Acellular matrix tube for canine urethral replacement: is it fact or fiction?
We evaluated the results of acellular matrix used as a tube for replacement of a relatively long segment of the canine urethra. The study included 9 female and 5 male mongrel dogs in which a 3 cm segment of the whole urethral circumference was excised and replaced by a tube of acellular matrix of the same length and width. The acellular matrix was obtained by excision of the whole urethra of donor female dogs that were sacrificed and not included in the study group. The retrieved urethra was treated to have complete cell lysis with maintenance of the fiber framework. In all dogs the urethra was stented for 4 weeks. Ascending urethrogram was done after stent removal every month until the dogs were sacrificed. The dogs were sacrificed at a rate of 1 weekly for 4 weeks and then monthly. If urine retention occurred, ascending urethrogram was performed and the dog was sacrificed. Before sacrifice the urethra was exposed and carefully examined. The whole specimen was then excised for histopathological examination. All dogs survived surgery and no postoperative complications were seen during urethral stenting. After stent removal all dogs had a urethral fistula and/or stricture, which increased in severity until urine retention occurred by the end of month 3. Exploration at 1, 2, 3 and 4 weeks showed an intact graft, although there was progressive shrinkage in length and urethral calibration also demonstrated progressive narrowing of the lumen. At 3 months there was marked shrinkage (length equaled 0.3 cm) and complete obliteration of the lumen. Histopathological examination showed progressive fibrosis, which was extensive by week 4. Acellular matrix tube is not able to replace a 3 cm segment of canine urethra.