To test the hypothesis that dual-modality intracorporeal lithotripters used during percutaneous nephrolithotomy create a degree of tissue trauma in the dual-modality mode (ballistic and ultrasonic) similar to that in the single-modality mode (ultrasonic).

The lithotripter devices tested were the Cyberwand and Swiss LithoClast Select. The activated probes, in both single- and dual-modality modes, were applied directly to the renal pelvis of 11 fresh nephrectomy specimens. The treated tissue sites were then processed for light microscopy and reviewed by a single genitourinary pathologist.

Microscopic examination of the renal pelvis after 2 seconds of direct contact showed minimal denudation of the urothelium, with no changes noted in the subepithelial or muscle layers for the 2 devices evaluated. Direct contact for 4 seconds showed urothelial denudation and subepithelial changes (n = 13 of 23). Muscle injury was observed in some dual-modality specimens (n = 6 of 12). Increasing the contact time to 8 seconds resulted in fragmentation of the muscle layers more frequently with both settings (n = 15 of 22), except for when the Cyberwand was used at the small stone setting (n = 0 of 7).

In the ex vivo setting, minimal differences were noted in the degree of histologic trauma between the Cyberwand and Swiss LithoClast Select at 2 seconds. However, both dual-modality devices resulted in muscle damage at 4 and 8 seconds of contact time. Care should be taken during clinical procedures to avoid prolonged contact with the renal pelvis to minimize the potential for tissue trauma.