1. 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

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

3. Background
Oracle – “Pee”
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

4. 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).

5. 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

6. 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

7. 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

8. 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

9. 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 ( cm H2O for boys & cm H2O for girls)
Normal voiding

10. 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 ,

11. 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)

12. 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

13. 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)

14. 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

15. 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)

16. 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

17. 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”.

18. 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