Background:
High Detrusor Leak point Pressure has long been believed to cause deterioration of the upper urinary tracts in neurologically affected bladders.(1) After McGuire’s landmark study proposed the cut off of 40 cms.(2), several other workers have shown evidence of upper tract damage at Detrusor Leak Point Pressure (DLPP) significantly less than this figure.(3) Besides, there are other factors (such as severe detrusor overactivity, presence of intravesical obstruction, presence of VU reflux and episodes of urinary sepsis), which are potentially responsible for upper tract damage in such cases.(4) The role of these factors have not been defined clearly yet.   

Aims and Objectives
The main aim of this study was to underline the precise contribution of these factors in the genesis of deterioration of the upper urinary tracts in the patients affected with neurogenic dysfunction of the bladder. An attempt was also made to identify the combination of various urodynamic parameters crucial to produce dilatation of the upper tracts in these patients.

Study Design and Methods :
We recruited 129 consecutive patients retrospectively over a period of 18 months (October 2018 to March 2020). They all had overt neuropathy and were referred for urodynamic evaluation to our centre. 
A complete history was taken including the history of neurologic illness and current urinary symptoms. Voiding diaries could be obtained from only 56 (43.4%) of them. Urine Cultures, biochemical information and recent ultrasound imaging was obtained on all these patients. 
All patients underwent non video invasive Urodynamic Investigation complying with the principles of Good Urodynamic Practice (ICS 2015). 
Bladder sensations, Detrusor compliance, Detrusor Overactivity and Capacity were recorded. DLPP was measured (using two observers) as lowest detrusor pressure required to demonstrate leakage at the meatus, in the absence of active detrusor contraction. End filling pressure and bladder volume at the leak point was recorded. 
Poor Detrusor Compliance was defined as <10 mls/cm H2O.

Results : 
Out of 129 patients who were studied, only 109 patients demonstrated leakage during the storage phase. 
Out of 129 cases, 79 patients showed dilatation of the upper urinary tracts, while 50 patients had normal upper tracts on recent Ultrasound. 
Detrusor Compliance, DLPP, Volume at first leakage and Detrusor Overactivity were documented separately for two groups and are tabulated as under. 
See Tables A (See Document 2)
Among 90 patients with poor detrusor compliance and Neurogenic Detrusor Overactivity, 62 patients had dilated upper urinary tracts (68.9%), leaving 31.1 % of patients having normal upper tracts.

Discussion : 
DLPP of more than 40 cms H2O had been considered as a risk factor for upper tract dilatation for a long time. However some recent studies have shown evidence of upper tract damage at DLPP significantly less than this figure. Our study substantiates this observation, although it also emphasizes that higher the DLPP, greater is the chance of upper tract dilatation.  
Other factors responsible for upper tract dilatation are observed to be presence of neurogenic Detrusor Overactivity. There is a suggestion that high pressure DO is possibly a higher risk factor independent of Detrusor compliance. 
However it must be noted that high pressure DO (as well as high LPP) can be documented only in the presence of either nonrelaxing or spastic urethral sphincter. As such in a case of incompetent urethral sphincter, leakage would occur before the detrusor pressure would rise.

Conclusion: 
Besides a high DLPP, other factors such as presence of neurogenic Detrusor Overactivity and poor detrusor compliance also appear to be important risk factors in the genesis of upper urinary tract dilatation in neurogenic dysfunction of the bladder. 
However, this study reiterates that the maintenance of high detrusor compliance, control of Detrusor Overactivity and treatment of the spastic sphincter obstruction are all essential factors in the better management of the upper urinary tracts in cases of neurogenic bladder dysfunction.

Musco S, Padilla-Fernandez B, Del Popolo G, et al. Value of urodynamic findings in predicting upper urinary tract damage in neuro-urological patients: A systematic review. Neurourology and Urodynamics.2018;37(5):1-19.
McGuire EJ, Woodside JR, Borden TA, Weiss RM. Leak point pressures. Urol Clin North Am. 1996 May;23(2):253-62.
Tarcan T, Demirkesen O, Plata M, Castro-Diaz D. Detrusor leak point pressures in patients with relevant neurological abnormalities. Neurology and Urodynamics. 2017;36(2):259-62.

Continence 7S1 (2023) 100922
DOI: 10.1016/j.cont.2023.100922