Practical Urological Ultrasound by Pat F. Fulgham & Bruce R. Gilbert

Author:Pat F. Fulgham & Bruce R. Gilbert
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

3D/4D Assessment of Levator Ani Complex

With the adoption of 3D/4D ultrasound, practitioners now have an alternative to magnetic resonance imaging in the evaluation of the levator ani complex in the axial plane. Advantages of 3D ultrasound in comparison to MRI include low cost, reproducibility, and real-time imaging where imaging planes can be modified for optimal visibility of anatomic structures. One recent multi-institutional study has found a sensitivity of 0.078 and specificity of 0.86 in detecting levator ani defects detected on MRI; however, because of interobserver disagreement the authors concluded widespread implementation may be limited [15]. The technique is similar to 2D imaging, with orientation set in the midsagittal plane. To obtain volumes, an acquisition angle between 70° and 85° is needed to capture pertinent anatomy (levator hiatus, vagina, paravaginal tissue, urethra, puborectalis muscle, anorectal angle). Higher acquisition angles may be needed in women with significant prolapse, as displacement of lateral structures may occur. Display modes for 3D ultrasound are best depicted in three cross-sectional planes including the axial, coronal, and midsagittal plane (Fig. 9.7) [16]. A thorough assessment of the pelvis can be conducted in real time, assessing for musculofascial defects, measuring downward displacement of pelvic organs, and the assessment of the levator hiatus with Valsalva maneuver. Special attention should be placed to the inferomedial aspect of the puborectalis muscle which can account for delivery-related trauma predisposing women to pelvic organ prolapse . The levator hiatus lies between the two muscle bellies of the puborectalis muscle’s attachment to the pubic bone. Within this space the urethra can be found anteriorly, the rectum posteriorly, and the vaginal canal medially. Measurements are taken at the midsagittal plane, measuring the anteroposterior distance, then an axial plane is used to obtain the anteroposterior and transverse diameter. Levator hiatus area measuring >25 cm2 has been defined as abnormal on Valsalva maneuver [17]. Defects in the levator ani complex can be quantified using tomographic ultrasound imaging (TUI), which displays an axial multislice image. This modality is performed while the patient is performing a pelvic contraction and begins at 5 mm below to 12 mm above the plane of minimal hiatal dimensions [18]. The slices are obtained in 2.5 mm intervals and eight images are produced. A score of zero is used if there are no defects graded with 16 being consistent with bilateral avulsion. Imaging in the 4D mode allows a real-time dynamic investigation of the pelvic floor. Valsalva maneuver can be done in real time to assess defects in the rectovaginal septum and detachment of the puborectalis from the pubis can be appreciated during voluntary levator contraction (as with Kegel exercise). Pelvic floor muscle contractility can be assessed in the midsagittal view and measured by the displacement of the bladder neck and reduction of levator hiatus anteroposterior diameter. Although pelvic floor muscle tone is important for continence, one recent study did not show a strong association with contractility measured on ultrasound or physical exam and urinary continence [19]. However, defects in the pubovisceral musculature delineated

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