Novel insight into the dynamics of male pelvic floor contractions through transperineal ultrasound imaging

Abstract

Purpose: Transperineal ultrasound imaging enables the minimally invasive assessment of pelvic floor muscle function. Although commonly used in women, the approach has rarely been reported in men. This approach has advantages because the midsagittal view visualizes a bony landmark and the entire urethral length. This allows investigation of the displacement of multiple points along the urethra and the unique mechanical actions of multiple muscles that could influence continence. We used a new transperineal ultrasound technique to compare the relative displacement of urethrovesical junction, anorectal junction and distal urethra during voluntary pelvic floor muscle contractions in continent men.

Materials and methods: We performed measurement and comparison of urethral displacement at specific urethral regions in 10 continent men (age range 28 to 41 years). Measures made on 2-dimensional midsagittal plane ultrasound images included the displacements of specific points along the urethra. Anatomical considerations suggest that these are caused by contraction of the levator ani, striated urethral sphincter and bulbocavernosus muscles. Pearson's correlation coefficient was used to investigate the relationship between displacements of pairs of points.

Results: Data show individual variation in displacement of the distal urethra (striated urethral sphincter contraction) and urethrovesical junction (levator ani contraction). A strong inverse linear relationship (0.723) between displacements of these points indicates 2 alternative strategies of urethral movement.

Conclusions: Transperineal ultrasound imaging allows the simultaneous investigation of multiple pelvic floor muscles by measuring urethral displacement. The data provide evidence of different but coordinated strategies of urethral displacement in men.

Fig. 1

(A) Male pelvic floor and associated structures viewed in the midsagittal plane. Bold arrows indicate hypothesized direction of movement during voluntary muscle contraction, based on anatomical description. (B) Participant position and experimental setup.

Fig. 2

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

Fig. 3

Group data showing the linear relationship between displacements of each possible pair of points of interest derived from pelvic structures. Absolute displacement values are shown with corresponding R² values.