Cystic duct occlusion by microwave tissue coagulator in rabbits

In this preliminary study a flexible bipolar microwave electrode, 1.8 mm in diameter, was designed to occlude the cystic duct in 18 rabbits. Thermal model tests were performed to evaluate the effect of the antenna and to master the coagulating condition. Through surgical cholecystostomy, the antenna was inserted into the proximal cystic duct for various coagulation treatments. Cholecystography showed that the cystic duct was occluded minutes to hours after coagulation. Histologically, the microwave technique induced a chronic inflammation and fibrosis which eventually obliterated the coagulated cystic duct permanently. In group A (30 mA for 20 s) the cystic duct epithelium regeneration occurred and surrounding liver damage was limited, while in groups B (50 mA for 10 s) and C (70 mA for 6 s) no epithelium regeneration was observed and injury to the liver was mild to moderate. It was found that microwaves generated at 50 mA for 10 s to occlude the rabbit's cystic duct are effective and less injurious.