Thermal changes in the canine prostate after transurethral balloon laser prostatectomy

The histological changes by transurethral balloon laserthermia were examined on 23 canine prostates. Immediately after treatment, three zones were observed; the coagulative zone treated over 60 degrees C for 20 min formed an inner layer, the degenerative zone treated between 60 to 46.1 degrees C surrounded the coagulative zone, and the intact zone treated below 46.1 degrees C formed the outer layer. Coagulative necrosis of the gland, swelling of collagen fibers, and thrombus of the vessels occurred in the coagulative zone, shedding and vacuolation around the nuclei of the epithelial cells and stromal edema were observed in the degenerative zone, while thermal changes were minimal in the intact zone. Both coagulative and degenerative zones developed necrosis and started to slough off within 1 week, forming a cavity in the central portion of the prostate. Reepithelialization of the cavity was complete at 4 weeks and the ducts of the prostate gland opened to the surface of the cavity. This treatment preserved the excretory tract of the prostate gland.