Percutaneous transperineal prostate cryosurgery using transrectal ultrasound guidance: animal model. Cryosurgery has previously been used successfully to treat prostatic carcinoma. Inability to monitor the freezing led to local complications that limited the use of this modality. Recent studies have shown that monitoring of the freezing process can be accomplished using real-time ultrasound. In this study, transrectal ultrasound guidance was used to guide a cryoprobe percutaneously, using a transperineal approach, into the prostate. The extent of freezing was then monitored using ultrasound, taking care not to freeze the urethra or the rectum. Six dogs had the procedure without any complications. This study demonstrates the feasibility of a noninvasive treatment for prostatic carcinoma. 