Stimulated pressure profile at rest: a noninvasive method for assessing urethral sphincter function

To validate a method for assessing urethral sphincter muscle function by recording rises in intraurethral pressure during repetitive pudendal nerve stimulations.

A supine urethral pressure profile at rest was performed on 12 stress-continent and 28 stress-incontinent patients during repetitive pudendal nerve stimulations applied near the ischial spine, and the intraurethral pressure increases were calculated for each third of the urethral functional length.

No significant difference in intraurethral pressure increases was seen between continent and stress-incontinent women. On the various regression curves, the intraurethral pressure increases showed a significant correlation with maximal urethral closure pressure values at rest and at stress (r = 0.36 to 0.54) and with the patient's age (r = 0.46), but not with pudendal nerve conduction times to the urethral sphincter on either side (r = 0.14 and 0.19).

This method (1) measures intraurethral pressure increases that correlate well with the anatomic location of the urethral sphincter muscle, (2) shows there is no significant difference between them in continent and stress-incontinent patients, except in patients with a low-pressure urethra, and (3) demonstrates that they correlate well with the maximal urethral closure pressure and the patient's age, but not with pudendal motor latencies to the urethral sphincter. This method gives us a mapping of the urethral sphincter activity, explaining why some patients with a low-pressure urethra have less urinary loss than others with the same urethral closure pressure.