An experimental study on endoscopic ultrasound-guided microwave ablation for porcine liver and pancreas

Objective To evaluate the feasibility and safety of endoscopic ultrasound-guided microwave ablation (EUS-MWA) for porcine liver and pancreas by assessing physiological state and pathological changes. Methods EUS-MWA was performed on liver and pancreas of 8 healthy pigs after general anesthesia. The needle size was 1.9 mm in diameter, and the power of ablation was 65 W, 10 min on liver and 60 W, 5 min on pancreas. The levels of blood amylase and hepatic transaminase were examined before and after the operation. All pigs underwent CT scan on the right postoperative day to assess the extent of ablation and complications. Two pigs were killed 6 hours after operation and 2 others were killed 24 hours after operation to assess structural damage around the puncture path. The remaining 4 pigs were raised to 2 weeks after operation to observe diet, activities and mental state. The ablated areas of liver and pancreas underwent pathological analysis after dissection, and non-ablation regions were treated as the control. Results All 8 pigs underwent EUS-MWA and their vital signs were stable during the operation. Except for the difficulty in locating the pancreas in one case, other surgical procedures were smooth and 18 ablations were performed totally (10 in liver and 8 in pancreas). CT scans showed quasi-circular low density lesions in the liver and pancreas, and the maximum diameter of the ablation area in liver and pancreas was 2.8±0.3 cm, 1.8±0.2 cm respectively. There was no free intraperitoneal gas, ascites or pleural effusion. The level of blood amylase increased at 6 hours after operation and the peak value occurred within 12-24 hours. The level of hepatic transaminase had a mild elevation. The rearing group showed transient food refusal and activity reduction after the operation, but all returned to normal within 1-2 days. No fever, vomiting or other abnormalities occurred. Puncture path burn, adjacent organ damage and bleeding was not observed except for one case of gastric wall burns during pancreas ablation. Pathology showed massive coagulative necrosis and peripheral bleeding area in the liver ablation center, and diffuse focal necrosis in the tissue of the pancreatic ablation area. Conclusion EUS-MWA is safe and feasible for porcine liver and pancreas, which can be used for the treatment of human liver and pancreatic diseases in the future. Key words: Ultrasonography; Microwaves; Endoscopes; Animal experimentation