“River effect” of radiofrequency ablation on relevant regional hepatocytes in living swine liver: a preliminary pathological study

Objective 　To establish the animal model of radiofrequency ablation (RFA) on living swine liver, and observe the pathologic changes caused by the "river effect (RE)"of RFA on relevant regional hepatocytes. Methods 　Three target segments of liver of each of 6 Guangxi BA-MA mini pigs were selected for ablation. Under the guidance of sonography, the tip of RFA electrode was inserted into the liver close to segmental outflow vessel, and every ablated point was heated for 6 minutes. Pathological changes of relevant downstream region along portal vein and hepatic artery were observed under microscope after RFA. Results 　The ablated region of the liver was oblong in shape with outer diameter of 2.2±1.1cm on gross inspection. Thermal damage (e.g. obvious dilated blood sinuses, with abundant inflammatory cell infiltration in portal vein region and necrosis of hepatocytes, etc.) was observed in downstream region of the relevant portal vein under microscope after RFA. However, liver tissue in adjacent area around the vessel was intact, and no obvious thermal damage was found. Conclusion 　The "river effect" during RFA for liver tissue may lead to thermal damage to hepatocytes along the downstream region of the regional portal vein, and this effect decreases gradually toward the surface of liver segment.