The evolution and state of modern technology for prostate cryosurgery.

Cryosurgery is the in situ ablation of a target tissue by application of extreme cold temperature. The ability of cryosurgery to ablate tissue is unquestioned. It is the controlled application of a cryoinjury in a manner to minimize morbidity that is problematic. Prostate cryosurgery is complicated by the proximity of the prostate to adjacent structures that are sensitive to a freeze injury, namely the urethra, rectal wall, and neurovascular bundles. Several recent technological advances have led to the development of an effective treatment protocol with acceptable morbidity. These include the advent of real-time transrectal ultrasound, cryomachines with almost instant freeze-thaw control through the use of the Joule-Thompson effect, and warming catheters to effectively preserve the integrity of the urethra and external sphincter. Further, temperature monitoring at the posterior margin of the prostate sometimes combined with an injection of saline solution into Denonvilliers fascia has reduced the occurrence of urethrorectal fistula formation to 0% to 0.5% in modern series. We review the key innovations of prostate cryosurgery that differentiate this state-of-the-art procedure from that used by early investigators to even that of the early 1990s. Potential future innovations, specifically related to image guidance of the procedure, are also addressed.