In vitro assessment of Ho:YAG laser lithotripsy for the treatment of canine urolithiasis

The Ho:YAG laser, used successfully in humans, may be effective for treating canine urolithiasis. The purpose of this study was to determine the in vitro effects of various Ho:YAG laser operating parameters on canine uroliths and a urethra model. Canine uroliths of known composition and cadaveric porcine urethral tissue were irradiated with the Ho:YAG laser. Fragmentation time was analyzed as a function of urolith composition, water weight, Hertz, pulse mode, and energy. All uroliths were completely fragmented with 20 seconds or less of laser irradiation. Calcium oxalate, cystine, and silica uroliths had significantly longer fragmentation times than struvite and urate uroliths. As Hertz rate increased, fragmentation time significantly decreased. No significant differences were noted in fragmentation time or total energy required for fragmentation between single and double pulse mode. Grossly visible urethral damage increased as total energy increased. Urethral damage scores were significantly higher in tissues treated with a 900 incident beam compared to those tissues treated with a 300 incident beam. Likewise, urethral damage scores were significantly higher in contact mode treated tissues compared to non-contact mode treated tissues. Based on these findings, the Ho:YAG laser may be useful for treating clinical cases of canine urolithiasis.