J Endourology 2009; 23(Suppl 1): A345.

Anti-retropulsion devices increase stone fragmentation efficiency with Holmium:YAG laser lithotripsy.

B Chew, L Jonat, D Lange, R Paterson, J Teichman

Background:  Increased power using Holmium:YAG laser lithotripsy may cause stone retropulsion that results in higher failure rates and prolonged procedures.  We hypothesized that anti-retropulsion devices would increase stone fragmentation efficiency for a given amount of laser energy during lithotripsy.

Methods:  UltraCal 30 stones (N=180) were divided into 6 groups: control group (no backstop device), 7 mm and 10 mm Stone Cone (Boston Scientific), NTrap (Cook Urological), and 7 mm and 10 mm Accordion (PercSys).  Each group was further divided into 3 power settings:  0.5J/10 Hz, 1 J/20 Hz, and 2 J/40 Hz to yield groups with sample sizes of 10.  A total of 500 Joules of energy was delivered in each trial.  Stones were placed in a horizontal 8.5 mm diameter acrylic tube immersed in saline.  The primary endpoint was stone fragmentation efficiency as defined by stone mass change for a given unit of energy.

Results:  At the lowest power setting, only the 7 mm Accordion and 10 mm Stone Cone increased stone fragmentation efficiency over control (p <0.05).  At the higher power settings (20 W and 80 W), all devices increased efficiency over controls (p < 0.001).  Stone retropulsion increased significantly with higher power settings in the absence of any device (p < 0.01).

Conclusion:  Anti-retropulsion devices increase stone fragmentation efficiency and facilitate high power lithotripsy compared to controls.  No device was shown to be clearly superior to any other.  Presumably, the improved efficiency was a result of increasing the contact time between the laser fiber and stone.  Migration of stone fragments was uncommon and no fragments larger than 2 mm migrated past any device.

90-1037 -01 rA