotripters for removal of ureteral stones? J Endourol. 2008;22:249-255) It is difficult to tell what the reasons for differences are. In the multivariate analysis of the present publication smaller stones (<10 mm), younger age, right-sided stones, and absence of ureteral stents were associated with significantly greater stone-free rates. The retreatment rates and the stone free rates of the 4 operators were not significantly different in the multivariate analysis.
The operator with the lowest retreatment rate had the highest stone free rate and vice versa. It seems that good machines need good operators to be good. Peter Alken |
