Objectives: To assess the potential safety and utility of cryoablation for treatment of selected renal tumors in a canine model.
Methods: Ultrasound and direct physical measurements (depth and width) of five cryolesions were compared. Cryolesions were examined histologically in 6 animals, which were killed at 4 hours, 2 days, 1 week, 3 weeks, 6 weeks, 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 kidney) cryolesions. Laparoscopic cryoablation was performed in 2 animals.
Results: A statistically significant association of physical and ultrasound 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 cryolesion. The boundary transition from normal to complete tissue necrosis occurred in 1 to 2 mm. Animals killed 3 weeks to 3 months after cryoablation revealed progressive organization with granulation tissue, chronic inflammation, hemosiderosis, fibrosis, and contraction of the cryolesion 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 cryolesion. Laparoscopic cryoablation was performed successfully in 2 animals without modification of standard laparoscopic methods.
Conclusions: Sonographic, histologic, and laparoscopic data in a canine model suggest that cryoablation may be a safe, feasible, and useful method for treatment of selected renal neoplasms.