How toPerform Cystometry Dr Sarah Knight MA PhD Clinical Scientist

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

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!

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?

Typical Equipment Commercially Available Urodynamic Equipment

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

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

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

Abdominal Pressure Measurement Non-sterile catheter with open protective balloon over end to prevent blockage by faecal matter Placed in anal canal at least 10-15 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

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

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

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

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

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

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

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 10-100 ml/min Slow <10 ml/min children or neurogenic patients Physiological – ambulatory urodynamics Trade off between time available and physiological relevance

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

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

Bladder Function Activity Capacity Sensations Compliance

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

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

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

Detrusor Over-activity

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

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

Bladder Compliance

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

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

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

Pre-micturition Pdet Max Pdet Pdet@Qmax Opening Time Qmax

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)

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

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

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

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

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)

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

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!

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