Percutaneous cryoablation of the kidney in a porcine model

Several reports have documented that renal cryoablation when used either vi a open or laparoscopic surgical techniques can be well tolerated in animal models. We sought to examine the feasibility of performing renal cryoablati on percutaneously, under ultrasound guidance, in a porcine model. A total o f 13 juvenile swine was treated. In each animal the lower pore of the left kidney was used as the target Each animal had serum drawn for Hct, Wbc, CK, BUN, creatinine, and myoglobin pre- and postcryoablation and again at the time of sacrifice. Animals were sacrificed at 0-42 days postoperatively, an d the treated renal units were harvested and submitted for histologic exami nation. The procedures were divided into three groups based on the extent o f the freeze time. Group 1 (n = 4) was treated for 3-4 min, single freeze; Group 2 (n = 3), 6-7 min, single freeze; and Group 3 (n = 6), a double free ze-thaw cycle, each for 10 min. None of the animals in this experiment died or experienced significant clinical deteriorations at any time post-treatm ent. No significant differences in any of the measured serum markers were n oted between pre- and post-treatment values. For animals in Groups I and 2 discrete cryolesions were created with sharp I-mm borders and no perirenal reaction/damage to surrounding structures. For animals in Group 3 large are as of renal infarction/cryolesions were produced, with significant perirena l reaction in 5/6 animals and gross hydronephrosis/total renal loss in 2/6. Percutaneous renal cryoablation appears to be well tolerated in the porcin e model which we used. Associated morbidity appears to be related to the ex tent of freezing, with a safety tolerance in the present study limited to t arget areas of approximately 3-5 cm(3). These findings suggest that a pilot study of percutaneous renal cryoablation for patients with 3-4-cm exophyti c lesions may be warranted. (C) 1999 academic Press.