There Are 3 Main Parts to The Urodynamics:
- Vaginal Ultrasound
- Voiding Study (Uroflowmetry, Postvoid Residual)
1. Vaginal Ultrasound
This occurs before and after emptying the bladder but can occur at other times in the urodynamics, seeking all the above information and, at times, other possible findings.
2. Voiding Study
The bladder is emptied on a special toilet where the urine flow rate (speed of emptying) is recorded as well as the volume emptied (voided volume). This test is called uroflowmetry. Professor Haylen’s charts, the Liverpool Nomograms (references 16 and 21 in the publication section), used widely around the world, will be used to determine whether the urine flow was at a normal rate. A centile number is determined. Around 50 is the mean. Above 50 is faster and below 50 is slower. Under 10 is abnormally slow. Above 90 is very fast.
b) Postvoid residual assessment (PVR)
In 1988, then Dr Haylen developed the use of vaginal ultrasound to measure bladder volumes in particular any urine remaining after bladder emptying (postvoid residual – reference 8, 11, 12, 14 in publication section). This has replaced urethral catheterisation for this assessment. Thirty millilitres (30mls) is the upper limit of normal from residuals from Associate Professor Haylen’s studies. Under 30mls are the residuals of 95% of normal women and 87% of women seeing him with bladder symptoms.
Over 30mls longer-term residual, the chances of recurrent urinary tract infections increases significantly.
Image of postvoid residuals and 65ml by transvaginal ultrasound, reducing to 4ml with a subsequent attempt at voiding.
These are crucial studies to measure “true” pressure in the bladder during bladder filling and emptying. Two separate pressures are needed: bladder and rectal. Very fine pressure tubes are necessary. Discomfort with this examination is generally brief and minor.
Information from this study includes:
a) Bladder capacity
b) Bladder sensitivity
c) Normal and abnormal bladder contractions (spasms)
d) Unusual bladder discomfort or pain on filling
Example of a cystometry trace that Professor Haylen will interpret during the clinical assessment.