A Preliminary Study on Quantitative Quality Measurements of the Urethral Rhabdosphincter Muscle by Supersonic Shear Wave Imaging in Women With Stress Urinary Incontinence

Objectives: To quantitatively assess the quality of the urethral rhabdosphincter muscle by measuring its shear wave velocity (V_s ) and calculating the Young modulus (E) with supersonic shear wave imaging (SSI).

Methods: This was a prospective study of 43 women with SUI and 52 female control participants who underwent a transperineal US examination with SSI. Supersonic shear wave imaging was performed at rest with a linear transducer and a specialized-preset procedure. The stability and validity of the shear waves were automatically assessed by the SSI procedure. The SSI images were visualized in a color-coded elastographic image. In the postprocessing analysis, the ventral part of the urethral rhabdosphincter muscle was manually outlined. The mean V_s and the mean E of the muscle were measured by the SSI procedure. The relationship between the mean V_s , mean E, and SUI was evaluated.

Results: The SSI examination was successfully performed in 40 patients with SUI (93.0%) and 40 female control participants (76.9%). No significant differences between the groups in age, body mass index, and parity were identified. For the SUI and control groups, the mean V_s values were 2.54 and 2.73 m/s, respectively, and the mean E values were was 19.7 and 22.7kPa. Significant correlations were found between SUI and the mean V_s as well as the mean E (Spearman correlation coefficients, -0.41 and -0.43; P < .05).

Conclusions: The mechanical properties of the urethral sphincter can be quantitatively assessed by SSI. The stiffness of the urethral rhabdosphincter muscle was significantly lower in women with SUI.