Three-dimensional transrectal ultrasound of the male urethral rhabdosphincter

Abstract

The rhabdosphincter of the male urethra is an omega-shaped loop of striated muscle fibers that surrounds the membranous urethra at its lateral and anterior aspects. We investigated whether this muscle can be visualized by means of three-dimensional ultrasound to define morphological and dynamic ultrasound criteria. We examined the rhabdosphincter of the male urethra in 77 patients by means of this new imaging technique; 37 patients presented with urinary stress incontinence after transurethral resection of the prostate or radical prostatectomy while 40 were fully continent after radical prostatectomy and served as a control group. Contractility of the muscle was quantified by a specially defined parameter (rhabdosphincter-urethra distance). The anatomical arrangement and the contractions of the rhabdosphincter-loop could be clearly visualized in three-dimensional transrectal and transurethral ultrasound; during contraction the rhabdosphincter retracts the urethra, pulling it towards the rectum. We detected defects and postoperative scarrings in the majority of the patients with postoperative urinary stress incontinence. Furthermore, the patients presented with thinnings in parts of the muscle and atrophies of the rhabdosphincter. The rhabdosphincter-urethra distance was significantly lower in the incontinent group than in the continent group (59 vs. 1.42 mm). Our study shows that the rhabdosphincter of the male urethra can be visualized by means of three-dimensional transrectal ultrasound. The sonographic pathomorphological findings of postoperative urinary stress incontinence are well correlated well with the clinical symptoms.

Novel Insight into the Dynamics of Male Pelvic Floor Contractions Through Transperineal Ultrasound Imaging

“…In young continent men, mean (SD) displacements of the inner margin of SUS to the dorsal aspect of urethra of 1.7(0.4) mm (transurethral) 26 and 1.4(0.2) mm (transrectal) 25 have been measured during voluntary contractions, whereas similar measures in men with incontinence show motion <1 mm. Although capable of measuring SUS displacement, these approaches assume the direction of SUS contraction is in a similar plane to the US beam (transverse plane), and intraurethral/rectal placement of the stiff probe is likely to mechanically affect the contraction.…”

“…Although the technique is used in men to measure bladder base movement for pelvic floor muscle assessment 27 , failure to consider SUS may limit interpretation from that technique given the well-documented importance of SUS for urinary continence in men. Likewise, predictions of male continence status based on SUS displacement alone 25, 26 may be flawed.…”

“…Transabdominal 15-17 , transrectal 18-20 , transvaginal 21, 22 and transperineal 23, 24 approaches image bladder and anorectal junction (ARJ) movements from LA contraction. In men, SUS anatomy and activation has been imaged with transrectal 25 and transurethral 26 approaches. Transperineal imaging is advantageous for both genders because the image includes a bony landmark to reference measures of motion (unlike the transabdominal approach).…”

“…However, only LA activation has been analysed in this manner from ARJ, urethra and urethra-vesical junction (UVJ) movements using transperineal US in women 23, 24 . In men, quantification of UVJ motion with transabdominal 27 and transperineal 28, 29 US, and SUS motion with transurethral 26 and transrectal US 25 has been investigated. However, these studies only evaluated single structures, generally involved limited quantification of movements, and did not consider the relative contributions of the multiple striated muscles with potential to influence continence.…”

A New Method to Quantify Male Pelvic Floor Displacement From 2D Transperineal Ultrasound Images

“…More invasive approaches have been used in men to quantify movement of single structures (transrectal ultrasound imaging for ARJ and transurethral for striated urethral sphincter [SUS] muscle contraction). 3–5 Transperineal ultrasound imaging has the potential to quantify displacement of multiple structures that can influence the urethra concurrently.…”