Loss of resilience contributes to detrusor underactivity in advanced age.

Volume hyposensitivity resulting from impaired sympathetic detrusor relaxation during bladder filling contributes to detrusor underactivity (DU) associated with aging. Detrusor tension regulation provides an adaptive sensory input of bladder volume to the brainstem and is challenged by physiological stressors superimposed upon biological aging. We recently showed that HCN channels have a stabilizing role in detrusor sympathetic relaxation. While mature mice maintain homeostasis in the face of stressors, old mice are not always capable. In old mice, there is a dichotomous phenotype, in which resilient mice adapt and maintain homeostasis, while non-resilient mice fail to maintain physiologic homeostasis. In this DU model, we used cystometry as a stressor to categorize mice as old-responders (old-R, develop a filling/voiding cycle) or old-non-responders (old-NR, fail to develop a filling/voiding cycle; fluctuating high pressures and continuous leaking), while also assessing functional and molecular differences. Lamotrigine (HCN activator)-induced bladder relaxation is diminished in old-NR mice following HCN-blockade. Relaxation responses to NS 1619 were reduced in old-NR mice, with the effect lost following HCN-blockade. However, RNA-sequencing revealed no differences in HCN gene expression and electrophysiology studies showed similar percentage of detrusor myocytes expressing HCN (Ih) current between old-R and old-NR mice. Our murine model of DU further defines a role for HCN, with failure of adaptive recalibration of HCN participation and intensity of HCN-mediated stabilization, while genomic studies show upregulated myofibroblast and fibrosis pathways and downregulated neurotransmitter-degradation pathways in old-NR mice. Thus, the DU phenotype is multifactorial and represents the accumulation of age-associated loss in homeostatic mechanisms.

Cuprizone-mediated demyelination reversibly degrades voiding behavior in mice while sparing brainstem reflex.

Multiple sclerosis (MS) is a chronic, progressively debilitating demyelinating disease of the central nervous system (CNS). Nearly 80% of MS patients experience lower urinary tract dysfunction early in their diagnosis. This significantly affects the quality of life, and in latter stages of disease is a leading cause of hospitalization. Previously, animal models have shown that inflammatory demyelination in the CNS causes profound bladder dysfunction, but the confounding influence of systemic inflammation limits the potential interpretation of the contribution of CNS demyelination to bladder dysfunction. Since the micturition circuit has myelinated neuronal connections in the cortex, brainstem, and spinal cord, we examined alterations in bladder function in the cuprizone model characterized by demyelinating lesions in the cortex and corpus callosum that are independent of T-cell-mediated autoimmunity. Herein, we report that a 4-week dietary cuprizone treatment in C57Bl/6J mice induced alterations in voiding behavior with increased micturition frequency and reduced volume voided, similar to human MS bladder dysfunction. Subsequently, recovery from cuprizone treatment restored normal bladder function. Demyelination and remyelination were confirmed by Luxol Fast Blue staining of the corpus callosum. Additionally, we also determined that an 8-week cuprizone treatment, resulting in chronic demyelination lacking spontaneous remyelination potential, is associated with an exacerbated voiding phenotype. Interestingly, while cuprizone-induced CNS demyelination severely affected conscious (cortical) urinary behavior, the brainstem and spinal cord reflex remained unchanged, as confirmed by urethane-anesthetized cystometry. This is the first study to show that cortical demyelination independent of inflammation can negatively impact urinary function.

Alzheimer's disease amyloidogenesis is linked to altered lower urinary tract physiology.

AIMS: While most Alzheimer's disease (AD) research emphasizes cognitive and behavioral abnormalities, lower urinary tract symptoms (LUTS) are observed in a third of AD patients, contributing to morbidity, poor quality of life, and need for institutionalization. Alzheimer's disease-associated urinary dysfunction (ADUD) has been assumed to be due to cognitive decline alone. While mouse studies have suggested that bladder innervation and voiding behavior may be altered in AD models, technical challenges precluded voiding reflex assessments. This study seeks to establish a mouse model of ADUD, and it seeks to characterize the noncognitive sequelae involved in AD-pathology associated alterations in the voiding reflex. METHODS: Having developed techniques permitting the assessment of bladder volume, pressure, and flow in mice, we now provide evidence of alterations in involuntary bladder control and increased response heterogeneity in a transgenic amyloidosis mouse model of AD using cystometry and tissue pharmacomyography. Tg-APP/PS1DE9 (PA) mice and their wild-type (WT) littermates (n = 6-8 per group) were used before plaque onset in the PA mice (4-6 months) and after plaque accumulation in the PA mice (8-10 months) in comparison to their WT control littermates. RESULTS: Novel findings include data suggestive of sphincteric discoordination, with pharmacological evidence of altered adrenergic mechanisms. CONCLUSIONS: Together, these data highlight the importance of addressing noncognitive sequelae of AD and offer novel translational insights into the debilitating impact of AD on LUTS and incontinence.

Blocking peripheral drive from colorectal afferents by subkilohertz dorsal root ganglion stimulation.

ABSTRACT: Clinical evidence indicates dorsal root ganglion (DRG) stimulation effectively reduces pain without the need to evoke paresthesia. This paresthesia-free anesthesia by DRG stimulation can be promising to treat pain from the viscera, where paresthesia usually cannot be produced. Here, we explored the mechanisms and parameters for DRG stimulation using an ex vivo preparation with mouse distal colon and rectum (colorectum), pelvic nerve, L6 DRG, and dorsal root in continuity. We conducted single-fiber recordings from split dorsal root filaments and assessed the effect of DRG stimulation on afferent neural transmission. We determined the optimal stimulus pulse width by measuring the chronaxies of DRG stimulation to be below 216 µs, indicating spike initiation likely at attached axons rather than somata. Subkilohertz DRG stimulation significantly attenuates colorectal afferent transmission (10, 50, 100, 500, and 1000 Hz), of which 50 and 100 Hz show superior blocking effects. Synchronized spinal nerve and DRG stimulation reveals a progressive increase in conduction delay by DRG stimulation, suggesting activity-dependent slowing in blocked fibers. Afferents blocked by DRG stimulation show a greater increase in conduction delay than the unblocked counterparts. Midrange frequencies (50-500 Hz) are more efficient at blocking transmission than lower or higher frequencies. In addition, DRG stimulation at 50 and 100 Hz significantly attenuates in vivo visceromotor responses to noxious colorectal balloon distension. This reversible conduction block in C-type and Aδ-type afferents by subkilohertz DRG stimulation likely underlies the paresthesia-free anesthesia by DRG stimulation, thereby offering a promising new approach for managing chronic visceral pain.

Best practices for cystometric evaluation of lower urinary tract function in muriform rodents.

AIMS: Rodent cystometry has provided valuable insights into the impact of the disease, injury, and aging on the cellular and molecular pathways, neurologic processes, and biomechanics of lower urinary tract function. The purpose of this white paper is to highlight the benefits and shortcomings of different experimental methods and strategies and to provide guidance on the proper interpretation of results. METHODS: Literature search, selection of articles, and conclusions based on discussions among a panel of workers in the field. RESULTS: A range of cystometric tests and techniques used to explore biological phenomena relevant to the lower urinary tract are described, the advantages and disadvantages of various experimental conditions are discussed, and guidance on the practical aspects of experimental execution and proper interpretation of results are provided. CONCLUSIONS: Cystometric evaluation of rodents comprises an extensive collection of functional tests that can be performed under a variety of experimental conditions. Decisions regarding which approaches to choose should be determined by the specific questions to be addressed and implementation of the test should follow standardized procedures.

The aging bladder phenotype is not the direct consequence of bladder aging.

AIMS: The prevalence of urinary dysfunction increases with age, yet therapies are often suboptimal. Incomplete understanding of the linkages between system, organ, and tissue domains across lifespan remains a knowledge gap. If tissue-level changes drive the aging bladder phenotype, parallel changes should be observed across these domains. In contrast, a lack of inter-domain correlation across age groups would support the hypothesis that urinary performance is a measure of the physiologic reserve, dependent on centrally-mediated adaptive mechanisms in the aging system. METHODS: Male and female mice across four age groups underwent sequential voiding spot assays, pressure/flow cystometry, bladder strip tension studies, histology, and quantitative PCR analyses. The primary objective of this study was to test the impact of age on the cortical, autonomic, tissue functional and structural, and molecular domains, and identify inter-domain correlations among variables showing significant changes with age within these domains. RESULTS: Behavior revealed diminished peripheral voiding and spot size in aged females. Cystometry demonstrated increased postvoid residual and loss of volume sensitivity, but the preservation of voiding contraction power, with almost half of oldest-old mice failing under cystometric stress. Strip studies revealed no significant differences in adrenergic, cholinergic, or EFS sensitivity. Histology showed increased detrusor and lamina propria thickness, without a change in collagen/muscle ratio. Adrb2 gene expression decreased with age. No consistent inter-domain correlations were found across age groups. CONCLUSIONS: Our findings are consistent with a model in which centrally-mediated adaptive failures to aging stressors are more influential over the aging bladder phenotype than local tissue changes.

Evidence of increased centrally enhanced bladder compliance with ageing in a mouse model.

OBJECTIVE: To test the hypothesis that ageing is associated with increasing neurogenic enhancement of bladder filling compliance. MATERIALS AND METHODS: Female B6 mice (aged 2, 12, 22 and 26 months) underwent cystometry while alive and immediately after death. Bladder compliance was calculated from pressure-time data. Pressure data were transformed using Fast Fourier Transform to obtain power spectra of bladder pressure variations attributable to contractile activity during filling in both alive and dead mice. A cut-off frequency (CF) was determined for each mouse, above which any power content would be primarily neurogenic. Compliance and power spectra results were compared among age groups, and correlations sought. RESULTS: A reversible loss of bladder compliance and non-voiding contractile (NVC) activity followed abolition of voiding reflexes in female colony mice in all age groups. Bladder filling compliance increased with age in urethane-anaesthetised and post-mortem conditions, and more so in the former. Power below the CF did not significantly vary with age. Neurogenic power increased with age, and significantly correlated with compliance. CONCLUSIONS: An increase in neurogenic power during filling accompanies increased centrally mediated compliance enhancement with age. A bladder control model in which brain processes related to micturition may compensate for age-associated changes; thereby preserving voiding function is suggested. Urinary dysfunction could be viewed as the result of homeostatic failure rather than strictly end-organ pathology.

Acute lower urinary tract dysfunction (LUTD) following traumatic brain injury (TBI) in rats.

AIMS: The aim of this study was to assess experimental traumatic brain injury (TBI)-induced lower urinary tract dysfunction (LUTD) by monitoring systemic and urodynamic parameters using an implantable telemetry system. METHODS: A single lateral fluid percussion TBI (FP-TBI; 3.4 atm) was administered to 10 female rats. Pressure micro-catheters were implanted in the abdominal aorta and bladder dome for simultaneous data recording. Hemodynamic and urodynamic variables recorded 24 hr before and 24 hr after injury were analyzed and compared. RESULTS: TBI in the acute phase resulted in LUTD affecting bladder emptying, characterized by failure of voiding reflex, high capacity bladder, increased voided volume, prolonged intermicturition intervals, and loss of compliance. The dominant symptom was urinary retention (100%) and incontinence (60%). The effects followed a pattern of initial loss of bladder function followed by either altered recovery of reflex micturition or a period of incontinence. With a moderate injury symptoms were temporary in 90% of animals and permanent in 10% of animals. Injury produced only transient hypertension (≤1 hr) with a maximum systolic pressure of 172.64 ± 14.53 mmHg (70% of animals). CONCLUSIONS: The results demonstrate that experimental FP-TBI causes temporary bladder dysfunction that in more severe cases becomes permanent. Telemetry recordings revealed a sequence of events following injury that establishes moderate TBI as a risk factor for neurogenic bladder disorder. Results also suggest a correlation between lateral FP-TBI and incontinence.

Pseudoreflux and detrusor overactivity due to accidental ureteral catheterization during cytometry in a pediatric patient.

We present the case of a 9-year-old girl with a neurogenic bladder who had accidental ureteral cannulation with the vesical catheter during cytometry. This is the first reported pediatric case described of this complication, the four prior cases all being in adults. The signs and symptoms of ureteral catheterization differed significantly in this patient from the adult cases. In our patient, malpositioning of the vesical catheter yielded a misleading pressure profile of primarily rhythmic pressure increases suggestive of severe detrusor overactivity and vesicoureteral reflux on fluoroscopy. The reading, however, actually reflected ureteric filling and peristalsis, and these findings resolved when the catheter was properly repositioned. This case highlights the possibility of inadvertent ureteral catheterization, and that, while rare, this complication should be kept in mind when new or unexpected DO or VUR is observed upon filling cystometry.

Evidence of central modulation of bladder compliance during filling phase.

AIMS: Bladder compliance is one expression of the pressure and volume relationship as the bladder fills. In addition to passive elements, autonomous micromotional detrusor activity contributes to this relationship. In the mouse cystometric model, compliance pressure contributes to voiding expulsive pressure. During attempts to isolate the detrusor contractile component of this filling pressurization, we found that compliance reversibly diminishes under conditions which remove central control from the micturition cycle. METHODS: Ten mature female mice underwent constant infusion pressure/flow cystometry under urethane anesthesia, and five awake mature female mice underwent constant infusion pressure cystometry. Following baseline cystometry, all mice were anesthetized with isoflurane to abolish the micturition reflex, and cystometry conducted with manual emptying of the bladders. Animals were then allowed to recover from isoflurane to re-establish the micturition reflex, and cystometry again conducted. The urethane group was also studied immediately post-mortem. Repeated measures comparisons of cystometric parameters were made across conditions. RESULTS: Compliance reversibly decreased in all mice with the abolishment of micturition responses by isoflurane anesthesia. A similar decrease was observed immediately post-mortem in the urethaned mice. Bladder filling and voiding were not different between the intact micturition segments of the testing. CONCLUSIONS: Enhanced compliance in mice with intact micturition responses suggests that autonomous micromotional activity is suppressed by central processes during normal filling. Since afferent activity during filling is also determined by the relationship between bladder pressure and volume, a feed-forward afferent signal conditioning mechanism may exist, creating novel therapeutic targets for urinary dysfunctions.

Detrusor expulsive strength is preserved, but responsiveness to bladder filling and urinary sensitivity is diminished in the aging mouse.

The prevalence of urinary symptoms increases with age and is a significant source of distress, morbidity, and expense in the elderly. Recent evidence suggests that symptoms in the aged may result from sensory dysfunction, rather than abnormalities of detrusor performance. Therefore, we employed a pressure/flow multichannel urethane-anesthetized mouse cystometry model to test the hypothesis that in vivo detrusor performance does not degrade with aging. Secondarily, we sought to evaluate sensory responsiveness to volume using pressure-volume data generated during bladder filling. Cystometric data from 2-, 12-, 22-, and 26-mo-old female C57BL6 mice were compared. All 2- and 12-mo-old mice, 66% of 22-mo-old mice, and 50% of 26-mo-old mice responded to continuous bladder filling with periodic reflex voiding. Abdominal wall contraction with voiding had a minimal contribution to expulsive pressure, whereas compliance pressure was a significant contributor. Maximum bladder pressure, estimated detrusor pressure, detrusor impulse (pressure-time integral), as well as indices of detrusor power and work, did not decrease with aging. Bladder precontraction pressures decreased, compliance increased, and nonvoiding contraction counts did not change with increasing age. Intervoid intervals, per-void volumes, and voiding flow rates increased with age. Calculations approximating wall stress during filling suggested loss of bladder volume sensitivity with increasing age. We conclude that aging is associated with an impaired ability to respond to the challenge of continuous bladder filling with cyclic voiding, yet among responsive animals, voiding detrusor contraction strength does not degrade with aging in this murine model. Furthermore, indirect measures suggest that bladder volume sensitivity is diminished. Thus, changes in homeostatic reserve and peripheral and/or central sensory mechanisms may be important contributors to aging-associated changes in bladder function.

Continuous uroflow cystometry in the urethane-anesthetized mouse.

PURPOSE: In vivo animal cystometry represents an accepted methodology for the study of lower urinary tract physiology. A particular advantage of the mouse model is the availability of genetically modified strains, offering the possibility of linking individual genes to relevant physiological events. However, small voided volumes complicate the ability to obtain reliable pressure-flow data by gravimetric methods, due to non-continuous drop formation and release during voiding. We investigated the feasibility of a simple non-gravimetric continuous urine collection system during cystometry under urethane anesthesia, and compared urethane-anesthetized with awake cystometry. METHODS: Cystometry was performed in awake and urethane-anesthetized female mice using a suprapubic tube. A simple, novel non-gravimetric method of urine collection was used in urethane-anesthetized animals to assess voided volume and permit flow rate calculations. Pressure and time-related variables were compared between groups. RESULTS: Voided urine collection appears to be complete and continuous in this model. Mean voided volume was 0.09 ± 0.020 ml, with an average flow rate of 0.029 ± 0.007 ml/sec. Urethane anesthesia delayed cystometric pressure/volume responses. However, micturition reflexes were intact and otherwise comparable between groups. Female mice void with pulsatile pressurization previously described in rats. CONCLUSION: Suprapubic voiding cystometry using a simple and reliable urine collection method under urethane anesthesia is feasible in mice, permitting the integration of voided volumes with pressure and time data. The inclusion of volume and flow data enhances the usefulness of the mouse model for in vivo assessment of detrusor and potentially sphincteric performance.

Post hoc interpretation of urodynamic evaluation is qualitatively different than interpretation at the time of urodynamic study.

OBJECTIVES: Intraobserver reliability of post hoc urodynamic interpretation is greater than interobserver reliability, attributable to interpreter bias. If post hoc interpretation is qualitatively similar to interpretation at the time of study by a urodynamicist in attendance ("live" interpretation), a similar intraobserver bias should be observed. We therefore evaluated the intra- and interobserver reliability of post hoc versus "live" interpretation. METHODS: Fifty-five consecutive urodynamic studies administered by each of two urodynamicists and interpreted at the time of study were de-identified and later re-interpreted by the same two physicians. History and exam findings, cystometric tracing, uroflow summary and radiographs were available for interpretation. Intraobserver (post hoc vs. live), interobserver (post hoc vs. live) and interobserver (post hoc vs. post hoc) reliability was assessed by correlation coefficients for quantitative data, and Cohen's kappa statistic for categorical data. RESULTS: Post hoc versus live interpretations demonstrated no superiority of intraobserver reliability. For categorical observations, intraobserver reliability was best for urodynamic observations, but worse for clinical diagnosis (kappa = 0.37) and primary treatment recommendation (kappa = 0.26). Interobserver reliabilities were similar to intraobserver. Post hoc/post hoc interobserver correlations for quantitative data were good to very good, r(2) = 0.611-0.914. CONCLUSIONS: In contrast to previously reported post hoc/post hoc comparisons, post hoc/live comparison demonstrated no superiority of intraobserver reliability. Urodynamic observations and impressions are more reliable than are clinical diagnosis and therapeutic recommendation based upon urodynamic evaluation. Unrecorded and heuristic observations at the time of study as well as interpreter judgment may thus be determinants of diagnostic interpretation of urodynamic evaluation.

Comparison of cystometric methods in female rats.

AIMS: Rat cystometry is a common model used to investigate urinary storage and voiding function. The effect of cystometric instrumentation in rat studies might be a source of deviation from normal physiologic responses. We hypothesized that transurethral catheterization would produce obstruction-related changes, and that suprapubic catheterization would limit volume-related functions as well as disrupt normal urothelial sensory function. We investigated the influence of transurethral and suprapubic catheterization on storage and voiding in the rat model. METHODS: Three groups of female SD rats 250-300 g under urethane anesthesia were studied. Cystometric and pseudoaffective responses to physiologic voiding with and without suprapubic catheter placement, and cystometry via suprapubic and transurethral catheterization were studied. RESULTS: In free-voiding animals, per-void volume was 1.8 +/- 0.2 ml with an average flow rate of 0.18 ml/sec, and intercontraction interval (ICI) 60 min. Suprapubic catheterization decreased the ICI and per-void volume consistent with capacity reduction. Suprapubic cystometry did not significantly alter parameters compared to voiding except for a shortened ICI. Bladder pressures and somatic responses were increased, and urine flow impaired by transurethral cystometry. Terazosin did not significantly improve voiding parameters. CONCLUSIONS: Other than volume-related parameter changes probably related to surgical compromise of bladder capacity, suprapubic catheterization does not alter the cystometric and physiologic responses to voiding when compared to normal, uninstrumented voiding. Transurethral cystometry appears to be obstructive and may activate nociceptive reflexes. For this reason, whenever possible, urodynamic testing using the rat model should employ suprapubic catheterization.

Does uroflow predict ISD?

AIM: The term superflow has been given to abnormally high flow rates in women, and has been thought to be indicative of intrinsic sphincteric deficiency (ISD), as ISD is associated with low urethral pressure. Pelvic organ prolapse (POP) damages the sphincteric mechanism extrinsic to the urethra. The aim of this study was to determine if ISD can be predicted from voiding flow rates in women with symptomatic POP. METHODS: The charts of 82 patients who had undergone surgery for repair of symptomatic vaginal prolapse were reviewed. Uroflow and urodynamic endpoints were compared between dry and stress incontinent patients, and correlations between abdominal leak point pressures (LPP) and pressure/flow data evaluated. RESULTS: Average maximum flow (Q(max)) at uroflow was greater than at urodynamics with no significant difference in voided volumes. Twenty eight patients were found to have urodynamic stress incontinence (SUI), and an additional 19 to have "occult" stress incontinence. Patients with SUI had higher flow rates at urodynamics than continent patients. Voiding detrusor pressures and flow rates were not different when categorized by LPP cutoffs of 100 and 60 cm/w. Abdominal leak point pressure did not significantly correlate with any uroflow or urodynamic pressure/flow parameter. CONCLUSIONS: Flow rates, whether determined by uroflow testing or at urodynamics, are not predictive of ISD as defined by a low abdominal leak point pressure, in patients with symptomatic POP. Either the effect of ISD on flow rates is a non-linear complex relationship or LPP does not adequately define ISD.

Transobturator tape, bladder perforation, and paravaginal defect: a case report.

Transobturator midurethral slings (TOT) have been shown to have less risk of vascular and visceral injury than tension-free midurethral slings. Routine cystoscopy has therefore not been felt to be necessary. A case of bladder perforation unrecognized at the time of TOT placement is presented. Findings at sling removal suggested that a clinically nonapparent paravaginal defect may have been instrumental in the injury. Consideration should be given to routine cystoscopy at the time of transobturator sling placement.

Current trends in the evaluation and management of female urinary incontinence.

Despite its common occurrence and often seemingly obvious causes, female urinary incontinence requires a thorough and thoughtful evaluation for its proper diagnosis and treatment. With rare exceptions, urinary incontinence is the result of failure of the sphincter mechanism to resist bladder pressures encountered during daily activities. This may be the result of sphincter failure, overactivity of the bladder detrusor muscle or both. In uncomplicated cases, the diagnosis is usually based on an evaluation in the office. Urodynamic and cystoscopic study may be helpful in complex, resistant and recurring cases of urinary incontinence of any cause. Most cases of incontinence may be classified as stress, urge or mixed urinary incontinence. Treatment of stress urinary incontinence focuses on supplementing the urethral continence mechanisms, particularly the urethral supports and periurethral striated muscle function. The current paradigm for the treatment of urge incontinence centres on pharmacologic therapy, primarily by correcting detrusor overactivity with antimuscarinic drugs. Other therapies aimed at altering sensorimotor function may be used in resistant cases. The treatment of mixed urinary incontinence requires consideration of the contribution of each of its components. With proper diagnosis, effective treatment is possible for most patients.