Experimental study on the influence of microwave tissue coagulation on both the hepatic vein and the portal vein

Objectives : This study was undertaken to examine the morphological influence of microwave tissue coagulation on the intrahepatic main vessels (both the hepatic vein and the portal vein). We have tried to confirm the harmlessness of microwave tissue coagulation to the intrahepatic main vessels.Methods : The adult mongrel dogs underwent the liver coagulation near the intrahepatic main vessel using the microwave tissue coagulator. The liver tissue was punctured and irradiated by the 15 mm needle electrode with a microwave energy of 60 watts for 30 seconds and then the electrode was charged with a dissociating electric current for 20 seconds. Group A : The distance was 5 mm from the tip of electrode to the intrahepatic main vessel wall. Group B : The tip of electrode attached to the intrahepatic main vessel wall. Just and on the seventh day after the operation, we obtained the coagulated liver tissue and the vessel wall specimens through sacrifices and they were histologically examined (hematoxylin-eosin stain, elastica van Gieson stain, and using scanning electron microscope).Results : Group A : The coagulation of 5 mm diameter from the vessel wall have not injured them at all. Group B : The tunica adventitia was partially injured and the other layers (tunica media and tunica interna) were slightly degenerated, each layers were discriminated. The seventh day after the operation, the vessel wall which was not destroyed and the bleeding was not observed.Conclusions : Results of this study suggests that the microwave tissue coagulation may be useful and harmless, if it is used on the 5 mm far from the intrahepatic main vessel. The bleeding was not observed, even if the tip of the electrode attaches to the intrahepatic main vessel wall.