title: Urethral replacement: a comparison between small intestinal submucosa grafts and spontaneous regeneration.
abstract: OBJECTIVE
  To evaluate the use of commercially available single-layer small intestinal submucosa (SIS) for urethral replacement, both as an onlay and as a tube, in a rabbit model.
  
  
  METHODS
  Thirty-six male rabbits were assigned to four experimental groups. Group 1 had the ventral wall of the penile urethra excised for 15 mm; in group 2 this created defect was patched with a SIS onlay graft; group 3 had complete excision of a 15 mm segment of the penile urethra; and in group 4, this created defect was replaced with a SIS tube graft. In all rabbits the urethra was stented for 2 weeks. A retrograde urethrogram was taken in all rabbits before death at 3, 6 and 12 weeks after surgery. The urethra was then exposed, examined carefully and excised for histopathological examination.
  
  
  RESULTS
  In groups 1 and 2 the retrograde urethrograms were normal in 13 rabbits and there was relative narrowing in two rabbits in group 1 and three in group 2. In groups 3 and 4 all rabbits developed urethral fistulae or strictures. Histological examination of the urethra showed epithelial regeneration supported by smooth muscle backing in all rabbits in group 1, while rabbits in group 2 showed no regeneration of smooth muscle. By contrast, rabbits in groups 3 and 4 showed incomplete regeneration and progressive fibrosis.
  
  
  CONCLUSIONS
  Single-layer SIS is not a suitable urethral substitute in this animal model. When used as an onlay, healing is inferior to spontaneous urethral regeneration, as SIS impedes smooth muscle cell regeneration. When used as a tube, there is complete scarring and urethral luminal occlusion.
authors.affiliation: Urology & Nephrology Center, Mansoura University, Mansoura, Egypt.
authors.forename: Ahmed
authors.initials: A
authors.lastname: El-Assmy
authors.forename: Mohamed Abd
authors.initials: MA
authors.lastname: El-Hamid
authors.forename: Ashraf T
authors.initials: AT
authors.lastname: Hafez
mesh_terms: D000818:Animals; D001187:Artificial Organs; D007413:Intestinal Mucosa / Q000637:transplantation*; D008297:Male; D011817:Rabbits; D012038:Regeneration; D014521:Urethra / Q000502:physiology* / Q000601:surgery