Lesion progression with time and the effect of vascular occlusion following radiofrequency ablation of the liver

Background: The effectiveness of radiofrequency ablation (RFA) under selective vascular occlusion and its effects on architecture and viability of normal liver parenchyma was studied in a porcine model. Methods: RFA was applied in the liver under general anaesthesia in 18 pigs. Six animals were killed immediately after the procedure and 12 at 24 h. RFA was performed sequentially under four conditions: (1) without vascular occlusion, (2) during occlusion of the hepatic artery, (3) during occlusion of the portal vein and (4) during occlusion of the hepatic artery and portal vein. Liver biopsies from the treated area were stained for conventional histological examination, reduced nicotinamide adenine dinucleotide diaphorase and S'-nucleotidase activity. Results: Vascular occlusion significantly increased the size of the coagulation centre after RFA. Combined portal venous and arterial occlusion had no additional effect on lesion size compared with venous or arterial occlusion alone. After 24 h, deterioration of viability was observed in the parenchyma up to 3 cm from the coagulated area. Conclusion: The efficacy of RFA in liver increases with occlusion of the portal vein or hepatic artery. The extent of secondary heat-induced necrosis in liver parenchyma should be considered for determination of the final size of the ablated area.