RENAL CRYOABLATION IN A CANINE MODEL

Objectives. To assess the potential safety and utility of cryoablation for treatment of selected renal tumors in a canine model. Methods. Ul trasound and direct physical measurements (depth and width) of five cr yolesions were compared. Cryolesions were examined histologically in 6 animals, which were killed at 4 hours, 2 days, 1 week, 3 weeks, 6 wee ks, and 12 weeks, Mortality/morbidity was assessed in 12 animals over a 1-month interval, where 6 animals received small (approximately 2 cm ) cryolesions and 6 animals received large (one third to one half of k idney) cryolesions. Laparoscopic cryoablation was performed in 2 anima ls. Results. A statistically significant association of physical and u ltrasound dimensions was observed (correlation coefficient R = 0.9295; P = 0.0001). Histologic studies in animals killed up to 1 week after cryoablation revealed complete coagulative necrosis within the cryoles ion. The boundary transition from normal to complete tissue necrosis o ccurred in 1 to 2 mm. Animals killed 5 weeks to 5 months after cryoabl ation revealed progressive organization with granulation tissue, chron ic inflammation, hemosiderosis, fibrosis, and contraction of the cryol esion with parenchymal loss. Untreated renal tissue was histologically normal in all kidneys. No mortality or morbidity was detected in the 12 animals followed for 30 days regardless of the size of the cryolesi on. Laparoscopic cryoablation was performed successfully in 2 animals without modification of standard laparoscopic methods. Conclusions. So nographic, histologic, and laparoscopic data in a canine model suggest that cryoablation may be a safe, feasible, and useful method for trea tment of selected renal neoplasms.