ENDOUROLOGY & LAPAROSCOPY

Prospective randomized comparative study of the effectiveness and safety of electrohydraulic and electromagnetic extracorporeal shock wave lithotriptors
Sheir KZ, Madbouly K, Elsobky E
From the Urology and Nephrology Center, Mansoura University, Mansoura, Egypt
J Urol. 2003; 170: 389-92

• Purpose: We compared the efficacy of 2 shock wave energy sources, electrohydraulic (Dornier MFL 5000, Dornier MedTech, Wessling, Germany) and electromagnetic (DLS, Dornier Lithotriptor S, Dornier MedTech), for the treatment of urinary calculi.
• Materials and Methods: A prospective randomized study of 694 patients with urinary stones was conducted during 12 months to compare the efficacy of the 2 machines. Entrance criteria were radiopaque single or multiple stones at any location within the kidney or the ureter, 25 mm or smaller that had not previously been treated by any means. Patients with congenital anomalies were excluded from this study with all other contraindications for extracorporeal shock wave lithotripsy. Following lithotripsy a plain abdominal film and tomograms were done 1 week after each session to determine if there were residual stones and assess the need for re-treatment. Patients were evaluated 4 weeks after lithotripsy by plane abdominal x-ray and spiral computerized tomography. Success was defined as no residual stones. Univariate and multivariate statistical analyses were performed for different variables that may have an impact on the success rate, including the type of lithotriptor. Comparisons of treatment parameters, complications and success rate for both lithotriptors were done.
• Results: Of 9 variables examined with univariate analysis 6 had a significant impact on the success rate. Of these 4 maintained their statistical impact on multivariate analysis. These were side, site of the stones, renal morphology and type of lithotriptor. Treatment time was significantly shortened for DLS (54 ± 32.9 minutes compared to 65.7 ± 44.7 for MFL, p < 0.001). The re-treatment rate was lower for DLS at 34% versus 51.6% for the MFL (p < 0.001). The overall success rate was 85.4%. It was 88.5% for DLS compared to 82.4% for MFL (p = 0.03). No statistically significant difference between the lithotriptors was noted for ureteral calculi (p > 0.05). The success rate was higher in the DLS group for renal stones especially lower caliceal and pyelic stones (p < 0.05). The success rate was higher in DLS group for stones 10 mm or smaller, 92.8% versus 85.3% for MFL (p = 0.03). The success rate was comparable in both groups for stones larger than 10 mm (81.8% for DLS versus 77.9% for MFL, p > 0.05). No statistically significant difference was found in the complication rate for the groups. Steinstrasse were noted in 4% of patients treated with MFL and 3% of those treated with DLS. Subcapsular hematomas were noted in 2 patients in each group. No procedures after extracorporeal shock wave lithotripsy were needed in either group.
• Conclusions: The electromagnetic lithotriptor (Dornier lithotriptor S) has significant clinical advantages over the electrohydraulic lithotriptor (Dornier MFL 5000) in terms of treatment time, re-treatment rate and success rate, although there is no difference in the complication rate.
  
• Editorial Comment
  As nice as it would be to conclude that this study provides definitive evidence with regards to one energy source over another, as the authors would like us to believe as suggested by their stress on the energy source rather than the particular lithotriptor throughout the text, it does not do that. Other differences between the lithotriptors make this conclusion invalid. The focal zone is 224 mm2 in the MFL and 175 mm2 in the DLS. The number of shock wave delivered was not provided. One might conclude reasonably, however, that indeed the DLS is a better machine than the MFL – primarily owing to the lower retreatment rate. Since the MFL is no longer in production, this information is not all that useful. One finding in the study that is very useful, however, is the minimal (0.6 %) rate of hematoma formation overall, despite the use of sensitive CT scans for surveillance. Other studies have suggested that hematoma formation might be more frequent with either machine, and given the sensitive radiographic assessment in this study I find this reassuring.

Dr. J. Stuart Wolf Jr.
Associate Professor of Urology
University of Michigan
Ann Arbor, Michigan, USA