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Radiofrequency Ablation of Liver Tumors: A New Cause of Benign Portal Venous Gas¹

¹ From the Departments of Radiology, Dana Farber Cancer Institute (T.O., E.V., S.S., K.T., S.G.S.) and Brigham and Women's Hospital (E.V., S.S., P.R.M., K.T., S.G.S.), Harvard Medical School, Boston, Mass. Received July 25, 2004; revision requested September 30; revision received November 30; accepted January 3, 2005. Address correspondence to E.V., Department of Radiology, St Joseph's Hospital and Medical Center, 350 W Thomas Rd, Phoenix, AZ 85013 (e-mail: Eric.vanSonnenberg{at}CHW.edu).

PURPOSE: To retrospectively describe and categorize the presence of portal venous gas (PVG) from radiofrequency (RF) ablation of hepatic tumors.

MATERIALS AND METHODS: The study was HIPAA compliant, and informed consent was waived. Thirty-four consecutive computed tomography (CT)-guided percutaneous RF ablations of liver tumors in 26 patients (13 men, 13 women; mean age, 69 years) with five hepatocellular carcinomas and 21 metastatic liver tumors (13 colon, five other, and three unknown primary tumors) were performed with an institutional review board–approved protocol. Two treatment modalities were used: RF ablation alone (13 procedures) and combined RF ablation and ethanol injection (21 procedures). Presence of PVG was quantified with three parameters: maximum length of a portal venous branch with gas, number of Couinaud segments in which PVG was seen, and total number of portal venous branch points with gas. Then an overall PVG score from 0 to 5 was determined. Also, when tumoral gas was seen on CT scans, the largest cross-sectional area of gas was measured. The two ablation methods were compared for quantities of PVG and tumoral gas. The role of N₂O anesthetic in PVG and tumoral gas formation during ablation also was studied. Statistical analyses were performed with Wilcoxon rank sum and Student t tests.

RESULTS: In 25 procedures (74%), gas was found in portal vein branches; in 30 procedures (88%), gas was also found in tumoral and peritumoral tissues. There was no significant difference in frequency of PVG between the ablation methods. Combined therapy yielded significantly greater lengths of PVG (P < .002) and more portal venous branch points (P < .001) than did RF ablation alone. Mean PVG score was 2.4 ± 0.4 (standard error of the mean) for combined therapy and 0.9 ± 0.2 for RF ablation alone (P < .004). N₂O anesthetic was associated with greater amounts of tumoral gas (P < .008) and PVG (P < .03). Tumoral gas, peritumoral gas, and PVG dissipated within 20 minutes after ablation in all patients. No morbidity or mortality was associated with PVG.

CONCLUSION: RF ablation is a common yet benign cause of transient PVG, tumoral gas, and peritumoral gas. Combined RF and ethanol ablation was associated with more PVG than was RF ablation alone.

© RSNA, 2005