OBJECTIVE: To assess the risk factors for haemorrhage and renal fracture associated with renal cryoablation. MATERIALS AND METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.
OBJECTIVE: To assess the risk factors for haemorrhage and renal fracture associated with renal cryoablation. MATERIALS AND METHODS: 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. RESULTS: 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. CONCLUSIONS: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.