Transurethral ultrasound: evaluation of anatomy and function of the rhabdosphincter of the male urethra.
OBJECTIVE
A combined anatomic-sonographic study was undertaken to investigate whether the anatomical arrangement and the contractions of the rhabdosphincter of the male urethra could be visualized by transurethral ultrasound. Furthermore, this new technique was compared with standard urodynamic tests.


METHODS
In 7 cadavers transurethral ultrasound was performed to define sono-morphological criteria of the rhabdosphincter, and the sonographic pictures were then compared to histological sections. In 48 patients the rhabdosphincter of the male urethra was investigated by transurethral ultrasound and urodynamic techniques. Of these patients 40 were completely continent after radical prostatectomy and 8 presented with urinary stress incontinence after transurethral resection of the prostate or radical prostatectomy. The decrease of the distance between the rhabdosphincter and the transducer during contraction served as quantitative parameter for the contractility of the muscle.


RESULTS
The anatomical arrangement and contractions of the rhabdosphincter loop could be clearly visualized on transurethral ultrasound (during contraction the rhabdosphincter retracts the urethra, pulling it towards the rectum). Ultrasound showed scars in 3 patients with postoperative urinary stress incontinence, thinning of the muscle in 3 complete atrophy of the rhabdosphincter in 2 and minimal contractions of the rhabdosphincter in 1. Urethral closure pressures were decreased and decrease in rhabdosphincter-transducer distance was statistically significantly decreased in the incontinent patients.


CONCLUSIONS
Our sono-morphological data and anatomical histological results strongly suggest that the rhabdosphincter constitutes the main component of the continence mechanism in post-prostatectomy patients. Unlike urethral pressure profiles, which can only reveal zones of higher intraluminal pressure between the bladder and the penile urethra, transurethral ultrasound is highly specific for measurement of the function of the rhabdosphincter.
Strasser
H
H
Department of Urology, University of Innsbruck, Austria.
Frauscher
F
F
Helweg
G
G
Colleselli
K
K
Reissigl
A
A
Bartsch
G
G
D006801:Humans; D008297:Male; D009119:Muscle Contraction; D014463:Ultrasonography; D014521:Urethra / Q000033:anatomy & histology / Q000000981:diagnostic imaging* / Q000502:physiology