Spiral nitinol biliary stents in a porcine model: Evaluation of the potential for use in benign strictures

Background and Study Aims: Self-expanding spiral nitinol stents are potenti ally removable and may be useful in the treatment of benign strictures, We evaluated the histologic response to stent placement and technical aspects of their placement and removal in a porcine model. Methods: Nine animals were studied, Stents were placed above the papilla in six surviving animals. After intervals of one, tno or three months cholang iography and attempted stent removal was performed. Four animals were then sacrificed acutely with their stent in place, and two were sacrificed after a one-month healing interval, The results of placement, follow-up cholangi ography and histology are reported, Results: Cholangiography and stent placement succeeded in 26 of 27 and 11 o f 16 attempts, respectively. Three placement failures were attributed to st ent/duct size disparity or a faulty release mechanism, resulting in stent k inking and/or duct twisting, Among the successfully deployed stents, two an imals developed strictures where stents traversed bifurcations and one exhi bited partial luminal compromise by tissue entrapment between coils. Fluoro scopically guided removal was successful in two of five stents positioned a bove the papilla, Histology was non-specific but minimally changed in those given a one-month healing interval after removal. Others exhibited moderat e inflammation, fibrosis and an intramural abscess at sites of induced stri cture, Conclusions: Spiral metal stents for the treatment of benign strictures rem ain experimental, Care must be taken to deploy them in bile ducts of adequa te diameter and endoscopic removal is not yet demonstrably reliable and saf e.