Pathophysiology of the Underactive Bladder: Evolving New Concepts

Lack of expression of miR-29a/b1 impairs bladder function in male mice

Lower urinary tract symptoms (LUTS) refer to various urological diseases, and incomplete bladder emptying is common among affected patients. The etiology of LUTS is largely unknown, and investigations of LUTS suggest that bladder fibrosis contributes to pathogenesis of LUTS. MicroRNAs (miRNAs) are short (∼22 nucleotides), non-coding RNAs that repress target gene expression by a combination of mRNA degradation and translation inhibition. The miR-29 family is best known for its anti-fibrotic role in various organs. miR-29 was decreased in bladders of patients with outlet obstruction and a rat model of bladder outlet obstruction, suggesting that miR-29 may contribute to impaired bladder function subsequent to tissue fibrosis. We characterized bladder function in male mice lacking expression of Mir29a and Mir29b-1 (miR-29a/b1). Lack of miR-29a/b1 resulted in severe urinary retention, increased voiding duration and reduced flow rate, and these mice failed to void or voided irregularly during anesthetized cytometry. Collagens and elastin were increased in bladders of mice lacking miR-29a/b1. These findings reveal an important role for miR-29 in bladder homeostasis and suggest the therapeutic potential of miR-29 to improve symptoms in patients with LUTS.

Detrusor Underactivity in Men with Bladder Outlet Obstruction

Detrusor underactivity (DU) and bladder outlet obstruction (BOO) are both common troublesome causes of lower urinary tract symptoms (LUTS) and often impact on quality of life simultaneously in men. This article aims to focus on DU with BOO in male patients.

METHODS

Original articles concerning DU with BOO were identified through literature research from PubMed and EMBASE database. We selected 38 articles in our review, including those concerning pathophysiology, evaluation, treatment and predictors for a successful BOO surgery for DU.

RESULTS

DU from BOO can result from several pathophysiological mechanisms. Although urodynamic study (UDS) is considered as a precise method to diagnose DU and BOO, there are some previous studies which proposed a non-invasive method to identify DU related to BOO. The treatment goal of DU is restoring bladder contractility using medication or surgery. Releasing outlet obstruction and resistance is the main strategy to restore bladder contractility when medication to directly increase bladder contractility has had limited efficacy.

CONCLUSIONS

DU from BOO is poorly understood and is largely under-researched. The etiology and pathophysiology still need to be evaluated. Effective and safe medication to restore bladder contractility is also lacking. It remains valuable to perform further research to reveal the unknown aspects of DU.

Female underactive bladder - Current status and management

Underactive bladder (UAB) is defined by the International Continence Society as a symptom complex characterized by a slow urinary stream, hesitancy, and straining to void, with or without a feeling of incomplete bladder emptying sometimes with storage symptoms. Until recently, the topic has received little attention in the literature probably due to a lack of consistent definitions and diagnostic criteria. We performed a literature review to identify articles related to the diagnosis and management of UAB, specifically in female patients. UAB is a common clinical entity, occurring in up to 45% of females depending on definitions used. Prevalence increases significantly in elderly women and women who live in long-term care facilities. The exact etiology and pathophysiology for developing UAB is unknown, though it is likely a multifactorial process with contributory neurogenic, cardiovascular, and idiopathic causes. There are currently no validated questionnaires for diagnosing or monitoring treatment for patients with UAB. Management options for females with UAB remain limited, with clean intermittent catheterization, the most commonly used. No pharmacotherapies have consistently been proven to be beneficial. Neuromodulation has had the most promising results in terms of symptom improvement, with newer technologies such as stem-cell therapy and gene therapy requiring more evidence before widespread use. Although UAB has received increased recognition and has been a focus of research in recent years, there remains a lack of diagnostic and therapeutic tools. Future research goals should include the development of targeted therapeutic interventions based on pathophysiologic mechanisms and validated diagnostic questionnaires.