This was an in vitro study comparing total fragmentation and fragment size varied by different Ho:YAG power settings. All stones were fragmented with 365 nm fiber, in an 8 mm diameter cylinder and applied 500 J of energy. In addition, a comparison of total fragmentation was made with and without retropulsion devices (Accordion and BackStop). As with previous studies, retropulsion increased as pulse energy was increased. The back-stop devices aided in eliminating retropulsion and greater total fragmentation by increasing the frequency/total time of contact of the stone and laser. In addition both the total fragmentation and fragment size increased as pulse energy increased. Furthermore, ablation craters in fragments >1mm were measured using optical computed tomography for different types of stones (uric acid, struvite, calcium oxalate monohydrate) and crater size increased proportionally to the increase in pulse energy. Moreover, pressure transients were measured by a needle hydrophone, and it was noted that pressure transients increased as pulse energy increased (<10 bars at 0.5J ad 20-30 bars at 2.0J pulse energy P<0.01), but overall remained low and is consistent with a photo- thermal mechanisms of fragmentation.
In conclusion, by utilizing a back-stop device, retropulsion is eliminated to produce greater total fragmentation. In addition, low pulse energy (0.2-0.5J) produced minimal retropulsion and tiny fragments, whereas high pulse energy (1.0-2.0J) produced greater retropulsion, and larger fragments. The authors conclude that the ideal setting depends on whether the urologist desires tiny debris to pass without utilizing a basket or larger fragments to remove with a basket. Utilizing an anti-retropulsion device may improve total fragmentation with either technique.
Overall, this podium session has been excellent and very informative. All presenters and their research showed significant promise and advancement for the field of ureteroscopy and endourology. With further research incorporating newer technologies, significant advances can be made in the near future and expand our abilities to answer clinical questions that will improve patient care.
Presented by Jason Lee, et al. at the American Urological Association (AUA) Annual Meeting - May 14 - 19, 2011 - Walter E. Washington Convention Center, Washington, DC USA
Reported for UroToday by Hak Lee, MD, Department of Urology, University of California, Irvine.