Correlating structure and function: three-dimensional ultrasound of the urethral sphincter

3D high frequency endovaginal ultrasound evaluation of urethral and pelvic morphology in stress urinary incontinence in first pregnancy

OBJECTIVE

We aimed to compare the morphological characteristics of pelvis and urethra in nulliparous pregnant women with and without stress urinary incontinence (SUI) by 3D high-frequency endovaginal ultrasound (3D-EVUS).

STUDY DESIGN

At 36-38 weeks of gestation, 40 nulliparous pregnant women with and without SUI underwent 3D-EVUS assessment. The anteroposterior and transverse diameters of levator hiatus (LH), pubovisceral muscle thicknesses at 3,9 and 12 o'clock, right and left paravaginal areas, symphysis angle, bladder-symphysis distance (BSD), uretral complex thickness (Ut), urethral complex width (Uw), urethral complex volume (UV), urethral length (UL), intramural urethra, rhabdosphincter thickness (Rt), rhabdosphincter width (Rw), rhabdosphincter length (RL), and rhabdosphincter volume (RV) were measured by 3D-EVUS.

RESULTS

Longer LH transverse diameter (34.8 ± 3.8 mm vs 31.1 ± 2.1 mm), shorter LH anteroposterior diameter (47.8 ± 6.2 mm vs 52.4 ± 2.6 mm), and wider symphysis angle (116.3 ± 5.6 vs 111.5 ± 5.3 degrees) were detected in nulliparous pregnant women with SUI compared those without SUI (p = 0.001, p = 0.001 and p = 0.013; respectively). RV of less than 1.26 cm³ was found to have a sensitivity of 100 % and a specificity of 100 % for the presence of SUI in nulliparous pregnant women.

CONCLUSIONS

Constitutionally different pelvic shape and decreased urethral rhabdosphincter measurements can be used to predict SUI in nulliparous pregnant women.

An International Continence Society (ICS) report on the terminology for pelvic floor muscle assessment

INTRODUCTION

The terminology for female and male pelvic floor muscle (PFM) assessment has expanded considerably since the first PFM function and dysfunction standardization of terminology document in 2005. New terms have entered assessment reports, and new investigations to measure PFM function and dysfunction have been developed. An update of this terminology was required to comprehensively document the terms and their definitions, and to describe the assessment method and interpretation of the finding, to standardize assessment procedures and aid diagnostic decision making.

METHODS

This report combines the input of members of the Standardisation Committee of the International Continence Society (ICS) Working Group 16, with contributions from recognized experts in the field and external referees. A logical, sequential, clinically directed assessment framework was created against which the assessment process was mapped. Within categories and subclassifications, each term was assigned a numeric coding. A transparent process of 12 rounds of full working group and external review was undertaken to exhaustively examine each definition, plus additional extensive internal development, with decision making by collective opinion (consensus).

RESULTS

A Terminology Report for the symptoms, signs, investigations, and diagnoses associated with PFM function and dysfunction, encompassing 185 separate definitions/descriptors, has been developed. It is clinically based with the most common assessment processes defined. Clarity and user-friendliness have been key aims to make it interpretable by clinicians and researchers of different disciplines.

CONCLUSION

A consensus-based Terminology Report for assessment of PFM function and dysfunction has been produced to aid clinical practice and be a stimulus for research.

Changes in Morphology of the Urethral Rhabdosphincter Postpartum

OBJECTIVE

The aim of the study was to determine the effect of pregnancy on urethral rhabdosphincter cross-sectional area (CSA) and any association of CSA to urinary symptoms.

METHODS

Nulliparous women planning pregnancy (N = 135) underwent standardized evaluations (symptom and quality of life [QOL] questionnaires, magnetic resonance imaging, ultrasonography, and neurophysiologic testing) between January 2008 and December 2013 (V1). The participants who became pregnant and gave birth underwent the same evaluations at 6 weeks (V2) and 6 months postpartum (V3). Participants who had magnetic resonance imaging data from both V1 and V3 were selected. We measured urethral rhabdosphincter CSA from high-resolution axial MRIs in a masked fashion. The mean CSA for each participant was calculated. The change from V1 to V3 was assessed.

RESULTS

Sixty-eight women were evaluated. There was a significant decrease of 0.05 cm2 (interquartile range, -0.03 to 0.16 cm2; P = 0.002) in the median sphincter CSA between V1 and V3. There was a significant increase in the median Urinary Distress Inventory (UDI) subscore of the Pelvic Floor Distress Inventory (PFDI) from V1 to V3 (median increase of 0 [IQR, 0 to 8.3]; P = 0.033), but this was not significantly correlated with the change in the urethral CSA (Spearman correlation, 0.199; P = 0.107). Increasing fetal weight was correlated with a decrease in CSA postpartum after vaginal birth (Spearman correlation, -0.340; P = 0.017).

CONCLUSIONS

There is a decrease in urethral rhabdosphincter CSA with worsening Urinary Distress Inventory scores from prepregnancy to postpartum, but these two do not correlate in this cohort with low symptom levels. Among women who give birth vaginally, decrease in rhabdosphincter CSA is correlated with increasing fetal weight, perhaps with ramifications to be seen later in life.

Urethral sphincter volume and urodynamic diagnosis

AIM

To compare urethral sphincter measurements in women with different urodynamic diagnoses using three-dimensional transperineal ultrasound (TPU).

METHODS

Women with lower urinary tract dysfunction having urodynamic studies (UDS) were prospectively recruited to this study. A detailed history and vaginal examination were conducted. Saline cystometry was performed and the women were divided into groups according to their urodynamic diagnosis, which were nondiagnostic urodynamics (NUDS), pure detrusor overactivity (PureDO), pure urodynamic stress incontinence (PureUSI) and mixed urinary incontinence (MUDS). Three-dimensional TPU was performed to measure total urethral sphincter volume, striated sphincter volume, core volume, sphincter length and maximum cross-sectional area. The ultrasound measurements were compared with the diagnostic urodynamics.

RESULTS

One hundred fifty women were included in the study. There were 37, 53, 22 and 38 women in the groups of NUDS, PureDO, PureUSI and MUDS respectively. The average striated sphincter volumes in these groups were 1.84 ml, 2.24 ml, 1.32 ml and 1.98 ml respectively. There was no difference in average age, body mass index or presence of prolapse in these groups. All measurements were larger in the PureDO and smaller in the PureUSI group compared with the NUDS group. The measurements in the MUDS group were larger than in the NUDS group and smaller than in the PureDO group but this difference was not statistically significant.

CONCLUSION

The urethral sphincter of women with PureDO is larger than in women with PureUSI. The value in women with MUDS was between the two. The size of the urethral sphincter appears to be related to the pathophysiology.

Does assessing urethral function allow the selection of the optimal therapy for recurrent SUI? Report from the ICI-RS 2017

AIMS

The management of recurrent stress urinary incontinence following failed previous continence surgery remains challenging. Whilst the role of urodynamic investigations has been questioned in the management of primary stress incontinence there is a widely held view that women with recurrent symptoms require further investigation although there is no agreement regarding which tests are required. We sought to understand what testing is recommended prior to managing this difficult cohort of patients.

METHOD

This research proposal was presented at the International Consultation on Incontinence Research Society (ICI-RS) in order to clarify our current knowledge regarding the assessment of urethral function and to set research priorities for the future.

RESULTS

Whilst the majority of clinicians would advocate urodynamic evaluation of women with recurrent stress incontinence following previous surgery there is no consensus of opinion as to which tests should be performed, on whom or where. The available evidence to date suggests that urethral function tests do have a role with regard to prognosis following surgery and also in planning the most appropriate surgical intervention.

CONCLUSION

The ICI-RS developed a list of research questions which may be able to assist in improving the investigation and management of women with recurrent SUI. Questions included whether patients felt the information gained via urethral function tests had an important role in their counseling regarding outcome of repeat SUI surgery.

Method and reliability of measuring midurethral area and echogenicity, and changes during and after pregnancy

Introduction and hypothesis

Internal closure of the urethral sphincter is one of the mechanisms in maintaining continence. Little is known about changes in the urethral sphincter during pregnancy. We designed this study to develop a reliable method to measure the area and mean echogenicity of the midurethra during and after pregnancy and to assess changes over time.

Methods

Two observers independently segmented the urethra as follows: in the sagittal plane, the urethra was positioned vertically, the marker was placed in the middle section of the lumen of the urethra, and eight tomographic US images of 2.5 -mm slices were obtained. The central image was selected, and area and mean echogenicity were calculated automatically. Intra- and interobserver reliability were determined by intraclass correlation coefficients (ICC) and their 95% confidence intervals (CI). Two hundred and eighty women underwent TPUS at 12 weeks and 36 weeks of gestation and 6 months postpartum, and 3D/4D transperineal ultrasound (TPUS) images of 40 pregnant nulliparous women were used for the reliability study. Paired t tests were used to assess changes in echogenicity and area.

Results

The ICC for measuring the area was substantial, at 0.77 and for measuring mean echogenicity was almost perfect, at 0.86. In the total study group (n = 280), midurethral area and mean echogenicity were significantly lower 6 months after delivery compared with 12 and 36 weeks of gestation.

Conclusions

Our protocol for measuring area and mean echogenicity of the midurethra is reliable. This study indicates that structural changes in the midurethraoccur during pregnancy.

Urethral distension as a novel method to simulate sphincter insufficiency in the porcine animal model

OBJECTIVES

To describe a novel animal model of intrinsic sphincter deficiency.

METHODS

The study was carried out on 10 female pigs. Injury to the urethral sphincter was induced by distension of the urethra. This was obtained by using the balloon of an 18-F Dufour catheter for 5 min followed by its retraction through the urethra without draining the balloon. The urethral pressure profile was evaluated before injury, immediately postinjury and at day 28 postinjury in the experimental group (n = 5), and on day 1 and day 28 in the control uninjured group (n = 5). The maximal urethral closure pressure, the functional urethral length and the area under curve of the urethral pressure profile were measured.

RESULTS

The mean maximal urethral closure pressure at the beginning of the experiment was 32 cmH(2) O, and the mean functional urethral length was 4.88 cm. The assessment at day 28 showed a reduction of the maximal urethral closure pressure (50% of the control, P > 0.05), the functional urethral length (52.5% of the control, P < 0.05) and the area under curve (52% of the control, P < 0.05) in injured pigs. Histologically, a fibrosis of the sphincter was detected without rupture of the muscle layer in all the samples.

CONCLUSIONS

The proposed porcine model can be used to obtain intrinsic sphincter deficiency-like urodynamic findings without rupturing the sphincter. This methodology can be applied to investigate therapies for intrinsic sphincter deficiency.

Ultrasound imaging of the pelvic floor: where are we going?

We produced a non systematic review of ultrasound imaging of the pelvic floor in women with urinary incontinence (UI) and/or pelvic organ prolapse (POP). We have searched the PubMed and Embase databases for the following PICO question: women; imaging; urinary incontinence, pelvic organ prolapse, pelvic floor, pelvic floor muscle, pelvic floor muscle training; physical examination, no imaging; diagnosis, prognosis, outcome. The production of a systematic review was deemed impossible based on the type and quality of the published evidence. Clinical research focused on the pathophysiology of the UI and POP looking relation between anatomic abnormalities, childbirth, the risk of UI or POP, the outcome of conservative treatment and reconstructive surgery. Published papers fall into the remits of diagnostic studies but often fail to comply with the recommendations of the STARD initiative. Most published evidence remains the product of a single institution effort and confirmatory studies are rarely found. Imaging studies in patients with UI did not provide evidence of any clinical benefit in the management of patients. In patients with POP, interesting correlations have been identified such as between childbirth, dimension of levator hiatus, avulsion of levator ani and risk of prolapse, but the non clinical benefit of pelvic floor imaging could still not be identified. Research on pelvic floor imaging requires a coordinated, international, multicentre effort to improve internal and external validity of imaging techniques, confirm observations published by single institutions and provide health technology assessment of imaging in the management of UI or POP patients.

Three-dimensional ultrasound imaging

This review is about the development of three-dimensional (3D) ultrasonic medical imaging, how it works, and where its future lies. It assumes knowledge of two-dimensional (2D) ultrasound, which is covered elsewhere in this issue. The three main ways in which 3D ultrasound may be acquired are described: the mechanically swept 3D probe, the 2D transducer array that can acquire intrinsically 3D data, and the freehand 3D ultrasound. This provides an appreciation of the constraints implicit in each of these approaches together with their strengths and weaknesses. Then some of the techniques that are used for processing the 3D data and the way this can lead to information of clinical value are discussed. A table is provided to show the range of clinical applications reported in the literature. Finally, the discussion relating to the technology and its clinical applications to explain why 3D ultrasound has been relatively slow to be adopted in routine clinics is drawn together and the issues that will govern its development in the future explored.

Striated muscle and nerve fascicle distribution in the female rat urethral sphincter

The anatomical basis for urinary continence depends on a thorough understanding of the tissues in the urethra. The objective of this study was to evaluate the morphology and neuroanatomy of urethral striated muscle, called the rhabdosphincter or external urethral sphincter, in normal female rats. Urethras from 12 female rats were dissected from the bladder, fixed, embedded in paraffin or epon, and sectioned every 1 mm. Striated muscle content was taken as the ratio of the striated muscle area to net urethral area. Nerve fascicles containing myelinated axons near the rhabdosphincter were counted and mapped. Both striated muscle content and number of nerve fascicles peak in the proximal third of the urethra, with a secondary peak at the distal end of the urethra. This secondary peak may correspond to an analog of the combined compressor urethrae/urethrovaginal sphincter located in the distal urethra in human. The rhabdosphincter has a variable distribution along the length of the urethra. In the middle and distal thirds of the urethra, the dorsal striated muscle fibers between the urethra and vagina become more sparse. The majority of nerve fascicles are contained in the lateral quadrants of the urethra, similar to the lateral distribution of somatic nerves in humans. In conclusion, this study demonstrates the normal distribution of the striated musculature and neuroanatomy in the urethra, with similarities to the human. It thus supports and extends the usefulness of the rat as an experimental model for studying urinary incontinence.

Role of three-dimensional ultrasound in assessment of women undergoing urethral bulking agent therapy

PURPOSE OF REVIEW

The technique of three-dimensional ultrasound imaging has been developed over the past 15 years, and has been particularly embraced by the field of obstetrics. More recently, advances have been made in gynecological applications, with promise demonstrated in pelvic floor and lower urinary tract imaging. A clinically useful extension of three-dimensional ultrasound imaging of the lower urinary tract is the assessment of urethral bulking agent therapy, as three-dimensional ultrasound imaging provides an objective means of assessing technical outcomes (i.e. periurethral position, configuration and volume of bulking agent). Our aim is to review recent developments in the use of three-dimensional ultrasound imaging in female incontinence, focusing on its role in the assessment of women undergoing urethral bulking agent therapy for stress urinary incontinence.

RECENT FINDINGS

Three-dimensional ultrasound imaging provides reproducible, affordable and clinically relevant information in the assessment of urethral bulking agent therapy with collagen. Serial, long-term three-dimensional ultrasound imaging assessment has enabled a definition of the technical outcome associated with a durable improvement in continence. The optimal volume varies widely between patients, but a circumferential or horseshoe-shaped periurethral configuration of collagen is strongly correlated with a durable improvement in continence. This finding is in agreement with limited data from a two-dimensional ultrasound assessment of Macroplastique.

SUMMARY

Three-dimensional ultrasound imaging provides an objective means of assessing technical outcomes from urethral bulking agent therapy not available previously. The volume and configuration information obtained allows for rational therapeutic decision-making, particularly with regard to determining the need for re-injection and recognizing the failure of an adequate therapeutic trial.

Three-dimensional transrectal ultrasound of the male urethral rhabdosphincter

The rhabdosphincter of the male urethra is an omega-shaped loop of striated muscle fibers that surrounds the membranous urethra at its lateral and anterior aspects. We investigated whether this muscle can be visualized by means of three-dimensional ultrasound to define morphological and dynamic ultrasound criteria. We examined the rhabdosphincter of the male urethra in 77 patients by means of this new imaging technique; 37 patients presented with urinary stress incontinence after transurethral resection of the prostate or radical prostatectomy while 40 were fully continent after radical prostatectomy and served as a control group. Contractility of the muscle was quantified by a specially defined parameter (rhabdosphincter-urethra distance). The anatomical arrangement and the contractions of the rhabdosphincter-loop could be clearly visualized in three-dimensional transrectal and transurethral ultrasound; during contraction the rhabdosphincter retracts the urethra, pulling it towards the rectum. We detected defects and postoperative scarrings in the majority of the patients with postoperative urinary stress incontinence. Furthermore, the patients presented with thinnings in parts of the muscle and atrophies of the rhabdosphincter. The rhabdosphincter-urethra distance was significantly lower in the incontinent group than in the continent group (59 vs. 1.42 mm). Our study shows that the rhabdosphincter of the male urethra can be visualized by means of three-dimensional transrectal ultrasound. The sonographic pathomorphological findings of postoperative urinary stress incontinence are well correlated well with the clinical symptoms.