Intrinsic sphincter deficiency (ISD) and urethral hypermobility are leading causes of stress urinary incontinence (UI) in women and require different treatment. Traditional diagnosis of UI is based on urodynamics (UDs). MRI is able to visualize urethra and periurethral tissues relevant to UI. Our purpose was to correlate MRI findings related to urethral sphincter and urethral ligaments with UDs results in women with UI.
METHOD AND MATERIALS
We evaluated 12 women with UI (mean age 57 ± 12) with MRI protocol including endocavitary imaging (14F endourethral coil and endovaginal or endorectal coil), and standard pelvic protocol with phased array coil. High-resolution T2W FSE images in three planes and sagittal SSFSE images during strain were obtained. We analyzed status and thickness of urethral sphincter muscle, sphincter length, status of urethra support ligaments, urethral mobility and bladder neck competency during strain. We correlated MR imaging findings with measurements of Valsalva leak point pressure (LPP), maximal urethral closure pressure (MUP), functional urethral length obtained from UDs and urethral Q-tip test mobility. Pearson’s product moment correlation coefficient was used for assessment of correlation between paired variables.
RESULTS
There was very high correlation (r = 0.93) between LPP and sphincter muscle length, high correlation (r = 0.83) between Q-tip mobility and hypermobility angle on MRI, and (r = - 0.74) between MUP and posterior striated muscle thickness of mid urethra. There was moderate correlation (r = 0.68) between functional length of urethra by UDs and length of sphincter muscle on MRI. 2 of 3 patients with low MUP, ≤ 20 mm H20 showed bladder neck funneling, a feature of ISD and 1 of 3 showed short urethral sphincter < 2 cm. All 9 patients with hypermobility > 30 degrees showed laxity, partial or complete disruption of periurethral ligaments and 3 showed vagino-levator separation.
CONCLUSION
By providing information about urethral morphology and supporting ligaments, MRI supplements UDs evaluation and may assist in classification of incontinent patients into hypermobility and ISD category, thus may guide the choice of therapy and post treatment follow-up.
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