We aimed to compare the vaginal wall thickness (VWT) measurement by two (2D-US) and pelvic floor muscle morphometry/function by four-dimensional translabial ultrasound (4D-TLUS)  in women with vaginal laxity (VL) who underwent treatment with radiofrequency (RF) or pelvic floor muscle training (PFMT) after 30 days and 6 months.

A secondary analysis of a randomized clinical trial that occurred between February 2020 and December 2021 was performed. Women between 18 and 60 years old with a self-reported complaint of vaginal laxity and classified by the Vaginal Laxity Questionnaire (very loose, moderately loose, slightly loose) were recruited from a tertiary hospital and  enrolled and treated with RF or PFMT for 12 weeks. At baseline, participants were assessed for sociodemographic and clinical data, answered validated questionnaires, and underwent physical and ultrasound examinations. For the questionnaires, we included the Female Sexual Function Index (FSFI) for sexual function, the Female Sexual Distress Scale-Revised (FSDS-R) for sexual distress, the International Consultation on Incontinence Questionnaire—Vaginal Symptoms (ICIQ-VS), for vaginal symptoms and quality of life. Regarding physical examination, participants underwent Pelvic Organ Prolapse Quantification (POP-Q) and Pelvic Floor Muscle Strength graduated by the modified Oxford scale (5-point). Ultrasound examiners were blinded for the groups. Transabdominal (TAUS) and transvaginal (TVUS) ultrasound were performed with 2D-US analysis. The 4D-TLUS was used for PFM morphometry/function assessment. We performed per-protocol (PP) and intention-to-treat (ITT) analysis (5% significance). We utilized the FSFI scoresfor sample size calculation since they found significant improvement in sexual function in participants with VL undergoing RF. If 
there is no difference between PFMT and RF, 66 patients are needed to obtain 90% certainty that the lower limit of a one-sided 95% confidence interval will be above the non-inferiority limit of -4 and standard deviation of 5. Data were extracted from the FSFI total score. Moreover, if we consider a percentage of 25% loss in the sample, was found  a total of 84 participants, with 42 in each group. This calculation was performed for the clinical trial, not for the US analysis as we did not have any previous data for this analysis [1].

There was a weak correlation between 2D TAUS and TVUS measurements and anterior-posterior diameter difference and VL perception, sexual function and vaginal symptoms. Women with ballooning presented significantly worse scoring in sexual function and vaginal symptoms; and higher TVL, Ba and Bp measurements (POP-Q classification) than women without ballooning. Measurements of the TAUS proximal vagina increased in the PFMT group after 6 months. TAUS/TVUS distal vagina measurements were reduced after 6 months of RF. Other 4D-TLUS measurements did not present differences according to the intervention and/or analysis.

To our knowledge, this is the first comparative study of US assessment of VWT and pelvic floor muscle morphometry and function in women with VL. This makes this section even harder to compare the literature with our findings, as there is scant data on this subject. 
Preliminary data suggest that the measurement of VWT may be useful for assessing vaginal changes [2]. In our sample, VWT measurements were thinner in the middle third vagina and thicker in the distal vagina, in both the RF group and the PFMT group and ultrasound techniques (TAUS and TVUS) at baseline assessment. We could also confirm that there was a correlation between TAUS and TVUS measurements [3].
The present study has limitations. In this study, we focused on the 4D-TLUS evaluation of measurements at rest and contraction of the pelvic floor muscles. Assessment of pelvic floor muscles in Valsalva would add value to our findings and could be useful in a future study. Another issue that should be considered is the fact that we did not use the histological evaluation of the participants to compare with the measurements of VWT. However, we intended to use ultrasound because it is less invasive, causes little discomfort and is part of the clinical practice of professionals who work in the care of women with VL or other sexual complaints. Moreover, the use of ultrasound for the objective assessment of VWT and the morphometry and contractile function of the pelvic floor muscles has contributed to the understanding of VL and raised questions for future studies about the importance of studying VL and the cost-effectiveness of treatment options such as energy-based devices.

Among women with VL, 2D-US measurements, whether abdominal or vaginal, of the VWT present a weak correlation with clinical instruments. Women with ballooning on 4D-TLUS presented significantly worse scoring in sexual function and vaginal symptoms; and higher TVL, Ba and Bp measurements.

Oliveira Brito LG, Pereira GM, Almeida CM, Martinho N, Andrade KC, Juliato CR. Pelvic floor muscle training versus radiofrequency for women with vaginal laxity: randomized clinical trial. Am J Obstet Gynecol 2023;228(3):S806. DOI:https://doi.org/10.1016/j.ajog.2022.12.033
Balica A, Wald-Spielman D, Schertz K, Egan S, Bachmann G. Assessing the thickness of the vaginal wall and vaginal mucosa in pre-menopausal  versus post-menopausal women by transabdominal ultrasound: A feasibility study. Maturitas. 2017;102:69-72. doi:10.1016/j.maturitas.2017.02.017
Pereira GMV, Juliato CRT, de Almeida CM, Valente IS, de Andrade KC, Brito LGO. Measurement of the vaginal wall thickness by transabdominal and transvaginal  ultrasound of women with vaginal laxity: a cross-sectional study. Int Urogynecol J. 2022;33(12):3563-3572. doi:10.1007/s00192-022-05184-8