Warping of the levator hiatus: how significant is it?

Hiatus and pelvic floor failure patterns in pelvic organ prolapse: a 3D MRI study of structural interactions using a level III conceptual model

BACKGROUND

A large urogenital hiatus in level III results in a higher risk of developing pelvic organ prolapse after birth and failure after prolapse surgery. Deepening of the pelvic floor and downward rotation of the levator plate have also been linked to prolapse. Currently we lack data that evaluates how these measures relate to one another and to prolapse occurrence and size.

OBJECTIVE

This study uses measurements from a published conceptual model to compare women with and without prolapse to determine the magnitude of difference between cases and controls and to quantify the interrelationships among different aspects of pelvic floor shape and structure.

STUDY DESIGN

Ninety-one women with anterior predominant prolapse and uterus in situ who had 3D MRI and 30 similar women with normal support were studied. Resting scans were used to avoid the influence of the prolapse dilating the hiatus. Measurements assessed 3 domains: hiatus size (urogenital and levator hiatus); length of the surrounding pelvic floor muscles (pubovisceral, puborectal, iliococcygeal muscles); the shelf-like posterior pelvic floor (levator plate shape, levator bowl volume), and bony pelvic dimensions. Effect sizes were calculated and principal component shape analysis performed to evaluate levator plate shape. z scores were calculated and a value greater than 1.68 (95th percentile) was considered the "failure" criterion. Frequency and severity of structural support site failure were analyzed by prolapse size.

RESULTS

Resting urogenital and levator hiatal areas were 68% and 59% larger in the prolapse group compared to controls. These area enlargements were 2 to 4 times larger than the anterior-posterior dimension enlargements (urogenital hiatus 36%; levator hiatus 13%). The greatest muscle length differences between groups occurred in the pubovisceral (34%) and puborectal (25%) muscles compared to the iliococcygeal muscle (8%)-roughly half the area differences. Levator bowl volume was 63% deeper with prolapse. Urogenital hiatus and levator hiatus areas were strongly correlated with pubovisceral and puborectal muscle length (0.7-0.8), while iliococcygeal muscle length had lower correlations (0.4-0.5). Levator bowl volume correlated strongly with hiatal enlargement (0.7-0.8) and muscle length (pubovisceral and puborectal muscles), moderately so with levator plate and iliococcygeal muscle, and weakly with bony dimension. Failure frequency increased with prolapse size for urogenital hiatus anterior-posterior (P=.001) and area (P=.019). By contrast, levator hiatus area was similar for all prolapse sizes (P=.288), while levator hiatus anterior-posterior failure was more common in larger prolapses (P=.018) but with smaller percentages of failure than levator hiatus area (P<.01). Both levator bowl volume (P=.015) and levator plate (P=.045) trended toward increasing failure with larger prolapse sizes. Among women with enlarged urogenital hiatus at straining, 43% and 28% had normal urogenital hiatus anterior-posterior and area at rest, respectively.

CONCLUSION

Changes in the shape and dimensions of the pelvic floor are complex and are not captured by a single measure (such as the urogenital hiatus anterior-posterior dimension, which does not capture its lateral expansion). The failure patterns were different between small and large prolapses. Understanding why could lead to improved prevention and treatments for level III failures.

Racial differences in the levator ani muscle and levator hiatus in individuals of reproductive age

BACKGROUND

Most studies on pelvic floor muscle morphology (dimensions, shape) and its relationship with patient characteristic risk factors of pelvic floor dysfunction (demographics, medical history) have largely pertained to White individuals with vaginas. There is a need to establish normative data on pelvic floor muscle anatomy and identify morphological differences in racially diverse cohorts that may play a role in racial differences in the prevalence and pathophysiology of pelvic floor dysfunction.

OBJECTIVE

This study aimed to compare levator ani muscle thickness and levator hiatal morphology and their association with patient characteristics, between asymptomatic Black and White women-identifying individuals with a vagina of reproductive age.

STUDY DESIGN

In this dual-site retrospective study, pelvic magnetic resonance images of asymptomatic individuals with a vagina aged 18 to 50 years with normal pelvic anatomy-defined as normal gastrointestinal, genitourinary, or reproductive systems-were collected and categorized by self-reported race (Black, White). All individuals were imaged in the axial plane at rest in the supine position for medical indications. From these images, the levator ani muscle thickness and levator hiatal dimensions were measured. The levator hiatal area was traced to create 2-dimensional models of levator hiatal shape. Statistical shape modeling with principal component analysis was performed to quantify levator hiatal shape given by principal component scores. One-way multivariate and univariate analysis of covariance tests evaluated racial differences in levator ani muscle and levator hiatal measures with adjustments for age, body mass index, and parity. Spearman rank correlation with Fisher's z transformation tests quantified and compared correlations between patient characteristics and levator ani muscle and levator hiatal measures by racial group.

RESULTS

A total of 112 participants were analyzed, with 59 Black and 53 White individuals. The Black cohort, compared to the White cohort, had a larger levator hiatal area (difference, 1.31 cm2; 95% confidence interval, 0.15-2.47), perimeter (difference, 0.95 cm; 95% confidence interval, 0.32-1.59), and anteroposterior diameter (difference, 0.53 cm; 95% confidence interval, 0.23-0.83). Of the patient characteristics, only parity-related correlations differed by race and were stronger in the White cohort than the Black cohort. Among White individuals, higher parity was associated with a larger levator hiatal area (r=0.60, P<.001), perimeter (r=0.49, P<.001), anteroposterior diameter (r=0.41, P=.002), and transverse diameter (r=0.49, P<.001), whereas among Black individuals, parity had no correlation with levator hiatal dimensions (r range, -0.07 to 0.00; all P>.60). Statistical shape modeling demonstrated that a more ovular, narrower levator hiatus shape predominated in Black individuals (P=.004) and correlated with higher body mass index in the Black (r=-0.45, P<.001) and White (r=0.54, P<.001) cohorts. Posterior distension of the levator hiatus (a more U-shaped levator hiatus) was associated with aging in only the Black cohort (r=-0.40, P=.002).

CONCLUSION

After controlling for age, body mass index, and parity, larger levator hiatal dimensions and a more ovular, narrower, U-shaped levator hiatus were observed in Black individuals compared to White individuals. Future longitudinal studies are necessary to gain further insight into causative mechanisms for racial morphological variability in pelvic floor muscles that may contribute to racial disparities in pelvic floor dysfunction risk.

Fully Automated Localization and Measurement of Levator Hiatus Dimensions Using 3-D Pelvic Floor Ultrasound

OBJECTIVE

To develop an algorithm for the automated localization and measurement of levator hiatus (LH) dimensions (AI-LH) using 3-D pelvic floor ultrasound.

METHODS

The AI-LH included a 3-D plane regression model and a 2-D segmentation model, which first achieved automated localization of the minimal LH dimension plane (C-plane) and measurement of the hiatal area (HA) on maximum Valsalva on the rendered LH images, but not on the C-plane. The dataset included 600 volumetric data. We compared AI-LH with sonographer difference (ASD) as well as the inter-sonographer differences (IESD) in the testing dataset (n = 240). The assessment encompassed the mean absolute error (MAE) for the angle and center point distance of the C-plane, along with the Dice coefficient, MAE, and intra-class correlation coefficient (ICC) for HA, and included the time consumption.

RESULTS

The MAE of the C-plane of ASD was 4.81 ± 2.47° with 1.92 ± 1.54 mm. AI-LH achieved a mean Dice coefficient of 0.93 for LH segmentation. The MAE on HA of ASD (1.44 ± 1.12 mm²) was lower than that of IESD (1.63 ± 1.58 mm²). The ICC on HA of ASD (0.964) was higher than that of IESD (0.949). The average time costs of AI-LH and manual measurement were 2.00 ± 0.22 s and 59.60 ± 2.63 s (t = 18.87, p < 0.01), respectively.

CONCLUSION

AI-LH is accurate, reliable, and robust in the localization and measurement of LH dimensions, which can shorten the time cost, simplify the operation process, and have good value in clinical applications.

Restoration of bladder neck activity and levator hiatus dimensions in Asian primipara: a prospective study

Pelvic floor muscle training (PFMT) reduces the symptoms in women with pelvic floor dysfunction (PFD); however, the optimal initial timing for secondary prevention of PFD by PFMT is not clear. To identify the optimal timing in Asian primiparas with vaginal delivery, bladder neck descent (BND), levator hiatus areas, and levator hiatus distensibility and contractility were assessed in 26 nulliparous women at 36 weeks of gestation and at 2, 4, 6, and 12 weeks postpartum. We found that BND increased significantly from 2 weeks onwards until 6 weeks postpartum (p = 0.004); the levator hiatus area at rest and contraction both showed the largest value at 2 weeks postpartum (p = 0.005 and p < 0.005 respectively), followed by a continuous decrease; the hiatus area during Valsalva manoeuvre, and the levator hiatus distensibility and contractility showed the lowest value at 2 weeks postpartum, followed by a continuous increase; the changes in BND showed no correlation with the changes in distensibility or hiatus area during Valsalva manoeuvre (p = 0.073 and 0.590 respectively). In Asian primiparas with vaginal delivery, the recovery of levator hiatus and bladder neck mobility begins at 2 and 6 weeks, respectively. This information could be useful in defining the best time to begin PFMT for secondary prevention of postpartum PFD in Asian primiparous women.IMPACT STATEMENTWhat is already known on this subject? Pelvic floor muscle training (PFMT) helps to reduce symptoms of pelvic floor dysfunction (PFD), however, there are no clear time strategies for the secondary prevention of PFD by PFMT in Asian primiparas with vaginal delivery.What do the results of this study add? This study was the first longitudinal study in Asian primipara to investigate the natural regeneration of pelvic floor functions in the early postpartum period by intensively monitoring the bladder neck mobility and levator hiatus dimensions at multiple time points. We found that bladder neck descent (BND) increased significantly from 2 weeks onwards until 6 weeks postpartum; the levator hiatus area at rest and contraction both showed the largest value at 2 weeks postpartum, followed by a continuous decrease; the hiatus area during Valsalva manoeuvre, and the levator hiatus distensibility and contractility showed the lowest value at 2 weeks postpartum, followed by a continuous increase; the changes in BND showed no correlation with the changes in distensibility or hiatus area during Valsalva manoeuvre.What are the implications of these findings for clinical practice and/or further research? Our study suggested that in Asian primipara, the recovery of bladder neck mobility after vaginal delivery begins at 6 weeks postpartum, while the levator hiatus muscle begins to recover within the first 2 weeks postpartum. Therefore, it could be useful in deciding the best time to start PFMT for secondary prevention of postpartum PFD in Asian primiparous women.

Which factors are associated with anal incontinence after obstetric anal sphincter injury?

OBJECTIVES

Obstetric anal sphincter injury (OASI) is an important factor in the etiology of anal incontinence. This study aimed to evaluate whether anal sphincter defects, levator avulsion or levator ballooning after OASI are associated with severity of anal incontinence. Furthermore, we evaluated whether factors such as constipation and altered stool consistency are associated with symptoms of incontinence after OASI.

METHODS

In this multicenter prospective observational cohort study, women with OASI were invited to participate at least 3 months after primary repair. All women completed validated questionnaires, including St Mark's incontinence score, Bristol stool scale (BSS) and Cleveland clinic constipation score (CCCS), and underwent four-dimensional (4D) transperineal ultrasound for assessment of the levator ani muscle and anal sphincter.

RESULTS

In total, 220 women were included. Median follow-up was 4 months (range, 3-98 months). Univariate linear regression analysis showed an association of St Mark's incontinence score with a residual defect of the external anal sphincter (EAS) (β, 1.55 (95% CI, 0.04-3.07); P = 0.045), higher parity (β, 0.85 (95% CI, 0.02-1.67); P = 0.046), BSS (β, 1.28 (95% CI, 0.67-1.89); P < 0.001) and CCCS (β, 0.36 (95% CI, 0.18-0.54); P < 0.001). However, multivariate linear regression found an association of St Mark's incontinence score only with BSS (β, 1.50 (95% CI, 0.90-2.11); P < 0.001) and CCCS (β, 0.46 (95% CI, 0.29-0.63); P < 0.001).

CONCLUSIONS

Residual defects of the EAS, detected on 4D transperineal ultrasound, are associated with severity of anal incontinence symptoms measured using St Mark's incontinence score 4 months after OASI repair. Furthermore, clinical factors such as constipation and altered stool consistency appear to influence this association and may therefore play a more important role in clinical management. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.

Investigating the association of the dimensions of genital hiatus and levator hiatus with pelvic organ prolapse: a systematic review

BACKGROUND AND HYPOTHESIS

Pelvic organ prolapse (POP) is a very common and distressing problem that affects women's quality of life. This systematic review aimed to investigate the association of the dimensions of the genital hiatus and levator hiatus at rest and Valsalva with POP.

METHODS

The Cochrane Library, PubMed, Scopus, Embase and Web of Science were searched on 25 April 2020. All data were analyzed using Review Manager 5.3.

RESULTS

Of the 1288 papers reviewed, 21 (n = 5145: 2909 women with POP and 2236 controls) were considered for meta-analysis. Compared with the normal pelvic floor group, the urogenital hiatus size in the POP group was significantly higher at rest (mean difference: 0.49; 95% CI: [0.43, 0.55], P < 0.00001) and at Valsalva (mean difference: 0.79; 95% CI: [0.70, 0.89], P < 0.00001). Also, the levator ani hiatus size in the POP group was significantly higher at rest (mean difference: 0.52, 95% CI: [0.25, 0.78], P < 0.0001) and at Valsalva (mean difference: 1.01; 95% CI: [0.73,1.28], P < 0.00001) compared with that in the normal pelvic floor group.

CONCLUSION

This systematic review showed that the sizes of the urogenital hiatus and levator ani hiatus and area of the levator hiatus in the POP group were significantly higher than those in the normal pelvic floor groups in both positions (rest or Valsalva maneuver). Also, in the POP group, the levator hiatus length at rest was significantly lower than that in the Valsalva maneuver.

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.