Urodynamic Studies How to Perform & Interpret • Definition Urodynamic Testing in Children – 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 Stuart B. Bauer, MD – It involves both invasive & non-invasive testing to Department of Urology assess these functions Children’s Hospital Boston – It tries to accomplish this objective in the least intrusive way in order to obtain meaningful & reproducible results
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Urodynamic Studies Urodynamic Studies Indications Armamentarium • Anatomic •Uroflow – Posterior urethral valves – Vesicoureteral reflux • Uroflow / EMG – Bladder exstrophy / epispadias • Cystometrogram • Neurologic – Myelodysplasia • Voiding pressure studies (VPS) – Tethered cord syndromes • Cystometrogram / VPS / sphincter EMG – Sacral agenesis – Spectrum of spastic diplegia • Cystometrogram / VPS / radionuclide • Functional cystogram – Day and nighttime incontinence – Recurrent UTI
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Preforming Meaningful Urodynamic Studies Preforming Meaningful Urodynamic Studies Asking the Right Question • Education Preparation • What information have you gained so far from – Parental acceptance ancillary investigation (Hx, PE, imaging)? – Patient understanding • What information do you want to glean from your investigation? – Familiarization with components of study • What study would efficiently answer the – Providing pre-testing materials (handouts, facility website) question(s) posed? • Could information be gained from non-invasive – Touring the facility beforehand (virtual touring) versus invasive studies? – Discussion with other ‘veteran’ families
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Performing Meaningful Urodynamics Performing Meaningful Urodynamics Urinary Flow Rate Urinary Flow Rate – Eliminating Artifacts • Definition – The real time measure of a urinary flow curve that ‘directed’ aim ‘random’ aim 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 Neveus T, et al: J Urol 2006; 176: 314-24 Austin PF, et al: NeuroUrol Urodynam 2016; 35: 471 ”Aiming” minimizes variations in flow rate
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Performing Meaningful Urodynamics Urinary Flow Rate – Optimal Parameters Urinary Flow Rate – Eliminating Artifacts Foot rests ‘Seat’ opening • 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 Proper posture, adequate foot rest & seat support - Nl production = 1 – 2 ml / kg / hr helps maximize pelvic floor relaxation during voiding Chang S, et al, Neurourol Urodyn, 2013; 32: 1014
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Urinary Flow Rate – Optimal Parameters Urinary Flow Rate - Types • Bell-shaped • Effect of urine volume – on flow rate parameters – 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 PVR = 32 PVR = 12 – Prolonged slow flow Chang S, et al, Neurourol Urodyn, 2013; 32: 1014 – organic obstruction
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Urinary Flow Rate Types - Examples Normal Flow Rate Bell Shaped Tower Staccato
Interrupted Plateau
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Predictability of a Flow Rate Flow Rate Patterns
Tower Flow – Cystometrogram – Overactive bladder Max = 50 ml / sec Staccato flow Interrupted flow
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Quantifying Urinary Flow Rates Bladder Scanner
• 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
Franco I, et al: Neurourol Urod. 2016; 35:836-46 Franco I, et al: Neurourol Urod. 2018; 37:1-12
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Indications for Uroflowmetry Flow Rate - Conclusions • Ideal test to get a sense of bladder capacity & • Day & night LUT symptoms unresponsive to ability to empty in a non-threatening manner timed voiding & / or taking time to empty • Provides clues to bladder function & potential • Recurrent non-febrile UTI causes of incontinence & / or urinary infection • Thick-walled bladder on renal / bladder echo or • Can direct clinician to appropriate next test to incomplete emptying on post-void echo confirm type of lower urinary tract abnormality • History of straining to void or complaints of •May reveal urine production as an etiology for prolonged flow or incontinence after voiding LUT symptoms • Recurrent terminal hematuria
Hoebeke P, et al: J Urol 183: 699, Feb. 2010
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Case Presentation Case Presentation
9 y/o ♂ with several What is your next step? weeks of dysuria & a. Refer to Nephrology two episodes of terminal hematuria b. Renal Ultrasound c. VCUG Flow rate – slow & d. Retrograde Urethrogram prolonged e. Flow / Patch EMG looking for dyssynergy Flow rate was repeated 3 times with similar findings
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Case Presentation Case Presentation
What is your next step? a. Refer to Nephrology b. Renal Ultrasound c. VCUG d. Retrograde Urethrogram e. Flow / Patch EMG looking for dyssynergy
Retrograde urethrogram – confirmed a stricture
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Flow + Patch EMG Placement of Patches for Flow / EMG
• Urinary flow rate combined with patch EMG pads 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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Uroflow /EMG in two 4 y/o girls with LUTS & RUTI Both suspected of Dysfunctional Voiding (DV) Indications for Flow + Patch EMG
• 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
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
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Performing Meaningful UDS - Cystometrogram Preforming Meaningful Urodynamic Studies • Determines capacity, compliance + presence of Cystometrogram overactivity of the bladder during its storage phase • Adherence to Protocol • Emptying (voiding) phase is part of the study – Bowel cleanout 1 - 2 days before • Performed with bladder + rectal catheters – Lower urinary tract modulating medications • Know what medications, dosage & frequency – Measures characteristics of the detrusor • Record when taken prior to study – Distinguishes overactive contractions from artifacts • Discontinuation timing if need to know change in of motion function – Have family bring favorite toy / video or provide • Fill rate / min < 10% of expected capacity • Natural fill, ambulatory cystometry is ideal but time consuming & impractical
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CMG Performance Cystometrogram Performance • Attention to Detail – ‘Zero’ transducers • Importance of Rectal Pressure Monitoring – Have child void into flowmeter, if toilet trained – Empty bladder (aspirate catheter after urine stops draining) Increasing bladder pressure – 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 Cystometrogram Performance • Effect of Bowel Cleanout • Effect of Varying Filling Rates • 38 pts underwent 3 CMGs CMG without bowel cleanout CMG with bowel cleanout – 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
Joseph D: J Urol 1992: 147; 444
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Cystometrogram Performance Cystometrogram Performance • Effect of Varying Filling Rate • Effect of Varying Filling Rate on Detrusor Overactivity CMG with DO – rapid vs slow fill CMG with rapid fill – CMG with slow fill – 20 ml/min 10 ml/min
Joseph D: J Urol 1992: 147; 444
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Cystometrogram Performance Cystometrogram Performance • Timing of DO – Importance of Early Observation • Timing of Adjunctive Bladder Modulating Medicines
CMG with DO early in filling CMG with DO later in filling CMG 24 hrs after last med CMG 6 hrs after last med
• DO can occur anytime – observe thruout the study
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Cystometrogram Performance Case Presentation • Importance of Urethral Pressure Measurements A 7 y/o ♂ with frequency, urgency + day & night wetting How would you read the following cystometrogram Notice: urethral & what would you do next? 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 Case Presentation Interpretation & next steps? Interpretation & next steps? a. Poorly compliant bladder; initiate reliable a. Poorly compliant bladder; initiate reliable bowel program bowel program b. Poorly compliant bladder; begin antimuscarinic b. Poorly compliant bladder; begin antimuscarinic medication medication c. Poorly compliant bladder; obtain VCUG c. Poorly compliant bladder; obtain VCUG d. Poorly compliant bladder; evaluate for d. Poorly compliant bladder; evaluate for diabetes insipidus diabetes insipidus e. Poorly compliant bladder; R/O dyssynergy with e. Poorly compliant bladder; R/O dyssynergy with Flow / Patch EMG Flow / Patch EMG
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Case Presentation Cystometrogram Performance A 7 y/o ♂ with frequency, urgency + day & night wetting • Effect of Low Bladder Outlet Resistance How would you read the following cystometrogram & what would you do next?
Notice: good compliance but Notice: poorly compliant but small capacity bladder when larger capacity bladder when bladder outlet resistance is bladder outlet resistance is low raised with an occlusive balloon
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Case Presentation Case Presentation A 6 y/o ♀ with urgency, and urge incontinence Interpretation & next steps? How would you read the following cystometrogram a. Normally compliant compliant bladder; initiate & what would you do next? reliable bowel program b. Poorly compliant bladder; begin antimuscarinic medication c. Overactive bladder; obtain VCUG d. Overactive bladder; begin antimurcarinic medication e. Poorly compliant bladder; consider intradetrusor botox injections
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Case Presentation Case Presentation Interpretation & next steps? A 6 y/o ♀ with urgency, and urge incontinence a. Normally compliant compliant bladder; initiate How would you read the following cystometrogram reliable bowel program & what would you do next? b. Poorly compliant bladder; begin antimuscarinic medication c. Overactive bladder; obtain VCUG d. Overactive bladder; begin antimurcarinic medication e. Poorly compliant bladder; consider intradetrusor botox injections
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Cystometrogram Performance Cystometrogram Performance • Knowing the Status of the Upper Urinary Tract • What is the True Detrusor Pressure?
Note the detrusor fill & equilibration pressures Note detrusor filling & voiding pressures are normal
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Cystometrogram Performance What is the TRUE Detrusor Pressure ∆
• Where do you measure compliance? (∆P/∆V) • 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 A: 163/50 = 3.2 residual volume to Pdetrusor at that volume of filling B: 100/10 = 10.0 • ‘Opening Pressure’ C: 63/40 = 1.6 - 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 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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Cystometrogram Performance Cystometrogram Performance • What is the True Detrusor Pressure? • Urodynamics Does Not Always Explain LUTS
Note the detrusor fill, residual volume & equilibration pressures Physically active teenage girl w stress incontinence, no enuresis or UTIs
Max Pdet Comparison to (+/- Leak) Equilibration Pressure
Pressure at Residual Volume Opening Compare detrusor Pressure EPEF Volume Equilibration Pressure P to same Fill at End of Filling Volume & Pressure 2 min PVR = 0 Time Note: normal CMG & normal flow rate with complete emptying
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Cystometrogram Performance Indications for CMG / Patch EMG • Urodynamics does not always explain lower urinary tract symptoms Physically active teenage girl w stress incontinence, no enuresis or UTIs 6 y/o girl with dysfunctional voiding, daily dampness & recurrent UTI Note: as the bladder fills to its capacity there is significant UDS reveals nl capacity, descent of the pelvic no overactivity & quieting floor leading to stress incontinence of the sphincter on voiding PVR = 0
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Cystometrogram Performance Cystometrogram Performance • Accuracy of Patch Electrodes • Importance of Sphincter Needle EMG CMG + patch EMG – ? response to DO / guarding reflex or DSD CMG + patch EMG – CMG + patch EMG – no response to DO response to DO with DO
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Cystometrogram Performance Urethral Sphincter Electromyogram (EMG) • Importance of Sphincter Needle EMG Placement of probes Normal motor units
Fibrillations - early sign of denervation
Polyphasic potentials - evidence for re-innervation
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Urethral Sphincter Electromyogram (EMG) Cystometrogram Performance Bulbocavernosus reflex Anocutaneous reflex L/R • Importance of Sphincter Needle EMG
CMG + needle EMG – assesses sphincter innervation & response to DO Credé response Valsalva response
Bladder filling Voiding Voluntary control
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Cystometrogram Performance Cystometrogram Performance • Patch vs Sphincter Needle EMG • Patch vs Sphincter Needle EMG
Needle EMG: Synergy after a short time
Is this guarding or DSD 2o tethering of her spinal cord?
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Indications for CMG / Patch vs Needle EMG Cystometrogram Performance • Indications • Accuracy of Sphincter Needle EMG - Obvious non-neurogenic dysfunction - Specific question regarding sphincter response to DO Needle EMG: - 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 CMG Performance • Attention to Detail • Accuracy of Sphincter Needle EMG – Know the question(s) you hope to answer by UDS Narrowed external Dyssynergy Denervated Fibrosis – Record every event thruout the study sphincter area – Look for DO early in filling as child may suppress them later Norm – Encourage child to void al • 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 UDS Helps Explain Radiologic Findings • Sometimes diuresis during the study can be substantial – Repeat CMG 2nd or 3rd time to answer the questions posed
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The End Goals for Urodynamic Studies in Children By posing & asking the right questions UDS
• 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
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