urodynamics

1. Urodynamics
Done by Amir saad fazaa
2021

2. NORMAL LUT TWO-PHASE FUNCTION:
Storage & Voiding

3. URODYNAMICS
 1954 Davis
• Dynamic study of transport, storage & evacuation of urine.
• Main goal of UDS: to reproduce pt.'s symptoms and determine their cause by various tests.
 UDS Armamentarium
• Cystometry(most important test), filling cystometry & voiding cystometry
• Uroflowmetry
• Urethral pressure studies
• Pressure flow micturition studies
• Video-urodynamic studies
• Electromyography

4. UDS is most useful when history, physical exam and simple tests are not sufficient to make an accurate diagnosis
and/or institute treatment
• Incontinence:
-recurrent incontinence in whom surgery is planned.
-mixed urge & stress symptoms.
-associated voiding problems.
-pts. with neurologic disorders.
-pts. with mismatch between signs and symptoms.
• Outflow Obstruction: -pt with LUTS, at least uroflow study.
• Neurogenic bladder: -all neurologically impaired patients with neurogenic bladder
dysfunction.
• Children with voiding dysfunction: -kids with daytime urgency and urge incontinence,
recurrent infection, reflux, or upper tract changes

5. Level 1 evidenced-based “indications” for its use are surprising lacking
Clinical role
 • Characterization of detrusor function.
 • Evaluation of bladder outlet.
 • Evaluation of voiding function.
 • Diagnosis and characterization of neuropathy.
Three important rules before starting UDS evaluation:
• 1. Decide on questions to be answered before starting a study.
• 2. Design the study to answer these questions.
• 3. Customize the study as necessary

6. Terminology for Common Urodynamic Terms and Observations According to the
International Continence Society Standardization Subcommittee
Two principal methods of urodynamic investigation exist:
 Conventional urodynamic studies: normally take place in the urodynamic
laboratory involving artificial bladder filling.
 Ambulatory urodynamic studies: a functional test of the lower urinary tract
using natural filling and reproducing the subject’s everyday activities.

7.  Intravesical pressure: the pressure within the bladder.
 Abdominal pressure: the pressure surrounding the bladder; currently it is estimated from
rectal, vaginal, or extraperitoneal pressure or a bowel stoma.
 Detrusor pressure: the component of intravesical pressure created by forces on the
bladder wall that are both passive and active.
 Filling cystometry: the method by which the pressure and volume relationship of the
bladder is measured during bladder filling.
 Physiologic filling rate: a filling rate less than the predicted maximum. Predicted
maximum is the body weight in kilograms divided by 4 and expressed as milliliters per
minute.
 Nonphysiologic filling rate: a filling rate greater than the predicted maximum.

8.  Urodynamic stress incontinence: noted during filling cystometry and defined as the
involuntary leakage of urine during increased abdominal pressure in the absence of a
detrusor contraction. This currently replaces genuine stress incontinence.
 Urethral pressure measurements:
Urethral pressure: the fluid pressure needed to just open a closed urethra.
Urethral pressure profile: a graph indicating the intraluminal pressure along the length of the
urethra.
Urethral closure pressure profile: the subtraction of intravesical pressure from urethral
pressure.
Maximum urethral pressure: the maximum pressure of the measured profile.
Maximum urethral closure pressure (MUCP): the maximum difference between the urethral
pressure and the intravesical pressure.
Functional profile length: the length of the urethra along which the urethral pressure exceeds
intravesical pressure in women.

9.  Abdominal leak point pressure(ALPP): the intravesical pressure at which urine leakage
occurs because of increased abdominal pressure in the absence of a detrusor
contraction.
 Detrusor leak point pressure(DLPP): the lowest detrusor pressure at which urine
leakage occurs in the absence of either a detrusor contraction or increased abdominal
pressure.

10. Urodynamic phases of micturition cycle
 Storage or filling phase
• Cystometrogram (CMG)
• Provocative maneuvers
• ALPP
• Urethral pressure measurements
Emptying
• Voiding pressure - flow study
• Urethral sphincter or pelvic floor electromyography (EMG)
• Post void residual

11. CYSTOMETRY
First introduced 1927
• Measurement of intravesical bladder pressure during bladder filling(measures volume-
pressure relationships).
• Used to assess bladder sensation, capacity, compliance, detrusor activity.
• Bladder access by transurethral catheter, or rarely by percutaneous suprapubic tube.
• Filling medium either gas (CO2) or liquid (water, saline, or contrast material at body temp).
• Liquid cystometry is more physiologic.
• Ideally, filling should be performed in standing position

12. CYSTOMETRY(contd...)
• Bladder filling either by diuresis or filling through a catheter.
• Filling – slow (up to 10 ml/min), physiologic – medium (10 to 100 ml/min) – fast (>
100 ml/min)
 • Children and pts with known bladder hyperactivity require slow fill rates.
 • Reference point:- superior edge of symphysis pubis.
 • All systems should be zeroed to atmospheric pressure.
 • No air bubbles.

13. CYSTOMETRY(contd...)
 • Single Vs multi-channel UDS:
-single: Pves only
-multi: Pves, Pdet, Pabd

14. CMG PARAMETERS
• Intravesical pressure(Pves): Total Pressure within the bladder.
• Abdominal pressure(Pabd): Pressure surrounding the bladder; currently estimated from rectal,
vaginal, or extraperitoneal pressure or a bowel stoma.
• Detrusor pressure(Pdet): Component of intravesical pressure created by forces on the bladder
wall, both passive and active.
• True detrusor pressure = Intravesical pressure - Intraabdominal pressure.(Pdet = Pves-Pabd)

15. • Physiologic filling rate: A filling rate < predicted maximum.
Predicted maximum = body weight in kg divided by 4 and expressed as ml/min.
• Non physiologic filling rate: A filling rate > predicted maximum.
• First sensation of bladder filling: Volume at which patient first becomes aware of bladder filling.
• First desire to void: Feeling during filling cystometry that would lead the patient to pass urine at
the next convenient moment.
• Strong desire to void: Persistent desire to void without fear of leakage.

16. • Compliance: - Relationship between change in bladder volume and change in Pdet
(Δvolume/Δpressure); measured in ml/cm H2O.
- Normal bladder is highly compliant( 40 -120 ml/H2O) , and can hold large volumes at low
pressure.
- Normal pressure rise during the course of CMG in normal bladder will be only 6-10 cm
H2O.
- Decrease compliance < 20 ml/cm H2O, poorly distensible bladder.

17. Impaired compliance is seen in
• neurologic conditions: spinal cord injury/lesion, spina bifida, usually results from increased
outlet resistance (e.g., detrusor external sphincter dyssynergia [DESD]) or decentralization in
the case of lower motor neuron lesions,
• Long-term BOO (e.g., from benign prostatic obstruction),
• Structural changes- radiation cystitis or tuberculosis.
• Impaired compliance with prolonged elevated storage pressures is a urodynamic risk
factor and needs treatment to prevent renal damage.

18. Urgency: A sudden compelling desire to void.
• Normal detrusor function: Allows bladder filling with little or no change in pressure, no
involuntary contractions.
• Detrusor overactivity: Involuntary detrusor contractions during the filling phase,
spontaneous or provoked.
• Storage greater than 40 cm H2O is associated with harmful effects on the upper tract.
• Overactive bladder: storage symptoms of urgency with or without urgency incontinence,
usually with frequency and nocturia.

19. • Abdominal leak point pressure(ALPP): Intravesical pressure at which urine leakage occurs
because of increased abdominal pressure in the absence of a detrusor contraction.
• ALPP is a measure of sphincteric strength or ability of the sphincter to resist changes in
Pabd
• Applicable to stress incontinence; ALPP can be demonstrated only in a patient with SUI.
• There is no normal ALPP, because patients without stress incontinence will not leak at any
physiologic Pabd.
• Lower the ALPP, weaker is the sphincter.
– ALPP<60 cm H2O: significant ISD
– ALPP 60-90 cm H2O: equivocal
– ALPP>90 cm H2O: little or no ISD

20. • Detrusor leak point pressure(DLPP): Lowest detrusor pressure at which urine leakage occurs
in the absence of either a detrusor contraction or increased abdominal pressure (risk with >
40cm H2O).
• Its a measure of Pdet in a patient with decreased bladder compliance.
• Higher the urethral resistance, higher the DLPP, the more likely is upper tract damage as
intravesical pressure is transferred to the kidneys.

22. UROFLOMETRY
• Non invasive study.
• Measurement of the rate of urine flow over time.
• Estimate of effectiveness of the act of voiding along with PVR.
• Influenced by
– effectiveness of detrusor contraction
– completeness of sphincteric relaxation
– patency of the urethra
• 3 methods used – gravimetric – rotating disk – electronic dipstick

24. Recorded variables during UFM study:
• Voided volume (VV in milliliters)
• Flow rate (Q in milliliters per second)
• Maximum flow rate (Qmax in milliliters per second)
• Average flow rate (Qave in milliliters per second)
• Voiding time (total time during micturition in seconds)
• Flow time (the time during which flow occurred in seconds)
• Time to maximum flow (onset of flow to Qmax in seconds)
• Optimal voids 200 to 400cc.
• Voids < 150cc are difficult to interpret.
• Pt. should be well hydrated with full bladder, but not overly distended bladder.
• Should be performed in privacy and pt.encouraged to void in his normal fashion.
• Qmax & shape of curve- more reliable indicators of BOO.
• Qmax- most reliable variable in detecting abnormal voiding.

25.  Normal uroflow curve is bell-shaped
 Flattened pattern: Obstruction
 Interrupted or straining pattern: Impaired bladder contractility, obstruction, or voiding
with/by abdominal straining.

26. Urethral pressure profilometry
• Urethral pressure profile (UPP): a graph indicating intraluminal pressure along the length of
urethra.
• Urethral pressure: fluid pressure needed to just open a closed urethra.
• UPP is obtained by withdrawal of a pressure sensor (catheter) along the length of urethra.

27. UPP Parameters:
• Urethral closure pressure profile is given by subtraction of intravesical pressure from
urethral pressure.
• Maximum urethral pressure is highest pressure measured along the UPP.
• Maximum urethral closure pressure (MUCP) : maximum difference between urethral
pressure and intravesical pressure.( 40- 60cmH2O)
• Functional profile length: length of urethra along which urethral pressure exceeds
intravesical pressure in women.

28. PRESSURE FLOW MICTURITION STUDIES
• Simultaneous measurement of bladder pressure and flow rate throughout the micturition
cycle.
• Best method of quantitatively analyzing voiding function.
• Access to bladder via transurethral or SPC 8F or less.
• Intra-abdominal pressure measured by balloon catheter in rectum or vagina.
• Men should void in standing position, while women seated on commode

29. Indications for pressure-flow studies:
1. to differentiate between pts with a low Qmax sec. to obstruction, from those sec.to poor
contractility.
2. Identify pt.with normal flow rates but high pressure obstruction.
3. LUTS in pt with hx of neurologic disease(CVA, Parkinson’s).
4. LUTS with normal flow rates (Qmax > 15cc/min).
5. younger men with LUTS.
6. Men whom LUTS s/o bladder instability rather than flow disorder.
7. Men with little endoscopic evidence of prostate occlusion

30. VIDEO-URODYNAMICS
• UDS with simultaneous fluoroscopic image of lower urinary tract.
• Equipment and technique: - CMG + PFS same as before but the study is conducted on a
fluoroscopy table, and the filling medium is a radiographic contrast agent.
• clinical applicability:
1. – complex BOO
2. – evaluation of VUR during storage &/or filling.
3. – neurogenic bladder dysfunction
4. – identification of associated pathology
• Primary BNO diagnosis & differentiation from dysfunctional voiding in women: only on VUDS.

32. ELECTROMYOGRAPHY (EMG)
• Study of the electric potentials produced by depolarization of muscle membranes.
• In case of UDS, EMG measurement of striated sphincteric muscles of the perineum is done
to evaluate possible abnormalities of pelvic floor muscle function. • EMG activity is
measured during both filling and emptying.
• EMG is performed via electrodes placed in (needle electrodes) or near (surface electrodes)
the muscle to be measured.

33. Most important information obtained from sphincter EMG is whether there is
coordination or not between the external sphincter and the bladder.
• EMG activity gradually increases during filling cystometry (recruitment) and then
cease and remains so for the time of voiding.
• Failure of the sphincter to relax or stay completely relaxed during micturition is
abnormal.
• In pt with neurologic disease, this is called detrusor-sphincter dyssenergia.
• In the absence of neurologic disease, it is called pelvic floor hyperactivity,or
dysfunctional voiding.

34. URODYNAMIC RISK FACTORS
Following urodynamics findings are potentially dangerous and usually require intervention to
prevent upper and lower urinary tract decompensation:
1. Impaired compliance
2. Detrusor external sphincter dyssynergia (DESD)
3. Detrusor internal sphincter dyssynergia (DISD)
4. High-pressure detrusor overactivity present throughout filling
5. Elevated detrusor leak point pressure (>40 cm H2O)
6. Poor emptying with high storage pressures

35. THANK YOU