A. Shafik et O. El-sibai, Effect of levator ani muscle contraction on urethrovesical and anorectal pressures and role of the muscle in urination and defecation, UROLOGY, 58(2), 2001, pp. 193-196
Objectives. To investigate the effect of levator ani muscle (LAM) (the main
muscle in the pelvic floor) contraction on the anorectal and urethrovesica
l pressures and elucidate its role in the mechanisms of defecation and urin
ation.
Methods. In 18 healthy volunteers (10 men and 8 women; mean age 38.6 +/- 10
.2 years), the LAM was stimulated to contract by a concentric needle electr
ode, and the anal, rectal, urethral, and vesical pressure responses were re
corded. The test was repeated once after LAM anesthetization with Xylocaine
injection and again after saline instead of Xylocaine injection into the L
AM.
Results. On LAM stimulation, the anal and urethral pressures had a signific
ant decline (both P <0.05), and the rectal and vesical pressures exhibited
no significant changes (both P >0.05). The anal, rectal, urethral, and vesi
cal pressures did not show significant changes on stimulation of the anesth
etized LAM; after saline injection, the pressure response was similar to th
at before injection (P >0.05). These results were reproducible.
Conclusions. LAM contraction lowers the anal and urethral pressures and app
ears to assist in the evacuation process. We therefore propose that the LAM
is a muscle of evacuation and that LAM dysfunction could lead to defecatio
n and urination disorders. UROLOGY 58: 193-197, 2001. (C) 2001, Elsevier Sc
ience Inc.