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The urethra and its supporting structures in women with stress urinary incontinence: MR imaging using an endovaginal coil
Kim JK, Kim YJ, Choo MS, Cho K-S
From the Departments of Radiology and Urology, Asian Medical Center, University of Ulsan, Seoul, South Korea
AJR Am J Roent. 2003; 180: 1037-44

• Purpose: The objective of this study was to evaluate the urethra and its supporting structures in patients with stress urinary incontinence using MR imaging with an endovaginal coil.
• Materials and Methods: We reviewed MR images obtained using an endovaginal coil in 63 patients with stress urinary incontinence and in 16 continent women. We compared the two groups for the thickness of the striated muscle, smooth muscle, and mucosa–submucosa of the urethra; degree of asymmetry of the puborectalis muscle; frequency of distortion in the periurethral, paraurethral, and pubourethral ligaments; degree of the vesicourethral angle; and dimension of the retropubic space. Using the status of the urethra and its supporting structures as our basis, we scored the risk of stress urinary incontinence for each woman on a scale of 0–5.
• Results: The striated muscle layer of the urethra was thinner in the group with stress urinary incontinence (mean ± SD, 1.9 ± 0.5 mm) than that in the continent group (2.6 ± 0.4 mm) (p < 0.001). A high degree of asymmetry of puborectalis muscle (> 1.5) was more frequent in the group with stress urinary incontinence (29%) than in the continent group (0%) (p = 0.015). Supporting ligaments were more frequently distorted in the incontinent group than in the continent group. Distorted periurethral ligaments were found in 56% of the patients with stress urinary incontinence versus 13% of the women who were continent; distorted paraurethral ligaments were found in 83% of the patients with stress urinary incontinence versus 19% of the women who were continent; and distorted pubourethral ligaments were found in 54% of the patients with stress urinary incontinence versus 19% of the women who were continent (p < 0.05). The group with stress urinary incontinence had a greater vesicourethral angle (148° vs. 125°) and larger retropubic space (7.5 vs. 5.1 mm) than did the women who were continent (p < 0.05). The score for the risk of stress urinary incontinence was higher in the group with stress urinary incontinence (3.3 ± 1.4) than in the women who were continent (1.0 ± 1.2) (p < 0.001).
• Conclusions: MR imaging with an endovaginal coil revealed significant morphologic alterations of the urethra and supporting structures in patients with stress urinary incontinence.
  
• Editorial Comment
  Recently several studies using different approaches has been shown that magnetic resonance imaging (MRI) may be a useful tool for the diagnosis of the problems of the female pelvic floor. Today’s use of MRI of the pelvic floor includes both anatomical/topographical images of high quality and functional imaging. Functional MRI when done preferentially in open MRI systems seems promising because allows a potential of simultaneously examining, micturition, bladder motion and pelvic floor muscles. The problem is that the quality of images obtained with open MRI equipments is not comparable with the high resolution images of the closed MRI systems with 1.5 Tesla. The main purpose of this excellent study is to demonstrate superb high resolution images of urethra and its supporting structures obtained with an endovaginal coil .These examinations were performed in normal women and in patients with stress urinary incontinence. It is clear that direct visualization of the morphology of theses structures is important in deciding treatment options. Although a more detailed depiction of minute structures was obtained with this special endovaginal coil, In our opinion diagnostic, high resolution images obtained with the regular pelvic phased array coils are sufficient for the adequate evaluation of these abnormalities. As with others closed-magnet-systems the main limitation of this study very well pointed out by the authors are that these patients underwent pelvic floor examination only in supine position. Some dynamic changes of the urethra and vesicourethral angle as well some bladder descents can be missed unless the patients are examined in sitting position and during micturition and bladder motion.

Dr. Adilson Prando
Department of Radiology
Vera Cruz Hospital
Campinas, São Paulo, Brazil