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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• 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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Joseph D: J Urol 1992: 147; 444


• 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


• Effect of Varying Filling Rate on Detrusor Overactivity

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CMG with DO – rapid vs slow fill

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• 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


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• 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


A 7 y/o ♂ with frequency, urgency + day & night wetting

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• 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


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• Knowing the Status of the Upper Urinary Tract

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Note detrusor filling & voiding pressures are normal


• What is the True Detrusor Pressure?

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Note the detrusor fill & equilibration pressures

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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


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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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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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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• Accuracy of Patch Electrodes

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CMG + patch EMG –no response to DO

with DO

CMG + patch EMG –response to DO


• Importance of Sphincter Needle EMG

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CMG + patch EMG – ? response to DO / guarding reflex or DSD

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Placement of probes


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



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CMG + needle EMG – assesses sphincter innervation & response to DO


• Patch vs Sphincter Needle EMG

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Is this guarding or DSD 2o tethering of her spinal cord?


• 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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• Accuracy of Sphincter Needle EMG

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Needle EMG:

UDS Helps Explain Radiologic Findings

Normal

Narrowed external sphincter area

Dyssynergy Denervated Fibrosis


• 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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How to Perform & Interpret Proper Urodynamics.revised.9.25 ...

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