MRI morphology of the levator ani muscle, endopelvic fascia, and urethra in women with stress urinary incontinence

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Abstract

Objective

To evaluate pathomorphologic changes of the levator ani muscle, endopelvic fascia, and urethra in women with stress urinary incontinence (SUI) by MRI.

Study design

Fifty-four women with SUI were examined by MRI (1.5 T): body phased-array coil, axial and coronal proton-density-weighted sequences.

Results

The urethral sphincter muscle showed a reduced thickness of its posterior portion (37%), an omega shape (13%) or higher signal intensity (50%); its abnormal configuration was associated with an increased signal intensity in 70% (p = 0.001). The levator ani muscle comprised an unilateral loss of substance in 30%, a higher signal intensity in 28%, and alterated origin in 19%. Central defects of the endopelvic fascia were present in 39% (n = 21), lateral defects in 46%. There was a significant association between loss of the symphyseal concavity of the anterior vaginal wall and lateral fascial defects (p = 0.001) and levator ani changes (p = 0.016).

Conclusion

MRI yields findings supporting current theories on the pathogenesis of SUI.

Introduction

Magnetic resonance imaging (MRI) provides detailed morphologic information on the stress urinary continence mechanism in vivo which correlates with findings in anatomic specimens [1], [2], [3], [4], [5] and even allows for assessing tissue quality [6]. Standardized MRI protocols [7] ensure interindividual morphologic comparison of the stress urinary continence mechanism. Delivery-related changes of this mechanism are depicted and can be classified as reversible and irreversible structural changes by repeat examination [6]. Interindividual comparison of the stress urinary continence mechanism in a homogeneous study population (nulliparae with normal urogynecologic findings) suggests that normal anatomic variations exist [7], which are assumed to contribute to the fact that the morphometry of the structures constituting the stress urinary continence mechanism in women with stress urinary incontinence is not significantly different from that of healthy women [8]. Qualitative changes such as the loss of the symphyseal concavity of the anterior vaginal wall are significantly more common in women with stress urinary incontinence [2], [8], [9], but have also been reported in women without symptoms [8]. It is still unclear whether these changes are constitutional or delivery-related.

Available MRI studies of the anatomy and pathology of the stress urinary continence mechanism have been performed in small, inhomogeneous study populations and the results do not yet allow for clearly defining the role of MRI in the diagnostic assessment of stress urinary incontinence. But the data do show that MRI clearly depicts the morphology and topography of the stress urinary continence mechanism. Open questions regarding the pathogenesis of stress urinary incontinence should therefore be answered making use of MRI [10], [11], [12]. The aim of the present study therefore was to identify stress-urinary-incontinence-related changes of the stress urinary continence mechanism consisting of the levator ani muscle, endopelvic fascia, and urethra as they are depicted by MRI. Based on these findings, a terminology of the MRI pathomorphology of the stress urinary continence mechanism in women with stress urinary continence is suggested.

Section snippets

Patients

Fifty-four women (mean age 52.1 ± 10.5 years; range 23–78 years; 75.9% aged 41–60 years) with proven stress urinary incontinence based on history (grade II according to Ingelman-Sundberg), clinical findings (positive stress test) [13], and urodynamic testing (sensory or motor urge symptoms were excluded in all women) were examined by MRI. MRI was performed in all women as part of their preoperative diagnostic workup after informed consent had been obtained. Women who additionally had clinically

Results

The pulse sequences used yielded analyzable images in all 54 cases.

Discussion

Defects of the levator ani muscle in the form of a unilateral loss of substance were rare in our patient population suggesting that such defects, while leading to mechanical dysfunction [16], are not the primary cause of stress urinary incontinence. The low incidence of levator ani defects alone in our study may be due to the fact that all patients were scheduled for urinary incontinence surgery. Our policy is to only operate on patients with proven reactivity of the pelvic floor or who have

References (46)

  • D. Beyersdorff et al.

    Sectional depiction of the pelvic floor by CT, MR imaging and sheet plastination: computer-aided correlation and 3D model

    Eur Radiol

    (2001)
  • I.L. Tan et al.

    Female pelvic floor: endovaginal MR imaging of normal anatomy

    Radiology

    (1998)
  • R. Tunn et al.

    MR imaging of levator ani muscle recovery following vaginal delivery

    Int Urogynecol J Pelvic Floor Dysfunct

    (1999)
  • R. Tunn et al.

    Static magnetic resonance imaging of the pelvic floor muscle morphology in women with stress urinary incontinence and pelvic prolapse

    Neurourol Urodyn

    (1998)
  • H.T. Huddleston et al.

    Magnetic resonance imaging of defects in DeLancey's vaginal support levels I, II, and III

    Am J Obstet Gynecol

    (1995)
  • H.R. Kirschner et al.

    Magnetic resonance imaging of the lower urinary tract

    Curr Opin Obstet Gynecol

    (1997)
  • D. Beyersdorff et al.

    Contribution of MRI in diagnosis of urinary stress incontinence without concomitant urogenital prolapse

    RöFo

    (2001)
  • A. Ingelman-Sundberg

    Urinary incontinence in women, excluding fistulas

    Acta Obstet Gynecol Scand

    (1952)
  • R. Tunn et al.

    Anatomical variations in the levator ani muscle, endopelvic fascia, and urethra in nulliparas evaluated by MR imaging

    Am J Obstet Gynecol

    (2003)
  • U. Ulmsten

    New aspects in pathophysiology of female urinary incontinence

  • M.A. Bredella et al.

    Denervation syndromes of the shoulder girdle: MR imaging with electrophysiologic correlation

    Skeletal Radiol

    (1999)
  • D. Jonas et al.

    Correlation between quantitative EMG and muscle MRI in patients with axonal neuropathy

    Muscle Nerve

    (2000)
  • C.M. McDonald et al.

    Magnetic resonance imaging of denervated muscle: comparison to electromyography

    Muscle Nerve

    (2000)
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