COMPARISON OF COVERED VERSUS UNCOVERED WIRE MESH STENTS IN THE CANINEBILIARY-TRACT

Self-expanding wire mesh stents have been developed for endoscopic pla cement across malignant biliary strictures, but tumor ingrowth may lim it the usefulness of open mesh stents. We reasoned that coating the wi re mesh might prevent tumor ingrowth. Tissue response to covered and u ncovered stents was compared in dogs. Stents were surgically placed in the bile ducts of 22 mongrel dogs through the sphincter of Oddi. Eith er a silicone-covered stent or an uncovered stent was inserted. Liver function test values remained normal throughout a 1- or 3-month study. Necropsy revealed that all ducts were unobstructed. Bile duct histolo gic examination revealed mild-to-moderate cellular infiltration in all animals. Mucosal hyperplasia was more marked in the animals with unco vered stents and the bare wires became deeply embedded in bile duct ep ithelium, whereas the wires of covered stents did not. We conclude tha t covered stents are well tolerated by the canine bile duct. These res ults suggest that such stents may be removable, making self-expanding metal stents an appropriate treatment for both benign and malignant bi liary strictures.