Pelvic floor disorders (PFD), such as pelvic organ prolapse (POP), are characterized by the reduced function of the pelvic organ support structures, such as the levator ani muscle [1]. One important clinical diagnostic assessment of PFD presence and severity is pelvic floor muscle strength, where the strength of a pelvic floor contract maneuver is evaluated, most commonly by digital palpation. Weak or absent voluntary contraction, as well as involuntary relaxation, are indicators of underactive pelvic muscle function [1]. A common pelvic floor strength assessment scale is the Modified Oxford Score (MOS), which rates muscle strength from zero (no contraction) to five (strong contraction). Digital assessment is based on finger sensitivity, training, and experience, and is thus inherently subjective [2]. A more objective method for quantifying pelvic floor muscle strength may aid in standardizing assessments. Colpodynamic imaging (CDI) provides a novel combination of vaginal distension, intra-vaginal pressure and volume monitoring, as well as real-time ultrasound imaging. While vaginal force sensors exist, they do not have the capability of concurrent real-time pelvic floor imaging. The application of CDI may provide an objective assessment of pelvic floor strength and approximation of vaginal capacity.

The objective of this original study was to characterize the real-time movement and shape change of a distended vagina during a contractile maneuver using CDI.

To perform CDI, a modified urodynamics system was used to fill an ultrathin, oversized bag in the vagina with water through a urodynamics catheter. This bag was retained using a novel device covering the introitus to prevent bag dislodgement during filling as well as providing a window for ultrasound (US) imaging. The bag was first filled to maximum vaginal capacity, indicated by the patient’s sensation of vaginal fullness. Then, 25 mL of water was removed to facilitate a pelvic floor contraction. The patient was then instructed to perform a pelvic floor contraction maneuver, which was captured using 2D transintroital midsagittal US video. Pressure within the bag before, during, and after the contraction was recorded for analysis.

As a preliminary study for developing an analytical technique for visualizing pelvic floor contraction, only US videos with adequate bag wall visibility and observed contraction were included in the analysis. The distended bag in the included US videos were manually segmented (3D Slicer, v4.11) and an automated script (Python, v3.7) was used to place discrete points along the perimeter of the segmented bag wall. These points began horizontally aligned at the pubic symphysis (PS) and were spaced at intervals of 1 cm superiorly and inferiorly. The location of these points were then reported for each frame of the US video. Several measures were derived from these segmentations and points, such as changes in 2D mid-sagittal bag area superior to the PS, minimum and maximum antero-posterior (A-P) lengths, as well as mid-sagittal bag area and A-P changes in the maximal change region (MCR), identified as the region which changes first and most significantly during contraction. For each parameter, the contraction slope, holding slope, and release slope was measured, providing temporal evaluation of contraction dynamics. To obtain average values, the patient contraction curves were averaged using ARCGen (MATLAB R2021a) [3].

Real-time US videos of the mid-sagittal plane during the contract maneuver were successfully captured and analyzed for nineteen patients (age 63±12 years). The discrete point placement (Figure 1A and 1B) provided data for analysis of vaginal shape parameter changes, namely for calculating contraction, holding, and release slope for each patient (Figure 1C). Average patient data was also visualized using ARCGen, providing overall parameter trends (Figure 1D). The parameter descriptions and average patient values for both the pressure and vaginal shape changes are listed in Table 1.

This original study demonstrated a novel method of capturing the real-time pressure, geometric shape changes, and motion of the distended vagina during a contractile maneuver. A trapezoidal curve is seen in the pressure data with a positive contraction slope, plateau, and negative slope for contraction release. Consistent trends were also observed among the patients’ US video data. In particular, an inverted trapezoidal curve was consistently observed for the bag area (both full and MCR), and AP length changes (minimum, maximum, and MCR). This trapezoid depicts a steep negative slope as the respective measure decreases, followed by a plateau during the contraction hold, and finishing with a release slope, which is more gradual than the contraction slope as the vaginal tissue relaxes.

Characterization of the effect of pelvic floor muscle activation on a distended vagina during contraction may provide an objective method of understanding pelvic floor-related impairments. This original initial investigation provides new understanding of pelvic floor biomechanics, which may help to better inform treatment options, such as pessary use or surgical intervention, for women suffering from PFDs. Comparing the shape changes and pressures from different PFDs could provide more in-depth information about the effects of PFDs on this assessment maneuver biomechanics. Further analysis of CDI US data may provide measures that can be used to compare the pelvic floor contraction between patients and serve as an objective measure of pelvic floor strength for PFD assessment. With further refinement and validation, the CDI system has the potential to clinically evaluate pelvic floor function.

Panman C.M.C.R., Wiegersma M., Kollen B.J., Burger H., Berger M.Y., and Dekker J.H. (2017), “Predictors of unsuccessful pessary fitting in women with prolapse: a cross-sectional study in general practice,” International Urogynecology Journal 28(2):307–313. doi: 10.1007/s00192-016-3107-4
Felicíssimo M.F., Carneiro M.M., Saleme C.S., Pinto R.Z., Fonseca A.M.R.M., and Silva-Filho A.L. (2010), “Intensive supervised versus unsupervised pelvic floor muscle training for the treatment of stress urinary incontinence: a randomized comparative trial.” International Urogynecology Journal 21:835–840. doi: 10.1007/s00192-010-1125-1
Hartlen D.C. and Cronin D.S. (2022), “Arc-Length Re-Parametrization and Signal Registration to Determine a Characteristic Average and Statistical Response Corridors of Biomechanical Data.” Frontiers in Bioengineering and Biotechnology 10:843148. doi: 10.3389/fbioe.2022.843148

Continence 7S1 (2023) 100961
DOI: 10.1016/j.cont.2023.100961