Elkoushy MA, Hassan JA, Morehouse DD, Anidjar M, Andonian S
Department of Surgery, McGill University, Montreal, Quebec, Canada
OBJECTIVES: 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 (smaller than 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.
Urology. 2011 Oct;78(4):759-63. doi: 10.1016/j.urology.2011.03.005. Epub 2011 May 7
PMID: 21550641 [PubMed - in process]
A 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 (smaller than 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.
|Retreatment rate (%)
|Stone free rate (%)
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.