Functional correlates of Doppler flow study of the female urethral vasculature

Analysis of urethral blood flow by high-resolution laser speckle contrast imaging in a rat model of vaginal distension

OBJECTIVE

To investigate the feasibility of laser speckle contrast imaging (LSCI) for monitoring urethral blood flow (UBF).

MATERIALS AND METHODS

In this study, 18 healthy, virgin female Sprague-Dawley rats aged 8-week-old were used. The animals were divided into the sham group (n = 9) and the vaginal distension (VD) group (n = 9). The sham group underwent one catheterization of the vagina without distension and the VD group underwent one VD. Following the VD or sham treatment for one week, LSCI assessment of urethral blood flow was performed during bladder filling and leak point pressure (LPP) process.

RESULTS

During the LPP process, in the VD group, the mean LPP was significantly lower than in the sham group (p < 0.05) and the mean UBF level was also significantly lower than in the sham group (p < 0.05) in the LPP condition. The mean relative change of UBF (Δ Flow) was significantly different between the sham group and VD group. The value was 0.646 ± 0.229 and 0.295 ± 0.19, respectively (p < 0.05). During the bladder filling process, the VD group had a significant lower mean UBF level than the sham group under full bladder conditions (p = 0.008). The mean ΔFlow was also significantly lower than in the sham group. The value was 0.115 ± 0.121 and 0.375 ± 0.127, respectively (p = 0.016).

CONCLUSIONS

The results confirmed that LSCI was able to determine UBF in female rats. The VD group had lower baseline UBF and lower increases in UBF during bladder filling and LPP process compared with the sham group.

Inverse correlation between urethral length and continence before and after native tissue pelvic floor reconstruction

Urethral length was evaluated retrospectively in patients with prolapse undergoing anterior native-tissue repair. Effects of age, prolapse stage, defect pattern, urodynamic and clinical stress test findings, and tension-free vaginal tape (TVT) surgery indication were analyzed using Mann-Whitney and Wilcoxon tests and linear and logistic regression. Of 394 patients, 61% had stage II/III and 39% had stage IV prolapse; 90% of defects were central (10% were lateral). Median pre- and postoperative urethral lengths were 14 and 22 mm (p < 0.01). Preoperative urethral length was greater with lateral defects [p < 0.01, B 6.38, 95% confidence interval (CI) 4.67-8.08] and increased stress incontinence risk (p < 0.01, odds ratio 1.07, 95% CI 1.03-1.12). Postoperative urethral length depended on prolapse stage (p < 0.01, B 1.61, 95% CI 0.85-2.38) and defect type (p = 0.02, B - 1.42, 95% CI - 2.65 to - 0.2). Postoperatively, TVT surgery was indicated in 5.1% of patients (median 9 months), who had longer urethras than those without this indication (p = 0.043). Native-tissue prolapse repair including Kelly plication increased urethral length, reflecting re-urethralization, particularly with central defects. The functional impact of urethral length in the context of connective tissue aging should be examined further.

Urinary Incontinence in Older Women: A Syndrome-Based Approach to Addressing Late Life Heterogeneity

Urinary incontinence is a prevalent pelvic floor disorder among women of all ages. However, in many older women, especially those who have multiple chronic conditions it may be a geriatric syndrome because of its shared characteristics of physical function impairments, cognitive decline, and mobility disability. The geriatric incontinence syndrome may represent a poorly characterized phenotype of UI among older women which in many ways reflects unhealthy aging. In this article, we explore the evidence behind these concepts together with potentiel impact on the diagnosis and management of UI in this group.

On Structure-Function Relationships in the Female Human Urethra: A Finite Element Model Approach

Remarkably little is known about urethral striated and smooth muscle and vascular plexus contributions to maintaining continence or initiating micturition. We therefore developed a 3-D, multiphysics, finite element model, based on sequential MR images from a 23-year-old nulliparous heathy woman, to examine the effect of contracting one or more individual muscle layers on the urethral closure pressure (UCP). The lofted urethra turned out to be both curved and asymmetric. The model results led us to reject the current hypothesis that the striated and smooth muscles contribute equally to UCP. While a simulated contraction of the outer (circular) striated muscle increased closure pressure, a similar contraction of the large inner longitudinal smooth muscle both reduced closure pressure and shortened urethral length, suggesting a role in initiating micturition. When age-related atrophy of the posterior striated muscle was simulated, a reduced and asymmetric UCP distribution developed in the transverse plane. Lastly, a simple 2D axisymmetric model of the vascular plexus and lumen suggests arteriovenous pressure plays and important role in helping to maintain luminal closure in the proximal urethra and thereby functional urethral length. More work is needed to examine interindividual differences and validate such models in vivo.

Progress in studies on pathological changes and future treatment strategies of obesity-associated female stress urinary incontinence: a narrative review

With the increasing prevalence of obesity worldwide, obesity-related female stress urinary incontinence (FSUI) has become a key health problem. Recent studies indicated that FSUI is primarily caused by obesity-related pathological changes, such as fat droplet deposition, and results in pelvic floor nerve, vascular, and urethral striated muscle injury. Meanwhile, treatments for obesity-associated FSUI (OA-FSUI) have garnered much attention. Although existing OA-FSUI management strategies, including weight loss, pelvic floor muscle exercise, and urethral sling operation, could play a role in symptomatic relief; they cannot reverse the pathological changes in OA-FSUI. The continued exploration of safe and reliable treatments has led to regenerative therapy becoming a particularly promising area of researches. Specifically, micro-energy, such as low-intensity pulsed ultrasound (LIPUS), low-intensity extracorporeal shock wave therapy (Li-ESWT), and pulsed electromagnetic field (PEMF), have been shown to restore the underlying pathological changes of OA-FSUI, which might be related by regulation endogenous stem cells (ESCs) to restore urine control function ultimately in animal experiments. Therefore, ESCs may be a target for repairing pathological changes of OA-FSUI. The aim of this review was to summarize the OA-FSUI-related pathogenesis, current treatments, and to discuss potential therapeutic options. In particular, this review is focused on the effects and related mechanisms of micro-energy therapy for OA-FSUI to provide a reference for future basically and clinical researches.

Size Does Not Make the Difference: 3D/4D Transperineal Sonographic Measurements of the Female Urethra in the Assessment of Urinary Incontinence Subtypes

Purpose. The objective was to evaluate the usefulness of transperineal ultrasound in the assessment of the urethral length and urethral lumen by 3D/4D transperineal sonography to discriminate between female patients with subtypes of urinary incontinence. Methods. A total of 150 female patients underwent an examination because of urinary incontinence. 41 patients were diagnosed with urgency urinary incontinence (OAB), 67 patients were diagnosed with stress urinary incontinence (SUI), and 42 patients were in the control group (CTRL). Three diameters of the urethral lumen (proximal (U1), medial (U2), and distal (U3)) and the urethral length were measured. By the assessment of the urethral lumen, the presence of the urethral funneling was evaluated. Results. We found a significant difference in the urethral length and urethral lumen U2 of OAB and SUI versus CTRL. The urethral length was significantly greater (P < 0.05) and the urethral lumen was significantly wider (P < 0.05) in the patients with urinary incontinence. The incidence of the urethral funneling was significantly higher (P < 0.05) in the study groups with urinary incontinence than in the control group. Conclusions. Our results have shown the urethral changes obtained by ultrasound in patients with urinary incontinence, but they are still insufficient to distinguish between subtypes of urinary incontinence.

Can we predict urinary stress incontinence by using demographic, clinical, imaging and urodynamic data?

OBJECTIVE

It has been claimed that urethral hypermobility and resting urethral pressure can largely explain stress incontinence in women. In this study we tried to replicate these findings in an unselected cohort of women seen for urodynamic testing, including as many potential confounders as possible.

STUDY DESIGN

This study is a retrospective analysis of data obtained from 341 women. They attended for urodynamic testing due to symptoms of pelvic floor dysfunction. We excluded from the analysis women with a history of previous anti-incontinence and prolapse surgery. All patients had a standardised clinical assessment, 4D transperineal pelvic floor ultrasound and multichannel urodynamic testing. Urodynamic stress incontinence (USI) was diagnosed by multichannel urodynamic testing. Its severity was subjectively graded as mild, moderate and severe. Candidate variables were: age, BMI, symptoms of prolapse, vaginal parity, significant prolapse (compartment-specific), levator avulsion, levator hiatal area, Oxford grading, midurethral mobility, maximum urethral pressure (MUP), maximum cough pressure and maximum Valsalva pressure reached.

RESULTS

On binary logistic regression, the following parameters were statistically significant in predicting urodynamic stress incontinence: age (P=0.03), significant rectocele (P=0.02), max. abdominal pressure reached (negatively, P<0.0001), midurethral mobility (P=0.0004) and MUP (negatively, P<0.0001). On multivariate analysis, accounting for multiple interdependencies, the following predictors remained significant: max. abdominal pressure reached (negatively, P<0.0001), cough pressure (P=0.006), midurethral mobility (P=0.003) and MUP (negatively, P<0.0001), giving an R(2) of 0.24.

CONCLUSIONS

Mid-urethral mobility and MUP are the main predictors of USI. Demographic and clinical data are at best weak predictors. Our results suggest the presence of major unrecognised confounders.

Assessment of urethral vascularity using 2D colour Doppler high-frequency endovaginal ultrasonography in women treated for symptomatic stress urinary incontinence: 1-year prospective follow-up study

INTRODUCTION

Urethral vascularity is responsible for organ perfusion. It is also believed to contribute to maintaining the normal tension in the urethral mucosa and contributes to approximately one third of urethral closure pressure. We hypothesised that in women undergoing treatment for stress urinary incontinence (SUI), there is no change in blood flow intensity.

METHODS

In this pilot study we recruited women attending the urogynaecology clinics between July and October 2009. Exclusion criteria included symptoms of pelvic organ prolapse or urinary tract infection. Colour Doppler ultrasound was performed at the level of the mid-urethra using a high-frequency (9-12 MHz) endovaginal ultrasonography (EVUS) focusing on the following vascular parameters: flow velocity (V), area of the vessels (A), intensity of perfusion (I), Tissue Pulsatility Index (TPI) and Tissue Resistance Index (TRI). Vascular assessments were repeated at 1 year.

RESULTS

We examined 67 women with symptoms of SUI (17 women had surgery and 50 conservative management, i.e., pelvic floor muscle exercises). The mean (± SD) age in the conservative and surgical groups was 46 (±11) and 40 (±9) years respectively and median (range) parity was 2 (0-8) in both groups. Compared to baseline, no statistically significant differences were observed within each group (p > 0.05) or between the values of vascular parameters (V, A, I, TRI and TPI) at 1 year. There was also no difference in vascular parameters between the two groups.

CONCLUSION

At 12 months there is no change in vascularity parameters in women who opt for conservative or surgical treatment of SUI.

Vascularity of the urethra in continent women using colour doppler high-frequency endovaginal ultrasonography

Objectives

To assess the urethral vascularity in continent women using colour doppler high frequency endovaginal ultrasonography (EVUS).

Methods

We recruited 61 continent women attending gynaecology clinics between July and October 2009. Exclusion criteria included symptoms of urinary incontinence, voiding dysfunction, pelvic organ prolapse or urinary tract infection. The participants underwent EVUS using high frequency (9-12 MHz) biplane transducer (type 8848 BK Medical), according to a standardised protocol. Colour Doppler US was performed in sagittal plane and in transverse plane at the level of the mid-urethra. Ten seconds video files were recorded and following vascular parameters: flow velocity (V_mix), area of the vessels (A_mix), intensity of vascularity (I_mix), pulsatility index (PI_mix) and resistance index (RI_mix) was evaluated.

Results

There were 30 nulliparous (49.2%) women and 31 multiparous women (50.8%) with a mean (±SD) age of 32 (±4) and 46 (±6) years respectively. Significant impairment of vascularity was observed in multiparous patients as compared to nulliparous and was reflected by increased values of RI_mix (p < 0.001) and PI_mix (p < 0.001), and decreased values of V_mix (p < 0.001), A_mix (p < 0.001), I_mix (p < 0.001) in axial and midsagittal sections of the midurethra. A significant decrease of mean value ± SD of I_mix- from 0.02 ± 0.02 in nulliparous to 0.005 ± 0.01 in multiparous was observed.

Cronbach alpha, used to assess vascular correlations and parity demonstrated a reduction when expressed only for vascular parameters, indicating that number of deliveries is an important factor while assessing urethral vascularity.

Conclusions

Compared to continent nulliparous women, continent multiparous women demonstrated a significant reduction in the vascularity parameters in all measured variables when parity was accounted for.

Advances in knowledge

This study provides the basis for further research in assessing urethral vascularity in women.

Effects of endogenous ovarian estrogen versus exogenous estrogen replacement on blood flow and ERβα and ERβ levels in the bladder

OBJECTIVE

Determine the effect of endogenous estrogen versus estrogen replacement therapy (ERT) on bladder blood flow (BBF) and estrogen receptors (ERs).

METHODS

BBF was determined with radiolabeled microspheres in luteal, follicular, pregnant, oophorectomized (Ovx) sheep, and Ovx sheep with ERT. Estrogen receptors (ERalpha, ERbeta) were quantified using Western blot analysis.

RESULTS

Compared to luteal and follicular ewes, BBF was reduced in pregnancy and following oophorectomy. Estrogen replacement therapy in Ovx sheep restored BBF to luteal levels. Estrogen receptor alpha predominated, whereas ERbeta was not detectable. Estrogen receptor-alpha levels were unaffected by the ovarian cycle and increased in pregnancy, as well as in Ovx sheep with and without chronic ERT.

CONCLUSION

The combination of diminished BBF and elevated ERalpha levels in both pregnant and Ovx sheep suggests an inverse relationship between BBF and ERalpha in the bladder. Although chronic ERT in Ovx sheep restored BBF, it did not restore ERalpha back to luteal levels.

Quantitative assessment of urethral vascularity in nulliparous females using high-frequency endovaginal ultrasonography

PURPOSE

To assess the vascular parameters in the urethra of nulliparous females and to compare the vascularity among various parts of the urethra, using high-frequency endovaginal ultrasonography (EVUS).

METHODS

Twenty-two nulliparous women, mean age 27 years, underwent EVUS using a biplane transducer at 12 MHz frequency. Color Doppler examinations of the urethra were recorded and further evaluated off-line using special software (Pixel Flux) for quantitative assessment of the vascularity. The urethra was divided into four regions of interest (ROIs) in the midsagittal plane and three ROIs in the axial plane. The following parameters were measured: velocity (V), perfused area (A), perfusion intensity (I), pulsatility index (PI), and resistance index (RI). Interobserver and intraobserver reproducibility analysis was also performed.

RESULTS

In midsagittal plane, the midurethra presented the highest value of V and lowest value of A. The intramural part showed the lowest value of I and the highest values of RI and PI. In the distal urethra, the highest value of I and the lowest value of RI was seen. In the axial plane, the values of V, A, and I were statistically significantly higher in the external part of the midurethra compared with the internal part. Excellent interobserver and intraobserver reproducibility was shown in the majority of parameters for the entire urethra.

CONCLUSIONS

Vascularity differs in different parts of the urethra. Pixel Flux is a valuable tool for providing reproducible quantitative analysis of vascular parameters for the entire urethra.

Stem cells for stress urinary incontinence: the adipose promise

Stress urinary incontinence (SUI), the most common type of incontinence in women, is a frequent and costly ailment responsible for an alteration in the quality of life. Although medical treatment gives some rather deceiving results, surgical techniques that include colposuspension or tension-free vaginal tape, employed in cases of urethral support defect, give a 5-year cure rate of more than 80%. However, these techniques could lead to complications or recurrence of symptoms. Recently, the initiation of urethral cell therapy has been undertaken by doctors and researchers. One principal source of autologous adult stem cells is generally used: muscle precursor cells (MPCs) which are the progenitors of skeletal muscle cells. Recently, a few research groups have shown interest in the MPCs and their potential for the treatment of urinary incontinence. However, using MPCs or fibroblasts isolated from a striated muscle biopsy could be questionable on several points. One of them is the in vitro cultivation of cells, which raises issues over the potential cost of the technique. Besides, numerous studies have shown the multipotent or even the pluripotent nature of stromal vascular fraction (SVF) or adipose-derived stem cells (ASCs) from adipose tissue. These cells are capable of acquiring in vitro many different phenotypes. Furthermore, recent animal studies have highlighted the potential interest of SVF cells or ASCs in cell therapy, in particular for mesodermal tissue repair and revascularization. Moreover, the potential interest of SVF cells or ASCs for the treatment of urinary incontinence in women is supported by many other characteristics of these cells that are discussed here. Because access to these cells via lipoaspiration is simple, and because they are found in very large numbers in adipose tissue, their future potential as a stem cell reservoir for use in urethral or other types of cell therapy is enormous.