1. How toPerform Cystometry
Dr Sarah Knight MA PhD
Clinical Scientist

2. Purpose of Cystometry Definition Principle Aim
Measurement of relationship between bladder pressure and volume
Principle
Clinical study of bladder and urethral function during micturition cycle
Storage Phase – filling cystometry
Voiding Phase – voiding cystometry
Aim
to reproduce patients symptoms and relate them to urodynamic findings to provide a pathophysiological explanation

3. Why, When, Who, How? Why? When? Who? How?
Cystometry can be performed to diagnose a condition, as surveillance, or to determine outcome of an intervention
When?
Conservative methods (voiding diaries/uroflowmetry) have failed to identify problem
Benefits out weigh risk (and cost)
Who?
Can be performed by trained nurses, doctors and clinical scientist – usually requires two people
How?
Hopefully this course will explain!

4. Getting Started Have conservative investigations been performed?
Does the referral state what symptoms the patient has and what the aim of the urodynamics is?
Take your own history and symptoms to ensure they can be reproduced
Explain the procedure to the patient, including risks
Infection, discomfort, bleeding
Verbal or written consent for catheterisation
Try and put patient at ease
Prophylactic anti-biotics?

5. Typical Equipment
Commercially Available Urodynamic Equipment

6. Catheters Fluid filled catheter with external transducer
Separate pressure and filling catheter
Dual lumen catheter
Disposable
External artefacts(tapping lines, filling pump)
Catheter tip transducer
Requires sterilisation
Less prone to external artefact
Costly

7. Parameters Recorded Intra-vesical pressure (Pves) usually in cmH2O
Intra-abdominal pressure (Pabd)
Detrusor pressure (Pdet = Pves - Pabd)
Sensations
Urine flow rate (Qmax)
Voided volume
Residual volume

8. Vesical Pressure Measurement
Aseptic Non-touch Technique for catheterisation
Use of antiseptic lubricant - Optilume ®
Dual lumen catheter – 10 Fr or 6 Fr for paediatrics
Smaller lumen makes it slower to withdraw fluids – may be problem for neurological patients with autonomic dys-reflexia
Separate filling line and pressure line
Piggy back pressure line in eye of filling line
Advance filling line whilst holding pressure line to unhook whilst in patient
If difficult to withdraw fluid, the pressure line may still be in eye

9. Abdominal Pressure Measurement
Non-sterile catheter with open protective balloon over end to prevent blockage by faecal matter
Placed in anal canal at least cm above anal verge
Assessment of anal tone can be made during insertion
Faecal loading can cause rectal contractions which produce artefacts
Can also use a stoma if no anus
Intra-vaginal pressure can also be used

10. Subtraction Cystometry
Purpose of subtracting Pabd from Pves is to remove influence of abdominal pressure from bladder pressure recording.
Without subtraction would be impossible to determine whether bladder pressure rise was due to detrusor contraction or increased abdominal pressure
Patients nearly always ask why they need an extra line in the anal canal – so have a good explanation ready

11. Zeroing Transducers
Ensure lines and transducers well flushed and free from air bubbles
Always zero transducers to atmospheric pressure, not inside patient
For external transducers, ensure placed at level of symphysis pubis

12. Resting Pressures
Ensure Pves and Pabd have been zeroed to atmosphere and transducers are at level of symphysis pubis
Resting pressure of Pves and Pabd may be between 5 and 50 cmH2O
Due to weight of body tissues sitting above abdomen, maybe higher in larger patients, and when standing.
Should be similar in both Pabd and Pves line
Therefore, resting detrusor pressure should be between -5 and 15 cmH2O
Check catheters and subtraction with regular coughs

13. Cough Test for Subtraction
Ask patient to cough and check trace on both Pabd and Pves
Should see an identical rapid rise in both traces giving a very small effect on Pdet.
Possible problems
Lines not flushed- air bubbles
Full rectum
Vesical line in bladder neck or urethra
Different diameter or length tubing

14. Pabd<Pves – try flushing rectal line
COUGH
COUGH
Pdet
Pdet
Pabd
Pabd
Pves
Pves
Pabd<Pves – try flushing rectal line
Phase lag due to different length lines
Pdet
Pdet
Pabd
Pabd
Pves
Pves
Pves not in bladder – reposition catheter
Good subtraction

15. Cough Test - cont If patient can’t cough (spinal cord injury)
Large inhale and exhale
Small press on abdomen
Continue cough test throughout urodynamic test to check subtraction
At least every minute

16. Filling Medium and Rate
Normally use saline at room temperature
Very cold medium can cause instability – ice water provocation test
Video- urodynamics uses radio-opaque medium
Fill rate – fast, medium, slow, physiological
Fast >100 ml/min provocation ↑, compliance ↓
Medium ml/min
Slow <10 ml/min children or neurogenic patients
Physiological – ambulatory urodynamics
Trade off between time available and physiological relevance

17. Patient Position Ask patient what provokes symptoms
Sitting or standing
Neurogenic patients may need to be supine
Voiding should be in normal position
Don’t assume men stand to void
Or women sit
Allow patient some privacy

18. Performing Cystometry
Cystometry effectively divided into 2 tests
Filling Cystometry
Storage Phase of Micturition Cycle
Bladder Function
Urethral Function
Voiding Cystometry
Voiding Phase of Micturition Cycle

19. Bladder Function
Activity
Capacity
Sensations
Compliance

20. Detrusor overactivity
Urethral Function
Continence
Leakage
Detrusor overactivity
Stress incontinence
Urethral Relaxation

21. Bladder Activity during Filling
Normal
Over-active
Detrusor over-activity (DO) can only be diagnosed from urodynamics
Neurogenic detrusor over-activity (NDO) if known neurological cause eg SCI, MS, myelomeningocele
Under-active
cannot be diagnosed from filling cystometry alone, requires voiding cystometry

22. Detrusor Over-activity
Phasic contraction of detrusor which may occur spontaneously or under provocation
Provocation can include
Hand washing
Changing position
Sound of water
Coughing
If detrusor over-activity observed ask about associated sensations
Observe for leakage – urgency incontinence

23. Detrusor Over-activity

24. Bladder Sensations
Unnatural to focus so much on sensations, avoid prompting
First sensation of filling
First desire to void
Strong desire to void
Urgency – Urgency Perception Scale (0-5)
Pain
Also impaired, absent or hyper-sensitive

25. Bladder Compliance
Normal bladder should be able to accommodate a large change in volume with a very small change in pressure – compliant
Compliance measured as change in volume/change in pressure
Normal bladder should be able to hold 400ml with less than 10 cmH2O increase in pressure
Normal compliance <40 ml/cmH2O
Filling rate can reduce compliance especially in neurogenic patients

26. Bladder Compliance

27. Urethral Function
During bladder filling the urethral closure mechanism will be either normal (continent) or incompetent (incontinent)
Urodynamic Stress Incontinence
Leakage of urine in absence of detrusor contraction observed during filling cystometry
Cough or Valsalva manoeuvre
Can be repeated in sitting and standing position
1 (severe), 3 (moderate) and 5 (mild) coughs
May also provoke DO – mixed incontinence

28. Bladder Capacity
Cystometric capacity is bladder volume at end of filling when patient has normal desire to void.
Voided volume + residual
Maximum cystometric capacity (MCC) is bladder volume when patient feels they can no longer hold on to urine, may be harder in neurological patients
Bladder capacity should be compared with that found in frequency and voiding diary

29. Voiding Cystometry Also known as Pressure-Flow studies
Continuous measurement of detrusor pressure during urine flow studies
Only way to determine reason for low flow rate - increased urethral resistance or decreased detrusor contraction
Performed once capacity is reached.
Filling line removed but pressure lines left in situ
Patient asked to void
Cough prior to and at end of test to ensure signal quality

30. Pre-micturition Pdet
Max Pdet
Opening Time
Qmax

31. Uroflowmetry Normal parameters measured as uroflowmetry Qmax (ml/s)
Qtime (s)
Void time (s) (may be longer than Qtime if flow is intermittent
Time to Qmax (s)
Voided volume (ml)
Residual volume (ml)

32. Detrusor Activity during Voiding
Normal
Detrusor contractions to empty bladder with normal flow rate
Under-active
Detrusor contraction unable to empty bladder or flow rate is lower than normal
Acontractile
No measured detrusor pressure change observed
May be difficult to determine whether lack of voiding is due to neurogenic or psychogenic factors (inhibition)
Check for abdominal straining

33. Bladder Contractility
Debate between physiologists and urologists over true meaning
Can be measured using ‘stop test’ during voiding
May not be possible in patients with stress incontinence
May inhibit voiding

34. Urethral Function during Voiding
Normal
Relaxed through voiding
Obstructed
Mechanical
Enlarged prostate, stricture
Normally gives rise to constantly elevated detrusor pressure
Urethral over-activity
Detrusor-sphincter dys-synergia
Dysfunctional voiding
Phasic flow and detrusor pressure

35. Bladder Outlet Obstruction Index
BOOI = – 2Qmax
BOOI > 40 Obstructed
BOOI 40 – 20 Equivocal
BOOI <20 Unobstructed

36. Bladder Voiding Efficiency (BVE)
Ratio of voided volume against total bladder volume
Requires accurate residual volume
Expressed as a %
BVE = 100% complete emptying
BVE = 0% complete retention
BLADDER VOIDING EFFICIENCY =
VOIDED VOLUME * 100
TOTAL BLADDER VOLUME (VOIDED VOL + RESIDUAL)

37. Residual Volume Remove through pressure line, or dual lumen catheter
ACCURACY
Remove through pressure line, or dual lumen catheter
Most accurate, but may not be possible if catheter passed during void
Ultrasound
Do at least 3 measurements
Calculate from difference between infused volume and voided volume
Bladder may not have been empty at start of test
High diuresis, especially if been drinking for free flowmetry

38. Problems during Cystometry
Movement of catheter into bladder neck or sphincter
Complete voiding of catheter
Expulsion of rectal catheter, especially if abdominal straining used
Inhibition of patient due to unusual surroundings
Overfilling of bladder or presence of catheters
Removal of catheter at end of test!

39. And finally…
Did we understand the patient’s history and symptoms to have best chance of useful investigation
? Were symptoms reproduced during investigation
Try and make patient as comfortable and relaxed as possible
? Was the fill and void typical for the patient
Anticipate, understand and reduce artefacts where possible
? Are we sure of quality of traces
Report findings with suggestions for management