Evidence of trigonal denervation and reinnervation after radical retropubic prostatectomy

Purpose: Urinary incontinence continues to be a major consequence of radical prostatectomy. To understand the pathophysiology of this dysfunction we studied the impact of autonomic innervation of the superficial trigone on postoperative urinary continence. Materials and Methods: To investigate nerve fiber density biopsies of the superficial trigone were obtained in 34 patients preoperatively as well as 6 weeks and 6 months postoperatively in 15 and 19, respectively. Specimens were Bouin fixed, paraffin embedded and processed for light microscopic immunohistochemical evaluation using an antibody against protein gene product 9.5, a general neuronal marker protein. In parallel we performed a comprehensive urodynamic evaluation, including determination of maximal urethral closure pressure and posterior urethral sensory threshold. Results: Postoperatively protein gene product 9.5 immunoreactive nerve fiber density was generally decreased. However, nerve fiber density after 6 weeks of incontinence in 12 of 15 patients was only 7%, while 3 of 15 who were continent preserved 36% of initial nerve fiber density. After 6 months nerve fiber density in 19 patients increased in 3 with incontinence to 20% and in 16 with continence to 44% of intraoperative density. Urinary incontinence was associated with decreased trigonal innervation, a high sensory threshold and low maximal urethral closure pressure. Conclusions: Protein gene product 9.5 immunoreactive nerve fiber density corresponds with posterior urethral sensory threshold and urinary continence. Thus, preserving trigonal innervation and postoperative reinnervation may be important factors for achieving early postoperative urinary continence after radical prostatectomy.