NEUROUROLOGY & FEMALE UROLOGY

Pubo-urethral ligament injury causes long-term stress urinary incontinence in female rats: an animal model of the integral theory
Kefer JC, Liu G, Daneshgari F
Glickman Urological Institute, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA
J Urol. 2009; 181: 397-400

• Purpose: We examined the long-term effects of pubo-urethral ligament deficiency as a potential model of stress urinary incontinence compared to an established model of stress urinary incontinence.
• Materials and Methods: A total of 21 female Sprague-Dawley rats were randomly assigned to 1 of 3 groups, including pubo-urethral ligament transection, sham pubo-urethral ligament transection and bilateral pudendal nerve transection. Leak point pressure was measured 28 days later via an implanted suprapubic catheter. After leak point pressure measurement all animals were sacrificed. The pubic arch and pelvic organs were harvested for histological examination. The Wilcoxon rank sum test was used to evaluate differences in leak point pressure among the experimental groups.
• Results: At 28 days after pubo-urethral ligament transection mean +/- SD leak point pressure was significantly decreased when comparing pubo-urethral ligament transection and pudendal nerve transection to sham treatment (15.75 +/- 6.46 and 15.10 +/- 4.98 cm H(2)O, respectively, vs. 42.56 +/- 11.58, p < 0.001). No difference was noted when comparing pubo-urethral ligament transection to pudendal nerve transection (p = 0.76), indicating the long-term durability of pubo-urethral ligament transection on inducing stress urinary incontinence in the female rat. Histological examination of en bloc suprapubic areas demonstrated an absent pubo-urethral ligament in the pubo-urethral ligament transection group, and an intact pubo-urethral ligament in the sham treated and pudendal nerve transection groups.
• Conclusions: Our results show that pubo-urethral ligament deficiency in the female rat induces long-term stress urinary incontinence that is comparable to that in the established stress urinary incontinence model via pudendal nerve transection. Our novel rat model could be used to investigate mechanisms of stress urinary incontinence in females, including the role of urethral hypermobility and potential therapeutic interventions for stress urinary incontinence.
  
  
• Editorial Comment
  An interesting look into the development of a laboratory model to analyze and evaluate stress urinary incontinence. The authors noted that pubo-urethral ligament transection was very similar to pudendal nerve transection in Sprague-Dawley rats in developing a model for stress urinary incontinence in the female rat. It is pointed out in the discussion that developing a model of stress urinary incontinence that avoids the use of pudendal nerve injury may help analyze nulliparous women who suffer with stress urinary incontinence. Much appreciation should go to the researchers in our field who help develop the models upon which to expand our ability to treat affected patients. Of note is that the support of structures of the female urethra including the pubo-urethral ligament had been reviewed in this journal in the past with some anatomic researchers noting that the pubo-urethral ligament may not be a ligament but instead mostly tissue containing smooth muscle cells (1). This is food for thought especially when quoting continence rates after suprameatal transvaginal urethrolysis which takes down the attachments of the urethra to the underside of the pubic bone (2). In a contrary view, this may also explain the rate of incontinence that is noted in patients after therapeutic pubectomy (3).

References
1. Fritsch H, Pinggera GM, Lienemann A, Mitterberger M, Bartsch G, Strasser H: What are the supportive structures of the female urethra? Neurourol Urodyn. 2006; 25: 128-34.
2. Petrou SP, Brown JA, Blaivas JG: Suprameatal transvaginal urethrolysis. J Urol. 1999; 161: 1268-71.
3. Petrou SP, O’Connor MI: Urological assistance during therapeutic pubectomy. J Urol. 2001; 165: 1185-7.

Dr. Steven P. Petrou
Associate Professor of Urology
Chief of Surgery, St. Luke’s Hospital
Associate Dean, Mayo School of Graduate Medical Education
Jacksonville, Florida, USA
E-mail: petrou.steven@mayo.edu