Anatomy of the urethral supporting ligaments defined by dissection, histology, and MRI of female cadavers and MRI of healthy nulliparous women.

OBJECTIVE

There has been no uniformity of opinion concerning the structures supporting the female urethra. Therefore, the aims of this prospective study were to define precisely the female urethral support structures at cadaveric anatomic dissection and histologic examination and to determine which of these structures can be detected on MRI of cadaveric specimens and of healthy volunteers.

SUBJECTS AND METHODS

Dissection of seven formalin-preserved cadavers (age at death, 25-50 years; no parity history available) was performed by a professor of anatomy to explore the anatomy of the urethral supporting ligaments and was followed by MRI of the cadaveric specimens with ligamentous markers in place and then by histologic analysis of the dissected ligaments. MRI of 17 healthy nulliparous women (age range, 20-35 years; mean age, 25.5 years) was then performed using T2-weighted, dual turbo spin-echo, balanced fast-field echo, and STIR sequences. A standardized grid system that allowed us to record structural observations on sequentially numbered axial MR images was used by a radiologist who then applied a 4-point grading scale to assess ligament visibility. Three authors--one radiologist, one anatomist, and one urologist--then compared the appearance of each ligament seen in a cadaveric specimen with its appearance on MR images of the same cadaver and on MR images of volunteers.

RESULTS

At cadaveric dissection we identified ventral and dorsal urethral ligaments. The ventral urethral ligaments included the pubourethral ligaments, which were found to consist of three separate components coursing anteroposterior from the bladder neck to the pubic bone; the periurethral ligament; and the paraurethral ligaments. Dorsal to the urethra, a slinglike ligament, which we believe should be named the "suburethral ligament," was identified. This ligament had a distinct plane of cleavage from the anterior vaginal wall. The MRI findings in the volunteers correlated with the MRI and gross anatomic findings in the cadavers. The proximal pubourethral, periurethral, paraurethral, and suburethral ligaments had visibility scores of 3 (moderately visible) or 4 (easily visible) on MRI in 47%, 65%, 47%, and 53% of volunteers, respectively.

CONCLUSION

Our results present evidence that may help resolve previous controversies regarding the MR appearance of the ventral urethral ligaments and that better define the course of the ligament dorsal to the urethra, the suburethral ligament. We hope that this detailed anatomic information about the structures involved in continence may lead eventually to improvements in the treatments for women with stress urinary incontinence.