Urodynamic investigation usually includes:
- urinary flow study (to assess urine flow rate, voided volume and voiding pattern)
- bladder and perineal ultrasound (to assess residual urinary volume and urethral mobility)
- cystometry (to assess bladder filling, storage and bladder pressures; to diagnose unstable bladdercontractions)
- urethral pressure profile (to measure maximal urethral pressure)
- stress testing (to diagnose urodynamic stress incontinence)
Why is it performed?
Urodynamic assessment is perfotrmed to objectively assess bladder filling (filling, storage and emptying) and urethral function. It is performed to obtain a definitive diagnosis or to eliminate a potential diagnosis.
Once a urodynamic diagnosis is made, appropriate and specific treatment can be implemented. If indicated, cystoscopy may be performed at the completion of the urodynamic investigation.
Which patients should be referred for urodynamics?
- patients with a complex picture of stress incontinence and urge incontinence
- women who have failed conservative treatment
- prior to surgery for stress incontinence
- women who have had previous continence surgery
- patients with symptoms of impaired bladder emptying
- prior to surgery for marked pelvic organ prolapse to exclude occult stress incontinence or impaired bladderemptying
- men with neurological problems
How is urodynamics performed?
Urodynamics is performed using computerised equipment and ultrasound imaging. The purpose of the examination is explained to the patient. The patient is asked to complete a bladder diary prior to urodynamicsassessment. The patient is instructed to attend with a comfortably full bladder.
The patient voids in private, into a toilet attached to a urodynamics computer. Initial flow rate and voided volumeare recorded. Residual urine volume is measured by bladder ultrasonography.
Measuring catheters are then inserted into the bladder and vagina (or rectum). These catheters are very fine (5-French) and generally do not cause the patient discomfort. All catheters used are disposable.
Bladder and urethral pressures are calculated using water-perfused catheters that measure the change in intravesical pressure during bladder filling (cystometry). The bladder is filled with sterile water at room temperature at a constant rate (usually 80 mls per minute, but reduced if the patient presents with symptoms of urethral or bladder pain syndromes) to a maximum bladder volume of 500 mls.
Urethral function is also assessed. The maximum urethral closure pressure is calculated. The calculation of this figure may influence the type of surgery recommended.
At the end of the study voiding studies are repeated, to assess voiding efficiency and residual urinary volume. Voiding pressure is also measured to exclude bladder outlet obstruction.
The results are then tabulated and urodynamics diagnosis made.