New research suggests that key parameters on pelvic floor magnetic resonance imaging (MRI) can play a significant role in predicting postpartum stress urinary incontinence (SUI) in primiparous women.
For the prospective study, recently published in Insights into Imaging, researchers compared data from pelvic floor MRI exams from 52 women with primiparous stress urinary incontinence (PSUI), 51 women with primiparous continence (PC) and a control group of 30 nulliparous women (NC). Inclusion criteria for the primiparous women in the study included natural conception, singleton delivery and gestational age of more than 37 weeks, according to the study.
The study authors found that an increased retrovesicourethral angle, decreased functional urethral length and the presence of bladder funnel on MRI during straining had 81.6 percent, 88.2 percent, and 82.5 percent area under the receiver operating characteristic curves (AUCs), respectively, for predicting SUI in primiparous women. The researchers emphasized that the combination of these factors had a 94.7 AUC, a 96.2 percent sensitivity rate and a 82.4 percent specificity rate in predicting SUI in this population.
While the study authors noted the incidence of bladder funnel in all of the study groups, there was an 88.5 percent incidence in the PSUI group in comparison to 23.5 percent in the PC cohort and 11.8 percent in the control group.
“The integrity of bladder neck closure was deficient in the PSUI group, as indicated by increased retrovesicourethral angle during straining, possibly due to decreased external support for the urethra and bladder neck,” wrote study co-author Wen Shen, M.D., Ph.D., who is affiliated with the Department of Radiology at Tianjin First Central Hospital and the School of Medicine at Nankai University in Tianjin, China, and colleagues.
“Our study confirms that primiparas with SUI had a shorter urethral length. The bladder funnel has been associated with lower maximum urethral closure pressure, reflecting the decrease in urethral sphincter function. In our study, the proportion of bladder funnel in primiparas with SUI was up to 88.5 percent, indicating a decreased tension of the urinary sphincter and reduced function of maintaining urethral closure in women in the PSUI group."
Three Key Takeaways
- Predictive factors. The combination of specific pelvic floor parameters observed on MRI exams, including an increased retrovesicourethral angle, decreased functional urethral length, and the presence of bladder funnel during straining, can serve as strong predictors (94.7 percent AUC) of postpartum stress urinary incontinence (SUI) in primiparous women.
- Urethral length and bladder function. The study highlights that primiparous women with SUI tend to have a shorter urethral length, which is associated with decreased urinary sphincter function. Additionally, the presence of a bladder funnel indicates a decrease in urethral sphincter function, contributing to SUI risk.
- Levator ani muscle changes. Primiparous women with SUI demonstrated a higher incidence of minor defects in the levator ani muscle (LAM) compared to those with continence. These changes in LAM function and morphology, including a larger levator hiatus area, suggest that hormonal changes during pregnancy and vaginal delivery-related factors may lead to pelvic floor relaxation and increased pelvic organ mobility, potentially contributing to SUI development.
The researchers found a nearly 25 percent higher incidence of minor defects of the levator ani muscle (LAM) in the PSUI (32.7 percent) cohort in comparison to the PC group.
In their assessments of LAM function and morphology, the researchers found that the PSUI group had a larger levator haitus area (LHA) at strain (2552.7 mm2 in comparison to 1719.7 mm2 for the PC cohort and 1292.9 mm2 for the NC cohort) and rest (1339.9 mm2 in contrast to 1136.2 in the PC group and 1107.6 mm2 in the NC group). The PSUI cohort also had significantly shorter bladder neck distance to the pubococcygeal line (B-PCL) and cervix distance to the pubococcygeal line (U-PCL) at strain in comparison to the PC and NC cohorts, according to the study authors.
“These changes were attributed to hormonal changes during pregnancy and extreme stretching or denervation of the LAM during vaginal delivery, which might lead to pelvic floor relaxation and reduce the support to the pelvic organs, eventually resulting in overactive movement of pelvic organs,” noted Shen and colleagues.
(Editor’s note: For related content, see “Can Placental MRI Help Identify Elevated Risks for Adverse Pregnancy Outcomes?”)
Beyond a limited sample size for the cohort, the researchers said other limitations of the study included a lack of assessment on whether pelvic floor parameters can have an impact on SUI severity, or the recovery and progression of postpartum SUI.
