basics of Urodynamic tests for lower urinary tract obstruction and incontinence.pptx

describes basics of urodynamics and tests

1. Urodynamics Egizeru Enedalew, GSR2

2. What is urodynamics? Urodynamics is a study that allows the direct assessment of lower urinary tract (LUT) function by the measurement of relevant physiological parameters. This assessment includes several types of studies including bladder diaries, free uroflowmetry, and post- void residual measurement, pad weight tests, filling cystometry , and voiding pressure/ flow studies. Types of urodynamics Based on the above definition, urodynamics can therefore be divided into two main types: ( i ) Non- invasive (ii) Invasive 2

3. Non- invasive urodynamics includes bladder diaries, pad weight testing, and free uroflowmetry. These are cheap, easy to do, and most importantly non- invasive, therefore do not cause any side effects to patients. They also form part of the basic assessment of patients presenting with lower urinary tract symptoms (LUTS), in addition to a full thorough history, including assessment of the effects on quality of life, focused clinical examination, and a urinalysis to look for infection, blood, glucose, and so on. 3

4. It is important to mention that although pad weight testing, to categorize the severity of urinary incontinence, may be a useful tool, it is not recommended by NICE as there is no consensus as to what a specific increase in pad weight implies and whether it would affect the treatment decision. Also, there is no agreement as to what constitutes mild, moderate, or severe incontinence, and it does not correlate with an invasive urodynamic diagnosis, and therefore has no implication on the decision of the type of surgical management. The International Continence Society (ICS) has standardized the methodology for a short one- hour pad test with <2 g urine loss being a negative test. There are also longer pad tests lasting 24 hours or more. 4

5. Classification Invasive urodynamics can be divided into: 1. Basic (a) filling cystometry (b) voiding pressure/ flow studies 2. Complex (a) videourodynamics (b) urethral function studies 3. Advanced (a) ambulatory urodynamics (b) neurophysiological testing 5

6. Principles of good urodynamic practice Urodynamics should start by formulating a urodynamic question for example why are you doing the test and what are you looking for? Before urodynamic studies are undertaken, it is recommended that a detailed history is taken, allowing the experienced clinician to tailor the investigation to the needs of the patient. Clinical assessment includes neurological testing, abdominal palpation, and rectal and vaginal examination (in women). With these findings established, the most appropriate urodynamic investigation can be selected. 6

7. Good urodynamic practice depends on: ◆ Having the appropriate indications for the test ◆ Performing the correct type of urodynamic test ◆ A first- rate technique ensuring good quality control ◆ Good and accurate interpretation of the results ◆ Conveying the important results in an accurate and relevant manner through good reporting, which could be understood by others and used in the future for comparison purposes in patients who may need repeat invasive urodynamics 7

8. Aims of invasive urodynamics The main aim of urodynamics is to reproduce the patient’s symptoms with a view to giving more information about the function of the bladder and urethra, or a diagnosis, on which management depends. In other words, the test should only be performed if it is going to change the management of a patient’s condition and should not be conducted unless conservative and medical therapy has been tried. The aims of the test include: ◆ Defining bladder and urethral function ◆ Providing a precise diagnosis ◆ Defining the most significant abnormality ◆ Allowing selection of the most appropriate treatment ◆ Predicting potential postoperative problems ◆ Assessing the results of treatment 8

9. Indications for invasive urodynamics ◆ Equivocal and/ or uninterpretable flow rates ◆ Incontinence not responding to conservative and medical therapy with a view to proceeding to more invasive treatments ◆ Diabetic and neurological patients to assess the compliance of the bladder and assess LUT function in greater detail to allow appropriate management ◆ Children and young patients who suffer with lower urinary tract dysfunction (LUTD) and not responding to conservative or medical therapy ◆ Large residuals, to try to define the cause of the residuals (i.e. is it the bladder or the urethra causing the problem and if there is any treatable cause) ◆ Persistent bothersome LUTS not responding to conservative or medical treatment ◆ Postoperative LUTD , such as bothersome incontinence after insertion of a mid- urethral sling ◆ When things don’t add up! For example, if a patient is complaining of incontinence, but is unable to distinguish between stress or urgency incontinence with no response to medical treatment 9

10. Physics of urodynamics Urodynamic studies aim to look at four things: ◆ How the bladder is behaving during storage and voiding ◆ How the urethra is behaving during storage and voiding Before understanding the physics of urodynamics, it is important to understand what normal LUT function is. During bladder filling, continence should be maintained, and this depends on detrusor relaxation and continuous urethral closure despite intravesical pressure changes. Detrusor muscle relaxation starts at the end of voiding and requires a normal bladder wall composition, which depends on the viscoelastic properties of the detrusor muscle and the inhibitory effect of the sympathetic nerves on the parasympathetic ganglion. Urethral closure is maintained by the bladder neck (proximal sphincter), distal sphincter mechanism, and voluntary pelvic floor contraction. During filling, there is relaxation of the inner longitudinal smooth muscle, contraction in the intraurethral striated muscle with periurethral support from the striated muscles of the pelvic floor and collagen of the endopelvic fascia. 10

11. For efficient voiding to occur , there needs to be urethral relaxation with normal urethral geometry and adequate expulsive force by bladder contraction. The urethra relaxes during voiding due to pelvic floor relaxation, relaxation of the urethral rhabdosphincter (intraurethral striated muscle), urethral shortening (contraction of inner longitudinal muscle), and funnelling of the bladder neck. There should also be a sustained detrusor contraction to generate the pressure to void. Sometimes voiding is achieved by the straining of abdominal wall muscles and the diaphragmatic muscle. In simple terms, flow takes place when the driving pressure exceeds the opposition to flow. Abnormalities in this function could lead to dysfunction of the LUT, which may or may not cause bothersome symptoms. 11

12. Therefore, flow rate alone is not enough to diagnose these problems and you need to measure bladder pressure as well, both while the patient is filling up (to detect overactivity), and when they are voiding (to measure bladder contraction). To measure the flow rate (Q) and voided volume (VV), a flow meter is used. VV is usually measured in millilitres (mL), while Q is measured in millilitres per second (mL/ s). Pressure in the bladder is measured using a pressure transducer, which converts a pressure to an electrical signal. 12

13. Since the bladder is not readily accessible to the outside world, the transducer is allied to a catheter. The most used systems are the fluid- filled catheters with external transducers. The pressure in the bladder (vesical pressure, pves ) has contributions from the bladder detrusor muscle ( pdet ) and from the abdominal pressure ( pabd ). It is not possible to measure pdet directly, and therefore to determine the pressure due to the bladder muscle alone ( pdet ), it is necessary to subtract the abdominal contribution. Abdominal pressure ( pabd ) is normally measured in the rectum, but can also be measured in the vagina, or via a stoma. The measurements are done during both bladder filling and voiding. 13

14. Filling cystometry Normal resting pressures in the intravesical bladder ( pves ) and intra-abdominal rectal ( pabd ) lines should be in the positive range +5 to +50 cmH2O (depending on body position and habitus) the resting detrusor pressure ( pdet ) should be between 0 and +10 cmH2O however, in clinical practice it can usually range from – 5 to +10 cmH2O.5 14

15. Patient position Filling cystometry should be done in the upright position , because ( i ) this is the physiological position, and (ii) because most patients complain of symptoms when upright and active. Women are therefore filled sitting on a commode with a flow meter situated below it to measure any leakage of urine during the test, and because most women void when sitting down. Men, on the other hand, are filled standing with the penis hanging over the flow meter, but not touching it. Filling patients in the supine position might miss detrusor overactivity in at least 30% of patients . 15

16. Measure at supine position , if there is severe detrusor overactivity that prevents filling, even at a reduced rate (10– 20 mL/ min), then the patient can be moved to Reduced mobility or severe disablement of patients (e.g. by neurological disease) Resting values for abdominal ( pabd ) and intravesical ( pves ) pressures depending on position: ◆ supine 0− 20 cmH2O ◆ sitting 15– 40 cmH2O ◆ standing 30– 50 cmH2O. 16

17. Filling medium and rate Filling medium H2o and normal saline at room or body to Filling rates Previously, three filling rates were defined by the ICS: ◆ Slow- fill: cystometry up to 10 mL/ min ◆ Medium- fill: cystometry between 10 and 100 mL/ min ◆ Fast- fill: cystometry when the rate is greater than 100 mL/ min 17

18. Currently, the term ‘ non- physiologic filling rate ’ is being used, and the precise filling rate should be stated. We recommend a filling rate of 50 mL/ min, which , although convenient in the setting of a busy urodynamic unit, is not so fast as to be grossly unphysiological; it also allows time to discuss symptoms with the patient and to assess whether those symptoms have been successfully reproduced. In a patient with very marked detrusor overactivity, the rate can be reduced to 30 mL/ min or lower. The upper limit of physiological filling is defined as: Filling rate (in mL/min)= Body mass, in kg÷4 18

19. Slower filling rates are indicated in patients with neurogenic bladders. Rapid filling is rarely used but can be a further provocative test for detrusor overactivity. The test and all side effects (e.g. risk of urinary tract infection) should be fully explained to the patient, and the importance of indicating any bladder sensations during the test, as they happen, should be emphasized. The symptoms can then be used to annotate the cystometry trace and help with interpretation. Before cystometry is performed, the patient undergoes free uroflowmetry. Any residual urine on subsequent catheterization is then measured. 19

20. A. Filling phase The filling phase starts when filling commences and ends once the patient is given permission to void by the urodynamicist . Assess the ff: Bladder sensation Detrusor activity Bladder compliance Bladder capacity, and Urethral function 20

21. 1. Bladder sensation During the filling phase the patient is asked to indicate the following: ◆ first desire to void (FDV)— this sensation may not be truly representative, owing to the interfering presence of the catheter; ◆ strong desire to void (SDV ); ◆ urgency (sudden compelling desire to void). Other terms that are also used during filling cystometry and related to bladder sensation include first sensation of bladder filling, bladder pain, and bladder sensation, which can be categorized as increased, normal, reduced, absent, or non- specific (seen mainly in neurological patients). 21

22. Bladder hypersensitivity It was defined as a condition where there is an early FDV at less than 100 mL and this persists and worsens, limiting the bladder cystometric capacity to 250 mL. This term has now been replaced with the term ‘increased bladder sensation ’, which is an early first sensation of bladder filling (or an early desire to void) and/ or an early strong desire to void, which occurs at low bladder volume and persists. The new term is subjective and thus it is not possible to quantify volumes. 22

23. 2. Detrusor activity Detrusor activity is described as either ‘ normal’ or ‘overactive ’. A normal detrusor allows bladder filling with little or no change in pressure with no involuntary phasic contractions occurring during cystometry , despite provocation. The presence of involuntary phasic detrusor contractions, occurring throughout filling, is diagnosed by detecting a rise in the detrusor pressure line (there is no lower limit for the amplitude of an involuntary detrusor contraction) and a similar rise in the vesical line with no rise in the abdominal line during filling cystometry . The patient should be asked whether there is any associated urgency and if the sensation mimics the one that is normally experienced and causes problems. Precipitating factors such as coughing or running water, used to provoke symptoms, may also induce detrusor overactivity, and should be annotated on the trace (Fig. 3.2.7). 23

24. If the detrusor is shown during cystometry to contract spontaneously or with provocation, then it is said to have phasic detrusor overactivity. Some patients will not experience any symptoms at the time of these contractions, in which case the significance of detrusor overactivity is unknown. If a single involuntary detrusor contraction occurs at the end of filling, with no overactivity during filling, then this is known as terminal detrusor overactivity , and if associated with incontinence it is known as detrusor overactivity incontinence. When there is a known neurological condition (e.g. multiple sclerosis), any detrusor overactivity observed is termed neurogenic detrusor overactivity (this replaces the older term of detrusor hyperreflexia). Detrusor overactivity is idiopathic if there is no identified cause. 24

25. 3. Bladder compliance The term bladder compliance describes the relationship between change in bladder volume and detrusor pressure (ΔV/ Δpdet ) and is measured in mL/ cmH2O. As a normal bladder fills, there is very little or no change in the pressure (i.e. the bladder is a low compliant system). As filling rates can alter bladder compliance, the filling rate of cystometry must always be documented. In neurologically normal patients, reduced compliance is usually artefactual owing to the bladder being filled excessively fast. Should compliance start to rise during filling, the filling should be stopped for approximately one minute to see if the compliance returns to normal: if compliance returns to normal, the increase is artefactual and secondary to fast filling; if compliance does not return to normal, then it is secondary to a pathological condition. In non-neurological patients, up to 1 cmH2O detrusor pressure increase per 40 mL is acceptable , and in neurological patients up to 20 mL/ cmH2O is acceptable. 25

26. 4. Urethral function During the filling phase, in normal patients , the urethral closure pressure remains positive (i.e. it is greater than the intravesical pressure), even at times of increased intra- abdominal pressure; hence, continence is maintained. To allow voiding, closure pressure falls as the urethra relaxes. If involuntary loss of urine is observed without detrusor overactivity, then the urethral closure mechanism is said to be incompetent. A diagnosis of urodynamic stress incontinence can be made if leakage is associated with an increase in intra- abdominal pressure that causes the intravesical pressure to exceed the intraurethral pressure in the absence of a detrusor contraction. When filling volume reaches 200 mL, filling is stopped, and the patient is asked to strain (Valsalva manoevre ) and then to cough to observe any leakage. These two manoeuvres increase intra- abdominal pressure above urethral closure pressure, and if there is an incompetent urethra, the patient will leak. 26

27. B. Voiding pressure/ flow studies Voiding pressure flow studies (PFS) are done at the end of the filling phase, when the patient is given permission to void. All patients should have an attempt at voiding if they are undergoing filling cystometry . PFS are most useful in the assessment of: ◆ Bladder outlet obstruction ◆ Dysfunctional voiding ◆ Preoperatively, for assessment of the voiding phase in patients having surgery for stress incontinence ◆ Incomplete bladder emptying/ large post- void residuals ◆ Neurological lower urinary tract dysfunction 27

28. Two key elements are assessed during voiding PFS: ◆ Detrusor pressure at maximum flow ( pdetQmax ) ◆ Maximum urine flow rate (Qmax) To assist near physiological normal voiding values, it is recommended that male patients void in the standing position, and women void in the seated position. 28

29. Technique ◆ The bladder is filled to normal capacity when the patient says the bladder is full. This should be done in conjunction with the bladder diary/ frequency volume chart, for normal average voided volumes during the day. ◆ Remove the single lumen filling catheters prior to voiding, leaving the single lumen pressure line or 16 G catheter in situ ( pves ). If the double lumen catheter is used, then there is no need to remove it prior to voiding ◆ Ask the patient to perform a single cough (quality control check) just before voiding to make sure the pressure line ( pves ) has not been displaced during catheter removal at the end of filling. ◆ Permission is then given to void — it is normal practice to leave the room at this point to allow the patient privacy. Voiding can sometimes be inhibited if the patient is not left alone to void. ◆ Ask the patient to do a single cough (quality control check) after voiding to make sure the pressure recording is accurate. ◆ Remove the pressure lines ( pves and pabd ). 29

30. ◆ If indicated (i.e. the patient voids less urine than you infused during filling), check residual urine. This can be done using the double lumen catheter if one is used, or by an ultrasound bladder scan. If the residual is high, the bladder may need to be emptied by an in/ out catheterization. Please note that if a double lumen catheter is used for filling, it should not be removed until after the pressure flow study is completed. We would recommend no greater than a size 6 Fr catheter in male patients to reduce the risk of obstruction during voiding. 30

31. Normal values during PFS: Male • pdetQmax = 40– 60 cmH2O • Qmax >15 mL/ s • Voided volume >150 mL Female • pdetQmax = 20– 40 cmH2O • Qmax >18 mL/ s • Voided volume >150 mL These baseline values should be interpreted in combination with the voiding time, flow pattern, assessment of post- void residual, and patient’s age. 31

32. Complications and difficulties ◆ Patient unable to void— may be related to environment or over-filling the bladder ◆ Catheter voided before Qmax is reached— PFS may need to be repeated ◆ Difficulty in removing vesical pressure ( pves ) line ◆ Technical difficulties with equipment (e.g. poor pressure transmission) ◆ Infection (2– 3%): antibiotics are not Routinely indicated ◆ Bleeding ◆ Discomfort from the catheters 32

33. Pressure flow analysis In men, two important indices need to be calculated: Bladder outlet obstruction index (BOOI )— Previously known as the Abrams- Griffiths number = pdetQmax − 2 × Qmax • BOOI >40 Obstructed • BOOI 20– 40 Slightly obstructed (Equivocal) • BOOI <20 Unobstructed (ii) Bladder contractility index (BCI) = pdetQmax + 5 × Qmax • BCI >150 Strong contractility • BCI 100– 150 Normal contractility • BCI <100 Weak contractility 33

34. In women there are no standardized nomograms and therefore it is more of a clinical judgement as to whether a woman has an underactive bladder or not, or whether she has obstruction or not. In general, a voiding pressure of less than 20 cmH2O with a Qmax of less than 12 mL/ s is regarded as an underactive bladder in women, depending on age and a Qmax of less than 12 mL/ s and pdet more than 40 cmH2O is obstructed. 34

35. 35

36. Advanced urodynamics 1. Videourodynamics Its indications include: ◆ Neurological patients including dysfunctional voiding ◆ Incontinence following anti- incontinence surgery ( e.g post- colposuspension ) ◆ Urinary incontinence after radical prostatectomy in men ◆ Anatomical abnormalities ◆ Paediatric patients ◆ Young men (<50 years old)— as they are unlikely to have benign prostatic obstruction 36

37. Urethral function tests The aim of these is to assess urethral function Performed in the following patient groups: ◆ Dysfunctional voiding ◆ Neurological ◆ Incontinence (e.g. prior to stress incontinence surgery or in post-prostatectomy patients) 37

38. There are two main urethral function tests: Urethral pressure profiles (UPPs) and Leak point pressures (LPP). LPP is the detrusor pressure or the intravesical pressure ( pdet or pves ) at which involuntary expulsion of urine from the urethral meatus is observed. Most UPPs are undertaken using the Brown and Wickham technique, which involves slow fluid perfusion (2 mL/ min) through a single lumen urethral pressure profile catheter. Resting bladder pressure is continuously monitored, either through a bladder pressure line (preferable option) or a pseudo- pressure abdominal or vaginal line. The UPP catheter is withdrawn at a rate of 1 mm/ sec. Continuous pressure measurement is taken to record the following pressure measurements 38

39. ◆ Maximum urethral closure pressure (MUCP) = maximum urethral pressure (MUP) minus resting bladder ( pves ) pressure ◆ Functional profile length— this is the urethral length from the start of the UPP to the MUP in men, and the full length of the profile (start to end of UPP) in women. UPP depends on patient position, volume of fluid in the bladder, pressure recording catheter used, and its orientation within the urethra. 39

40. There are two main types of leak point pressures : Detrusor (DLPP) and abdominal (ALPP). DLPP is the lowest pressure at which urine leakage occurs in the absence of either a detrusor contraction or increased abdominal pressure and applies mainly in patients with low compliance bladders. ALPP is the intravesical pressure at which urine leakage occurs due to increased abdominal pressure in the absence of a detrusor contraction. ALPP can be divided into Valsalva (VLPP) or cough (CLPP) leak point pressures. 40

41. ALPP is performed during filling cystometry : with the patient in the upright position, once the bladder is filled to 200 mL. The patient is asked to cough and perform Valsalva manoeuvres with increasing pressures by increments of 20 cmH2O, starting from 40 cmH2O up to 120 cmH2O. If the patient does not leak, ALPPs are performed every 100 mL after that until capacity. If the patient fails to leak and they are complaining of stress urinary incontinence, the filling line is removed at capacity and they are asked to perform different provocative manoeuvres such as jumping, squatting, running on the spot, and so on to try to make the patient leak and reproduce their symptoms. 41

42. In women who suffer with stress urinary incontinence, the normal value for MUCP is 92— age. An MUCP of less than 20 cmH2O is indicative of ISD. This low MUCP is equivalent to an ALPP of less than 60 cmH2O. If ALPP is greater than 90 cmH2O, then that indicates stress incontinence secondary to urethral hypermobility. There is level 2 evidence, with grade B recommendation, for the use of UPPs and LPP. They can be helpful in certain circumstances, particularly in distinguishing between ISD and urethral hypermobility, in women with stress urinary incontinence. This may then allow the clinician to decide as to what type of anti- incontinence procedure the patient should have. 42

43. UPPs could also be helpful in patients with an artificial urinary sphincter to measure the closure pressure of the device and see if it is still the same as when it was implanted, and in patients who complain of leakage after sphincter insertion. Nonetheless, UPPs and LPPs should not be used as single factors on their own to grade the severity of incontinence, and their results should be judged in relation to other urodynamic tests (such as filling cystometry ) and to the clinical examination. They may help to judge the severity of incontinence, or to further ‘subcategorize’ patients with stress (predominant) incontinence. The ICS have produced a standardization document on how UPPs should be done and measured. 43

44. Thank you 44