An internally covered (lined) self-expanding metal esophageal stent: tissue response in a porcine model

BackgroundSelf-expandable metal stents (SEMS) palliate malignant dysphagia but may embed in tissue, produce granulation tissue, and prevent removal.ObjectiveOur purpose was to evaluate in a porcine model the tissue response induced by a new esophageal SEMS completely coated internally rather than externally.DesignEight Yucatan pigs were studied. Each animal underwent placement of 2 stents: 1 study stent and 1 control stent. SEMS were placed proximally or distally by random assignment. Follow-up endoscopy was performed 1, 2, 3, and 4 weeks after implantation. Ease of stent removal was assessed at 2 weeks and 4 weeks after placement.SettingAnimal laboratory.InterventionsEndoscopic placement of study stents (Alveolus ES-STS, Alveolus, Inc, Charlotte, NC; 18 mm diameter, fully covered internally) and control stents (Ultraflex stent, Boston Scientific, Natick, Mass; microvasive, 18 mm midbody, subtotally covered externally).Main Outcome MeasurementsExtent of granulation tissue and stent-induced esophageal injury.ResultsThe tissue hyperplasia response of the study stents was endoscopically graded as mild to moderate. All study stents were endoscopically removed easily and atraumatically. Control stents produced severe granulation tissue formation with complete embedding of the uncovered stent ends; endoscopic removal was possible but resulted in trauma and endoscopically visible bleeding. Histopathologic findings revealed minimal tissue response at the ends of the study stents and severe pseudopolyps in the embedded portion of the control stent. Stent migration occurred in 7 of 8 study stents and 4 of 8 control stents.LimitationsAnimal model lacks stricture.ConclusionsFully internally lined SEMS may resist tissue embedding and hyperplasia and may be removable. Human studies are needed to assess applicability to treatment of benign and malignant esophageal disease.