The axial location of structural regions in the urethra:A magnetic resonance study in nulliparous women.

OBJECTIVE: To define and quantify the appearance and location of distinct regions of the bladder neck and urethra by using axial magnetic resonance images from healthy, continent, nulliparous women. METHODS: Seventy-eight asymptomatic, healthy, nulliparous women (mean age 29.2 ± 5.4 years) volunteered for this study. All women were proven continent on urodynamic examination. Axial proton density magnetic resonance images of the pelvic floor were analyzed at 5-mm intervals. A geometric origin was established at the internal urethral meatus. The presence or absence of each of six structural regions—the bladder base, bladder neck, striated urethral sphincter, compressor urethrae and urethrovaginal sphincter, perineal membrane, and distal urethra—was then noted in each more distal image. The proportion of women in whom a structural region was seen at each 5-mm interval was recorded. RESULTS: The striated urogenital sphincter was observed at 5–25 mm distal to the bladder base. It was observed 10 and 15 mm below the bladder base in 91% (95% confidence interval [CI] 85%, 98%) and 99% (95% CI 97%, 100%), respectively, of all women. The perineal membrane, marking the distal end of the muscular urethra, was located 20–35 mm distal to the bladder base. The length of the muscular region of the urethra ranged from 20 to 35 mm (mean 24 mm, 95% CI 24, 25 mm). CONCLUSION: Magnetic resonance images allow the normal appearance and location of urethral and bladder neck structures to be quantified in healthy, continent, nulliparous women

Appearance of the levator ani muscle subdivisions in magnetic resonance images.

OBJECTIVE: Identify and describe the separate appearance of 5 levator ani muscle subdivisions seen in axial, coronal, and sagittal magnetic resonance imaging (MRI) scan planes. METHODS: Magnetic resonance scans of 80 nulliparous women with normal pelvic support were evaluated. Characteristic features of each Terminologia Anatomica–listed levator ani component were determined for each scan plane. Muscle component visibility was based on pre-established criteria in axial, coronal, and sagittal scan planes: 1) clear and consistently visible separation or 2) different origin or insertion. Visibility of each of the levator ani subdivisions in each scan plane was assessed in 25 nulliparous women. RESULTS: In the axial plane, the puborectal muscle can be seen lateral to the pubovisceral muscle and decussating dorsal to the rectum. The course of the puboperineal muscle near the perineal body is visualized in the axial plane. The coronal view is perpendicular to the fiber direction of the puborectal and pubovisceral muscles and shows them as “clusters” of muscle on either side of the vagina. The sagittal plane consistently demonstrates the puborectal muscle passing dorsal to the rectum to form a sling that can consistently be seen as a “bump.” This plane is also parallel to the pubovisceral muscle fiber direction and shows the puboperineal muscle. CONCLUSION: The subdivisions of the levator ani muscle are visible in MRI scans, each with distinct morphology and characteristic features

The urethra during pelvic floor contraction: Observations on three-dimensional ultrasound

OBJECTIVE: To investigate with three-dimensional ultrasound how voluntary pelvic floor contractions influence the morphology of the female urethra's components

Three-dimensional ultrasound of the female urethra: comparing transvaginal and transrectal scanning

Objectives To compare transvaginal and transrectal three-dimensional ultrasound in determining the morphology and measurements of the female urethra

Transperineal and endovaginal ultrasound for evaluating suburethral masses: comparison with magnetic resonance imaging

Objective To evaluate the utility of pelvic floor ultrasound (US) in the detection and evaluation of suburethral masses, using magnetic resonance imaging (MRI) as the reference standard. Methods This was a retrospective analysis of US and MRI scans of all women with a suburethral mass on clinical examination at a single urogynecology clinic over a 13-year period (February 2007 to March 2020). All women were examined using two-dimensional transperineal US (2D-TPUS) with or without three-dimensional endovaginal US (3D-EVUS). All patients underwent unenhanced T1-weighted and T2-weighted MRI, which was considered the reference standard in this study. Presence of a suburethral mass and its size, location, connection with the urethral lumen and characteristics were evaluated on both pelvic floor US and MRI. Agreement between pelvic floor US and MRI was assessed using intraclass correlation coefficients (ICC; 3,1). Results Forty women suspected of having a suburethral mass on clinical examination underwent both MRI and US (2D-TPUS with or without 3D-EVUS). MRI detected a suburethral mass in 34 women, which was also detected by US. However, US also identified a suburethral mass in the remaining six women. Thus, the agreement between US and MRI for detecting a suburethral mass was 85% (95% CI, 70.2–94.3%). The ICC analysis showed good agreement between MRI and 2D-TPUS for the measured distance between the suburethral mass and the bladder neck (ICC, 0.89; standard error of measurement (SEM), 3.64 mm) and excellent agreement for measurement of the largest diameter of the mass (ICC, 0.93; SEM, 4.31 mm). Good agreement was observed between MRI and 3D-EVUS for the measured distance from the suburethral mass to the bladder neck (ICC, 0.88; SEM, 3.48 mm) and excellent agreement for the largest diameter of the suburethral mass (ICC, 0.94; SEM, 4.68 mm). Conclusions 2D-TPUS and 3D-EVUS are useful in the imaging of suburethral masses. US shows good-to-excellent agreement with MRI in identifying and measuring suburethral masses; therefore, the two modalities can be used interchangeably depending on availability of equipment and expertise