Tu1037 Outflow of Hepatocytes Into the Hepatic Vein During Radiofrequency Ablation in Porcine Liver

[Background and Aims] Sporadic cases of unexpected recurrence, such as intrahepatic dissemination, extrahepatic seeding, and rapidly growing recurrence have been described following radiofrequency ablation (RFA). Some reports speculated that RFA during energy application may increase intratumoral pressure and favor intravascular spread of the tumor. Therefore, we examined the existence of hepatocytes in the hepatic vein during RFA. [Subjects and Methods] A total of 3 pigs with a mean body weight of 58.8 ± 5.7 kg were intubated and general anesthesia were maintained. Using the 8-Fr sheath inserted into the left jugular vein, a guidewire was used to guide a 4-Fr catheter to the hepatic vein. After median laparotomy, needle electrodes were inserted inside the liver, and RFA was performed near the catheter. A cooled-tip RF needle electrode was used for RFA. Ablation was performed by increasing output by 10 W/min, starting at 40 W. The duration of ablation was 6 min. The blood was collected by placing the catheter 10mm from the needle electrode tip. Fifteen RFA sessions of 3 animals were examined to detect exfoliated tissues. In every RFA session, 30 ml of the down-streaming blood in the vessel attached to the irradiated part was collected to a heparinized syringe and separated by using Ficoll-gradient method. Cell fractions were incubated with the culture medium for 15 hours. The number of cell clusters attached on culture dishes were counted and examined immunohistochemically for albumin as a hepatocyte marker. [Results] The results of immunohistochemistry showed that albumin-positive cells were found in cell clusters those were attaching and spreading on the culture dish. The margin of the cluster showed membrane ruffling. That means the live hepatocytes being trapped in the outbound vessel of RFA treated site. Various sizes of clusters were found. The clusters were classified in four as S-1 (5 to 10 cells), S-2 (11 to 20 cells), S-3 (21 to 50 cells), and S-4 (more than 50 cells) according to the constituted cell amount. The mean number of cell clusters found in every RFA was S-1; 9 ± 7.1, S-2; 5.1 ± 5.7, S-3; 0.6 ± 0.8, S-4; 0.5 ± 0.8, respectively. Smaller sizes of clusters (S-1 and S-2) were more frequently found (P, 0.01 vs. S-3 and S-4). These clusters were never found in the blood before RFA. Therefore, it should be concluded that the cell cluster was derived from the liver and was artificially exfoliated tissue masses by RFA. [Conclusions] The present results demonstrate that hepatocytes are pushed out alive into the hepatic vein from the hepatic lobules by RFA. These results suggested that a risk of dissemination due to RFA exists.