Long-term retention of endoscopically placed hydrogel prostheses at the lower esophageal sphincter in pigs

Background: Using flexible endoscopic methods, hydrogel prostheses can be safely placed, retained for long periods of time, and removed from the esophageal submucosa of pigs. This new technique may have future applications in the treatment of gastroesophageal reflux disease in selected situations. Methods: In a controlled, prospective trial, farm pigs (n = 28) or Sinclair mini-swine (n = 18) underwent sequential placements of 2–13 pliable, radio-opaque hydrogel prostheses into the submucosa of the esophagus during a single endoscopy session. A novel endoscope-overtube device was used. Followup endoscopy and/or fluoroscopy sessions were video-recorded at 6-week, 12-week, 6-month, and yearly intervals. The endoscopic removal of hydrogels was tested in vivo. Necropsy specimens were inspected for signs of chronic inflammation. Results: Overall, 98% of delivery attempts were successful (288/293). Only three hydrogels were lost after 6 weeks. Short-term animals (n = 36) retained 88% of hydrogels for periods up to 6 months. Intact hydrogels (n = 12) were easily removed from four animals at endoscopy. Long-term subjects had two or three hydrogels per animal, using either a beveled-needle device (six pigs) or a trocar design (four pigs). Trocar design: nine of nine prostheses retained at 3 years (100%). Needle design: nine of 10 prostheses retained at 3 years (90%). No significant adverse event occurred. Growth curves were similar between groups. All hydrogels remained pliable to gross inspection upon in vivo removal or necropsy. Pathology showed minimal fibrosis and no chronic inflammation. Conclusions: A novel endoscopic overtube device allows for the successful delivery of multiple hydrogel prostheses with acceptable safety and long term retention rates. These hydrogel prostheses can also be easily removed from the submucosal space of the esophagus.