Thermal damage to normal and hyperplastic prostates due to transurethral balloon laser therapy in dogs

Fourteen dogs were studied to determine the level of thermal damage to the normal or benign hyperplastic prostate. Prostates were heated transurethrally by a balloon laser probe (Nd: YAG laser) at various temperatures for 20 min. Coagulative necrosis was observed in the prostate when it was heated above 45.4 degrees C for 20 min. Tissue damage in the bladder neck occurred above 49.4 degrees C, damage to the urethral mucosa occurred above 46.5 degrees C, and damage to the urethral sphincter occurred above 43.2 degrees C. It was calculated that there was a 50% probability of necrosis of the prostate gland occurring when prostatic tissue was treated at 45.0 degrees C for 20 min. Striated muscle cells in the urethral sphincter were more heat-sensitive than smooth muscle cells of the bladder neck or transitional cells of the urethral mucosa. This basic information is essential for the safe application of Nd: YAG laser hyperthermia to the prostate gland.