Pathophysiological mechanisms in detrusor underactivity: Novel experimental findings

(A)voiding misdiagnosis: prediction of detrusor underactivity vs. bladder outlet obstruction using pre-urodynamic nomogram in male patients with LUTS

PURPOSE

Our study aimed to develop a noninvasive model using a combination of the set of clinical data and uroflowmetry (UFL) to differentiate between detrusor underactivity (DU) and bladder outlet obstruction (BOO) in non-neurogenic male patients with lower urinary tract symptoms (LUTS).

METHODS

Data from 229 men with LUTS, diagnosed with DU or BOO on a pressure-flow study (PFS), were retrospectively analyzed, including medical history, Core Lower Urinary Tract Symptoms score (CLSS) questionnaire, UFL and PFS. Uni- and multivariate logistic regression were utilized for the prediction analyses.

RESULTS

Of the cohort, 128 (55.9%) patients were diagnosed with DU. A multivariate logistic regression analysis identified less prevalent nocturia (OR 0.27, p < 0.002), more prevalent intermittency (OR 2.33, p = 0.03), less prevalent weak stream (OR 0.14, p = 0.0004), lower straining points in CLSS (OR 0.67, p = 0.02), higher slow stream points in CLSS (OR 1.81, p = 0.002), higher incomplete emptying points in CLSS (OR 1.31, p < 0.02), lower PVR ratio (OR 0.20, p = 0.03), and present features of fluctuating (OR 2.00, p = 0.05), fluctuating-intermittent (OR 3.09, p < 0.006), and intermittent (OR 8.11, p = 0.076) UFL curve shapes as independent predictors of DU. The above prediction model demonstrated satisfactory accuracy (c-index of 0.783).

CONCLUSION

Our 10-factor model provides a noninvasive approach to differentiate DU from BOO in male patients with non-neurogenic LUTS, offering a valuable alternative to invasive PFS.

Clinical features and sequelae of detrusor underactivity: a study of possible cause and effect

PURPOSE

To describe the clinical presentation and urodynamic findings in detrusor underactivity (DU) patients and investigate the association between DU and straining related complications such as pelvic organ prolapse (POP), inguinal hernia, and hemorrhoids.

METHODS

We retrospectively reviewed all consecutive patients who underwent urodynamic studies (UDS) from 2012 to 2023, divided into two groups: those with evidence of DU (n = 573), and control subjects with normal voiding parameters (n = 522). Exclusion criteria were patients who lacked sufficient data, those with obstructive voiding parameters, and those who had received intravesical botulinum toxin injections within the previous nine months. Demographic information, clinical presentation, straining related complications, and UDS findings were compared between the two groups using univariate statistical analysis.

RESULTS

The male DU group had a statistically significant higher prevalence of spinal disease and previous cerebrovascular accidents, while the female DU group had a statistically significant higher prevalence of spinal disease, multiple sclerosis, diabetes, previous colorectal surgery, previous transabdominal gynecological surgery, POP surgery, and recurrent UTIs. Female DU patients had a higher prevalence of pronounced vaginal bulging symptoms, recurrent POP, inguinal hernia, and hemorrhoids. The predominant LUTS were voiding symptoms (81.2% in males and 77.9% in females), followed closely by storage symptoms (66.2% in males and 74.7% in females). The median Qmax, PdetQmax, and PVR were 6 ml/sec, 18 cmH2O, 190 ml for male DU patients, and 8 ml/sec, 11 cmH2O, and 200 ml for female DU patients, respectively.

CONCLUSION

Risk factors for DU that were identified include age, neurological diseases (spinal disease, CVA in men, MS in women), diabetes and transabdominal surgery (colorectal, gynecological) that can cause pelvic denervation in women. DU patients commonly present with both voiding and storage symptoms. There is approximately twice the risk of having POP surgery and inguinal hernia, an eight-fold risk of hemorrhoids, and a three-fold risk of recurrent UTIs for females. This is thought to be secondary to increased intra-abdominal pressure during urinary straining.

Summary Paper on Underactive Bladder from the European Association of Urology Guidelines on Non-neurogenic Male Lower Urinary Tract Symptoms

BACKGROUND AND OBJECTIVE

The European Association of Urology (EAU) Guidelines Panel on non-neurogenic male lower urinary tract symptoms (LUTS) aimed to develop a new subchapter on underactive bladder (UAB) in non-neurogenic men to inform health care providers of current best evidence and practice. Here, we present a summary of the UAB subchapter that is incorporated into the 2024 version of the EAU guidelines on non-neurogenic male LUTS.

METHODS

A systematic literature search was conducted from 2002 to 2022, and articles with the highest certainty evidence were selected. A strength rating has been provided for each recommendation according to the EAU Guideline Office methodology.

KEY FINDINGS AND LIMITATIONS

Detrusor underactivity (DU) is a urodynamic diagnosis defined as a contraction of reduced strength and/or duration, resulting in prolonged bladder emptying and/or failure to achieve complete bladder emptying within a normal time span. UAB is a terminology that should be reserved for describing symptoms and clinical features related to DU. Invasive urodynamics is the only widely accepted method for diagnosing DU. In patients with persistently elevated postvoid residual (ie, >300 ml), intermittent catheterization is indicated and preferred to indwelling catheters. Alpha-adrenergic blockers are recommended before more invasive techniques, but the level of evidence is low. In men with DU and concomitant benign prostatic obstruction (BPO), benign prostatic surgery should be considered only after appropriate counseling. In men with DU and no BPO, a test phase of sacral neuromodulation may be considered.

CONCLUSIONS AND CLINICAL IMPLICATIONS

The current text represents a summary of the new subchapter on UAB. For more detailed information, refer to the full-text version available on the EAU website (https://uroweb.org/guidelines/management-of-non-neurogenic-male-luts).

Underactive Bladder and Detrusor Underactivity: New Advances and Prospectives

Underactive bladder (UAB) is a prevalent but under-researched lower urinary tract symptom that typically occurs alongside detrusor underactivity (DU). Unlike UAB, DU is a urodynamic diagnosis which the International Continence Society (ICS) defines as "a contraction of reduced strength and/or duration, resulting in prolonged bladder emptying and/or a failure to achieve complete bladder emptying within a normal time span". Despite the widespread prevalence of UAB/DU, there are significant gaps in our understanding of its pathophysiological mechanisms, diagnosis, and treatment compared with overactive bladder (OAB) and detrusor overactivity (DO). These gaps are such that clinicians regard UAB/DU as an incurable condition. In recent years, the understanding of UAB has increased. The definition of UAB has been clarified, and the diagnostic criteria for DU have been considered more comprehensively. Meanwhile, a number of non-invasive diagnostic methods have also been reported. Clinical trials involving novel drugs, electrical stimulation, and stem cell therapy have shown promising results. Therefore, this review summarizes recent reports on UAB and DU and highlights the latest advances in their diagnosis and treatment.

Establishment of an overactive bladder model in mice

BACKGROUND

Overactive bladder (OAB) is a syndrome characterized by symptoms of urinary urgency, often accompanied by frequent urination and nocturia or urge incontinence.

METHODS

Twenty female ICR mice were randomly divided into pBOO (partial bladder outlet obstruction) and control groups. The mouse OAB model was constructed by ligating the bladder outlet. Eight weeks after the operation, the methods of voiding spot on paper (VSOP), isolated detrusor muscle, and HE staining were used for analysis and research.

RESULTS

After the operation, two mice in the experimental and one in control died, and one in the control groups had an abnormal bladder size, so it was excluded from the statistical analysis. Eight weeks after the operation, there was an insignificant difference (P = 0.15) in the body weight of mice in the pBOO (26.54 ± 2.62 g) and the control group (24.84 ± 1.76 g). The number of urinations in 12 h was significantly higher (P < 0.001) in the pBOO (7.63 ± 1.19) than in the control group (4.13 ± 0.99). Also, the 12-h urine volume of pBOO (1491.23 ± 94.72 μL) was significantly greater (P = 0.006) than that of the control group (1344.86 ± 88.17 μL). The isolated bladder of the pBOO mice was significantly heavier than that in the control group (53.16 ± 1.79 mg vs. 24.54 ± 1.80 mg, P < 0.001), the horizontal and vertical length of the bladder in pBOO group were larger than those in the control group (P < 0.001). The detrusor thickness of pBOO group (357.50 ± 11.88 µm) was significantly thicker than that of control group (258.52 ± 17.22 µm, P < 0.001), and the isolated muscle strip was more sensitive to carbachol stimulation. According to HE staining, the bladder wall of the pBOO mice was significantly thickened.

CONCLUSIONS

A pBOO-mediated mouse OAB model was successfully established by ligating the bladder outlet.

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.

DU Is Induced by Low Levels of Urinary ATP in a Rat Model of Partial Bladder Outlet Obstruction: The Incidence of Both Events Decreases after Deobstruction

Objectives. To investigate, in initial phases of bladder outlet obstruction (BOO), the urinary ATP levels, the incidence of detrusor underactivity (DU), and if they change after deobstruction. Methods. Adult female Wistar rats submitted to partial BOO (pBOO) and sham-obstruction were used. Cystometry was performed 3 or 15 days after pBOO and fluid was collected from the urethra for ATP determination. Bladders were harvested for morphological evaluation of the urothelium. DU was defined as the average of voiding contractions (VC) of sham-operated animals, with 3 SD at 15 days after the sham surgery. In another group of animals in which pBOO was relieved at 15 days and bladders were let to recover for 15 days, the incidence of DU and ATP levels were also accessed. The Kruskal–Wallis test was followed by Dunn’s multiple comparisons test, and Spearman’s correlation test was used. Results. DU was present in 13% and 67% of the bladders at 3 and 15 days after pBOO, respectively, and in 20% of the bladders at 15 days after deobstruction. ATP levels were significantly lower in DU/pBOO versus sham and non-DU/pBOO rats. A strong positive correlation between ATP levels and VC/min was obtained (r = 0.63). DU bladders had extensive areas in which umbrella cells appeared stretched, the width exceeding that presented by sham animals. Conclusions. Low urothelial ATP parallels with a high incidence of DU early after pBOO.

Muscarinic M3 positive allosteric modulator ASP8302 enhances bladder contraction and improves voiding dysfunction in rats

OBJECTIVES

Muscarinic M₃ (M₃ ) receptors mediate cholinergic smooth muscle contraction of the bladder. Current drugs targeting bladder M₃ receptors for micturition disorders have a risk of cholinergic side effects due to excessive receptor activation and insufficient selectivity. We investigated the effect of ASP8302, a novel positive allosteric modulator (PAM) of M₃ receptors, on bladder function in rats.

METHODS

Modulation of carbachol-induced increases in intracellular Ca²⁺ was assessed in cells expressing rat muscarinic receptors. Potentiation of bladder contractions was evaluated using isolated rat bladder strips and by measuring intravesical pressure in anesthetized rats. Conscious cystometry was performed to investigate the effects on residual urine volume and voiding efficiency in rat voiding dysfunction models induced by the α₁ -adrenoceptor agonist midodrine and muscarinic receptor antagonist atropine, and bladder outlet obstruction. To assess potential side effects, the number of stools and tracheal insufflation pressure were measured in conscious and anesthetized rats, respectively.

RESULTS

ASP8302 demonstrated PAM effects on the rat M₃ receptor in cell assays, and augmented cholinergic bladder contractions both in vivo and in vitro. ASP8302 improved voiding efficiency and reduced residual urine volume in two voiding dysfunction models as effectively as distigmine bromide, but unlike distigmine bromide did not affect the number of stools or tracheal insufflation pressure.

CONCLUSIONS

Our results in rats indicate that ASP8302 improves voiding dysfunction by potentiating bladder contraction with fewer effects on cholinergic responses in other organs, and suggest a potential advantage over current cholinomimetic drugs for treating micturition disorders caused by insufficient bladder contraction.

The effectiveness of parasympathomimetics for treating underactive bladder: A systematic review and meta-analysis

AIMS

Biological rationale suggests that parasympathomimetics (cholinergic receptor stimulating agents) could be beneficial for patients with underactive bladder. However, no systematic review with meta-analysis addressing potential benefits or adverse effects exists. The aim of this review was to assess the effectiveness, both benefits and harms, of using parasympathomimetics for the treatment of underactive bladder.

METHODS

The protocol was registered in PROSPERO, and searches undertaken in PubMed, Embase, and CENTRAL, including randomized and non-randomized controlled trials of patients with underactive bladder, comparing parasympathomimetic to placebo, no treatment, or other pharmaceuticals. Risk ratios, odds ratios, and mean differences were calculated.

RESULTS

Twelve trials with 3024 participants were included. There was a significant difference between parasympathomimetics and comparators (favoring parasympathomimetics) in the number of patients with urinary retention (risk ratio 0.55, 95% confidence interval [CI] 0.3-0.98, p = 0.04, low quality of evidence). There was no difference in mean postvoid volume overall (MD -41.4 ml, 95% CI -92.0 to 9.1, p = 0.11, low quality of evidence). There was a significant difference at up to 1 week post-intervention, favoring parasympathomimetics (MD -77.5 ml, 95% CI -90.9 to -64.1, p < 0.001, low quality of evidence), but no difference at 1 month post-intervention. There was no difference in adverse events (odds ratio 1.19, 95% CI 0.62-2.28, p = 0.6, moderate quality of evidence).

CONCLUSIONS

The evidence supporting the use of parasympathomimetics is of low quality, with relatively short follow-up durations. Overall, it is not possible to draw clear evidence-based conclusions from the current literature, presenting the use of parasympathomimetics for treating underactive bladder as a key area that requires future well-controlled clinical trials.

New mouse model of underactive bladder developed by placement of a metal ring around the bladder neck

OBJECTIVE

To develop a new mouse model of underactive bladder (UAB) caused by chronic bladder outlet obstruction (BOO).

METHODS

BOO was created in 6-week-old male C57BL/6 mice using surgery to loosely place a silver jump ring around the bladder neck of each mouse. Micturition behavior (assessed with a metabolic cage) and cystometry were used to evaluate bladder function at 8 and 16 weeks after BOO. Following completion of the functional studies, the bladders of the mice were excised, weighed, and subjected to histological analysis.

RESULTS

Micturition behavior analysis showed that mice subjected to BOO for 16 weeks had a lower frequency of micturition (7.3 ± 1.1 vs 12.5 ± 3.0 times/d, P < .05) and volume per void (106.0 ± 0.1 vs 133.9 ± 3.2 μL, P < .05) than mice subjected to BOO for 8 weeks. Cystometry revealed that mice subjected to BOO for 16 weeks had lower baseline pressure (8.4 ± 0.6 vs 14.0 ± 0.7 cmH₂ O, P < .01) and micturition pressure (13.9 ± 1.1 vs 42.8 ± 1.7 cmH₂ O, P < .05) than mice subjected to BOO for 8 weeks. BOO caused progressive increases in bladder mass and collagen deposition over time.

CONCLUSIONS

We successfully established a novel mouse model of UAB using surgery to place a silver jump ring loosely on the bladder neck. BOO initially induced bladder overactivity but subsequently resulted in UAB due to deterioration of detrusor smooth muscle contractility and progressive deposition of collagen in the bladder wall.

Understanding underactive bladder: a review of the contemporary literature

Underactive bladder (UAB) is characterized by prolonged voiding, hesitancy, and slow and/or intermittent stream with or without a sensation of incomplete bladder emptying. The overlap of UAB lower urinary tract symptoms with those of overactive bladder or bladder outlet obstruction, as well as its multifactorial etiology, make UAB study, as well as its diagnosis and management, a very arduous and challenging task. Therefore, despite its incidence and significant impact in the quality of life of both men and women, UAB remains a poorly understood urologic condition with insufficient and ineffective treatment options available. In this review, we will focus on the etiology theories that have been proposed and the animal models available to test those theories.

EP2 and EP3 receptors as therapeutic targets for underactive bladder/detrusor underactivity due to diabetic cystopathy in a type 1 diabetic rat model

OBJECTIVES

Diabetic cystopathy (DC) is recognized as one of the major etiologies of underactive bladder (UAB)/detrusor underactivity (DU). Although DC was first reported about three decades ago, there is a distinct lack of effective pharmacological management methods for UAB/DU due to DC with a robust certainty of evidence. In this study, we investigated whether EP2 and EP3 receptors are promising targets of pharmacological management of UAB/DU due to DC.

METHODS

We used streptozotocin (STZ)-induced diabetic Sprague-Dawley rats with postvoid residual urine (PVR) greater than 0.1 mL. Sixteen weeks after induction of diabetes, we performed awake single cystometry after oral administration of the vehicle, an α-blocker (tamsulosin [TAM], 0.1 and 0.3 mg/kg), a cholinesterase inhibitor (distigmine [DIS], 0.3 and 1.0 mg/kg), or an EP2/3 dual agonist (ONO-8055, 0.01 and 0.03 mg/kg). We compared cystometric parameters after administration of the vehicle and drugs using a paired t test. P < .05 was considered to be statistically significant.

RESULTS

Compared with the vehicle, TAM significantly decreased maximum intravesical pressure during voiding (Pmax), while DIS significantly increased it. However, neither drug significantly affected PVR or the residual urine rate (RUR). On the other hand, ONO-8055 significantly decreased PVR and tended to decrease RUR, although it did not significantly affect Pmax.

CONCLUSION

The present study was unable to demonstrate that stimulation of EP2 and EP3 receptors caused major improvements in UAB/DU due to DC. However, this equivocal result could arise from inherent limitations of the STZ-induced diabetic rat as a UAB/DU model.

Detrusor Underactivity and Underactive Bladder in Women: What Is New?

Purpose of Review

Detrusor underactivity (DU) and its symptom-based correlation, the underactive bladder (UAB), are common problems encountered in urological practice. Whilst DU has been defined for many years, only recently has UAB received a formal definition and there is now accumulating literature based on this condition. In this article, we reviewed the recent literature on the aetiology, pathogenesis, diagnosis and management of DU/UAB in women.

Recent Findings

Detrusor underactivity is diagnosed on urodynamic studies but there still remains a lack of widely recognised and accepted diagnostic criteria. Commencing treatment based on the diagnosis of UAB, with or without a PVR measurement, is perhaps feasible due to the lower occurrence of BOO in women and specific clinical features that may distinguish this group. Prospective studies attempting to correlate UAB with the underlying DU are needed before this approach could be considered.

Summary

Detrusor underactivity/UAB in women requires a separate consideration from men due to the anatomical and functional differences in the lower urinary tracts between both genders and consequent differences in pathologies affecting them. The aetiology of DU remains largely unknown, but is probably multifactorial, including myogenic, neurogenic and vasculogenic factors. There remains a lack of any simple effective drug treatments, whilst apart from sacral neuromodulation for the specific subgroup with non-obstructive urinary retention, no safe and effective surgical treatment is currently available. Often, permanent or intermittent bladder drainage with a catheter is the final solution.

Bladder overactivity and post-void residual: Which relates more to systemic atherosclerotic markers?

OBJECTIVE

Several studies have shown relationship between the lower urinary tract dysfunction (LUTD) and atherosclerosis. However, no study is available to see which LUTD relates more to atherosclerosis, among detrusor overactivity and post-void residual. In order to answer this question, we present data of urodynamic and atherosclerosis tests.

METHODS

We performed standard urodynamics and two atherosclerosis tests, i.e., a cardio-ankle vascular stiffness index (CAVI) test and a duplex carotid ultrasonography.

PATIENTS

We have 183 patients; 109 men (mean age 66.3 years), 74 women (mean age 66.4 years); all age > 60 years.

RESULTS

Detrusor overactivity is related with high CAVI value (p < 0.05) but not with carotid intima-media thickness. Post-void residuals did not show such relation.

CONCLUSION

Urodynamic LUTD, particularly detrusor overactivity that may indicate central etiology is positively related with systemic atherosclerosis as measured by CAVI. Post-void residuals that may indicate peripheral etiology did not show such relation.