The effect of changes of posture on the urethral closure pressure in healthy women.

The effect of changes of posture on hydrodynamic parameters considered important for the maintenance of urinary continence was investigated in 14 healthy women. The subjects were investigated in the supine and erect positions using a previously described technique for simultaneous urethrocystometry, including recording of the urethral pressure profile. It was found that a change from the supine to the standing position increased the maximum intravesical pressure from a mean value of 13 mmHg to 22 mmHg. There was a simultaneous increase in the maximum intra-urethral pressure from a mean of 66 mmHg to 82 mmHg. As a consequence, the urethral closure pressure increased from a mean of 53 mmHg to 60 mmHg. The functional length of the urethra increased from 25 mm to 28 mm, and the absolute length from 28 mm to 36 mm. It is concluded that in healthy women, a change from the supine to the standing position causes a rise in the maximum intra-urethral pressure and an increase in the absolute and functional lengths of the urethra. These effects counteract the simultaneous increase in bladder pressure, and can be regarded as compensatory mechanisms for the maintenance of continence.