Purpose: The treatment of small renal tumors continues to evolve in parallel with advances in ablative technology. We compared the lesion geometry of 3, 17 gauge cryoneedles to determine the most effective distance and configuration of the cryoneedles in an in vivo porcine kidney model.
Materials and methods: Argon gas based renal cryoablation was performed in 6 pigs using a laparoscopically assisted percutaneous approach. Cryoablation using a single cryoneedle and a template of 3 cryoneedles with various ice ball shapes, including elliptical, bulb-shaped and standard 17 gauge cryoneedles (Galil Medical, Plymouth Meadow, Pennsylvania) was performed in 3 pigs. Three additional pigs underwent renal cryoablation using elliptical cryoneedles in 3 triangular template configurations with the cryoneedles spaced 1, 1.5 and 2 cm apart, respectively. The animals were sacrificed a minimum of 2 weeks following treatment.
Results: Elliptical cryoneedles achieved the largest area of necrosis when used in single and template configurations. When used in a template configuration of 3 needles 1, 1.5 and 2 cm apart from each other the calculated volume of necrosis was 4.3 x 4.5 x 2.5, 4.9 x 4.1 x 2.5 and 4.0 x 4.5 x 2.5 cm, respectively.
Conclusions: Using a single 17 gauge cryoneedle is inadequate for treating most small renal tumors. Cryoneedles with an elliptical ice ball are most effective for achieving consistent and reliable tissue destruction. The 1.5 cm template configuration generated the largest area of necrosis. Our data suggest that with the current technology renal cryoablation should be limited to lesions not greater than 4 cm.