Pathologic changes following transurethral canine prostatectomy with a cylindrically diffusing fiber

Transurethral laser prostatectomy was performed on eight mongrel dogs employing a cylindrically diffusing fiber delivery system and a 1.06 mu Nd:YAG laser. Each dog received 15,000 joules of laser energy delivered to the prostate in one continuous dose of 25 watts for 10 minutes. Gross and histopathologic examinations of serial sections of the prostate were performed postoperatively after intervals of 2 hours to 7 weeks. Grossly, a spherical zone of destruction averaging 2.8 cm in diameter was present in dogs except one. Histopathologic changes in the prostate consisted of acute coagulative necrosis with interstitial edema at 2 hours, becoming hemorrhagic by 24 hours. A prominent circular area of acute coagulative necrosis with progressively larger areas of liquefaction and hemorrhage was present in prostates harvested from 4 days to 1 week after lasing. Initial re-epithelization of the resulting cavity was observed at 3 weeks with nearly complete epithelialization 7 weeks after laser treatment. The simplified fiber placement and lack of postoperative complications in this small group of dogs suggest that the cylindrically diffusing fiber could offer significant advantages over laterally deflecting fibers for transurethral prostatectomies in the dog model.