Effects of selective autonomic and pudendal denervation on the urethral function and development of retention in female dogs

Purpose: This trial is an experimental approach to the possible causes of c ontinence and voiding problems after urethra sparing radical cystectomy and orthotopic bladder substitution in women. Materials and Methods: Between January 1996 and January 1999 we included 24 mongrel female dogs in this 4-phase study of 6 dogs each. The effects of a utonomic denervation of the urethra (phase 1) and urethral transection just distal to the bladder neck (phase 2) on the urethral pressure profile were recorded. In phase 3 the effects of autonomic denervation, urethral transe ction and pharmacological manipulation of the denervated transected urethra on the urethral pressure profile were studied in succession. In phase 4 th e effects of pudendal nerve transection and pharmacological blockade were r ecorded. In the 12 phases 2 and 3 dogs the transected urethra was re-anasto mosed to the bladder neck. Acute experiments were repeated after 2 and 6 mo nths, urethrocystoscopy was done and post-void residual urine was estimated . Two of the latter dogs were sacrificed 6 months after the acute experimen t and the urethras were histopathologically examined. Results: Autonomic denervation resulted in a 46% to 48% decrease in mean ma ximal pressure in the proximal urethra in phases 1 and 3 (p <0.001) with no significant effect on the distal urethra. Urethral transection in phase 2 did not affect the urethral pressure profile. Phentolamine injection after urethral denervation and transection in phase 3 produced a further reductio n of 11.3% and 46.3% in mean resting pressure in the proximal and distal ur ethra, respectively, while succinyl choline produced a 38.1% further decrea se in the distal urethra. Unilateral and bilateral pudendal denervation red uced pressure in the distal urethra significantly but not in the proximal u rethra. When phentolamine was given thereafter, a further decrease of 38% a nd 2.4% resulted in resting pressure values in the proximal and distal uret hra, respectively. The change in distal urethral pressure was marginally si gnificant after succinyl choline injection (p = 0.05). Results were reprodu cible after 2 and 6 months. The proximal urethra remained patent with no po st-void residual urine after autonomic denervation. There was no significan t urethral fibrosis after realignment of the transected urethra in the 2 sa crificed phases 2 and 3 dogs. Conclusions: From this study we concluded that autonomic denervation reduce d pressure in the proximal urethra by less than 50%. Continuity of the uret hra with the bladder is not necessary for proper urethral function. After a utonomic denervation the proximal urethra remained patent with no subsequen t fibrosis. In addition, no post-void residual urine was noted. Bilateral p udendal denervation did not completely block activity of the distal urethra . The nonneuromuscular components had a small role in the creation of ureth ral closure function.