Influence of large intrahepatic blood vessels on the gross and histological characteristics of lesions produced by radiofrequency ablation in a pig liver model


Ichiro Shimizu, MD, Department of Digestive and Cardiovascular Medicine, Tokushima University School of Medicine, Kuramoto-cho, Tokushima 770-8503, Japan.
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Abstract: Aims: To determine whether the presence of large intrahepatic blood vessels (≥3 mm) affect radiofrequency (RF)-induced coagulation necrosis, the gross and histological characteristics of RF-ablated areas proximal to or around vessels were examined in normal pig livers.

Methods: An RF ablation treatment using a two-stepwise extension technique produced 12 lesions: six contained vessels (Group A), and the other six were localized around vessels (Group B).

Results: Gross examination revealed that the longest and shortest diameters of the ablated lesions were significantly larger in Group B than in Group A. In Group A, patent vessels contiguous to the lesion were present in a tongue-shaped area, whereas the lesions in Group B were spherical. Staining with nicotinamide adenine dinucleotide diaphorase was negative within the ablated area; but, if vessels were present in the ablated area, the cells around the vessels in an opposite direction to the ablation were stained blue.

Conclusions: Roll-off can be achieved with 100% cellular destruction within a lesion that does not contain large vessels. The ablated area was decreased in lesions that contained large vessels, suggesting that the presence of large vessels in the ablated area further increases the cooling effect and may require repeated RF ablation treatment to achieve complete coagulation necrosis.