PURPOSE: Gianturco self-expanding metallic stents have been useful in cases of benign biliary stenoses; however, the stents have not worked well in the presence of intraluminal tumor because of tumor growth between the wire struts. Stents were covered with polymeric membranes, which may prevent tumor ingrowth, and the feasibility of using these covered stents in the common bile duct was studied in healthy adult dogs. MATERIALS AND METHODS: Initially, stents (10 x 6 mm) covered with polycaprolactone (PCL), segmented polyether polyurethane (SPP), and silicone were placed in the common bile duct of dogs and were followed up for 3-12 months. Subsequently, four types of modified silicone-covered stents were evaluated. Rough-surface, small-diameter (3-mm), half-covered, and tapered stents were placed and followed up for 3 months. RESULTS: In the initial study, the SPP and silicone membranes remained intact, but the PCL covering broke in all dogs. In all but two dogs, luminal narrowing caused by varying degrees of papillary mucosal hyperplasia at both ends of the stent was observed. In the subsequent study, mucosal hyperplasia was considerably reduced by using half-covered stents and was virtually eliminated with tapered stents. All small-diameter stents migrated into the bowel. CONCLUSION: These studies suggest that tapered Gianturco self-expanding stents covered with silicone may be useful in the biliary tract in cases of intraluminal tumor.
PURPOSE: Gianturco self-expanding metallic stents have been useful in cases of benign biliary stenoses; however, the stents have not worked well in the presence of intraluminal tumor because of tumor growth between the wire struts. Stents were covered with polymeric membranes, which may prevent tumor ingrowth, and the feasibility of using these covered stents in the common bile duct was studied in healthy adult dogs. MATERIALS AND METHODS: Initially, stents (10 x 6 mm) covered with polycaprolactone (PCL), segmented polyether polyurethane (SPP), and silicone were placed in the common bile duct of dogs and were followed up for 3-12 months. Subsequently, four types of modified silicone-covered stents were evaluated. Rough-surface, small-diameter (3-mm), half-covered, and tapered stents were placed and followed up for 3 months. RESULTS: In the initial study, the SPP and silicone membranes remained intact, but the PCL covering broke in all dogs. In all but two dogs, luminal narrowing caused by varying degrees of papillary mucosal hyperplasia at both ends of the stent was observed. In the subsequent study, mucosal hyperplasia was considerably reduced by using half-covered stents and was virtually eliminated with tapered stents. All small-diameter stents migrated into the bowel. CONCLUSION: These studies suggest that tapered Gianturco self-expanding stents covered with silicone may be useful in the biliary tract in cases of intraluminal tumor.