Parkinson’s disease (PD) is a chronic neurological syndrome that affects the basal ganglia with a consequent decrease in dopaminergic function. Detrusor overactivity is the most common Lower Urinary Tract Dysfunction (LUTD) due to the disinhibition of the voiding reflex because of this decrease in dopaminergic function. Another LUTD associated with PD is sphincter bradykinesia. Defined by ICS as impaired and hindered relaxation of the sphincter during voiding attempt resulting in delay of urine flow. This dysfunction has been described in up to 11% of symptomatic PD patients. 
In men with PD this condition may coexist with benign prostatic hyperplasia (BPH). This condition may worsen or mimic a functional BOO in these patients and produce a complicated clinical picture that requires urodynamic testing for clarification and appropriate treatment decisions [ ].
External sphincter electromyography (EMG) can study external sphincter function during voiding and diagnose DRUE by showing increased bioelectrical activity of this muscle during voiding. However, this technique cannot measure the biomechanical impact of this phenomenon on voiding function.
According to the model of collapsible urethra, Schaeffer [ ] described a urodynamic parameter called passive urethral resistance relationship (PUUR) to measure urethral resistance and therefore the presence of BOO during voiding. This author also defined a second urethral resistance parameter called Dynamic Urethral Resistance Relationship (DURR) to describe urethral behaviour when it is not completely relaxed. 
Virseda et al. [  ] proved that the DURR parameter has two different patterns that allow us to differentiate between the organic or static obstruction of patients with BPH and the dynamic or functional obstruction of spinal cord injury patients. Our hypothesis is that this parameter can also differentiate between organic and functional BOO in men with PD. Therefore, our objective is to study the distribution of DURR patterns in males with PD and BOO and compare it with its distribution in men with BOO due to BPH.

A case-control study was carried out. To calculate the required sample size, we used the data published by Virseda et al [3]. these authors observed that 83% of BPH patients had a DURR type B compared to only 4% of patens with spinal cord injury. Extrapolating these results to our study a minimum of 14 patients would be necessary, to reach a two-sided significance level of 95%, and a statistical power of 80%.
The total number of patients included in the study was 44 males, divided into two groups of 23 each. Group 1 (cases) consisted of patients with Parkinson disease according to standard criteria, and BOO, while Group 2 (controls) was made up of patients with BPH and BOO. The inclusion criteria for patients in Group 1 were: stable Parkinson Disease with an evolution time of at least four years and a Urethral Resistance Factor (URA) greater than 29 cm H2O. For patients in Group 2, the inclusion criteria were: Aged over 49 years, no neurological impairment, LUT functional symptoms, enlarged prostate on ultrasound or digital rectal examination, URA value greater than 29 cm H2O, and a compressive obstruction (minimum opening pressure greater than 35 cm H2O). Patients who urinate with the aid of abdominal straining were excluded to avoid artifact because this is a cause of type A DURR.
A urodynamic study was then carried out with a Solar polygraph (MMS, Enschede, Holland) according to the specifications of the International Continence Society (ICS) and the protocols of Good Urodynamic Practices (GUP). The perineal EMG activity in these patients was recorded using anal electrodes. The detrusor pressure and voiding flow rate values were analysed using the computer program incorporated in the urodynamic equipment, obtaining the urethral resistance parameters: Bladder Outler Obstruction Index (BOOI), URA and urethral opening pressure and the detrusor contractility values: Wmax and W80-20. This computer program also enables the parameter DURR to be presented graphically. 
From the DURR graphs calculated by the program, we defined two patter types of DURR according to Virseda et al. Pattern A: characterized by at least three spikes with the intermediate spike larger than the initial or final spikes. Pattern B: characterized by two large initial or final spikes, intermediate spikes are allowed provided that their size is small (figure 1).

The comparison between groups is shown in table 1. We observed a statistically significant difference in terms of the type of DURR. Patients with PD had significantly more DURR type A than BPH patients (70% versus 1%). However, the percentage of patients with increased EMG activity during voiding was similar in both groups. There was no relationship between EMG activity and the type of DURR pattern (p=0,191)

The most difficult thing is to find the cause of BOO in PD patients. In our study we found that perineal EMG was unable to distinguish between functional or organic obstruction. However, we found a significant difference in DURR pattern between PD and BPH patients. Pattern A which is characteristics of functional obstruction was significantly more frequent among PD patients. Only one patient with BPH had this pattern. Pattern B which is characteristic of organic obstruction was shown in only 32% of these patients and in 96% of patients with BPH.
DURR measures the increment of urethral resistance due to muscular activity of the urethra during. This activity comes from two sources: a delayed smooth muscular relaxation of bladder outlet due to increased sympathetic stimulation, and an external sphincter contraction during voiding. These increments are represented on the DURR graph by an initial or final spike (pattern B) in case of delayed smooth muscle relaxation, or by multiples spikes during voiding (pattern A) in case of intermittent contraction of the external sphincter.
The obstructive effect of BPH is due to two components: The passive component due to the compression of the prostate on the urethra, responsible for the increase in opening pressure, and the active component due to the increase in the tone of the prostatic smooth muscle fibres which surround the urethra. This active component would be responsible for delaying the relaxation of the bladder outlet, causing a urinary flow deviation from its theoretical values, which are reflected in the initial and final spikes of pattern B.

In conclusion we can state that PD patients have more significatively more frequent functional bladder outlet obstruction compared with BPH patients. This finding is consistent with the utility of DURR pattern to differentiate between types of bladder outlet obstruction.

Godmer M, Guinet-Lacoste A, Charvier K, Luauté J, Rode G, Soler JM, Hadiji N. Existe-t-il une obstruction autre que prostatique dans la Maladie de Parkinson Idiopathique? [Is there any obstruction other than prostatic obstruction in Idiopathic Parkinson's Disease?]. Prog Urol. 2019 ;29(11):579-585.
Schaefer W. The contribution of the bladder outlet to the relation between pressure and flow rate during micturition. In: Hinman F, editor. Benign prostatic hypertrophy. New York: Springer Verlag; 1983. 450–69.
Vírseda M, Salinas J, López A, Esteban M. Usefulness of Dynamic Urethral Resistance Relation (DURR) measurement for differential diagnosis between static and dynamic urinary obstruction in male spinal cord injury patients. Neurourol Urodyn. 2012;31(4):549-55

Continence 12S (2024) 101607
DOI: 10.1016/j.cont.2024.101607