Evaluation of polymer-coated balloon-expandable stents in bile ducts

The long-term patency of and biologic response to the presence of polymer-coated balloon-expandable intraluminal stents in the bile ducts was studied in 18 dogs. Metallic stents coated with two different polymers (silicone rubber and segmented polyether-polyurethane) were placed in 12 dogs and uncoated stents in six, and animals were killed after 4, 12, and 24 weeks of observation. Cholangiograms were obtained at 1, 4, 6, 12, and 24 weeks, depending on length of follow-up. All bile duct segments containing stents remained patent throughout the follow-up periods. Characteristic luminal narrowings due to hyperplastic papillary mucosa occurred with all three stent types. Although no difference could be found in the degree of narrowing of the most restrictive segment among the three stent types, mucosal proliferation was most extensive with the uncoated stent. Lack of concretion buildup and benign tissue response encourage the development of a clinically useful expandable biliary endoprosthesis.