A new method to quantify male pelvic floor displacement from 2D transperineal ultrasound images

Abstract

Objective: To develop a method to quantify displacement of pelvic structures during contraction of the pelvic floor muscles from transperineal ultrasound images in men and investigate the reliability of the method between days.

Methods: Ten healthy male volunteers (aged 28-41 years) attended 2 separate data collection sessions. Ultrasound images were recorded during voluntary pelvic floor muscle contractions in cine-loop (video) format with the transducer aligned in the midsagittal plane on the perineum. Five anatomic points were defined to represent contraction from striated urethral sphincter (SUS), levator ani (LA), and bulbocavernosus (BC) muscles. Displacement of each point was calculated between the relaxed and contracted-state images. Intraclass correlation coefficient (ICC) values were calculated from displacement data to assess reliability of the method between days.

Results: Displacements of the 5 anatomic points closely matched predictions based on anatomic considerations of the male pelvic musculature. ICC values for displacement data calculated from 1, 2, and 3 repetitions ranged between 0.82 and 0.95 for ICC (2,1), 0.85 and 0.97 for ICC (2,2), and 0.86 and 0.97 for ICC (2,3), respectively.

Conclusion: The new method reliably calculates displacements of points previously validated for women (ano-rectal junction and bladder base) in addition to new measures of muscle actions (SUS and BC) specific to men. Future use might include assessment of clinical populations to understand how these displacements relate to symptoms of incontinence.

Fig. 1

Anatomical depiction of the male pelvic floor and associated structures viewed in the midsagittal plane with an ultrasound transducer placed on the perineum. Bold arrows indicate hypothesized direction of movement during voluntary muscle contraction based on anatomy.

Fig. 2

Transperineal ultrasound images made in the (A) relaxed and (B) contracted states. (C, D) Borders and points of interest superimposed on the US images. (E) Overlaid borders of the two images; dark circles indicate the points of interest in the relaxed state and light circles from the contracted state. (F) Ellipse defined by user-selected points “-a”, “a” and “b” with coordinate system used for image analysis based at origin “a”.

Fig. 3

Pelvic structures are shown for a relaxed image with points used for displacement analyses highlighted (P1–P5). Dark circles indicate resting position and light circles indicate position during maximal voluntary contraction. Arrows highlight the direction and amplitude of movement of each point of interest for a representative participant (same participant as Fig. 2). Range of displacements for the group is shown for each measure.

Fig. 4

MRI (A, C) and transperineal ultrasound (B, D) images from participant #8 in the (A, B) relaxed and (C, D) contracted states. (C, D) Borders and points of interest superimposed on the US images. (E, F) Overlaid borders of the two images; dark circles indicate the points of interest in the relaxed state and light circles from the contracted state.