Magnetic Resonance Imaging Anatomy of the Female Genitalia in Premenopausal and Postmenopausal Women

Abstract

We used contrast enhanced magnetic resonance imaging (MRI) of the female genital organs to describe normal anatomy and differences between premenopausal and postmenopausal women. A total of 12 healthy premenopausal and 9 healthy postmenopausal women underwent MRI. A 1.5 Tesla system with phased array coils anterior and posterior to the pelvis was used to produce T1-weighted images before and after intravenous administration of MS-325 (Epix Medical, Cambridge, Massachusetts), a new gadolinium based blood pool contrast agent. Select structural dimensions were measured for reference. The clitoris and vestibular bulbs were well delineated on T1-weighted post-contrast images. The clitoral unit formed a brightly enhancing, wishbone-shaped structure lying just anterior to the inverted V of the bulbs, which surrounded the urethra and vagina. The urethral complex had a target-like appearance with layers that were discernible on T1 post-contrast images. The urethra, vagina and rectum formed a distinct complex within uniformly enhancing soft tissue. The vagina was well visualized in premenopausal subjects but without distinguishable mucosal rugae or clearly separate layers in postmenopausal subjects. Postmenopausal subjects were also observed to have smaller labia minora width, vestibular bulb width, vaginal width and wall thickness, and cervical diameter. Pelvic and genital structures were not well visualized on T1 noncontrast images. To our knowledge we describe detailed female genital anatomy for the first time using MRI with MS-325 contrast medium. The clitoris, vestibular bulbs, labia majora and minora, urethra, vagina, cervix and rectum are well visualized on T1 post-contrast images. The observed genital anatomy on MRI was consistent with descriptions in current anatomical texts. Differences in the female genitalia between premenopausal and postmenopausal women were discernible on MRI. These data are important for future studies using MRI for evaluating anatomical anomalies, postoperative changes and female sexual function.