Clinicopathologic effects of cryotherapy on hepatic vessels and bile ducts in a porcine model

Background: The proximity of a hepatic tumor to major vessels and bile ducts limits the use of cryotherapy because of the potential damage to these structures. However, the effects of cryotherapy on major hepatic vessels and bile ducts are not well understood. Methods: Nine pigs underwent laparotomy and intraoperative ultrasound to identify hepatic vessels larger than 5.0 mm. Cryotherapy consisting of two freeze-thaw cycles was performed, incorporating the identified vessel. In four pigs the Pringle maneuver was performed to determine the effects of partial vascular occlusion on the hepatic parenchyma and structures undergoing cryotherapy. The animals were sacrificed 30 days postoperatively, and the livers were processed for histologic examination. Results: Eight of the nine livers had vessels larger than 5.0 mm incorporated into the iceball, with all vessels having evidence of infarction but remaining patent. All the livers had major bile ducts incorporated in the iceball, with eight having evidence of infarction. The Pringle maneuver had no real effect on the degree of vessel and bile duct infarction. There was no incidence of hepatic bleeding, liver fracture, bile leak, or hemobilia. Conclusions: Cryotherapy results in the infarction of major hepatic vessels and bile ducts but can be safely performed in the porcine model. Proximity of tumors to major vascular and biliary structures may not be a contraindication to the use of cryotherapy. Further studies are necessary to determine whether cryotherapy can be used in humans.