Evaluation of urethral morphology and function in female patients with stress urinary incontinence by static and dynamic pelvic floor MRI and diffusion tensor imaging / 中华放射学杂志

ABSTRACT

Objective:To explore the value of the static and dynamic pelvic floor MRI and diffusion tensor imaging (DTI) in evaluating the morphology and function of urethra in patients with stress urinary incontinence (SUI).Methods:From July 2020 to February 2021, a total of 28 patients with SUI and 45 age-matched healthy controls were prospectively collected at the First Affiliated Hospital of Zhengzhou University. The static and dynamic pelvic floor MRI and DTI were performed for all subjects. The thickness of internal and external sphincter of middle urethra were measured on static MRI images. The functional urethral length (FUL) was measured both on static and maximal strain phase of dynamic MRI images, then the difference of FUL was calculated. The presence of bladder neck funneling and urethra opening were observed on static and dynamic MRI. The muscle fiber bundle image of urethral sphincter complex was obtained by post-processing of DTI original images. The anisotropy fraction (FA), apparent diffusion coefficient (ADC) and three eigenvalues (λ1, λ2, λ3) of annular sphincter and central longitudinal muscle in middle urethra were measured. The independent sample t test and chi-square test were used to analyse the difference of measured parameters in MRI, parameters of DTI and imaging signs between the two groups. Results:Compared with healthy controls, the SUI patients showed that the thickness of external sphincter in middle urethral and FUL in static status and maximal strain phase were significantly decreased ( t=-3.95, -5.72, -8.41, all P<0.001), the difference of FUL between static status and maximal strain phase was significantly increased ( t=4.41, P<0.001). The positive rate of bladder neck funneling in static status and maximal strain phase, urethral opening in maximal strain phase of SUI group increased significantly (χ2=23.09 , 22.25, 26.59, all P<0.001). In SUI group, the FA value of middle urethral annular sphincter decreased significantly ( t=-3.48, P=0.001), while the ADC, λ2 and λ3 values increased significantly ( t=3.19, 2.15 , 2.06, and P=0.002, 0.038 , 0.046, respectively). There was no significant difference in DTI parameters of middle urethral longitudinal muscle between the two groups (all P>0.05). Conclusions:Static and dynamic MRI and DTI techniques can objectively evaluate the changes of urethral morphology and function of SUI patients. The thinning of the external sphincter in the middle urethra, shortening of the FUL and the destruction of the microstructure of the annular sphincter fiber bundle were the main alterations of SUI patients.