Objectives: During the last 2 decades, ultrasonography has been proposed for the morphologic evaluation of the urethral rhabdosphincter. The aims of this study were to evaluate the feasibility of a simple sonographic technique for the assessment of the urethral rhabdosphincter morphology by using a 2-dimensional (2D) transvaginal transducer and to evaluate any associations between the sonographic parameters of rhabdosphincter morphology with the presence of urodynamic stress incontinence (USI).
Methods: This was a prospective study of women who underwent urodynamic studies and an introital 2D ultrasonography and divided in 2 groups based on the presence or absence of USI. Measurements included rhabdosphincter thickness at the 3-o'clock (right) and 9-o'clock (left) positions and the rhabdosphincter outer (Π) and inner circumference (π). Based on these values, the mean thickness of the rhabdosphincter (R + L / 2), the rhabdosphincter differential perimeter (Π - π), and area (A - α) were also calculated.
Results: Statistical analysis showed that women with a rhabdosphincter area of less than 0.65 cm, mean thickness of less than 0.24 cm, and differential perimeter of less than 1.08 cm had 3.98, 5.67, and 5.41 times greater odds for USI, respectively. Receiver operating characteristic curve analysis results showed that the optimal cutoff values for the prediction of USI from rhabdosphincter thickness, differential perimeter. and surface area were 0.24 cm (79.6% sensitivity, 63.4% specificity), 1.08 cm (70.8% sensitivity and 69.1% specificity), and 0.65 cm (71.9% sensitivity, 57.1% specificity), respectively.
Conclusions: Introital ultrasonography with a 2D transvaginal probe allowed the visualization of the urethral rhabdosphincter morphology in greater than 90% of the cases. Sonographic measurements showed that patients with USI had a thinner urethral rhabdosphincter than did women with a normal sphincteric mechanism.