Physiopathologie de l’hypoactivité détrusorienne de la personne âgée

The low dopamine hypothesis: A plausible mechanism underpinning residual urine, overactive bladder and nocturia (RON) syndrome in older patients

INTRODUCTION

Aging is associated with a combination of several lower urinary tract (LUT) signs and symptoms, including residual urine, overactive bladder and nocturia. One of the mechanisms of this LUT dysfunction that has not been discussed in dept so far is the role of dopamine (DA).

METHODS

In this narrative review, we explore the dopaminergic hypothesis in the development of this combination of LUT signs and symptoms in older adults.

RESULTS

DA is one of the neurotransmitters whose regulation and production is disrupted in aging. In synucleinopathies, altered DAergic activity is associated with the occurrence of LUTS and sleep disorders. Projections of DAergic neurons are involved in the regulation of sleep, diuresis, and bladder activity. The low dopamine hypothesis could explain the genesis of a set of LUT signs and symptoms commonly seen in this population, including elevated residual urine, Overactive bladder syndrome and Nocturia (discussed as the RON syndrome). This presentation is however also common in older patients without synucleinopathies or neurological disorders and therefore we hypothesise that altered DAergic activity because of pathological aging, and selective destruction of DAergic neurons, could underpin the presentation of this triad of LUT dysfunction in the older population.

CONCLUSION

The concept of RON syndrome helps to better understand this common phenotypic presentation in clinical practice, and therefore serves as a useful platform to diagnose and treat LUTS in older adults. Besides recognizing the synucleinopathy "red flag" symptoms, this set of multi-causal LUT signs and symptoms highlights the inevitable need for combination therapy, a challenge in older people with their comorbidities and concomitant medications.

Clinical study of the effects of deep brain stimulation on urinary dysfunctions in patients with Parkinson's disease

Purpose: To evaluate the effect of deep brain stimulation (DBS) on urinary dysfunctions in Parkinson’s patients.

Patients and methods: A total of 416 patients, diagnosed with Parkinson’s disease (PD) based on the UK Parkinson’s Disease Society Brain Bank Diagnostic Criteria, were enrolled in the study, including 307 males and 109 females. The effects of DBS treatment on urinary functions during urination and bladder storage of these patients were evaluated using testing and assessment scales, such as the American Urological Association Symptom Index (AUA-SI), Overactive Bladder Symptom Scores (OAB-SS), Quality Of Life Scale (QOL), and urodynamic tests. The data were statistically analyzed with the chi-square test and  both independent-samples t-test and paired-samples t-test were used in this study.

Results: Symptoms of urinary dysfunctions, such as urinary frequency, urgency, and incontinence, in the patients with PD were notably relieved by DBS treatment (P<0.05), and the OAB-SS and bladder storage problems were greatly improved as well (P<0.05). Compared with those in male patients, DBS surgery significantly improved the AUA-SI, urinary symptom scores, and QOL in female PD patients (P<0.05), as well as other functional indicators related to the urinary tract, including the maximum urinary flow rate, detrusor pressure at peak flow, and residual urine volume in female PD patients (P<0.05).

Conclusion: DBS surgery is effective in improving urinary functions in PD patients, as primarily reflected by the alleviation of urinary symptoms such as urinary frequency, urgency, and incontinence. Female PD patients displayed better urinary function outcomes from DBS treatment than did male patients.

A Comprehensive Review of Overactive Bladder Pathophysiology: On the Way to Tailored Treatment

CONTEXT

Current literature suggests that several pathophysiological factors and mechanisms might be responsible for the nonspecific symptom complex of overactive bladder (OAB).

OBJECTIVE

To provide a comprehensive analysis of the potential pathophysiology underlying detrusor overactivity (DO) and OAB.

EVIDENCE ACQUISITION

A PubMed-based literature search was conducted in April 2018, to identify randomised controlled trials, prospective and retrospective series, animal model studies, and reviews.

EVIDENCE SYNTHESIS

OAB is a nonspecific storage symptom complex with poorly defined pathophysiology. OAB was historically thought to be caused by DO, which was either "myogenic" (urgency initiated from autonomous contraction of the detrusor muscle) or "neurogenic" (urgency signalled from the central nervous system, which initiates a detrusor contraction). Patients with OAB are often found to not have objective evidence of DO on urodynamic studies; therefore, alternative mechanisms for the development of OAB have been postulated. Increasing evidence on the role of urothelium/suburothelium and bladder afferent signalling arose in the early 2000s, emphasising an afferent "urotheliogenic" hypothesis, namely, that urgency is initiated from the urothelium/suburothelium. The urethra has also recently been regarded as a possible afferent origin of OAB-the "urethrogenic" hypothesis. Several other pathophysiological factors have been implicated, including metabolic syndrome, affective disorders, sex hormone deficiency, urinary microbiota, gastrointestinal functional disorders, and subclinical autonomic nervous system dysfunctions. These various possible mechanisms should be considered as contributing to diagnostic and treatment algorithms.

CONCLUSIONS

There is a temptation to label OAB as "idiopathic" without obvious causation, given the poorly understood nature of its pathophysiology. OAB should be seen as a complex, multifactorial symptom syndrome, resulting from multiple potential pathophysiological mechanisms. Identification of the underlying causes on an individual basis may lead to the definition of OAB phenotypes, paving the way for personalised medical care.

PATIENT SUMMARY

Overactive bladder (OAB) is a storage symptom syndrome with multiple possible causes. Identification of the mechanisms causing a patient to experience OAB symptoms may help tailor treatment to individual patients and improve outcomes.