The Establishment Of Canine Tracheoesophageal Fistula Model And The Experimental Study Of Esophageal Double Patch Repairing Tracheal Defect

Background Acquired tracheoesophageal fistula(TEF) is a rare refractory disease which usually results from erosion of the adjacent walls of the trachea and esophagus due to a variety of causes. For the large defect, with persistent infection and friability of the tissues, the treatment is very difficult. Esophageal double patch repairing tracheal defect, a new surgical procedure designed in our department, has been used in 11 esophageal stent–related TEF patients and the results were satisfied. However, some issues arisen by this procedure just like the morphological change, the pathophysiological change and the structural as well as functional change are still far from clear. So the canine model of TEF was established and these questions were studied.Objective 1) To establish the canine model of tracheoesophageal fistula and to provide a good, stable animal model for further research on TEF. 2) To observe the morphological and histopathological change as well as the healing progress of the field of operation after receiving the double patch repairing TEF, thus,laying the theological foundations for further improvement of surgical treatment of TEF.Methods 1) 28 healthy dogs were randomly divided into 3 groups: groups A (12) and B (12) for the establishment of canine model of TEF, and group C (4) as blank control. 2) Methods of model establishment: A longitudinal incision was made along the esophagus to split open the esophageal lumen, and the anterior wall of esophagus and tracheal membranous were incised. Incision edges were sutured to form a traffic TEF. Models were verified by postoperative bronchoscopy. 3) 7 days after the model was made, a double patch technique was applied to groups A and B. The esophagus was mobilized above and below the fistula, approximately 2 cm away from the fusion of the trachea with the esophagus. A longitudinal incision was made along the esophagus. Then the esophagus was transected 2 cm proximal and distal to the fistula site to form two esophageal patches, a long one and a short one. The short patch was sutured to the left edges of the fistula with interrupted sutures and closed the fistula completely. Then the long esophageal wall patch covered the short patch. The mucosal and submucosal layer of long patch of esophageal wall in group A was stripped,while those in group B kept intact. 4) 4 canines in groups A and B were sacrificed 1, 2, and 8 weeks postoperative respectively. The survival of experimental animals, the morphological and histopathological change of fistula site were observed, and the tracheal stenosis index and hydroxyproline level of the patch were measured.Results 1) Canine tracheoesophageal fistula model was established successfully. 2) Groups A and B animals survived to the scheduled time, and the anastomosis between patch and trachea healed up well with sufficient blood supply. No tracheal stenosis occurred in group A, while the stenosis index was significantly higher in group B at 8 weeks postoperative(0.170±0.007) than control group(0.137±0.010). The two layers of patches fused together well without the formation of cysts in group A, while 2 cases of cyst formed between the two layers of patches in group B. 3) The increase of hydroxyproline level,as well as Masson collagen staining of esophageal patch tissues were significantly earlier and higher in group A compared with group B.Conclusion 1) The established surgical model of TEF is reliable for the research of TEF. 2) The anastomosis between patch and trachea healed up well during the esophageal double patch reparing. 3) It might be helpful to prevent the tracheal stenosis and the formation of cyst by removing the mucosal and submucosal layer of the long esophageal patch.