Covered retrievable prostatic urethral stents: Feasibility study in a canine model

PURPOSE: To evaluate the feasibility of use of a covered, retrievable prostatic urethral stent and to determine urethrographic and histologic changes in the prostate induced by the stent in a canine model. MATERIALS AND METHODS: Polytetrafluoroethylene-covered retrievable nitinol stents were placed in the normal prostatic urethras of 13 dogs. The stents were removed 8 weeks after placement. The dogs were killed immediately after stent removal (group 1, n = 5) or 8 weeks after stent removal (group 2, n = 8). Retrograde urethrograms were obtained every 2 weeks after stent placement and after stent removal in dogs that had not been killed. The histologic changes in the prostate were compared between the two groups. RESULTS: Stent placement was technically successful in all dogs. In two dogs, a second stent was placed because of migration of the first stent into the urinary bladder. Stent removal was successful in 12 dogs. One stent was removed in its expanded state. On follow-up urethrograms, dilation of the prostatic urethra persisted until animals were killed (P = .14). The mucosal hyperplasia that occurred after stent placement at both ends of the stent gradually decreased after stent removal (P < .001). Histologic examination revealed prostate glandular atrophy and periurethral fibrosis, which did not differ between the two groups (P = .72 and P = .83, respectively). Papillary hyperplasia of the uroepithelium and submucosal inflammatory cell infiltration was decreased significantly in group 2 compared with group 1 (P = .002, P = .011, respectively). CONCLUSIONS: Covered retrievable prostatic urethral stents seem to be feasible for use in the canine prostatic urethra. The stent-induced prostatic urethral dilation and prostate glandular atrophy persist until 8 weeks after stent removal.