Techniques of coagulation laser prostatectomy for narrow divergence angle fibers

Although laser prostatectomy has become an accepted technique for the treatment of obstructive prostatism, considerable debate remains about which laser prostatectomy method to use in various treatment situations. This article discusses the different methods of noncontact side-firing coagulation laser prostatectomy using narrow divergence angle fibers (< 30 degrees). Static treatment strategies that have been successfully employed with widely divergent beams are not appropriate for fibers producing narrow divergence angle beams. Narrow divergence angle beams produce a small diameter spot on the prostatic urethra and far larger power density. Additionally, neodymium/yttrium aluminum garnet light scatters relatively poorly within prostatic tissue. Most light continues along the path of through transmission until ultimate tissue absorption and conversion into heat. The width and total volume of the coagulated lesion is therefore limited when using a narrow divergence angle fiber to produce static lesions. Probe movement is essential. Rapid (> 2 mm/s) probe movement produces only superficial coagulation. An initial dwell period of approximately 3 s is also important to maximize coagulated tissue volume. Scanning strategies where the fiber is moved through the prostatic urethra in longitudinal and radial directions are discussed and compared. Radial and longitudinal scanning methods produce similar coagulation defects. Treatment using a rocking motion within a limited volume of tissue may increase coagulation depth. No technique is ideal for all clinical situations. Vaporization prostatectomy or contact laser transurethral incision of the prostate is appropriate for primary treatment of glands < 30 g or as adjunctive therapy to facilitate early catheter removal. Alternative treatment methods are compared to noncontact coagulation prostatectomy.