Gross and histologic relationships of the retropubic urethra to lateral pelvic sidewall and anterior vaginal wall in female cadavers: clinical applications to retropubic surgery.

BACKGROUND: Knowledge of the retropubic space anatomy is essential for safe entry and surgical applications within this space.

OBJECTIVE: The objectives of this study were to examine the gross and histologic anatomy of the retropubic urethra, paraurethral tissue, and urethrovaginal space and to correlate findings to retropubic procedures.

STUDY DESIGN: Anatomic relationships of the retropubic urethra were examined grossly in unembalmed female cadavers. Measured distances included: lateral urethral wall to arcus tendineus fascia pelvis at the level of urethrovesical junction and at 1 cm distal. Other measurements included retropubic urethral length and distances from internal urethral opening to each ureteric orifice. Microscopic examination was performed at the same levels examined grossly in separate nulliparous specimens. Descriptive statistics were used for data analyses.

RESULTS: In all, 25 cadavers were examined grossly. Median distance from lateral urethral wall to arcus tendineus fascia pelvis at the level of urethrovesical junction was 25 mm (range, 13-38 mm). At 1 cm distal, the median distance from aforementioned structures was 14 mm (10-26 mm). Median length of the retropubic urethra was 23 mm (range 15-30 mm). Four nulliparous specimens, ages 12 weeks, and 34, 47, and 52 years, were examined histologically. No histologic evidence of a discrete fascial layer between bladder/urethra and anterior vagina was noted at any level examined. Tissue between the urethra and the pelvic sidewall skeletal muscle was composed of dense fibrous tissue, smooth muscle bundles, scant adipose tissue, blood vessels, and nerves. The smooth muscle fibers of the vaginal muscularis interdigitated with skeletal muscle fibers in the pelvic sidewall at both levels examined. No histologic evidence of "pubourethral ligaments" within the paraurethral tissue was noticed.

CONCLUSION: A 2-cm "zone of safety" exists between the urethra and arcus tendineus fascia pelvis at the urethrovesical junction level. Suture or graft placement within this region should minimize injury to the urethra, pelvic sidewall muscles, and bladder. Knowledge that the shortest length of retropubic urethra was 1.5 cm and shortest urethra to arcus tendineus fascia pelvis distance was 1 cm highlights the importance of maintaining dissection and trocar entry site close to pubic bone to avoid bladder and/or urethral injury. Histologic analysis of paraurethral tissue supports the nonexistence of pubourethral ligaments.