Urethral pressure variations in women with neurourological symptoms: III. Relationship to urethral wall venous plexus

Twenty-five women were investigated in order to find out if the urethral submucous venous plexus may influence urethral pressure variations. Urethral and bladder pressure were measured with a microtip transducer catheter. Electromyography (EMG) and integrated EMG from the urethral striated muscle were recorded using a concentric needle electrode. Blood volume in the urethral submucous venous plexus was measured with a urethral photopletysmograph probe. In 9 women without neurourological symptoms, during squeezing there was increased urethral striated muscle activity, increased urethral pressure and decreased blood volume. When they were asked to void the opposite was found. In 16 patients with marked urethral pressure variations a negative correlation was found between the maximum urethral pressure and the photopletysmograph tracing. In 7 of 8 patients a negative correlation was found also between the integrated EMG tracing and the photopletysmograph tracing, but a positive correlation was found between the maximum urethral pressure and the EMG of the urethral striated muscle. In 1 of the 8 patients no correlation was found between EMG activity and maximum urethral pressure and between EMG activity and the photopletysmograph tracing. The results demonstrate that the urethral venous plexus becomes emptied secondary to contractions of the urethral striated and/or smooth muscle and filled with blood secondary to relaxation of the same muscles. Hence, the urethral venous plexus does not influence the urethral pressure actively.