Effect of vaginal ultrasound probe on lower urinary tract function

Vaginal ultrasonography has been advocated as an alternative to videocystourethrography. Ultrasound avoids the potential risks of X-rays and reduces the cost of equipment. We have investigated the effect of the vaginal probe on the physiology of the bladder and urethra. A series of 24 women underwent urethral pressure profilometry, with and without a vaginal probe in situ. There was a significant increase in maximum urethral pressure, functional urethral length and area under the profile curve both at rest and during stress in the presence of the device. This was due to stretching and compression of the urethra by the probe. Transmission pressure ratios were significantly increased for the first 3 quartiles of the urethra. Twenty women underwent lateral bead chain urethrocystography with and without a vaginal probe. At rest, the probe resulted in elevation of the bladder neck and apposition to the symphysis pubis, and during a Valsalva manoeuvre the descent of the bladder neck was restricted by the presence of the probe. These results indicate that a vaginal probe alters the position and function of the lower urinary tract. We postulate that incontinence is reduced as a result of the probe. The use of vaginal ultrasonography in the assessment of women with urinary incontinence is therefore not recommended.