Further developments in the "swine model" for teaching diagnostic and interventional endoscopic ultrasound

Purpose: We have previously developed a swine model for teaching EUS that was used as a method of hands-on instruction at the first ASGE course on EUS. The purpose of this study was to try to further improve this model as well as to create focal lesions for EUS imaging. Methods: Experiments were performed in three farm pigs (sus scrofa) under general anesthesia. Endosonography was then performed with a linear array echoendoscope. Under EUS guidance, about 20 ml of 10% lipid emulsion was injected into the submucosa to create a submucosal lesion. The pancreas was visualized and EUS guided FNA of the pancreas was performed. A needle was passed into the mediastinum under EUS guidance and 3-4 cc of saline was injected to create a focal lesion mimicking a lymph node (LN). An attempt was made to confirm injection site during "sham" EUS guided celiac block by mixing saline with Fast Green, a dye with affinity for nervous tissue, and injecting this mixture trans-gastrically on either side of the celiac artery under EUS guidance. After completion of the experiments the pigs were euthanized and the abdomen was explored. Results: The 10% lipid emulsion injection produced a 4 cm hypoechoic submucosal mass by EUS which was then punctured with a needle to mimic EUS guide FNA. The saline injection in the mediastinum created an 11 mm, oval, hypoechoic lesion in the mediastinum to masquerade as a mediastinal LN. EUS guided FNA needle was then advanced transesophageally into the center of this lesion to mimic EUS guided FNA of a lymph node. Abdominal exploration of the pigs revealed green dye around the celiac artery with green staining of the celiac ganglion confirming injection in this area. Cytopathologic examination of pancreatic FNA slides revealed pancreatic cells confirming pancreatic puncture. Conclusions: The swine model is not only useful for teaching general principles and normal anatomy during EUS but it may be a useful model for teaching intervenuonal techniques such EUS guided FNA of focal lesions in the mediastinum, gastric wall, and pancreas; and EUS guided celiac nerve block.