HISTOMORPHOLOGICAL CHANGES AFTER NEODYMIUM-YAG LASER-COAGULATION OF THE HUMAN PROSTATE WITH THE SIDE FOCUS FIBER - EFFECT OF POWER SETTING AND TIME

The objective of our study was to determine optimal treatment paramete rs and appropriate methods of examination for neodymium:yttrium-alumin um-garnet (Nd:YAG) high-power laser coagulation of the human prostate in relation to power setting and time. Transurethral free-beam laser c oagulation was performed with the Side-Focus side-firing laser fiber i n ten patients prior to planned radical surgery, of whom six underwent transperitoneal laparoscopic lymphadenectomy and laser coagulation 4- 9 days prior to open surgery. Depth and volume of coagulated prostatic tissue were measured at power setting/time combinations of 40 W/90 s and 60 W/60 s, respectively, while holding total energy delivery const ant. Microscopic examination in the early phase showed that epithelial cells had become loose from the basal-cell membrane. By 4-9 days ther e was evidence of conspicuous squamous epithelial metaplasia with a hi gh proliferation rate as a sign of reepithelialization. Using the Side Focus side-firing laser fiber, both treatment modalities showed compa rable volume coagulation. In contrast there was a significant differen ce between those prostates removed at 4-9 days and those removed at 60 -210 min after laser coagulation. We conclude that laser-induced chang es in the human prostate are conclusively discernible only after 4 day s.