Urinary bladder function and its control in healthy females

Biodegradable ring-shaped implantable device for intravesical therapy of bladder disorders

Intravesical instillation is an efficient drug delivery route for the local treatment of various urological conditions. Nevertheless, intravesical instillation is associated with several challenges, including pain, urological infection, and frequent clinic visits for catheterization; these difficulties support the need for a simple and easy intravesical drug delivery platform. Here, we propose a novel biodegradable intravesical device capable of long-term, local drug delivery without a retrieval procedure. The intravesical device is composed of drug encapsulating biodegradable polycaprolactone (PCL) microcapsules and connected by a bioabsorbable Polydioxanone (PDS) suture with NdFeB magnets in the end. The device is easily inserted into the bladder and forms a 'ring' shape optimized for maximal mechanical stability as informed by finite element analysis. In this study, inserted devices were retained in a swine model for 4 weeks. Using this device, we evaluated the system's capacity for delivery of lidocaine and resiquimod and demonstrated prolonged drug release. Moreover, a cost-effectiveness analysis supports device implementation compared to the standard of care. Our data support that this device can be a versatile drug delivery platform for urologic medications.

On Structure-Function Relationships in the Female Human Urethra: A Finite Element Model Approach

Remarkably little is known about urethral striated and smooth muscle and vascular plexus contributions to maintaining continence or initiating micturition. We therefore developed a 3-D, multiphysics, finite element model, based on sequential MR images from a 23-year-old nulliparous heathy woman, to examine the effect of contracting one or more individual muscle layers on the urethral closure pressure (UCP). The lofted urethra turned out to be both curved and asymmetric. The model results led us to reject the current hypothesis that the striated and smooth muscles contribute equally to UCP. While a simulated contraction of the outer (circular) striated muscle increased closure pressure, a similar contraction of the large inner longitudinal smooth muscle both reduced closure pressure and shortened urethral length, suggesting a role in initiating micturition. When age-related atrophy of the posterior striated muscle was simulated, a reduced and asymmetric UCP distribution developed in the transverse plane. Lastly, a simple 2D axisymmetric model of the vascular plexus and lumen suggests arteriovenous pressure plays and important role in helping to maintain luminal closure in the proximal urethra and thereby functional urethral length. More work is needed to examine interindividual differences and validate such models in vivo.

Underactive bladder: Pathophysiology and clinical significance

Underactive bladder (UAB) is a voiding disorder which generates disabling lower urinary tract symptoms (LUTS) due to the inability to produce an effective voiding contraction sufficient to empty the bladder. The underlying abnormality, that is usually appreciated when performing urodynamic studies, has been defined by the International Continence Society (ICS) as detrusor underactivity (DUA). DUA is a common yet under-researched bladder dysfunction. The prevalence of DUA in different patient groups suggests that multiple aetiologies are implicated. Currently there is no effective therapeutic approach to treat this condition. An improved understanding of the underlying mechanisms is needed to facilitate the development of new advances in treatment. The purpose of this review is to discuss the epidemiology, pathophysiology, common causes and risk factors potentially leading to DUA; to aid in the appropriate diagnosis of DUA to potentially improve treatment outcomes.

Neuromodulation of the neural circuits controlling the lower urinary tract

The inability to control timely bladder emptying is one of the most serious challenges among the many functional deficits that occur after a spinal cord injury. We previously demonstrated that electrodes placed epidurally on the dorsum of the spinal cord can be used in animals and humans to recover postural and locomotor function after complete paralysis and can be used to enable voiding in spinal rats. In the present study, we examined the neuromodulation of lower urinary tract function associated with acute epidural spinal cord stimulation, locomotion, and peripheral nerve stimulation in adult rats. Herein we demonstrate that electrically evoked potentials in the hindlimb muscles and external urethral sphincter are modulated uniquely when the rat is stepping bipedally and not voiding, immediately pre-voiding, or when voiding. We also show that spinal cord stimulation can effectively neuromodulate the lower urinary tract via frequency-dependent stimulation patterns and that neural peripheral nerve stimulation can activate the external urethral sphincter both directly and via relays in the spinal cord. The data demonstrate that the sensorimotor networks controlling bladder and locomotion are highly integrated neurophysiologically and behaviorally and demonstrate how these two functions are modulated by sensory input from the tibial and pudental nerves. A more detailed understanding of the high level of interaction between these networks could lead to the integration of multiple neurophysiological strategies to improve bladder function. These data suggest that the development of strategies to improve bladder function should simultaneously engage these highly integrated networks in an activity-dependent manner.

Influence of sildenafil on blood oxygen saturation of the obstructed bladder

Background

Blood oxygen saturation (BOS) is decreased in a low-compliant, overactive obstructed bladder. The objective of this study is to determine the effect of Sildenafil (SC) on bladder function and BOS) in an in vivo animal model of bladder outlet obstruction.

Methods

Thirty-two guinea pigs; sham operated (n = 8), sham operated + SC (n = 8), urethrally obstructed (n = 8) and urethrally obstructed + SC (n = 8) were studied during an 8 week period. BOS of the bladder wall was measured by differential path-length spectroscopy (DPS) before obstruction, at day 0, and at week 8. The bladder function was evaluated by urodynamic studies every week.

Results

Before surgery and after sham operation all study parameters were comparable. After sham operation, bladder function and BOS did not change. In the obstructed group the urodynamic parameters were deteriorated and BOS was decreased. In the group obstruction + SC, bladder compliance remained normal and overactivity occurred only sporadic. BOS remained unchanged compared to the sham group and was significantly higher compared to the obstruction group.

Conclusions

In an obstructed bladder the loss of bladder function is accompanied by a significant decrease in BOS. Treatment of obstructed bladders with SC yields a situation of high saturation, high bladder compliance and almost no overactivity. Maintaining the microcirculation of the bladder wall might result in better bladder performance without significant loss of bladder function. Measurement of BOS and interventions focussing on tissue microcirculation may have a place in the evaluation / treatment of various bladder dysfunctions.

Non-invasive evaluation of bladder outlet obstruction in men suspected of benign prostatic hyperplasia: usefulness of the d index

OBJECTIVE

To compare a new index of voiding dysfunction (D) based purely on free uroflow vs. Abrams-Griffiths (A-G) number obtained from intubated flow, for classification of bladder outlet obstruction in men.

PATIENTS AND METHODS

Urodynamic tracings of 60 non-neurological patients (30 before transurethral resection of the prostate and of 30 men suspected of benign prostatic hyperplasia included in a medical therapy trial) were retrospectively analyzed. The Valentini-Besson-Nelson model was used to evaluate the value of the D index. A-G was obtained from intubated flows. Obstruction was defined as D > 32.5 cm H2O (translation of A-G criterion).

RESULTS

D showed 82.05% sensitivity with 66.66% specificity; the positive predictive value was 82.05% and the negative predictive value 66.66% for the whole population, 83.3 vs. 80.9% sensitivity with 58.3 vs. 77.7% specificity for pre- transurethral resection of the prostate vs. medical therapy group.

CONCLUSION

D index which can be obtained from a free uroflow appears as a valuable alternative to invasive urodynamic investigations when the diagnosis of bladder outlet obstruction needs to be more solidly established before a treatment decision or in men suspected of benign prostatic hyperplasia who elect for watchful waiting.

Evidence of a functional effect of transient transurethral catheterization on micturition in women

INTRODUCTION AND HYPOTHESIS

The objective of this study is to evaluate the effect of transient catheterization on uroflow parameters.

METHODS

Consenting women (ages 18-90) provided an uninstrumented uroflow pre- and post-indicated in urodynamic procedures. Voided volume, Qmax, and Qave were recorded for both uninstrumented uroflows. Uroflow curves were classified as "normal" or "abnormal." Pre- and post-urodynamic uroflow data were compared.

RESULTS

Thirty-five patients were included in the study. There was a statistically significant decrease in Qave from the pre- to the post-urodynamic uroflows from 14.71 to 10.55 ml/s (p = 0.012). Additionally, 28.6% of uroflow tracing patterns changed from "normal" to "abnormal," whereas only one (2.9%) changed from "abnormal" to "normal" (p = 0.031).

CONCLUSIONS

This study showed a degradative effect of transient catheterization on uroflow parameters, suggesting that catheterization may cause more than simply a passive obstructive effect. Urethral stimulation due to catheterization may perturb detrusor urethral function, altering voiding and possibly filling performance.

Review of invasive urodynamics and progress towards non-invasive measurements in the assessment of bladder outlet obstruction

OBJECTIVE

This article defines the need for objective measurements to help diagnose the cause of lower urinary tract symptoms (LUTS). It describes the conventional techniques available, mainly invasive, and then summarizes the emerging range of non-invasive measurement techniques.

METHODS

This is a narrative review derived form the clinical and scientific knowledge of the authors together with consideration of selected literature.

RESULTS

Consideration of measured bladder pressure urinary flow rate during voiding in an invasive pressure flow study is considered the gold standard for categorization of bladder outlet obstruction (BOO). The diagnosis is currently made by plotting the detrusor pressure at maximum flow (p(detQmax)) and maximum flow rate (Q(max)) on the nomogram approved by the International Continence Society. This plot will categorize the void as obstructed, equivocal or unobstructed. The invasive and relatively complex nature of this investigation has led to a number of inventive techniques to categorize BOO either by measuring bladder pressure non-invasively or by providing a proxy measure such as bladder weight.

CONCLUSION

Non-invasive methods of diagnosing BOO show great promise and a few have reached the stage of being commercially available. Further studies are however needed to validate the measurement technique and assess their worth in the assessment of men with LUTS.

Treatment strategy according to findings on pressure-flow study for women with decreased urinary flow rate

PURPOSE

In women who reported a weak urinary stream, the efficacy of treatment chosen according to the urodynamic findings on pressure-flow study was prospectively evaluated.

MATERIALS AND METHODS

Twelve female patients with maximum flow rates of 10 mL/sec or lower were analyzed in the present study. At baseline, all underwent pressure-flow study to determine the degree of bladder outlet obstruction (BOO) and status of detrusor contractility on Schäfer's diagram. Distigmine bromide, 10 mg/d, was given to the patients with detrusor underactivity (DUA) defined as weak/very weak contractility, whereas urethral dilatation was performed using a metal sound for those with BOO (linear passive urethral resistance relation 2-6). Treatment efficacy was evaluated using the International Prostate Symptom Score (IPSS), uroflowmetry, and measurement of postvoid residual urine volume. Some patients underwent pressure-flow study after treatment.

RESULTS

Urethral dilatation was performed for six patients with BOO, while distigmine bromide was given to the remaining six showing DUA without BOO. IPSS, QOL index, and the urinary flow rate were significantly improved in both groups after treatment. All four of the patients with BOO and one of the three with DUA but no BOO who underwent pressure-flow study after treatment showed decreased degrees of BOO and increased detrusor contractility, respectively.

CONCLUSIONS

Both BOO and DUA cause a decreased urinary flow rate in women. In the short-term, urethral dilatation and distigmine bromide are efficacious for female patients with BOO and those with DUA, respectively.

Variation in invasive and noninvasive measurements of isovolumetric bladder pressure and categorization of obstruction according to bladder volume

PURPOSE

We developed a noninvasive test that provides an estimate of isovolumetric bladder pressure by measuring the pressure required to interrupt voiding using controlled inflation of a penile cuff. We noted variation in serial measurements obtained during a single void and, therefore, we determined whether this represents variation in detrusor contraction strength, as predicted in previous studies, or measurement error.

MATERIALS AND METHODS

A total of 36 symptomatic men underwent simultaneous invasive and noninvasive pressure flow studies. Corresponding values of isovolumetric bladder pressure and cuff interruption pressure were recorded at each flow interruption and grouped according to bladder volume to calculate measurement error and bias at various points during a void. Individual variation in the 2 measurements across a range of normalized bladder volumes was then examined using ANOVA.

RESULTS

Cuff interruption pressure showed a consistent level of accuracy as an estimate of isovolumetric bladder pressure across a range of volumes. There were similar, statistically significant differences in isovolumetric bladder pressure and cuff interruption pressure recorded at specific volume increments with the highest values seen in the mid range and the lowest seen at lower bladder volumes (each p <0.01). When plotting, the maximum recorded value of cuff interruption pressure in each individual on our proposed noninvasive pressure flow nomogram provided the best diagnostic accuracy for obstruction.

CONCLUSIONS

This study shows that cuff interruption pressure varies in the expected manner with bladder volume and provides a consistent estimate of isovolumetric bladder pressure throughout a void. These data provide important guidance for interpreting noninvasive pressure flow studies and classifying obstruction on the proposed nomogram.

Basics of pressure-flow studies

Pressure-flow studies of voiding contain information about urethral resistance or obstruction and about the detrusor contraction or contractility. A fundamental problem, discussed in this paper, is how to disentangle these two. A second, more difficult, problem is how to evaluate them in a simple, clinically useful way. Plots of detrusor pressure against flow rate during the course of voiding offer a helpful adjunct to conventional urodynamic curves showing changes with time. Many ways of assessing urethral obstruction from these plots have been proposed that have somewhat differing aims but, in practice, produce rather similar results. Agreement on a standard method is needed to allow the comparison of results obtained in different centers. Detrusor contractility has been less extensively studied but methods for assessing it are available.

Estimation of the maximum contraction velocity of the urinary bladder from pressure and flow throughout micturition

The contractility of the urinary bladder can be adequately described in terms of the parameters P0 (isometric pressure) and Vmax (maximum contraction velocity). In about 12% of urodynamic evaluations of patients these clinically relevant parameters can be calculated from pressure and flow rate as measured during micturition. A method was developed of estimating Vmax for any micturition from these signals. The properties of this estimated contractility parameter were clinically tested and are discussed.