Histopathologic Evaluation of the Canine Prostate Following Electrovaporization

Abstract

Transurethral electrovaporization of the prostate (TVP) for symptomatic benign prostatic hypertrophy (BPH) has proven to be efficacious with minimal patient morbidity. When compared to transurethral resection of the prostate (TURP), TVP demonstrates comparable postoperative flow rates, American Urologic Association (AUA) symptom score indices, and a potential cost savings. However, in the human studies it has not been possible to correlate these clinical parameters with procedure-related histopathologic changes in the prostate immediately postoperative or during wound healing. The following study was done using a canine model in an effort to evaluate these histopathologic changes. Fifteen hounds (25-35 kg.) underwent antegrade electrovaporization of the prostate, via an open cystotomy, using a Circon ACMI USA series resectoscope and video equipment. The dogs were sacrificed and the prostates harvested at various intervals postoperatively (0-11 weeks). The prostates were evaluated grossly as well as histologically for cavitary defects, depth of necrosis, and cellular response. Prostates examined immediately following the procedure demonstrated superficial necrosis (less than 2 mm.) in the region of vaporized tissue. One week postoperatively, the vaporized regions demonstrated an intense acute inflammation amidst superficial necrosis with focal hemorrhage and dystrophic calcification. Transient glandular cystic changes developed, but were resolving by seven weeks postoperatively. Re-epithelialization was underway by the third postoperative week and epithelial stratification underway by the fifth week. There was no extension of the initial two millimeter zone of necrosis at any time point examined. TVP in the canine model vaporizes prostatic tissue at the site of contact. Only a shallow remnant of necrosis remains at the site of vaporization, indicating the highly localized effect of this technique. Healing at the site of vaporization occurs in a rapid and expected manner. These data provide a histopathologic rationale for the minimal morbidity and the efficacious nature of this technique demonstrated in clinical studies.