Risk factors associated with renal parenchymal fracture during laparoscopic cryoablation

To assess the risk factors for haemorrhage and renal fracture associated with renal cryoablation. In a porcine model, 120 cryoablations were administered in 26 pigs, with five groups of 24 ice-balls each; in groups 1 and 2 asynchronous cryoprobe activation was evaluated for the 1.47- and 3.4-mm cryoprobes (IceRods, Galil Medical, Plymouth Meeting, PA, USA), respectively; in group 3, three-3.4 mm cryoprobes were used to examine synchronous probe activation; in group 4 the 1.47-mm cryoprobe was used to examine single-probe activation with premature cryoprobe extraction; and in group 5 we used a new 'guillotine' technique for upper-pole renal cryoablation. Ice-ball fractures and haemorrhage were characterized by the location, length and depth of each fracture, was well as the degree of bleeding. In all, 26 domestic pigs successfully had renal cryoablation procedures. In group 1 and 4 there were no episodes of renal fracture; in group 2 renal fracture occurred in 10 (42%) trials. Group 3 had 22 (92%) renal fractures during the freeze/thaw cycle. Group 5 had 13 (54%) renal fractures during the freeze/thaw cycle, and there was an additional ice-ball fracture during probe removal once in 24 times. Renal fracture is most common with the application of larger 3.4-mm cryoprobes in the synchronous and asynchronous setting. Under standard application, smaller (1.47-mm) cryoprobes result in little renal fracture or bleeding. The use of the guillotine technique is associated with a greater risk of renal fracture.