Levator hiatus dimensions and pelvic floor function in women with and without major defects of the pubovisceral muscle

Feasibility and reproducibility of new technique for measurement of transverse diameter of levator ani muscle hiatus using two-dimensional transperineal ultrasound in nulliparous women with term pregnancy

OBJECTIVES

The aim of the present study was two-fold. Firstly, we aimed to develop and describe a technique for measurement of the transverse diameter (TD) of the levator ani muscle (LAM) hiatus in the coronal view using two-dimensional (2D) transperineal ultrasound (TPUS) in nulliparous women with a term pregnancy. Secondly, we aimed to evaluate the feasibility and reproducibility of 2D-TPUS assessment of LAM hiatal TD and assess intermethod agreement between 2D-TPUS and three-dimensional (3D) TPUS measurement of TD in the axial plane, which is considered the gold standard in nulliparous women with term pregnancy.

METHODS

We recruited a group of nulliparous women with term pregnancy before the onset of labor. The study was conducted in two phases: Phase 1 involved developing and describing the 2D-TPUS technique for measuring LAM hiatal TD, and Phase 2 focused on assessing the technique's feasibility, reproducibility and intermethod agreement with 3D-TPUS measurement of LAM hiatal TD. In Phase 1, we enrolled 30 women. Each woman underwent acquisition of a 3D-TPUS volume, which was analyzed using multiplanar mode to identify and determine the appearance of the lateral borders of the LAM in the coronal plane, at the level of the plane of minimal hiatal dimensions. These borders were used as landmarks for TD measurement. Additionally, we measured the distance between the plane used for TD measurement and the center of the urethra in the axial view. In Phase 2, we recruited 100 women. Each woman underwent acquisition of three 2D-TPUS videoclips in the coronal plane, each encompassing a sweep of the entire LAM hiatus, and a 3D volume, all obtained during rest. On the 2D videoclips, TD was measured twice by one operator and once by another operator. In the 3D volume, TD was measured once, by one operator, in the axial plane; this measurement was considered the gold standard. Each operator was blinded to all other measurements during their assessments. We analyzed intraobserver and interobserver reproducibility and performed an intermethod (2D vs 3D) comparison. Bland-Altman analysis was conducted, and Levene's W0 test and Student's t-test were performed to explore clinical factors that might contribute to systematic differences.

RESULTS

In Phase 1, we identified successfully the landmarks denoting the lateral borders of the LAM hiatal TD in the coronal view. These appeared as two symmetrical hypoechogenic indentations located at the inner border of the hyperechogenic structure of the LAM, at the point of maximum distance between the two sides of the LAM. The distance between the urethra and the plane where TD should be measured using 3D-TPUS in the axial plane had a median of 4 mm and varied from 0 to 9 mm. This enabled us to describe a method for assessing LAM hiatal TD in the coronal plane using 2D-TPUS. In Phase 2, LAM hiatal TD was measured successfully in all 2D and 3D acquisitions from the entire group of 100 women. The analyses for intraobserver and interobserver reproducibility and the intermethod comparison (2D vs 3D) revealed almost perfect agreement in TD measurements using 2D-TPUS, with intraclass correlation coefficients of 0.95 (95% CI, 0.92-0.96), 0.87 (95% CI, 0.78-0.92) and 0.85 (95% CI, 0.78-0.90), respectively. The average differences between measurements were 0.1 mm for intraobserver, 1.0 mm for interobserver and 0.2 mm for intermethod repeatability. No systematic differences were observed in any of the measurement sets, except in the interobserver analysis, although this difference was clinically not significant (38.2 vs 37.2 mm, P = 0.01). None of the examined clinical factors (maternal body mass index and maternal age) exhibited a statistically significant impact on intraobserver, interobserver or intermethod reliability.

CONCLUSIONS

Utilizing our technique, described herein, to measure the LAM hiatal TD in the coronal view using 2D-TPUS is not only feasible but also highly reproducible and accurate in nulliparous women with term pregnancy. Moreover, it yields measurements that are comparable to those obtained in the reconstructed axial plane generated by 3D-TPUS. © 2024 International Society of Ultrasound in Obstetrics and Gynecology.

Hiatal failure: effects of pregnancy, delivery, and pelvic floor disorders on level III factors

INTRODUCTION AND HYPOTHESIS

The failure of the levator hiatus (LH) and urogenital hiatus (UGH) to remain closed is not only associated with pelvic floor disorders, but also contributes to recurrence after surgical repair. Pregnancy and vaginal birth are key events affecting this closure. An understanding of normal and failed hiatal closure is necessary to understand, manage, and prevent pelvic floor disorders.

METHODS

This narrative review was conducted by applying the keywords "levator hiatus" OR "genital hiatus" OR "urogenital hiatus" in PubMed. Articles that reported hiatal size related to pelvic floor disorders and pregnancy were chosen. Weighted averages for hiatal size were calculated for each clinical situation.

RESULTS

Women with prolapse have a 22% and 30% larger LH area measured by ultrasound at rest and during Valsalva than parous women with normal support. Women with persistently enlarged UGH have 2-3 times higher postoperative failure rates after surgery for prolapse. During pregnancy, the LH area at Valsalva increases by 29% from the first to the third trimester in preparation for childbirth. The enlarged postpartum hiatus recovers over time, but does not return to nulliparous size after vaginal birth. Levator muscle injury during vaginal birth, especially forceps-assisted, is associated with increases in hiatal size; however, it only explains a portion of hiatus variation-the rest can be explained by pelvic muscle function and possibly injury to other level III structures.

CONCLUSIONS

Failed hiatal closure is strongly related to pelvic floor disorders. Vaginal birth and levator injury are primary factors affecting this important mechanism.

Validation of shear wave elastography as a noninvasive measure of pelvic floor muscle stiffness

OBJECTIVES

To investigate the validity of shear wave elastography (SWE) as a measure of stiffness of the puborectalis muscle by examining: (1) the relationship between puborectalis muscle stiffness and pelvic floor muscle (PFM) activation at different intensities; and (2) the relationship between puborectalis stiffness and pelvic floor morphometry during contractions at different intensities.

METHODS

Fifteen healthy asymptomatic women performed 6-s isometric PFM contractions at different intensities (0, 10%, 20%, 30%, 50%, 75%, and 100% of maximal voluntary contraction) guided by intravaginal electromyography (EMG). Stiffness of the puborectalis muscle was measured using SWE by calculating the average shear modulus in regions of interest that contained puborectalis muscle fibers parallel to the transducer. Pelvic floor morphometry was assessed in the mid-sagittal plane using transperineal B-mode ultrasound imaging. Shear modulus, EMG (root mean square amplitude) and pelvic floor morphometry parameters were normalized to the value recorded during maximal voluntary contraction. To assess the relationship between stiffness and pelvic floor activation/morphometry, coefficient of determination (r² ) was calculated for each participant and a group average was computed.

RESULTS

Shear modulus and EMG were highly correlated (average r² ; left 0.90 ± 0.08, right 0.87 ± 0.15). Shear modulus also strongly correlated with bladder neck position (x-axis horizontal coordinates relative to the pubic symphysis), anorectal rectal angle and position, levator plate angle, and antero-posterior diameter of the levator hiatus (average r² : range 0.62-0.78).

CONCLUSIONS

These findings support the validity of SWE to assess puborectalis muscle stiffness in females. Stiffness measures were strongly associated with PFM EMG and pelvic floor morphometry and may be used to indirectly assess the level of activation of the puborectalis muscle without the use of more invasive techniques. By overcoming limitations of current assessment tools, this promising noninvasive and real-time technique could enable important breakthrough in the pathophysiology and management of pelvic floor disorders.

Effects of Different Delivery Modes on Pelvic Floor Function in Parturients 6–8 Weeks after Delivery Using Transperineal Four-Dimensional Ultrasound

Objective

To evaluate the effects of different delivery modes on pelvic floor function in parturients 6–8 weeks after delivery using transperineal four-dimensional ultrasound.

Methods

Pelvic floor function 6–8 weeks after delivery in 40 vaginal delivery parturients between November 2018 and December 2020 was assessed by four-dimensional ultrasound, with 40 selective cesarean section delivery parturients as a control group. The imaging results of the two groups were compared.

Results

The levels of clinical indexes such as UVJ-M, A_r, A_v, θ, D_r, D_v, and ARJ-VDv in the selective cesarean section group were significantly lower than those in the vaginal delivery group 6–8 weeks after delivery (P < 0.05). However, no significant difference in CV-VD was observed under Valsalva action and at rest between the two groups (P > 0.05). No significant difference in ARJ-VD was found at rest between the two groups (P > 0.05). The incidence of pelvic organ prolapse in the selective cesarean section group (40.0%) was significantly lower than that in the vaginal delivery group (62.5%) (P < 0.05). No significant difference in the parameters of pelvic diaphragm hiatus at rest was observed between the two groups (P > 0.05). The parameters of pelvic diaphragm hiatus under maximum Valsalva action in the vaginal delivery group were significantly higher than those in the selective cesarean section group (P < 0.05). Whether the patient was complicated with diabetes had no significant effect on the functional injury of pelvic floor muscle (P > 0.05).

Conclusion

The pelvic floor function 6–8 weeks after delivery was significantly more affected in vaginal delivery than in selective cesarean section. Selective cesarean section had certain but limited protective effect on maternal pelvic floor tissue.

Mechanisms of hiatus failure in prolapse: a multifaceted evaluation

INTRODUCTION AND HYPOTHESIS

We investigated whether factors influencing pelvic floor hiatal closure are inter-related or independent, hypothesizing that (1) hiatus size is moderately correlated with levator defect, pelvic floor muscle strength, and change in hiatus size with contraction and (2) urogenital hiatus (UGH) and levator hiatus (LH) measures are similar in patients with anterior wall (AW) and posterior wall (PW) prolapse.

METHODS

This cross-sectional case-control study included subjects with AW prolapse (n = 50), PW prolapse (n = 50), and normal support (n = 50). Hiatus measurements and levator defects were assessed on MRI, and vaginal closure force was measured with an instrumented speculum. Pearson correlation coefficients and simple and multivariable linear regression models were performed.

RESULTS

During contraction, LH narrowed 47% more in the PW compared to AW group (p = 0.001). With straining, LH lengthened 34% more in the PW than AW group (p < 0.001). With straining, UGH and LH lengthening was greater by 72% and 44% in those with major compared to no/minor defect (p < 0.001 and p = 0.004). Contraction strength explained, at most, 4% of UGH (r = 0.17) or LH (r = 0.20) shortening during contraction (r = 0.17 and r = 0.20, respectively), indicating that these factors are largely independent. After controlling for prolapse size, resting UGH and levator defect status were associated with straining UGH (p < 0.001, p = 0.004), but muscle strength and resting tone were not.

CONCLUSIONS

Hiatus measures are complex and differ according to prolapse occurrence and type. They are, at best, only weakly correlated with pelvic floor muscle strength and movement during contraction.

Value of high-frequency two-dimensional ultrasound on evaluating puborectalis muscle

PURPOSE

To explore the value of high-frequency two-dimensional (2D) ultrasound on demonstrating the morphology of puborectalis muscle and detect muscle avulsion.

METHODS

High-frequency 2D ultrasound and tomographic ultrasound image (TUI) were peformed to demonstrate puborectalis muscle and detect muscle avulsion respectively among 158 women with or without significant pelvic organ prolapse (POP) (POP quantification grade 2 or higher). Mean values were compared using student's t test between women with or without avulsion defects. We performed Cohen's Kappa analysis to examine the test agreement between high-frequency 2D ultrasound and TUI mode. Pearson correlation analysis was performed to explore the relationship between the thickness of puborectalis muscle and the measurements of levator-urethra gap (LUG).

RESULTS

The result of high-frequency 2D ultrasound in detecting muscle avulsion agreed well with TUI mode (Kappa 0.88, P < 0.05). Women with muscle avulsion had thinner muscles and larger LUG measurements than those with normal muscle insertion (P < 0.05). Pearson correlation analysis revealed the negative relationship between the thickness of puborectalis muscle and LUG measurements (r = - 0.73).

CONCLUSION

The study confirmed that it was feasible to observe the morphology of puborectalis muscle and detect muscle avulsion by high-frequency 2D ultrasound.

Impact of levator muscle avulsions on Manchester procedure outcomes in pelvic organ prolapse surgery

INTRODUCTION

Levator ani muscle avulsions potentially increase recurrence after anterior colporrhaphies. We aimed at evaluating the impact of avulsions on anatomical and patient-reported outcomes 1 year after the Manchester procedure for primary anterior compartment pelvic organ prolapse.

MATERIAL AND METHODS

Prospective cohort study of 189 women undergoing the Manchester procedure between October 2014 and January 2017. Avulsions were diagnosed by transperineal ultrasound. Women with and without avulsions were compared for 1-year postoperative outcomes; Pelvic Organ Prolapse Quantification measurements, subjective satisfaction (1-worse to 4-cured), failure (new prolapse treatment), response to validated questionnaires on pelvic floor distress and sexual function, and a composite outcome (subjectively cured and optimal anterior compartment outcome (stage 0-I)). Optimal mid-compartment outcome was defined as cervix ≥5 cm above the hymen. Factors potentially associated with poor anatomical outcomes (anterior compartment stage ≥II) or pelvic floor distress were analyzed using regression analyses.

RESULTS

Fewer women with avulsions (present in 50.8%) obtained optimal mid-compartment outcomes (88.2% vs 77.1%; P = 0.05). The groups were otherwise similar in terms of mid-compartment reduction, anterior compartment results, failure rate, subjective satisfaction, pelvic floor/sexual symptoms, and combined optimal subjective and anatomical outcome. Only preoperative anterior compartment stage ≥III was associated with poor anatomical outcome (P < 0.01). A high preoperative symptom score was associated with a high postoperative symptom score (P < 0.001).

CONCLUSIONS

Although fewer women with avulsions obtained optimal mid-compartment results, avulsions had no impact on other anatomical or symptomatic outcomes 1 year after the Manchester procedure for primary anterior compartment prolapse.

Recommended standardized terminology of the anterior female pelvis based on a structured medical literature review

BACKGROUND

The use of imprecise and inaccurate terms leads to confusion amongst anatomists and medical professionals.

OBJECTIVE

We sought to create recommended standardized terminology to describe anatomic structures of the anterior female pelvis based on a structured review of published literature and selected text books.

STUDY DESIGN

We searched MEDLINE from its inception until May 2, 2016, using 11 medical subject heading terms to identify studies reporting on anterior female pelvic anatomy; any study type published in English was accepted. Nine textbooks were also included. We screened 12,264 abstracts, identifying 200 eligible studies along with 13 textbook chapters from which we extracted all pertinent anatomic terms.

RESULTS

In all, 67 unique structures in the anterior female pelvis were identified. A total of 59 of these have been previously recognized with accepted terms in Terminologia Anatomica, the international standard on anatomical terminology. We also identified and propose the adoption of 4 anatomic regional terms (lateral vaginal wall, pelvic sidewall, pelvic bones, and anterior compartment), and 2 structural terms not included in Terminologia Anatomica (vaginal sulcus and levator hiatus). In addition, we identified 2 controversial terms (pubourethral ligament and Grafenberg spot) that require additional research and consensus from the greater medical and scientific community prior to adoption or rejection of these terms.

CONCLUSION

We propose standardized terminology that should be used when discussing anatomic structures in the anterior female pelvis to help improve communication among researchers, clinicians, and surgeons.

Is curved three-dimensional ultrasound reconstruction needed to assess the warped pelvic floor plane?

OBJECTIVES

Caudal distension of the female pelvic floor is common and results in perineal descent and a caudally curved levator hiatus (warping). Image reconstruction of the pelvic floor using currently available ultrasound techniques involves a linear approach (flat-plane reconstruction). We aimed to evaluate the feasibility, reproducibility and potential usefulness of a new three-dimensional (3D) technique capable of reconstructing a curved plane of the levator hiatus.

METHODS

Primiparous women were recruited to undergo a 3D/four-dimensional transperineal ultrasound examination 3-6 months after delivery. Levator ani muscle warping was evaluated on Valsalva maneuver by measuring the distance between the plane extending from the pubic rami to the anorectal angle and the plane of minimal hiatal dimensions on the coronal plane. Warping distance was used to reconstruct a curved plane of the levator hiatus using the curved OmniView volume contrast imaging (VCI) technique (C-OV). Intra- and interobserver reproducibility of the C-OV technique were assessed, as was intermethod agreement between the C-OV technique and the linear OmniView-VCI (L-OV) technique, for the measurement of levator hiatal area on Valsalva maneuver.

RESULTS

Measurement of the levator hiatal area using C-OV was feasible in all 84 women recruited. The warping distance ranged from -3.5 to 9.7 mm, confirming that the 1-2-cm slice thickness traditionally used for linear reconstruction was adequate for proper assessment of levator hiatal area in our population. C-OV showed excellent intra- and interobserver reproducibility, as well as excellent agreement with the L-OV technique for measuring levator hiatal area. No systematic difference was demonstrated in any of the reproducibility studies performed.

CONCLUSIONS

3D reconstruction of the warped levator hiatal plane is feasible and highly reproducible. In our population, reconstruction of a curved plane to correct for levator hiatal warping did not offer any benefit over the traditionally performed linear reconstruction. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Ethnic differences in the levator hiatus and pelvic organ descent: a prospective observational study

OBJECTIVE

To date, most studies on functional anatomy of the pelvic floor have focused on Caucasian women. There is scant information on this topic involving other ethnic groups. The aim of this study was to investigate levator hiatal area and pelvic organ descent in three racially diverse ethnic groups of healthy nulliparous South Asian, Caucasian and black South African women, using three/four-dimensional (3D/4D) transperineal ultrasound (TPS).

METHODS

Nulliparous women aged 18-40 years from three different ethnic groups were recruited for this prospective observational study between June 2012 and April 2015. After informed consent and clinical examination of the pelvic floor, all patients underwent a 3D/4D-TPS examination. Ultrasound volumes were captured at rest, on maximum pelvic floor muscle contraction (PFMC) and on maximal Valsalva maneuver. Analyses of variance and covariance were performed to compare the three ethnic groups, and a post-hoc Bonferroni pairwise test was applied.

RESULTS

A total of 207 nulliparous women were recruited, comprising 41 South Asian, 69 Caucasian and 97 black women. After controlling for age and body mass index, all measurements of mean levator hiatal area at rest, on PFMC and on Valsalva were higher in black women (all P < 0.0001). Post-hoc Bonferroni pairwise comparison revealed that black women had greater pelvic organ descent and levator hiatal area compared with South Asian and Caucasian women (P < 0.0001).

CONCLUSION

This comparative study indicates that there are significant differences in levator hiatal area and pelvic organ mobility between Caucasian, South Asian and black ethnic groups. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Reliability of new three-dimensional ultrasound technique for pelvic hiatal area measurement

OBJECTIVE

To assess the reproducibility of a new technique for three-/four-dimensional (3D/4D) ultrasound imaging of the pelvic floor: OmniView™ volume contrast imaging (VCI) for measurement of the pelvic hiatal area on maximum contraction and Valsalva maneuver. In addition, we aimed to study the intermethod agreement between the new technique and the 3D/4D render method.

METHODS

We acquired one static 3D and two dynamic 4D transperineal volumes (one obtained during contraction and one during Valsalva maneuver) from 35 nulliparous asymptomatic healthy volunteers and 35 women with symptoms of pelvic floor dysfunction. Each 3D dataset was analyzed using the OmniView-VCI technique to measure the pelvic hiatal area at rest, on maximum contraction and on maximum Valsalva. Analysis was performed twice by the same operator and once by another operator in order to assess intra- and interobserver reproducibility. All measurements were repeated by one operator using the 3D/4D render method to evaluate the intermethod agreement. Reproducibility and intermethod agreement were studied by means of intraclass correlation coefficients (ICC) and the Bland-Altman method.

RESULTS

Measurement of hiatal area using the OmniView-VCI technique showed excellent intraobserver and interobserver reproducibility in both asymptomatic and symptomatic women at rest, on contraction and on Valsalva maneuver. In addition, excellent agreement was demonstrated between OmniView-VCI and 3D/4D render in both groups (ICCs on Valsalva in asymptomatic and symptomatic women were 0.894 and 0.975, respectively). No systematic difference was noted in any of the reliability studies performed.

CONCLUSIONS

OmniView-VCI is a reliable method for pelvic hiatal area measurement. Both rendering mode and OmniView-VCI can be used interchangeably for assessing pelvic hiatal area. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.

Impact of childbirth and mode of delivery on vaginal resting pressure and on pelvic floor muscle strength and endurance

OBJECTIVE

We sought to study impact of delivery mode on vaginal resting pressure (VRP) and on pelvic floor muscle (PFM) strength and endurance, and whether these measurements differed in women with and without urinary incontinence.

STUDY DESIGN

We conducted a cohort study following 277 nulliparous women from midpregnancy to 6 weeks postpartum. Manometer was used for PFM measurements; differences were analyzed by t test (within groups) and analysis of variance (between groups).

RESULTS

Only VRP changed significantly (10% reduction, P = .001) after emergency cesarean section. After normal and instrumental vaginal delivery, VRP was reduced by 29% and 30%; PFM strength by 54% and 66%; and endurance by 53% and 65%, respectively. Significant differences for all PFM measures (P < .001) were found when comparing cesarean vs normal and instrumental vaginal delivery, respectively. Urinary continent women at both time points had significantly higher PFM strength and endurance than incontinent counterparts (P < .05).

CONCLUSION

Pronounced reductions in VRP and in PFM strength and endurance were found after vaginal delivery. Continent women were stronger than incontinent counterparts.