Detrusor Pre Leak Point Pressure : A more reliable parameter to predict the risk to the upper urinary tracts?

Yande S1, Joshi M2, Rawal K1

Research Type

Clinical

Abstract Category

Urodynamics

Abstract 325
Open Discussion ePosters
Scientific Open Discussion Session 21
Thursday 30th August 2018
13:25 - 13:30 (ePoster Station 1)
Exhibition Hall
Incontinence Urodynamics Techniques Neuropathies: Peripheral Voiding Dysfunction
1. Ruby Hall Clinic, 2. Crystal Centre for Advanced Urodynamics
Presenter
S

Shirish Yande

Links

Poster

Abstract

Hypothesis / aims of study
Detrusor Leak Point Pressure (DLPP) is a relatively established urodynamic parameter to predict the risk to the upper urinary tracts in patients of Neurogenic Bladder Dysfunction. 
However the parameter is not sufficiently standardized till date. Besides there are potential technical artefacts in its measurement due to the presence of urodynamic pressure catheter in the urethra during measurement. 

We at our centre, have designed a method of measuring the leak point pressure by withdrawing the catheter at the point of leakage and reintroducing it as the leak stops. The pressure measured at this point is the natural bladder pressure to which the upper urinary tracts are exposed to prior to leakage. We called this pressure Detrusor Preleak Point Pressure (DPLPP). 

We would like to study the leak point pressure with both the techniques in atleast 40 consecutive cases referred to our department and then correlate our findings with the result of conventional leak point pressure. This will help us to identify if this new parameters offers better accuracy in predicting the risk to upper urinary tract when compared to conventional parameter.
Study design, materials and methods
This is a prospective study of 42 consecutive cases of neurogenic bladder dysfunction, who were referred for Urodynamic evaluation to our Centre between July 2016 and December 2017. 
Maximum Voided Volume was estimated from the Frequency / Volume Chart. Where Frequency / Volume Chart was not available, bladder capacity was noted from the latest USG report.
A 6F bilumen catheter was introduced after voiding. Residual urine volume was drained and recorded. Filling rate was calculated as (Maximum voided volume / 10) mls / minute of Normal saline at room temperature in supine position. 
Two persons determined the DLPP by watching for leak as the appearance of the fluid drop at the meatus and the recorded pressure simultaneously. This was recorded as the DLPP. 
The bilumen catheter was then gently removed without disconnecting it from the pressure transducer. Fluid from the urethra was then allowed to leak freely onto the flow transducer below. As the leak stopped, the bilumen catheter was reintroduced into the bladder and the pressure at that instant was measured and recorded.  
We called this point DPLPP (Detrusor Pre-leak Point Pressure) and attempted to correlate its values with the conventional DLPP as well as with the upper tract deterioration.
Results
Measured Detrusor Pre-leak Point Pressures (DPLPP) were found to be consistently lower than the conventional Detrusor Leak Point Pressures (DLPP) in 42 patients, although there was a wide variation of pressure differences between the two vales in individual patients. 

Measured DPLPP ranged from 29 cms of H2O to 84 cms. of H2O with a mean pressure of 42 cms. in tese patients, whereas measured DPLPP ranged from 19 cms. of H2O  to 51 cms. of H2O in the same group of patients. All these figures were found to be statistically significant (p value < 0.05 using paired t test). 

Other risk factors like neurogenic detrusor Overactivity, vu reflux, detrusor compliance and overall bladder capacity have also not been found to have a statistically significant correlation to Upper urinary tract dilatation, although upper tract dilatation was noted in all patients who had DLPP greater than 41 cms. of H2O and DPLPP of 26 cms. of H2O.
Interpretation of results
Reliability of measurement of DLPP needs some special considerations. Theoretically the dynamics of the urethra could be altered by the presence of urethral catheter in two ways.

e.	Mechanical occlusion of the urethra and 
f.	Straightening of the urethra by the presence of a rigid catheter.

Since the results of DPLPP have been found to be consistently lower (and statistically significant), this study suggests that the conventional measurement of DLPP may have multiple artifacts in its measurements.
Concluding message
The key point appears to be the pressure inside the bladder and its duration in the 24 hour cycle to which the upper tracts are exposed. 

Detrusor Pre-Leak Point Pressure (DPLPP) is just one more parameter. It promises to have a closer correlation to sustained bladder volumes and pressure that the upper urinary tracts are exposed to. However when used in conjunction with other important parameters like total compliance, vu reflux, Detrusor  Overactivity and bladder capacity it may  potentially add accuracy in prediction of the upper urinary tract deterioration in patients with neuropathic bladders.
Figure 1
References
  1. ICS Teaching Module : Detrusor Leak Point Pressures in Patients with Relevant Neurological Abnormalities TufanTurcan et al. Neurourology and Urodynamics November 2015
  2. Leak Point Pressures : Edward McGuire et al Urologic Clinics of North America Vol 23>Number 2. May 1996
  3. Predictors of upper tract damage in pediatric neurogenic bladder (Accepted manuscript): Prakash R et al : Journal of Pediatric Urology (February 2017)
Disclosures
Funding This investigation was performed as a part of service offered by the Centre. No financial grants or funding was accepted for this study. Clinical Trial No Subjects Human Ethics Committee Institutional Ethics Committee, Poona Medical Fondation Helsinki Yes Informed Consent Yes
28/03/2024 06:20:57