Histomorphology of canine urethral sphincter systems, including three-dimensional reconstruction and magnetic resonance imaging.
OBJECTIVE
To present a detailed anatomic description and comparison of the smooth and striated urethral sphincter in male and female dogs. We performed a thorough histologic evaluation, three-dimensional reconstruction, and magnetic resonance imaging of the lower urinary tract of male and female dogs.


METHODS
The lower urinary tract anatomy was investigated in 16 male and 18 female dogs by serial sectioning, including immunohistochemical staining and three-dimensional reconstruction. Magnetic resonance imaging performed in 5 male and 5 female dogs before histologic investigation helped to demonstrate the anatomy in vivo.


RESULTS
A urethral sphincter muscle in both sexes existed without muscular connection to the pelvic floor. It ran circularly and consisted of an inner smooth and outer striated muscular part. In the female dog, the striated muscle encircled the urethra and vagina in the caudal third of the membranous urethra (musculus urethrovaginalis). A urinary diaphragm (diaphragma urogenitale) could not be found histologically or by magnetic resonance imaging.


CONCLUSIONS
The dog is a suitable animal model for investigations of the urethral sphincter. In the female dog, attention should be given to the special topography of the musculus urethrovaginalis.
Stolzenburg
Jens-Uwe
JU
Department of Urology, University of Leipzig, Leipzig, Germany.
Neuhaus
Jochen
J
Liatsikos
Evangelos N
EN
Schwalenberg
Thilo
T
Ludewig
Eberhard
E
Ganzer
Roman
R
D000818:Animals; D004285:Dogs / Q000033:anatomy & histology*; D005260:Female; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D008297:Male; D014521:Urethra / Q000033:anatomy & histology*