Percutaneous Radiofrequency Ablation for Hepatic Tumors Abutting the Diaphragm: Clinical Assessment of the Heat-Sink Effect of Artificial Ascites

OBJECTIVE. This study was designed to assess whether artificial ascites has a heat-sink effect on the ablation zone for percutaneous radiofrequency ablation (RFA) of hepatic tumors abutting the diaphragm. MATERIALS AND METHODS. We retrospectively assessed 28 patients who underwent percutaneous RFA for the treatment of a single nodular hepatic tumor that abutted the diaphragm from July 2000 to December 2006. All patients underwent ultrasound-guided RFA using internally cooled electrodes. A single ablation for 12 minutes was applied using 3-cm active-tip electrodes. We divided patients into two groups on the basis of whether artificial ascites was introduced before RFA: Group A consisted of patients who received artificial ascites with a mean of 760 mL of a 5% dextrose in water solution (n = 15) and group B consisted of patients who did not receive artificial ascites (n = 13). The volume of the ablation zone was measured on CT images obtained immediately after the ablation procedure, and imaging findings were compared for both groups using the Student's t test. We also compared the local tumor progression rate between both groups using the chi-square test (mean follow-up, 37.4 months). RESULTS. There was no significant difference between the two patient groups with regard to age, sex, Child-Pugh class, or tumor location (p > 0.05). The tumors were significantly smaller in group A patients (mean +/- SD, 1.6 +/- 0.5 cm) than in group B patients (2.1 +/- 0.7 cm) (p = 0.019). The mean volume of the RFA zone was 31.6 +/- 11.9 cm(3) in group A patients and 30.9 +/- 11.0 cm(3) in group B patients. There was no significant difference between the groups in the ablation volume (p = 0.871). Local tumor progression was noted in four patients (26.7%) in group A and in three patients (23.1%) in group B. There was no significant difference in the local tumor progression rate between the two groups (p = 0.83). CONCLUSION. Artificial ascites did not show a heat-sink effect on the volume of the ablation zone after percutaneous RFA for the treatment of a hepatic tumor abutting the diaphragm.