Ex vivo model for renal fracture in cryoablation

To demonstrate the formation of fractures due to cryoablative therapy in a controlled model and validate the new model for the study of the complication of fractures during renal cryoablation.

Endocare PERC-17 (1.7 mm) and Galil 17 ga IceRod (1.47 mm) probes were selected because of similar diameter and reported ice-ball size. The ex vivo model used here was a porcine kidney obtained at the supermarket. The kidneys were subsequently bivalved. The cryoprobes were inserted running just underneath the cut surface, entering the lateral surface of the kidney, and directed toward the medial surface of either the upper or lower pole. In this manner, we avoided the major calyces and involved the most parenchyma. Freeze-thaw-freeze cycles of various durations were performed. The probes were frozen parallel to each other at a distance of 20 mm apart.

Evidence of cryoablation-induced fracture included popping sounds noted during thaw and cracks that became visible during the phase of second freeze. Cracks were noted to extend from the probe through the parenchyma. In multiple probe freezes, the intervening zone between the 2 ice-balls had smoother ice and the fractures that appeared there originated at either probe. Fracture formation was only observed with the Endocare probes, with single or parallel freezes. No fractures were noted in the IceRod freezes.

The bivalved ex vivo kidney is an inexpensive, representative, and demonstrative model for study of fracture during cryoablation.