ICS TEACHING MODULE Urodynamics in children Part 2 ICS TEACHING MODULE Urodynamics in children Part 2. THE PRESSURE FLOW ANALYSIS IN CHILDREN Jian G Wen MD,Ph.D, Jens C Djurhuus, Dr. Med.Sci, Peter F.W.M Rosier MD, PhD, Stuart Bauer, MD 1. Pediatric UD Center, First Affiliated Hosptial of Zhengzhou University, China 2. Department of Clinical Medicine, Aarhus University,Denmark 3 Department of Urology, University Medical Centre Utrecht, The Netherlands 4. Department of Urology, Boston Children’s Hospital, USA

Pressure flow study: outline Indications Interpretation Technique Background Recommendations Uroflow Pdet EMG Pabd Pves Pressure flow study Conclusions

Background Oracle – “Pee” 1000-2000 B. C. In China Pressure flow study (PFS) is an important tool to evaluate the voiding function in children with lower urinary tract dysfunction (LUTD)/lower urinary tract symptoms (LUTS) PFS is defined as measuring the detrusor pressure & uroflow during the micturition or voiding phase. It begins when the child & the urodynamicist decide that 'permission to void' has been given or when uncontrollable voiding begins This section follows the guideline from ICS & ICCS on Good Urodynamic Practice http://www.ics.org/

Pressure flow study (PFS) PFS has become the gold standard in assessing LUTD/LUTS During PFS Qmax, voided volume & detrusor pressure are recorded During voiding the either detrusor or urethral sphincter may be classified as normal, underactive, or overactive PFS can be obtained subsequent to filling cystometry with no specific additional equipment (apart from a flowmeter).

Indications Congenital malformations of the lower urinary tract (i.e., exstrophy, epispadias ureteroceles, multiple bladder diverticula) The procedure must have an impact on treatment strategies It is undertaken after history taking, physical examination, voiding diaries & uroflow/patch EMG recordings, if these measures do not answer the questions related to causes, nor provide effective management schemes for LUTD

Technique: the setting is the same as in cystometry Intravesical instillation 6F double lumen catheter Pabd Pves Vinfus Pressure  sensor  Water pump Bladder & abdominal pressures are recorded simultaneously Pressure flow study in children Pves Flowmeter

Technique: voiding phase EMG Volume The voiding is initiated when the urodynamicist allows, or when uncontrollable voiding begins During the recording a flowmeter connected to the urodynamic equipment allows flow rate parameters to be juxtaposed against pressure data & correlated with one another T Pabd Pves Pdet ml/s Vol EMG

Technique: parameters recorded during voiding phase Pabd Pves Pdet Qura Time Pabd. void.max Pblad. void.max Pdetr.void.max Qmax Opening time Prevoid pressure Opening pressure The maximum flow rate pressure The terminology of voiding phase

Interpretation: normal voiding detrusor function Normal voiding is achieved by a voluntary, continuous detrusor contraction which leads to complete emptying of the bladder within an acceptable time span If the DSD occurred during the voiding, the Pdetr.void.max is higher than that of adults (118 - 127 cm H2O for boys & 72 - 75 cm H2O for girls) Normal voiding

Interpretation: voiding pressure The mean (SD) for a, post-void residual urine volume b, bladder capacity c, maximum voiding pressure d, detrusor pressure on voiding e, bladder compliance in males (green) & females (red) in children of varying age groups From Wen, et al. British Journal of Urology 1998 81, 468-73

Detrusor underactivity (arrow) Interpretation: detrusor underactivity (DU) DU is defined as a contraction of reduced strength and/or duration, resulting in prolonged bladder emptying and/or a failure to achieve complete bladder emptying within the normal time span. This often results in an increase of PVR on the completion of voiding. Detrusor underactivity (arrow)

Interpretation: acontractile detrusor An acontractile detrusor displays decreased contractile activity during urodynamic assessment Voiding phase Pdet Pves Pabd Acontractile detrusor in a child with neurogenic bladder; urination achieved by increasing abdominal pressure

High voiding detrusor pressure with low Qmax (arrow) Interpretation: voiding phase The voiding efficiency is calculated by functional bladder capacity (Vfun.max.cap) /maximum bladder capacity (Vmax.cap) High voiding detrusor pressures which may be induced by significant resistance as is seen in BOO. Conversely, if urethral resistance is low this may be reflected by a low pressure contraction High voiding detrusor pressure with low Qmax (arrow)

Interpretation: voiding phase Pressure at maximum flow, in combination with corresponding maximum uroflow, give a clinically relevant grading of bladder outlet with obstruction when used in a formula Pdet T ml/s Without obstruction Obstruction

Interpretation: voiding phase DSD during voiding: a sustained or increased response or intermittent changes in urethral sphincter activity during the voiding phase DSD is common in infant boys. High Pdet.void.max in infants or a staccato detrusor pressure curve during voiding indicates the existence of DSD An increased response in urethral sphincter activity during the voiding phase (Arrow)

Post voiding contraction Interpretation: voiding phase A post voiding contraction indicates a detrusor contraction which occurs immediately after micturition has ended. Its clinical relevance is still unclear but it may be related to detrusor overactivity Post voiding contraction Voiding phase A 2.5 months old baby with normal voiding

Interpretation: how to exclude the artifact The parameters of free flow measurement such as the PVR & maximum flow rate are useful tools to be compared with the flow pattern during PFS. If the flow rate & PVR show big difference from that obtained from PFS, it indicates that artifacts may exist. For example, the flow rate was lower & the PVR substantially higher significantly compared to these parameters from the free flowmetry (before catheterization), the PFS results may be not representative of “obstructed”, or “underactive” or “DSD” or “dysfunctional”.

Conclusions PFS is an useful tool to evaluate lower urinary tract function in children Investigators must keep in mind that normal bladder capacity increases with increasing age. DSD is common in infant boys so high Pdetr.void.max is often seen To understand the characteristics in PFS, knowing normal voiding parameters as well as following ICS & ICCS recommendations are the basis of successful testing