Biliary small intestinal submucosa covered Z-stents: Preliminary results in an animal model

Background. Purpose of the study was to test the function and biological response of metallic stents covered with small intestinal submucosa (SIS) in the swine biliary system. Materials and methods. A total of 9 SIS-covered single Z-stents were placed in the common bile duct (CBD) in 6 pigs. Stents were delivered into the CBD at laparotomy via the gall bladder and the cystic duct. Animals were sacrificed or died at 2 weeks (n=1), 4 weeks (n=1), 8 weeks (n=2), and 10 weeks (n=2) after stenting and histological studies were performed. Results. Nine stents were deployed in 6 animals. During follow-up, 3 stents in 3 animals (2, 4, and 10 weeks) remained stable, while one stent shifted distally in CBD and 5 of them turned sideways. All stents remained patent. Duct dilatation and bile slugging were noted at 10 weeks. The SIS-membrane was present at 2 weeks, but was not histologically distinct at 4 weeks and later. Histological study showed no significant inflammatory changes in the bile duct in any pig. Mucosal hyperplasia was absent in 2 of 3 stable stents at 2 and 10 weeks, and 1 distally shifted stent at 10 weeks. Mild mucosal hyperplasia was seen at the distal stent end in 1 stable stent at 4 weeks and in 5 dislodged stents at 8 and 10 weeks. Conclusions. Even when the study is limited by dislodgment of high percentage of placed stents, the results in stable stents conducting the bile flow suggest that SIS helps to prevent bile duct inflammation and mucosal hyperplasia typical for uncoated stents. Further studies, particularly with improved wet SIS are warranted.