Individual variations in aging of the male urethral rhabdosphincter in Japanese.

Although the degenerative changes with aging of the male urethral rhabdosphincter (URS) have been investigated, its individual morphological variations are still unclear. To provide an anatomical basis for clinical evaluation of the individual URS function in the aged, we investigated the structural differences in the URS of 25 elderly Japanese men using semiserial sections stained immunohistochemically and by hematoxylin-eosin. Before removal of the histological specimens, we dissected the ischioanal fossa and labeled several structures by carbon particles to allow proper orientation during the histological observations. In addition, macroscopic slices (10 mm thickness) made from five other male pelves were examined and, when necessary, followed by routine histological procedure to confirm the gross observations. An extended circular URS (over (1/2) circumferential configuration) was found in 15/25 cadavers, but showed very limited height (proximal-distal length) and thickness. A more restricted URS, including even a thin, arc-like pattern, was observed in the remaining cadavers. The attachment of the URS to the smooth muscle layer was loose and usually clearly separated. Continuation between the URS and deep transverse perineal muscle was sometimes observed. The thick fascia of the levetor ani, with high content of smooth muscles, usually provided the lateral or dorsal insertions of the URS. Our results in elderly Japanese subjects suggest that the sphincteric action is weak or incomplete. We suggest that the elderly URS maintains continence by retracting the urethra backward and upward with the aid of the levator sling, rather than the real sphincteric action expected in younger men.