Experimental hepatic radiofrequency ablation using wet electrodes: electrode-to-vessel distance is a significant predictor for delayed portal vein thrombosis

The aim of this study was to examine possible explanatory variables associated with acute and delayed portal vein thrombosis after hepatic radiofrequency (RF) ablation using wet electrodes. Coagulations were created within 1.5 cm of the right portal vein (RPV) branch in 12 pigs with (n=6) or without (n=6) Pringle manoeuvre. Sham operations with Pringle manoeuvre were performed in four animals. Rotational portal venography was performed prior to ablation, 10 min after ablation and 4 days after ablation. Vessel diameters and vessel patency was determined from the portal venograms. Distance between the ablation electrode and RPV was measured from 3-dimensional reconstructions of the portal venograms. The portal veins were examined by microscopy. Delayed portal vein thrombosis was found in two of six animals in the Pringle group and three of six animals in the control group 4 days after ablation (P=1.0, Fisher’s exact test). All five occurrences of delayed portal vein thrombosis were found in the six animals with a distance between the ablation electrode and RPV of 5 mm or less (P=0.030), indicating that the electrode-to-vessel distance may be an independent explanatory factor for delayed portal vein thrombosis after RF ablation with wet electrodes.