A novel murine model for the study of human renal cryoablation

to develop a reproducible, non-debilitating in vivo murine model of human renal cryoablation using a standard closed argon-delivery system.

Custom engineered 2-mm conical tip cryoprobes for use on the standard argon-based cryoablation unit (Endocare, Inc. Irvine, CA, USA) were used to create small controllable iceballs (−160 °C) in the mouse kidney. The time to create a 4-mm cryolesion was compared using a contact vs puncture technique in 10 mice. To show consistency of the induced-freeze injury, a 4-mm iceball was created in 20 murine renal units and the time to creation and the size of the resultant cryolesion measured. To investigate lesion regression and histological changes, we created a 4-mm renal cryolesion in 28 mice and killed four each at 1, 3, 7, 14, 21, 28, and 35 days. The measured coronal cross-sectional area of the cryoablation site at necroscopy was compared to the initial calculated area as a percentage. To assess renal preservation, blood urea nitrogen (BUN) and creatinine levels at 1 week after cryoablation or sham ablation was compared (10 mononephric mice in each group).

The time to create the desired iceball was 1.9 times quicker using the puncture vs the contact technique. The mean (sd) time to forming a 4-mm iceball was 35.3 (4.8) s with a mean maximum length of the resultant post-thaw injury of 5.7 (0.5) mm and a 9% coefficient of variance. Regression analysis of the two-dimensional cross-sectional coronal area of the cryolesion showed a statistically significant linear pattern of regression over time (P = 0.037) and classic histological findings. There was no significant difference in the BUN or creatinine levels in mononephric mice 1 week after cryotherapy compared with the sham-ablated controls.

We describe a reproducible, non-debilitating, easily manipulated murine model for the study of human renal cryoablation.