Stone Disease: New Technology

In this session, particular attention was paid to newer developments in ancillary devices to be used during ureteral stone retrieval. Sharma and colleagues at Loyola (Abst. 1680) compared the load release pressure of the stone cone (Boston Scientific, Natick, MA) and a new ureteral occlusion device (Cook Urological, Spencer, IN) in vitro. Both devices were designed for prevention of proximal stone migration during intracorporeal lithotripsy; however, a potential complication of these devices is stone entrapment with inability to disengage the device from the stone within a narrow ureter. Accordingly their test device consisted of trying to pull a 3 mm bead through a urethane tube with a 3 mm point of constriction. The stone cone released the bead with a mean load of 0.190 lbs and the ureteral occlusion device released the bead at a mean load of 0.861 lbs. (p<.01). While these differences were statistically significant, from a clinical standpoint, both release pressures are quite low and thus the clinical significance of this difference may well be moot.

Albala and colleagues at Duke presented their clinical results with an investigational radially expanding ureteral stone sweeper (Fossa, Boston, MA) (Abst. 1681) that has 15-17 collapsible baskets along its length. The stent is to be used during shock wave or ureteroscopic lithotripsy procedures. It is specifically designed to capture and facilitate subsequent removal of small stones upon its extraction, which in this study occurred anywhere from 3- 49 days after the lithotripsy procedure. Stones were removed with the stent in 40% of cases while in another 52% of cases; patients passed stones after the stent was removed. Only 8% of patients had residual stones. However, the stent was difficult to remove in 3 patients, and 2 patients required additional analgesia at the time of outpatient stent removal. No ureteral complications have been noted thus far. The stone sweeper stent remains investigational and further clinical studies are apparently ongoing.

Two papers in this session addressed one of the latest developments in shock wave lithotripsy, dual pulse delivery. McAteer and colleagues from Indian University (Abst. 1674) using a Duet dual pulse lithotripter (Direx, Natick,MA) compared stone fragmentation from synchronous (i.e. simultaneous) dual pulses, 10 µs delayed asynchronous dual pulses, and a pulses delivered by a single electrode. The authors demonstrated that stone breakage was most efficient with synchronous dual pulses while asynchronous delivery was the least efficient. Similarly, Sheir and co-workers from Mansoura reported a clinical study with a bidirectional synchronous twin pulse shock wave lithotripter (Twinheads, FMD, Lorton, VA) (Abst. 1679). They treated 55 patients with a mean stone size of 12.5 mm. No major complications were noted except for mild hematuria in 25 patients and flank pain in 4 patients. At 14 days follow- up, 34% of the patients were stone free, 40% of the patients had stones < 5 mm and were stone free at 1 month follow- up, and 26% of the patients had residual stones > 5mm. Patients with residual stones > 5mm underwent repeat treatment and eventually all became stone free. The safety and efficacy of the bidirectional synchronous twin pulse shock wave lithotripsy appears to have the potential to rival the outcomes with the HM3. Additional confirmatory clinical studies are anxiously awaited.

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