Removable Covered Expandable Biliary Stent with a Proximal Lasso: Proof of Principle Testing in An Animal Model

Abstract

Rationale: Progressive dilation with plastic stents is the initial therapy of choice to treat benign biliary strictures, but requires repeated interventions which is cumbersome for patients and expensive. The use of fully covered self expandable metal stents (FCSEMS) that are removable may reduce the number of endoscopic procedures and be more effective. Removal of (covered) expandable metal stents is complicated in some cases and frequently unsuccessful. By pulling the distal stent-end the whole surface area must detach from the common bile duct (CBD) at once, making removal sometimes impossible and causing disruption of the wire mesh. This problem could be overcome by using a proximal lasso by which the stent is removed inside-out, level by level. Aim: To test the feasibility of removal of a FCSEMS using a proximal lasso (Hanaro TM, M.I. Tech Co., Ltd, Seoul, Korea) from the biliary tree in an animal model. Methods: Feasibility experiments were performed in two female pigs weighing 25 kg with a normal biliary anatomy. Following a cholangiogram, a 30 Fr 6 cm FCSEMS with a proximal lasso was inserted over a guidewire by means of 10 Fr delivery catheter system. One stent was placed across the papilla, a second stent was placed within the common bile duct. FCSEMS removal was attempted during the same procedure after 30 minutes by pulling the proximal lasso with a rat toothed foreign body retrieval forceps. Results: FCSEMS were successfully placed in both pigs. Fluoroscopic control showed that both FCSEMS were fully expanded. In the first pig the proximal lasso was easily grasped from within the duodenal lumen. By pulling the lasso the stent was removed inside-out. In the second pig, the proximal lasso was retained within the CBD, but was easily retrieved using an extraction balloon. Subsequently, the lasso was grasped and the stent was removed, inside-out. At visual inspection, after removal both stents had an intact wire mesh and covering. A control cholangiogram showed no signs of perforation. Conclusion: Removal of FCSEMS using a proximal lasso (inside-out) was feasible, even when the stent was deployed within the CBD, not crossing the papilla. From a technical viewpoint, the use of a proximal lasso may provide the mandatory assurance that FCSEMS indeed can be removed when used to dilate benign biliary stenoses. This would obviate the need for frequent plastic stent exchanges and may enhance treatment efficacy. Studies in humans are underway.