'Gold standard' lithotripter wins clearance comparison

March 1, 2009

Various aspects of shock wave lithotripsy (SWL) were the focus of several abstracts presented at the World Congress of Endourology & SWL here. Data from one U.S. group seemed to suggest, however, that SWL's "gold standard" offers better stone fragmentation and clearance than at least one newer device.

Shanghai, China-Various aspects of shock wave lithotripsy (SWL) were the focus of several abstracts presented at the World Congress of Endourology & SWL here. Data from one U.S. group seemed to suggest, however, that SWL's "gold standard" offers better stone fragmentation and clearance than at least one newer device.

Separately, researchers reported beneficial effects of using an escalating voltage SWL strategy.

A comparison study from Washington University School of Medicine in St. Louis retrospectively evaluated 129 consecutive patients who had undergone SWL with either the unmodified Dornier HM3 (Dornier MedTech America, Kennesaw, GA) or the Modulith SLX-F2 (Karl Storz, Kennesaw, GA). Seventy-one patients were treated with the HM3 and 58 with the Modulith SLX-F2. Patients were classified as either stone free/having asymptomatic fragments ≤2 mm or as having asymptomatic residual fragments ≤4 mm, based on kidney, ureter, or bladder (KUB) x-ray or computed tomography imaging at 6 weeks and at 3 months after treatment with SWL.

The auxiliary procedure rate was 11% for the HM3 group versus 25% for the SLX-F2 group (p=.09), whereas 5.8% of those treated with the HM3 required re-treatment compared to 3.8% for those treated with the Storz device (p=.9).

The investigators concluded that the "gold standard" HM3 demonstrates better stone fragmentation and clearance compared to the SLX-F2 and that "success" should be better defined.

Shock rate safety studies

A study from the Columbia University Medical Center, New York, examined both the stone-free rate and the renoprotective effects of voltage escalation on 40 patients with similar age, sex distribution, and stone size (median, 8 mm) who were undergoing SWL. Patients were divided into two groups. Those in a dose escalation protocol were subjected to 500 shocks at 14 kV, 1,000 shocks at 15 kV, and 1,000 shocks at 16 kV; those randomized to undergo a fixed strategy received 2,500 shocks at 16 kV.

Stone-free rate (defined as <2-mm fragments) was assessed by KUB x-ray. Renal injury was evaluated by measurement of beta-2 microglobulin and microalbumin before treatment, immediately after treatment, and 1 week after treatment.

At 3 months, 89% of the patients in the voltage escalation group were stone-free compared to 48% in the fixed voltage group (p<.05) at 3 months, reported lead author Mantu Gupta, MD, director of the New York-Presbyterian Hospital Kidney Stone Center and director of endourology at Columbia.

No significant differences were noted in markers of renal parenchymal injury in the immediate postoperative period; however, urinary microalbumin measured at 1 week post-SWL approached statistical significance (p=.07) in favor of escalating voltage.

"Dose escalation demonstrates better stone fragmentation and potentially provides protection from renal parenchymal damage due to shock wave lithotripsy," Dr. Gupta explained.