Utilizing intelligent pelvic floor ultrasonography combined with real-time shear wave elastography for evaluating female pelvic floor functions

Introduction

Pelvic floor disorders (PFD) refer to a range of dysfunctions in women caused by damage to the supportive structures of the pelvic floor, including muscles, ligaments, and fascia. The most common symptoms are stress urinary incontinence (SUI) and pelvic organ prolapse (POP), though dyspareunia and chronic pelvic pain may also occur (1). SUI is characterized by involuntary leakage of urine from the internal urethral orifice during episodes of increased intra-abdominal pressure (e.g., sneezing, coughing, laughing, or physical exertion), while POP typically presents with sensations of perineal swelling, incomplete or obstructed urination, and defecatory difficulties. In China, approximately 40–50% of married and parous women experience varying degrees and manifestations of PFD (1).

The levator ani muscle (LAM), a central component of pelvic floor support, is essential for maintaining pelvic organ stability and functions as a sphincter for the urethra, vagina, and anal canal. The puborectalis muscle, a key part of the LAM complex, is often implicated in the pathogenesis of PFD when compromised (2). Meanwhile, three-dimensional (3D) ultrasound, particularly in volume rendering (Render) mode, offers comprehensive visualization of the puborectalis, allowing for detailed assessment of LAM continuity, symmetry, and hiatus morphology (3). In addition, tomographic ultrasound imaging (TUI) mode facilitates evaluation of LAM integrity across different axial planes with contraction states recommended for enhanced assessment of LAM avulsion and rupture (4).

Previous studies have consistently demonstrated LAM degradation and thinning, along with increased hiatus dimensions in patients with PFD (5-7). Real-time shear wave elastography (SWE) provides clinicians with a means to assess tissue elasticity internally, acting as a virtual “finger” (8). SWE enables the assessment of pelvic floor muscle elasticity, thereby reflecting changes in puborectalis firmness across various physiological states (9,10). Notably, Young’s modulus of puborectalis exhibits a decrease in patients with PFD (11).

In this study, our primary focus revolved around the application of intelligent pelvic floor ultrasound and SWE technology to assess the changes in pelvic floor function. The use of intelligent pelvic floor ultrasound facilitated meticulous and dynamic scrutiny of pelvic floor organ anatomy and mobility. Concurrently, SWE emerged as a valuable tool for assessing changes in the elasticity and firmness of the LAM. Through this integrative approach, the ultrasonic diagnostic repertoire for PFD was enriched by furnishing comprehensive insights into pelvic floor dynamics and tissue characteristics. We present this article in accordance with the STROBE reporting checklist (available at https://qims.amegroups.com/article/view/10.21037/qims-2025-143/rc).

Methods

Study participants

A group of 142 women who visited the Gynecology and Obstetrics Ultrasound Department of our hospital between December 2021 and October 2022 were randomly enrolled and completed a questionnaire regarding symptoms associated with pelvic floor dysfunction disorders. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the Ethics Committee of The Fourth Hospital of Hebei Medical University (No. 2024KY140) and informed consent was obtained from all individual participants. These patients were categorized into two groups based on the presence of symptoms associated with PFD, encompassing SUI, POP, abnormal bowel function, dyspareunia, and chronic pelvic pain, among others: the PFD group comprised 71 cases, with a mean age of 44.75±9.20 years; and the non-PFD group comprised of 71 cases, with ages ranging from 20 to 68 years and a mean age of 41.68±11.47 years.

The patients were further divided based on the outcome of pelvic floor ultrasound examinations, resulting in the classification into two-dimensional (2D) abnormal and 2D normal groups, as well as 3D abnormal and 3D normal groups. The criteria for defining abnormality were as follows: (I) 2D abnormalities were characterized by the bladder and rectal ampulla positions being lower than the reference line level, or cervical position lower than the reference line level +15 mm (12). (II) 3D abnormalities were defined by a hiatus area of ≥20 cm² during maximal Valsalva maneuver (13).

The normal control group, derived from 54 women within the non-PFD group who exhibited normal pelvic function, had a mean age of 42.59±11.53 years. Inclusion criteria for the normal control group encompassed participants with normal pelvic floor ultrasound findings and the absence of hysterectomy within the non-PFD group. Exclusion criteria comprised of patients with substantial pelvic masses (≥5 cm), within one year postpartum, unable to adequately perform LAM contraction and Valsalva maneuver, or possessing a history of pelvic floor surgical intervention.

Instruments

The Mindray Resona 8 color Doppler ultrasound diagnostic instrument, equipped with a 3D volumetric probe operating at a frequency range of 8–12 MHz, was utilized with intelligent pelvic floor software.

The Supersonic Imagine Aixplorer color Doppler ultrasound diagnostic instrument, featuring an intracavitary probe operating at a frequency range of 3–12 MHz, was utilized, complemented by SWE imaging software.

Examination methods

Preparation

• Before the examination, patients were instructed to empty their bowel and bladder and assume the lithotomy position.
• Patients received detailed instructions regarding the examination procedures to ensure comprehension and effective completion of pelvic floor muscle contraction and Valsalva maneuver. Effective pelvic floor muscle contraction was characterized by maximal anal contraction and elevation, movement of pelvic organs towards the cephalad or caudal direction, or narrowing of the LAM hiatus, with a duration of ≥3 s. Effective Valsalva maneuver entailed deep inspiration followed by breath retention and maximal downward exertion of force to elevate abdominal pressure, thereby displacing pelvic organs dorsally and caudally, or enlarging the LAM hiatus, with a duration of ≥6 s (14). All commands were given by the same practitioner.
• Substantial quantities of sterile coupling agent were applied to the probe, followed by encasing the probe with a thin disposable rubber sleeve and uniformly applying sterile coupling agent onto the rubber sleeve surface. The probe was positioned on the perineum of the participant, ensuring snug adherence to prevent gas interference both inside and outside the rubber sleeve as well as gas accumulation between the probe and perineum, which could affect image visualization.

Pelvic floor ultrasound

2D ultrasound

The standard median sagittal section of the pelvic floor was obtained by positioning the probe upward and longitudinally on the participants’ perineum. Care was taken to avoid compressing the perineum with the probe, maintaining a distance between the probe and the pubic symphysis of <1 cm while ensuring an included angle of approximately 45° between the central axis of the pubic symphysis and the horizontal plane. This section provided clear visualization of the pubic symphysis, urethra, bladder neck, part of the bladder, vagina, rectum, anal tube, anal sphincter, anal levator plate, and surrounding structures (refer to Figure S1A).

A reference line was established with the posterior inferior border of the pubic symphysis as the marker point. Organs situated below this line were denoted by “+”, while those above were denoted by “−”.

The following observation indices were recorded:

• Resting state positions of the bladder/uterus/rectum were determined by vertical distances between the bladder neck/lowest point of cervix/rectal ampulla and the reference line (see Figure S1B).
• Valsalva state positions of the bladder/uterus/rectum were similarly measured as vertical distances between the bladder neck/lowest point of cervix/rectal ampulla and the reference line (see Figure S1C).
• Bladder neck descent (BND) was calculated as the discrepancy in distance between the bladder neck and the posterior inferior border of the pubic symphysis in the resting and Valsalva states.
• Urethral rotation angle (URA) represented the difference in urethral tilt angle between resting and Valsalva states (see Figure S1C).
• Identification of the presence of an internal urethral orifice funnel was noted (see Figure S1D).

3D ultrasound

To obtain the pelvic floor axial plane, the participants were instructed to perform the Valsalva maneuver following the acquisition of the 2D standard median sagittal section of the pelvic floor. Subsequently, the 3D imaging mode was activated, and the Render mode was selected to generate the pelvic floor axial plane. The A-plane function was enabled, and the Z-axis was rotated to position the sampling frame along the line connecting the surface of the posterior inferior border of the pubic symphysis to the center of the puborectalis ring, thereby establishing the LAM hiatus axial plane. Utilizing the “Automatic pelvic floor” option facilitated the automatic marking of the internal urethral orifice, rectal ampulla, and center of the puborectalis ring, and enabled the automatic determination of the LAM hiatus area (LHA), as depicted in Figure S2A. Observation indices included: LHA during the Valsalva maneuver. Notably, due to racial differences, variations exist in the LHAs of women globally. A study outside of China indicated that an LHA during the Valsalva maneuver of <25 cm² is indicative of normalcy (13). Conversely, a large-scale clinical investigation conducted in China indicated that the LHA of adult women typically falls <20 cm² during maximal Valsalva maneuver (13).

To obtain the axial planes of the LAM at various levels, patients were instructed to perform contraction movements, after which the TUI mode was engaged. By using a display mode of 3×3 planes with an inter-layer spacing of 2.5 mm, axial planes were acquired. Notably, on the 4th to 6th images, the pubic symphysis was observed to show stages of opening, approaching closure, and closure, facilitating clear visualization of symmetrical and slightly hyperechoic bilateral puborectalis muscles. These structures were observed to originate from the medial surface of the pubic branch on each side, extending toward the posterior aspect of the anorectal angle, and ultimately connecting with muscle fibers on the contralateral side, forming a U-shaped configuration, as depicted in Figure S2B.

Observation indices included assessment of the LAM integrity during contraction. Criteria for identifying compromised integrity encompassed unilateral or bilateral interruption of puborectalis continuity, bilateral LAM asymmetry, loss of the characteristic U-shaped structure, presence of proliferating fibrous connective tissues at the disconnected end of the muscle, irregular and disordered local echoes, and distinct separation of puborectalis and pubis. Notably, the presence of these phenomena on the 4th to 6th images was indicative of complete LAM avulsion (partial avulsion if only some criteria were met).

Real-time SWE

• Building upon the standard median sagittal section of the pelvic floor, the probe was maneuvered laterally to the left and right until achieving clear visualization of the anterior segment of the puborectalis on both sides. Subsequently, SWE functionality was activated, with the sampling frame positioned over the anterior segment of the puborectalis to the fullest extent possible. Image capture occurred upon optimal filling of the color signal within the region of interest (ROI), with adjustment of the Q-box diameter to 5 mm.
• Observation indexes comprised of the determination of the mean value (Emean), minimum value (Emin), and maximum value (Emax) of Young’s modulus for the anterior segment of the puborectalis on both left and right sides across resting contraction, and Valsalva states, as illustrated in Figure S3. Data acquisition involved three measurements per parameter, with results subsequently averaged for analysis.

Statistical analysis

SPSS 26.0 statistical software was used to conduct normality tests and homogeneity tests of variance for all measurement data. Measurement data conforming to a normal distribution were presented as mean ± standard deviation (x¯±s). For such data, the independent samples t-test was used to compare two groups if the variance was homogeneous; otherwise, the t-test was used for comparison between the two groups. Paired-sample t-tests compared Young’s modulus values for the left and right puborectalis muscles. For measurement data that did not adhere to a normal distribution, values are expressed as median (P25, P75). The Mann-Whitney U test was applied for comparisons between two groups, while the Kruskal-Wallis rank-sum test was used for comparisons among multiple independent groups. The Bonferroni test was subsequently used for multiple comparisons.

Enumeration data were presented as frequency and percentage (%), with the Chi-squared test used for comparisons between two groups. Statistical significance was determined at a threshold of P<0.05.

Results

General information of patients

In the PFD group, 57 cases presented symptoms of SUI, while 5 cases exhibited symptoms of POP. Additionally, 7 cases manifested symptoms of both SUI and POP, while 2 cases displayed other PFD symptoms. Notably, patients exhibiting symptoms related to both SUI and POP accounted for 97.18% of the PFD group [(57+5+7)/71]. There were no statistically significant differences observed in age, body mass index, and menstrual status among the participants between the PFD group and the non-PFD group, with P>0.05, as detailed in Table 1.

Comparison of pelvic floor muscle function between the PFD group and the non-PFD group

All participants enrolled in this study exhibited intact LAMs. In the group diagnosed with PFD, women demonstrated a statistically significant decrease in the resting and Valsalva-induced positions of the bladder and uterus, as well as in the Valsalva-induced position of the rectum, compared to those without PFD (P<0.05). Conversely, parameters such as bladder neck mobility, URA, internal urethral orifice funnel formation rate, and LHA during the Valsalva maneuver were significantly higher in the PFD group than in the non-PFD group (P<0.05), as detailed in Table S1.

• The comparison of Young’s modulus between the left and right puborectalis muscles within the normal control group revealed no statistically significant difference (P>0.05), as shown in Table 2. Consequently, subsequent analyses did not differentiate between the right and left sides of the puborectalis muscles, with data from both sides being integrated.
• Statistically significant differences were observed in the overall distribution of Young’s modulus within the puborectalis muscle across its resting, contraction, and Valsalva states in the normal control group (P<0.05). Specifically, Young’s modulus exhibited the following hierarchical order: contraction > Valsalva > resting, as presented in Table 3.
• No statistically significant differences in Young’s modulus were found between the PFD and non-PFD groups (P>0.05), as detailed in Table 4.
• Within the PFD group, Young’s modulus of the puborectalis muscle was notably reduced in the 2D abnormal subgroup compared to the 2D normal subgroup during the resting state (P<0.05). Similarly, Young’s modulus was reduced in the 3D abnormal subgroup compared to the 3D normal subgroup (P<0.05). However, no statistically significant differences in Young’s modulus of the puborectalis muscle between the 2D and 3D abnormal subgroups and their respective normal counterparts were observed during contraction and the Valsalva maneuver (P>0.05), as detailed in Table 5.
• Conversely, in the non-PFD group, no significant differences in Young’s modulus of the puborectalis muscle were noted between the 2D and 3D abnormal subgroups and their corresponding normal groups (P>0.05), as detailed in Table S2.

Discussion

The female pelvic floor anatomy comprises complex and finely coordinated structures such as the pelvic floor muscles that are responsible for supporting the pelvic organs and sealing the pelvic outlet, as well as the pelvic floor connective tissues and pelvic organs (15). According to the “hammock” hypothesis, the stability of the “hammock” relies not only on supporting structures such as fascial ligaments but also on the LAM, which plays a pivotal role (16). The LAM interlaces with ligaments and fascia, primarily aligning with the pelvic fascia tendon arches, and contributes significantly to maintaining pelvic organs’ normal position and function.

In this study, we selected the anterior portion of the puborectalis muscle, where it attaches to the pubic symphysis, for assessment due to its easily identifiable measurement site, substantial thickness changes during contraction compared to the middle and posterior portions, and increased susceptibility to injury (17). As the primary support structure maintaining pelvic floor function, pelvic floor muscles not only uphold the normal position of pelvic organs but also exert forces on the urethra and bladder toward the cranial and abdominal directions during LAM contraction to maintain urethral closure pressure and regulate urinary voiding (18). Injury or relaxation of these muscles can precipitate PFD symptoms, such as SUI, POP, obstructed urination and defecation, and chronic pelvic pain. In this study, 97.18% of participants in the PFD group exhibited symptoms related to SUI and POP.

Pelvic floor ultrasound has emerged as a widely used diagnostic modality for PFD, due to its notable advantages such as cost-effectiveness, noninvasiveness, real-time visualization, and patient acceptability. It allows for the assessment of organ positions when compared to a reference line in both resting and Valsalva states, facilitating a dynamic observation of organ movement within the anterior, middle, and posterior compartments towards the caudal and dorsal directions during the Valsalva maneuver (19). Patients with PFD often exhibit characteristic ultrasound findings such as POP, heightened bladder neck mobility, increased URA, funnel-shaped internal urethral orifice, increased LHA, and potential LAM rupture. In our study, compared to the non-PFD group, patients with PFD revealed lower bladder and uterus positions during both resting and Valsalva states, along with a lower position of the rectal ampulla during the Valsalva state, and an increased LHA. 2D pelvic floor ultrasound enables precise depiction of the specific positions of pelvic organs, while 3D ultrasound allows for LHA assessment. Our findings revealed that in women experiencing PFD symptoms, even during the resting state without abdominopelvic pressure, the pelvic floor muscles and fascia were injured, leading to POP due to weakened support. During the Valsalva maneuver, the increase in abdominal pressure adds to the compression of the pelvic floor support structures that are already damaged and are unable to support the pelvic floor organs, making them more susceptible to organ prolapse.

This aligns with a prior study conducted in China (20). Furthermore, bladder neck mobility, URA, and internal urethral orifice funnel formation rate were notably increased in the PFD group during the Valsalva state when compared to the non-PFD group. Increased abdominal pressure accentuated the pushing effect on lax pelvic floor muscles, further exacerbating bladder neck mobility and URA. Consistent with the study indicating increased bladder neck mobility in patients with SUI, a significantly higher funnel formation rate of the internal urethral orifice was observed in the PFD group (43.7%) compared to the non-PFD group in our study (4.2%) (16). This funnel-shaped change in the internal urethral orifice during the Valsalva state indicates its importance as a diagnostic indicator for SUI (21).

Advanced pelvic floor ultrasound techniques offer detailed visualization of pelvic organ positions, while the axial plane allows observation of the LAM hiatus. However, these techniques solely depict anatomical changes within the pelvic floor and cannot quantitatively assess LAM muscle strength. Whereas, SWE technology provides a means to gauge tissue hardness by measuring Young’s modulus, with higher values indicating greater tissue stiffness (22). SWE was used in our study to assess pelvic floor muscle hardness. We found no statistically significant differences in Young’s modulus between the left and right puborectalis muscles across all three states within the normal control group. This indicates that puborectalis muscle hardness remains consistent and balanced bilaterally in healthy individuals. Consequently, we recommend against distinguishing between the left and right puborectalis muscles when assessing Young’s modulus in future studies.

Furthermore, we observed a hierarchy of puborectalis muscle hardness: contraction state > Valsalva state > resting state. SWE demonstrated sensitivity in detecting these changes, wherein active muscle contraction led to a substantial increase in muscle hardness. Conversely, during the passive stretching of muscles in the Valsalva state, hardness decreased compared to contraction but remained higher than in the resting state. These observations are consistent with changes in the Young’s modulus of the puborectalis muscle as measured by SWE. Previous studies have typically focused on comparing muscle hardness between resting and contraction states or between resting and diastolic states. However, this study extends these comparisons to include all three physiological states, offering a more detailed analysis and providing a valuable reference point for future research. Furthermore, our findings indicate that parameters such as Emean, Emin, and Emax exhibit consistent trends when comparing between left and right sides and across the three states. Given that Emean offers a representative value of Young’s modulus, it is proposed as the primary parameter for evaluation in future studies.

We further analyzed results within the PFD and non-PFD groups based on abnormal and normal pelvic floor ultrasound findings, respectively. Among patients with PFD symptoms and abnormal pelvic floor ultrasound results, we observed a decrease in Young’s modulus of the puborectalis muscle in the resting state. This alignment between SWE technology and pelvic floor ultrasound underscores the use of Young’s modulus in providing data support for PFD symptoms (23). The observed decline in pelvic floor muscle strength, coupled with reductions in collagen fibers and damage to elastin within supporting pelvic floor tissues, contributes to structural laxity and increased pelvic floor mobility, corroborating previous findings (24-26). However, no statistically significant differences in Young’s modulus of the puborectalis muscle were noted between the pelvic floor’s abnormal and normal groups during contraction and the Valsalva maneuver. This could be attributed to varying degrees of coordination during these movements, potentially affecting Young’s modulus measurement. Given the stability of muscle condition in the resting state, unaffected by subjective factors such as contraction force or abdominal pressure, we recommend using Young’s modulus of the puborectalis muscle to reflect changes in pelvic floor function.

In the non-PFD group, 2D pelvic floor ultrasound showed abnormalities in 17 cases (23.94%) and 3D pelvic floor ultrasound showed abnormalities in 14 cases (19.72%). Pelvic floor ultrasound can detect anatomical abnormalities of the pelvic floor in some women without symptoms of PFD, suggesting that pelvic floor ultrasound is an examination method that can detect pelvic floor abnormalities at an early and sensitive stage. No significant difference in Young’s modulus of the puborectalis muscle was observed between those with abnormal and normal pelvic floor ultrasound findings. This indicates that while the puborectalis function may remain intact or in a compensatory phase, weakness in pelvic floor support structures other than muscle (e.g., pelvic floor fascia and connective tissues) may contribute to reduced support force. LAM training helps to improve the overall support of the pelvic floor and reduces the pressure on the pelvic floor fascia and connective tissues, providing an indirect protective and compensatory effect on the pelvic floor fascia and connective tissues. Moreover, during LAM training, the movement of LAM can promote blood circulation in the pelvic floor area. Adequate blood circulation can provide sufficient oxygen and nutrients to the pelvic floor fascia and connective tissues, helping to maintain these tissues in a healthy state, enhance their elasticity and toughness, and promote repair after injury.

In summary, pelvic floor ultrasound enables the observation of pelvic organ movement displacement and the assessment of pelvic floor muscle morphology, while SWE technology offers a quantitative assessment of pelvic floor muscle hardness, providing valuable data on muscle strength. The integration of these methods holds promise for enhancing the diagnostic capabilities for PFD. However, several limitations of this study warrant acknowledgment: (I) The sample size is relatively small, necessitating further investigation with an expanded sample size to enhance statistical power and generalizability. (II) The collection of the general conditions of the participants lacks comprehensiveness, failing to account for factors such as pregnancy and childbirth, which can significantly impact female pelvic floor muscles. Future studies should incorporate detailed information on the number of pregnancies, childbirths, and delivery modes to enhance comparability among enrolled participants. (III) Participant grouping based solely on the presence or absence of PFD symptoms introduces inherent bias due to subjective factors. Subsequent studies should track clinical diagnoses and surgical interventions among all participants to assess the diagnostic use of pelvic floor ultrasound and SWE for PFD. (IV) SWE measurements may be influenced by factors such as examination site depth, gain adjustment, and operator proficiency, potentially affecting data accuracy. To reduce this, in our study, we utilized repeated measurements and consistent operators to minimize measurement error.

Conclusions

Intelligent pelvic floor ultrasound offers early and sensitive detection of abnormalities in pelvic floor organ positions and changes in LHA, furnishing a valuable diagnostic foundation for PFD. Concurrently, SWE provides quantitative insights into puborectalis muscle hardness, muscle strength, and changes in LAM hardness across different pelvic floor states, providing robust data support for PFD symptoms. By integrating intelligent pelvic floor ultrasound with SWE, a comprehensive array of multi-index and multi-modal parameters is available, bolstering the diagnosis of PFD.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://qims.amegroups.com/article/view/10.21037/qims-2025-143/rc

Data Sharing Statement: Available at https://qims.amegroups.com/article/view/10.21037/qims-2025-143/dss

Funding: This work was supported by Health Commission of Hebei Province (Nos. 20250755 and 20200026), and Department of Finance of Hebei Province (No. 361006).

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://qims.amegroups.com/article/view/10.21037/qims-2025-143/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the Ethics Committee of The Fourth Hospital of Hebei Medical University (No. 2024KY140) and informed consent was obtained from all individual participants.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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