how to perform & interpret proper urodynamics.revised.9.25
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How to Perform & InterpretUrodynamic Testing in Children
Stuart B. Bauer, MD
Department of Urology
Children’s Hospital Boston
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• Definition
– Urodynamics is the physiologic study of the lower urinary tract during its 2 phases of the micturition cycle in an attempt to re-create the normal pattern of urinary storage & evacuation
– It involves both invasive & non-invasive testing to assess these functions
– It tries to accomplish this objective in the least intrusive way in order to obtain meaningful & reproducible results
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Urodynamic Studies
• Anatomic– Posterior urethral valves – Vesicoureteral reflux– Bladder exstrophy / epispadias
• Neurologic– Myelodysplasia– Tethered cord syndromes– Sacral agenesis– Spectrum of spastic diplegia
• Functional– Day and nighttime incontinence– Recurrent UTI
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Urodynamic StudiesIndications
• Uroflow
• Uroflow / EMG
• Cystometrogram
• Voiding pressure studies (VPS)
• Cystometrogram / VPS / sphincter EMG
• Cystometrogram / VPS / radionuclide cystogram
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Urodynamic StudiesArmamentarium
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Preforming Meaningful Urodynamic StudiesAsking the Right Question
• What information have you gained so far from ancillary investigation (Hx, PE, imaging)?
• What information do you want to glean from your investigation?
• What study would efficiently answer the question(s) posed?
• Could information be gained from non-invasive versus invasive studies?
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Preforming Meaningful Urodynamic Studies
• Education Preparation– Parental acceptance– Patient understanding– Familiarization with components of study– Providing pre-testing materials (handouts, facility
website)– Touring the facility beforehand (virtual touring)– Discussion with other ‘veteran’ families
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• Definition– The real time measure of a urinary flow curve that
records velocity / second + cumulative voided volume
• Optimal Conditions– Arrive ‘well’ hydrated but NOT overdistended– Bladder scan prior to obtaining flow - estimate size– Flow meter located in a private setting – Boys - instruct ‘aim’ at a specific site– Girls - provide foot support– Girls – adequate sized ‘seat’ for comfortable support
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Neveus T, et al: J Urol 2006; 176: 314-24Austin PF, et al: NeuroUrol Urodynam 2016; 35: 471
Performing Meaningful Urodynamics Urinary Flow Rate
‘random’ aim
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Performing Meaningful Urodynamics Urinary Flow Rate – Eliminating Artifacts
‘directed’ aim
”Aiming” minimizes variations in flow rate
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Performing Meaningful Urodynamics Urinary Flow Rate – Eliminating Artifacts
Foot rests ‘Seat’ opening
Proper posture, adequate foot rest & seat support helps maximize pelvic floor relaxation during voiding
• Volume voided > 50% of expected capacity for age: (EBC [ml] = age [years] x 30 + 30)
• ‘Ideal’ volume ~ between 65 – 115% of EBC
• Residual urine via bladder scan - < 6% of EBC or < 10 ml
• Repeat flow rate to confirm flow characteristics
• Denote time since prior void to get a sense of urine production- Nl production = 1 – 2 ml / kg / hr
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Urinary Flow Rate – Optimal Parameters
Chang S, et al, Neurourol Urodyn, 2013; 32: 1014
• Effect of urine volume – on flow rate parameters
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Urinary Flow Rate – Optimal Parameters
Chang S, et al, Neurourol Urodyn, 2013; 32: 1014
PVR = 12PVR = 32
• Bell-shaped– Smooth rounded flow - normal
• Tower– Explosive flow - 2o OAB
• Staccato– Sharp peaks / troughs– Overactive external urethral sphincter
• Interrupted– Discreet peaks with no flow in between peaks– Underactive bladder with straining to empty
• Plateau– Prolonged slow flow – organic obstruction
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Urinary Flow Rate - Types
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Bell Shaped
Interrupted Plateau
Tower Staccato
Urinary Flow Rate Types - Examples
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Normal Flow Rate
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Predictability of a Flow Rate
Tower Flow –Max = 50 ml / sec
Cystometrogram –Overactive bladder
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Flow Rate Patterns
Interrupted flow Staccato flow
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Quantifying Urinary Flow Rates
Franco I, et al: Neurourol Urod. 2016; 35:836-46Franco I, et al: Neurourol Urod. 2018; 37:1-12
• Created ‘Flow Index’ (FI)
• Reproducible & reliable means to estimate a particular flow in children without the use of a flow nomogram
• Predictive of bell, plateau, & tower flow patterns
• ‘FI’ is a mathematical manipulation that allows for compensation for the increasing variation around the mean with an increasing volume
• FI = Qact/Qest = P⍵act/Pact)/(P⍵est/Pest)
• Flow Index = Actual Qmax / Estimated Qmax
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Bladder Scanner
• Day & night LUT symptoms unresponsive to timed voiding & / or taking time to empty
• Recurrent non-febrile UTI
• Thick-walled bladder on renal / bladder echo or incomplete emptying on post-void echo
• History of straining to void or complaints of prolonged flow or incontinence after voiding
• Recurrent terminal hematuria
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Hoebeke P, et al: J Urol 183: 699, Feb. 2010
Indications for Uroflowmetry
• Ideal test to get a sense of bladder capacity & ability to empty in a non-threatening manner
• Provides clues to bladder function & potential causes of incontinence & / or urinary infection
• Can direct clinician to appropriate next test to confirm type of lower urinary tract abnormality
• May reveal urine production as an etiology for LUT symptoms
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Flow Rate - Conclusions
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Flow rate – slow & prolonged
Flow rate was repeated 3 times with similar findings
Case Presentation
9 y/o ♂ with several weeks of dysuria & two episodes of terminal hematuria
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Case Presentation
What is your next step?a. Refer to Nephrologyb. Renal Ultrasoundc. VCUGd. Retrograde Urethrograme. Flow / Patch EMG looking for dyssynergy
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Case Presentation
What is your next step?a. Refer to Nephrologyb. Renal Ultrasoundc. VCUGd. Retrograde Urethrograme. Flow / Patch EMG looking for dyssynergy
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Retrograde urethrogram – confirmed a stricture
Case Presentation
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• Urinary flow rate combined with patch EMGpads placed on the perineum
• Assesses activity of the urethral sphincter during micturition
• Distinguishes ‘dysfunctional voiding’ from straining to empty
• Directs treatment to biofeedback training versus timed voiding & other measures to improve emptying
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Flow + Patch EMG
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Placement of Patches for Flow / EMG
This ♀ with urgent voiding has confirmed Dysfunctional Voiding
This ♀ with only mild urge to void despite a voided volume 180% of EBC study reflects straining to void or Underactive Bladder
Both suspected of Dysfunctional Voiding (DV)Uroflow /EMG in two 4 y/o girls with LUTS & RUTI
• Staccato or interrupted pattern on initial uroflow
• Incomplete emptying on initial flow rate
• Cystometric evidence of voiding pressure & / or incomplete voiding
• ‘Spinning top deformity’ on VCUG for recurrent UTI
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Indications for Flow + Patch EMG
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• Determines capacity, compliance + presence of overactivity of the bladder during its storage phase
• Emptying (voiding) phase is part of the study
• Performed with bladder + rectal catheters
– Measures characteristics of the detrusor
– Distinguishes overactive contractions from artifacts of motion
• Fill rate / min < 10% of expected capacity
• Natural fill, ambulatory cystometry is ideal but time consuming & impractical
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Performing Meaningful UDS - Cystometrogram Preforming Meaningful Urodynamic StudiesCystometrogram
• Adherence to Protocol– Bowel cleanout 1 - 2 days before– Lower urinary tract modulating medications
• Know what medications, dosage & frequency • Record when taken prior to study• Discontinuation timing if need to know change in
function
– Have family bring favorite toy / video or provide
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CMG Performance• Attention to Detail
– ‘Zero’ transducers– Have child void into flowmeter, if toilet trained– Empty bladder (aspirate catheter after urine stops draining)– Know status of upper urinary tract
• Hydronephrosis & / or hydroureter• Presence of reflux
– Obtain UA & send for culture• Consider delaying study if (+) U/A
– Recheck all connections to pump, transducers– Have child as comfortable as possible when starting– Make sure all channels are recording
• Test with cough, Credé, initially & throughout filling CMG
– Never ‘rush through’ the study
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Cystometrogram Performance
• Importance of Rectal Pressure Monitoring
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Increasing bladder pressure
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Cystometrogram Performance
• Effect of Bowel Cleanout
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CMG without bowel cleanout CMG with bowel cleanout
• Effect of Varying Filling Rates
• 38 pts underwent 3 CMGs– medium (20% EBC / min), slow (2% of EBC / min) then,
medium fill again
• Findings– Detrusor Pr. > 40 cm H2O = occurs twice rate in medium fill
– ∆ in Pr. > 15 cm H2O = only occurred in medium fill
• Conclusion– Bladder filling rate affects detrusor pressure
measurements
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Cystometrogram Performance
Joseph D: J Urol 1992: 147; 444
Cystometrogram Performance
• Effect of Varying Filling Rate
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CMG with rapid fill –20 ml/min
CMG with slow fill –10 ml/min
Joseph D: J Urol 1992: 147; 444
Cystometrogram Performance
• Effect of Varying Filling Rate on Detrusor Overactivity
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CMG with DO – rapid vs slow fill
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Cystometrogram Performance
• Timing of DO – Importance of Early Observation
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CMG with DO early in filling CMG with DO later in filling
• DO can occur anytime – observe thruout the study
• Timing of Adjunctive Bladder Modulating Medicines
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CMG 24 hrs after last med CMG 6 hrs after last med
Cystometrogram Performance
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Cystometrogram Performance
• Importance of Urethral Pressure Measurements
Notice: urethral instability can be a cause for urinary incontinence that may be missed when the child does not have a corresponding overactive contraction
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Case Presentation
How would you read the following cystometrogram & what would you do next?
A 7 y/o ♂ with frequency, urgency + day & night wetting
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Case Presentation
Interpretation & next steps?a. Poorly compliant bladder; initiate reliable
bowel programb. Poorly compliant bladder; begin antimuscarinic
medicationc. Poorly compliant bladder; obtain VCUGd. Poorly compliant bladder; evaluate for
diabetes insipiduse. Poorly compliant bladder; R/O dyssynergy with
Flow / Patch EMG
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Case Presentation
Interpretation & next steps?a. Poorly compliant bladder; initiate reliable
bowel programb. Poorly compliant bladder; begin antimuscarinic
medicationc. Poorly compliant bladder; obtain VCUGd. Poorly compliant bladder; evaluate for
diabetes insipiduse. Poorly compliant bladder; R/O dyssynergy with
Flow / Patch EMG
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Case Presentation
How would you read the following cystometrogram & what would you do next?
A 7 y/o ♂ with frequency, urgency + day & night wetting
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Cystometrogram Performance
• Effect of Low Bladder Outlet Resistance
Notice: good compliance but small capacity bladder when bladder outlet resistance is low
Notice: poorly compliant but larger capacity bladder when bladder outlet resistance is raised with an occlusive balloon
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Case Presentation
A 6 y/o ♀ with urgency, and urge incontinenceHow would you read the following cystometrogram & what would you do next?
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Case Presentation
Interpretation & next steps?a. Normally compliant compliant bladder; initiate
reliable bowel programb. Poorly compliant bladder; begin antimuscarinic
medicationc. Overactive bladder; obtain VCUGd. Overactive bladder; begin antimurcarinic
medicatione. Poorly compliant bladder; consider intradetrusor
botox injections
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Case Presentation
Interpretation & next steps?a. Normally compliant compliant bladder; initiate
reliable bowel programb. Poorly compliant bladder; begin antimuscarinic
medicationc. Overactive bladder; obtain VCUGd. Overactive bladder; begin antimurcarinic
medicatione. Poorly compliant bladder; consider intradetrusor
botox injections
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Case Presentation
A 6 y/o ♀ with urgency, and urge incontinence
How would you read the following cystometrogram & what would you do next?
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• Knowing the Status of the Upper Urinary Tract
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Note detrusor filling & voiding pressures are normal
Cystometrogram Performance
• What is the True Detrusor Pressure?
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Cystometrogram Performance
Note the detrusor fill & equilibration pressures
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Cystometrogram Performance
A: 163/50 = 3.2
B: 100/10 = 10.0
C: 63/40 = 1.6
(∆P/∆V)• Where do you measure compliance?
What is the TRUE Detrusor Pressure
• Equilibrated Pdetrusor at End Filling- Allows Pdetrusor to accommodate to infused volume - Measurement may not be filling-rate dependent- If leakage occurs before cessation of filling, compare the
residual volume to Pdetrusor at that volume of filling
• ‘Opening Pressure’ - Measure of Pdetrusor on initial catheterization before
draining bladder- Compare to Pdetrusor at that same volume during infusion- Represents Pdetrusor under natural filling (from kidneys)- Teach parents of children on CIC to measure at home- Create a Pressure Volume curve over time
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Kaefer M, et al: J Urol 1997; 158:1268 MacQuaid J, et al: Equilibrated bladder pressure… New England AUA, Montreal, Sept 7, 2017
∆
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• What is the True Detrusor Pressure?
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Note the detrusor fill, residual volume & equilibration pressures
Cystometrogram Performance
Pde
tru
sor
Time
Max Pdet(+/- Leak)
Opening Pressure
Pressure at Residual Volume
Equilibration Pressureat End of Filling
2 min
Comparison toEquilibration Pressure
Compare EPEF Volume
to same Fill Volume & Pressure
• Urodynamics Does Not Always Explain LUTS
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Cystometrogram Performance
Physically active teenage girl w stress incontinence, no enuresis or UTIs
Note: normal CMG & normal flow rate with complete emptying
PVR = 0
• Urodynamics does not always explain lower urinary tract symptoms
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Cystometrogram Performance
Physically active teenage girl w stress incontinence, no enuresis or UTIs
Note: as the bladder fills to its capacity there is significant descent of the pelvic floor leading to stress incontinence
PVR = 0
Indications for CMG / Patch EMG
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6 y/o girl with dysfunctional voiding, daily dampness &recurrent UTI
UDS reveals nl capacity,no overactivity & quietingof the sphincter on voiding
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Cystometrogram Performance
• Accuracy of Patch Electrodes
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CMG + patch EMG –no response to DO
with DO
CMG + patch EMG –response to DO
Cystometrogram Performance
• Importance of Sphincter Needle EMG
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CMG + patch EMG – ? response to DO / guarding reflex or DSD
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Cystometrogram Performance
Placement of probes
• Importance of Sphincter Needle EMG
Normal motor units
Polyphasic potentials- evidence for re-innervation
Fibrillations- early sign of denervation
Urethral Sphincter Electromyogram (EMG)
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Urethral Sphincter Electromyogram (EMG)
Bulbocavernosus reflex
Credé response
Bladder filling
Anocutaneous reflex L/R
Valsalva response
Anocutaneous reflex L/R
VoidingVoluntary control
Cystometrogram Performance
• Importance of Sphincter Needle EMG
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CMG + needle EMG – assesses sphincter innervation & response to DO
Cystometrogram Performance
• Patch vs Sphincter Needle EMG
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Is this guarding or DSD 2o tethering of her spinal cord?
Cystometrogram Performance
• Patch vs Sphincter Needle EMG
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Needle EMG: Synergy after a short time
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Indications for CMG / Patch vs Needle EMG
• Indications- Obvious non-neurogenic dysfunction- Specific question regarding sphincter response to DO- Evaluate for 2o spinal cord tethering
• Contra-indications- Evaluating a known / suspected neurologic lesion- Repeating study after spinal cord surgery- Importance of knowing precise sacral spinal cord
function- Evaluation after pelvic surgery
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Cystometrogram Performance
• Accuracy of Sphincter Needle EMG
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Needle EMG:
UDS Helps Explain Radiologic Findings
Normal
Narrowed external sphincter area
Dyssynergy Denervated Fibrosis
Cystometrogram Performance
• Accuracy of Sphincter Needle EMG
CMG Performance• Attention to Detail
– Know the question(s) you hope to answer by UDS– Record every event thruout the study– Look for DO early in filling as child may suppress them later– Encourage child to void
• Run sink faucet, pour warm water on thigh, perineum, toes• Engage parent to work encourage their child• Don’t ‘give up’ easily when child doesn’t want to void
– If no void, record ‘equilibration pressure’ & compare with max detrusor fill pr. at capacity
– Record voided volume & residual urine, to know urine production during the study – compare to volume infused
• Sometimes diuresis during the study can be substantial
– Repeat CMG 2nd or 3rd time to answer the questions posed
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Goals for Urodynamic Studies in Children
• Characterizes lower urinary tract function in an efficient, reliable, reproducible manner
• Enhances understanding of lower urinary tract function in various disease states
• Differentiates between possible treatment alternatives
• Helps promote effective therapy• Explains outcomes with validated measures
By posing & asking the right questions UDS
The End
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