Non-invasive characterization of real-time bladder sensation using accelerated hydration and a novel sensation meter: An initial experience

Dynamic analysis of the individual patterns of intakes, voids, and bladder sensations reported in bladder diaries collected in the LURN study

The goal of this study was to develop the novel analytical approach and to perform an in-depth dynamic analysis of individual bladder diaries to inform which behavioral modifications would best reduce lower urinary tract symptoms, such as frequency and urgency. Three-day bladder diaries containing data on timing, volumes, and types of fluid intake, as well as timing, volumes, and bladder sensation at voids were analyzed for 197 participants with lower urinary tract symptoms. A novel dynamic analytic approach to bladder diary time series data was proposed and developed, including intra-subject correlations between time-varying variables: rates of intake, bladder filling rate, and urge growth rate. Grey-box models of bladder filling rate and multivariable linear regression models of urge growth rate were developed for individual diaries. These models revealed that bladder filling rate, rather than urine volume, was the primary determinant of urinary frequency and urgency growth rate in the majority of participants. Simulations performed with the developed models predicted that the most beneficial behavioral modifications to reduce the number of urgency episodes are those that smooth profiles of bladder filling rate, which might include behaviors such as exclusion of caffeine and alcohol and/or other measures, e.g., increasing number and decreasing volumes of intakes.

A stepwise approach for functional near infrared spectroscopy measurement during natural bladder filling

Background

Functional near infrared spectroscopy (fNIRS) is a versatile, noninvasive, and inexpensive tool that can be used to measure oxyhemoglobin (O2Hb) changes in the cortical brain caused by increasing bladder sensation during filling in upright posture. This study's purpose is to provide a rigorous methodologic template that can be implemented for comparative studies of fNIRS in the diagnosis and management of lower urinary tract symptoms including overactive bladder (OAB) and other forms of lower urinary tract dysfunction.

Methods

Participants without any urologic conditions completed a validated oral hydration protocol facilitating and equilibrating natural bladder filling. First desire to void and real time bladder sensation (0-100%) were recorded using a Sensation Meter. A 24-channel fNIRS template simultaneously recorded prefrontal cortical O2Hb. Each channel was analyzed between "first desire" to void and 100% sensation, defined in this study as the period of "high sensation". Channels were sub-divided by cortical regions: right (nine channels), left (nine channels), middle (six channels).

Results

A total of eight participants (male: n=4, female: n=4) were enrolled with mean age 39±19.9 years and body mass index (BMI) of 25±3.93 kg/m2. There were no differences in age, BMI, race, or OAB survey scores based on biological sex. Signal acquisition improved with power bank use, postural head support for motion reduction, and head cap optimization. Acceleration-based concurrent motion measurement was effectively utilized to remove motion artifacts. O2Hb concentration patterns appeared irregular during low sensation and increased during high sensation after first desire across the frontal cortex.

Conclusions

Employing a stepwise approach, this study defined a methodological guide for improved prefrontal fNIRS signal acquisition and analysis during bladder filling. The technique demonstrated that prefrontal fNIRS cortical O2Hb increases with elevated bladder sensation in normal subjects and sets the stage for comparative studies in individuals with OAB and other forms of lower urinary tract dysfunction.

Dynamic analysis of the individual patterns of intakes, voids, and bladder sensations reported in bladder diaries collected in the LURN study

The goal of this study was to perform an in-depth dynamic analysis of individual bladder diaries to inform which behavioral modifications would best reduce lower urinary tract symptoms, such as frequency and urgency. Three-day bladder diaries containing data on timing, volumes, and types of fluid intake, as well as timing, volumes, and bladder sensation at voids were analyzed for 197 participants with lower urinary tract symptoms. A novel dynamic analytic approach to bladder diary time series data was proposed and developed, including intra-subject correlations between time-varying variables: rates of intake, bladder filling rate, and urge growth rate. Grey-box models of bladder filling rate and multivariable linear regression models of urge growth rate were developed for individual diaries. These models revealed that bladder filling rate, rather than urine volume, was the primary determinant of urinary frequency and urgency growth rate in the majority of participants. Simulations performed with the developed models predicted that the most beneficial behavioral modifications to reduce the number of urgency episodes are those that smooth profiles of bladder filling rate, which might include behaviors such as exclusion of caffeine and alcohol and/or other measures, e.g., increasing number and decreasing volumes of intakes.

Repeatability of Ultrasound-Defined Bladder Shape Metrics in Healthy Volunteers

Purpose

Patients and Methods

Results

Conclusion

Influence of visual and auditory cues about bladder volume on real-time filling sensation in healthy volunteers

Auditory/visual (A/V) cues can trigger urgency in some individuals with overactive bladder (OAB), and patient-reported bladder sensation can be characterized during non-invasive oral hydration studies. The aim of this investigation was to test the hypothesis that A/V cues of bladder volume can alter patient-perceived bladder sensation during hydration studies. Healthy volunteers without urinary symptoms based on ICIq-OAB survey scores were recruited for an oral hydration study where they completed two fill/void cycles. The study was repeated twice, one week apart. Throughout bladder filling, participants reported real-time sensation (0-100%) using a Sensation Meter, and bladder volumes were measured at 5 min intervals with both 3D ultrasound and BladderScan^®. Participants were divided into a Cues(+) group that was allowed to view their ultrasound images and hear volume measurements of the BladderScan^® every 5 min and a Cues(-) group that was not exposed to these A/V cues. The A/V Cues(+) group had 10 participants (5 women and 5 men) and the Cues(-) group had 10 participants (7 women and 3 men). During the second visit, the Cues(+) group demonstrated decreased sensation compared to the Cues(-) group in the slower first fill, but not the faster second fill. The results of this study demonstrate that A/V cues about bladder volume can acutely alter sensation during hydration studies in healthy individuals with normal bladder function.

Irregular bladder shapes identified in women with overactive bladder: an ultrasound nomogram

In this study, an ultrasound-based bladder shape nomogram was developed using data from women without overactive bladder (OAB) and tested in women with OAB to identify irregular bladder shapes. The goal was development of a nomogram that can ultimately be used for non-invasive identification of a bladder shape-associated OAB phenotype. Transabdominal 3-dimensional (3D) bladder ultrasound images were collected at 1-minute intervals during urodynamics studies and at 5-10-minute intervals during oral hydration studies. These prospective studies enrolled women with and without OAB based on International Consultation on Incontinence questionnaire on OAB (ICIq-OAB) question 5a (OAB 5a≥2, without OAB 5a<2). Bladder perimeters were manually traced and refined using GE 4D-View software. Nomograms for the transverse, sagittal and coronal perimeter-volume relationships were developed for women without OAB. A power model was used to approximate upper and lower nomogram bounds with 95% confidence intervals. Nomograms were tested using data from women with OAB, and each participant was classified as having an irregular bladder shape based on the number of perimeter values outside the nomogram bounds. Nomograms were developed using 533 images from 27 women without OAB (14 from urodynamics and 13 from hydration studies) and were tested using 264 images from 24 women with OAB (16 urodynamics and 8 hydration). The sagittal perimeter nomogram provided the best results, with irregular sagittal perimeters identified in 6/24 (25%) women with OAB and 0/27 (0%) without OAB. An irregular sagittal perimeter was significantly associated with OAB (P<0.05). Ultrasound-based nomograms may enable feasible, non-invasive identification of a subgroup of women with bladder shape-associated OAB.

Artifacts and abnormal findings may limit the use of asymptomatic volunteers as controls for studies of multichannel urodynamics

BACKGROUND

Multichannel urodynamics is the gold standard for the evaluation of lower urinary tract symptoms (LUTS). When performing studies to validate new adjuncts to urodynamic testing with control patients undergoing urodynamic investigation, there is difficulty in the interpretation of urodynamic results in the asymptomatic patient due to artifacts and the invasive nature of the procedure. The purpose of this investigation was to examine urodynamics in asymptomatic volunteers in order to better understand the role of control participants in urodynamic research studies.

METHODS

Asymptomatic volunteers with no LUTS were recruited to undergo standard urodynamic testing as a comparison group in a study evaluating novel urodynamic techniques. To be eligible, participants had to report no LUTS, score ≤1 on all symptom questions of the International Consultation on Incontinence Questionnaire Overactive Bladder Module (ICIq-OAB) survey, have no medical conditions or to undergo any medications that affect bladder function. The urodynamics was done according to ICS standards. All tracings were evaluated by an expert neuro-urologist. Data were analyzed categorically for the presence or absence of low compliance (<30 mL/cmH20), detrusor overactivity, bladder outlet obstruction (Bladder Outlet Obstruction Index [BOOI]>40), weak contractility (bladder contractility index [BCI]<100), straining to void, poorly sustained detrusor contraction, uncoordinated EMG activity, and intermittent flow.

RESULTS

A total of 24 participants completed the study including 10 men and 14 women. All participants had at least 1 urodynamic abnormality/artifact with an average of 4.43±1.28 abnormalities/participant. The most common abnormalities included uncoordinated electromyography (EMG) activity (87.50%), straining to void (79.17%), and intermittent flow (70.83%). There were no significant differences for sex, age, Body Mass Index.

CONCLUSIONS

This study demonstrated that healthy, asymptomatic volunteers have high rates of abnormal urodynamic findings, suggesting that asymptomatic participants are not the ideal controls in research studies that involve urodynamic testing.

Cognitive components of behavioral therapy for overactive bladder: a systematic review

INTRODUCTION AND HYPOTHESIS

Behavioral therapy is the first-line treatment for overactive bladder (OAB); however, the cognitive components of behavioral therapy for OAB have not been evaluated. The purposes of this systematic review were to describe the cognitive components of behavioral therapy for OAB and evaluate their effectiveness as well as to describe their rationale and origins.

METHODS

Searches were conducted on the PubMed, CINAHL, Web of Science, Cochrane and PEDro databases. Inclusion criteria were single-arm or randomized controlled trials on OAB treatment that utilized behavioral therapy, with a description of a cognitive component of the behavioral therapy. Study participants were neurologically intact adults (n = 1169). Study methodological quality was assessed with the PEDro and Newcastle-Ottawa scales.

RESULTS

Five studies were included, published between 2009 and 2020. Methodological quality was variable. All studies reported a reduction of symptoms in participants receiving behavioral therapy. Cognitive components of behavioral therapy were not extensively described. Distraction was the most common cognitive strategy for managing urgency. The relative impact of the cognitive aspect of behavioral therapy could not be evaluated, and the cognitive aspects of behavioral therapy appear to be accepted wisdom, traceable to several key authors, that has not been subjected to scientific investigation.

CONCLUSIONS

Behavioral therapy for OAB appears useful, but its cognitive components are not well described, their relative importance has not been evaluated or ascertained, nor have they been rigorously studied.

Bladder wall micromotion measured by non-invasive ultrasound: initial results in women with and without overactive bladder

OBJECTIVE

Rhythmic contractions of the bladder wall during filling result from the synchronization of bladder wall micromotion and are often observed in the urodynamic tracings of individuals with urinary overactive bladder (OAB). This study's objective was to develop a novel, non-invasive method to measure bladder wall micromotion and to conduct an initial study to test the hypothesis that elevated micromotion is associated with OAB.

METHODS

This prospective study enrolled women with OAB and asymptomatic volunteers as measured by the ICIQ-OAB survey. After filling the bladder to 40% cystometric capacity, 85 second cine-loops were obtained using a GE Voluson E8 ultrasound system with an 8 MHz curved, abdominal probe. A custom correlation-based texture tracking MATLAB algorithm was used to measure changes in the bladder wall thickness over time and correlate with changes in vesical pressure. Significant bladder wall micromotion was defined as changes in wall thickness with amplitudes higher than 0.1 mm in the frequency range of 1.75-6 cycles/minute as calculated from Fast Fourier Transform (FFT) analysis. The micromotion algorithm was tested on 30 women including 17 with OAB and 13 asymptomatic volunteers.

RESULTS

Micromotion was identified in 41% of subjects with OAB and 0% of asymptomatic volunteers, indicating a significant association of micromotion with OAB (Fisher's exact test, P=0.010). Micromotion was also found to have a significant association with a clinical diagnosis of detrusor overactivity (Fisher's exact test, P=0.031). Frequencies with elevated micromotion correlated with frequencies of vesical pressure fluctuations.

CONCLUSIONS

The feasibility of a non-invasive method to measure bladder wall micromotion was demonstrated using transabdominal anatomical motion mode (M-mode) ultrasound. Presence of micromotion was significantly associated with OAB and with urodynamic-identified rhythm.

Comparison of Sensation Event Descriptors in Participants with Overactive and Normal Bladders during Non-Invasive Hydration Studies

PURPOSE

Despite the importance of alterations in bladder sensation, objective metrics to characterize sensation outside of urodynamics remain limited. A real-time sensation meter enables recording of sensation event descriptors throughout filling. The purpose of this study was to evaluate the differences in sensation event descriptor patterns between normal participants and those with OAB.

METHODS

Normal and OAB participants were enrolled from responses to the ICIq-OAB survey question on urgency (Q5a: 0 vs. ≥ 3). Real-time bladder sensation on a 0%-100% scale was recorded on a validated tablet sensation meter throughout two fill-void cycles. The first and second fills were considered "slow" and "fast" respectively. After each sensation meter change (sensation event), a pop-up screen asked participants to characterize sensation with one or more of these descriptors: "tense," "pressure," "tingling," "painful," and/or "other." Oral hydration was achieved by rapid consumption of 2L G2^® Gatorade.

RESULTS

Data from 29 participants (12 normal/17 OAB) were analyzed. The rate of filling from bladder volume and fill duration, was greater for the fast fill in both groups. In the slow fill, "tingling" (64 ± 3% OAB vs. 77 ± 3% normal, p=0.008) and "tense" (78 ± 3% OAB vs. 94 ± 1% normal, p<0.001) occurred at lower sensations in OAB participants.

CONCLUSION

During only the slow fill, OAB individuals experience the sensation descriptors of "tingling" and "tense" at earlier sensations than normal individuals. Therefore, this non-invasive method to evaluate real-time sensation descriptors during filling may identify important sensation patterns and improve understanding and phenotyping of OAB.

Should we be revisiting LUT basic science and clinical measurement of LUT sensation to improve patient care? ICI-RS 2019

AIMS

This article reviews current knowledge of the underpinning mechanisms of how the bladder senses fullness locally and also revisits clinical measurements of lower urinary tract sensation. The former represents cellular sensing during bladder filling whereas the latter describes the sensations leading to conscious perception of bladder fullness.

METHODS

The topic was discussed in a "think tank" session at the 2019 International Consultation on Incontinence-Research Symposium in Bristol, UK; summarized in the present review.

RESULTS

Recent advances in the basic science of bladder sensing relating to (a) the bladder wall-urothelial cells, sensory nerves, interstitial cells, and smooth muscle cells and (b) putative chemo/mechanosensors in the urethra-paraneurons or "brush cells" are discussed. Validated clinical measurement of lower urinary tract sensation is reviewed in the context of how this could be better harnessed for patient benefit. We discuss the potential of app/tablet/mobile technology based on triggers and distractors to override aberrant local sensing/higher sensation and how these technologies could be utilized in treatment.

CONCLUSIONS

We conclude that a better understanding of bladder sensation is essential to inform clinical management of lower urinary tract symptoms.

Comparative-fill urodynamics in individuals with and without detrusor overactivity supports a conceptual model for dynamic elasticity regulation

AIMS

Dynamic elasticity was previously identified in individuals with overactive bladder (OAB) using comparative-fill urodynamics (UD) and is a biomechanical mechanism for acutely regulating detrusor wall tension. On the basis of this data, a conceptual model of dynamic elasticity regulation mediated through a balance of passive mechanisms and active contractions was constructed. The present study tested this model by determining whether individuals with detrusor overactivity (DO) exhibit less dynamic elasticity than individuals without DO.

METHODS

Individuals with and without urgency based on International Consultation on Incontinence Questionnaire-OAB surveys were prospectively enrolled in a comparative-fill UD study. An initial fill defined the presence or absence of DO and determined cystometric capacity. Three additional fills were employed with either passive emptying via a catheter or active voiding. To identify dynamic elasticity, average filling pressures (P_ves ) were compared for fill 1 (before strain softening), fill 2 (after strain softening), and fill 3 (after active void). A dynamic elasticity index was defined.

RESULTS

From 28 participants, those without DO showed decreased P_ves during filling after strain softening and restored P_ves during filling following active voiding, revealing dynamic elasticity. Participants with DO did not show dynamic elasticity. A dynamic elasticity index less than 1.0 cmH₂ O/40% capacity was identified in 2 out of 13 participants without DO and 9 out of 15 with DO, revealing a significant association between DO and reduced/absent dynamic elasticity (P = .024).

CONCLUSIONS

This study supports a conceptual model for dynamic elasticity, a mechanism to acutely regulate detrusor wall tension through a balance of competing active contractile and passive strain mechanisms. Improved understanding of this mechanistic model may help us to identify novel treatment strategies for OAB.

Bladder volume correction factors measured with 3D ultrasound and BladderScan

INTRODUCTION

The aim of this study was to investigate conventional 3D ultrasound and portable BladderScan volume measurements and implement correction factors to ensure accurate volume metrics.

MATERIALS AND METHODS

Healthy participants without urinary urgency were recruited for a prospective hydration study in which three consecutive voids were analyzed for two separate visits. Just before and after voiding, 3D ultrasound and BladderScan volumes were measured. Estimated voided volumes were calculated as the volume immediately prior to void minus any post void residual and were compared to actual voided volumes measured using a graduated container. Percent errors were calculated, and an algebraic method was implemented to create correction factors for 3D ultrasound and BladderScan.

RESULTS

Sixteen individuals completed the study, and six voids were recorded for each participant. A total of 96 volume measurements ranging from 0 mL to 1050 mL with an average of 394 +/- 26 mL were analyzed. Both 3D ultrasound and BladderScan significantly underestimated voided volumes with averages of 296 +/- 22 and 362 +/- 27, respectively. Average percent error for the 3D ultrasound group was 30.1% (pre-correction) and 20.7% (post-correction) (p < 0.01) and 22.4% (pre-correction) and 21.8% (post-correction) for the BladderScan group (p = 0.20). The voided volume correction factors for 3D ultrasound and BladderScan were 1.30 and 1.06, respectively.

CONCLUSION

BladderScan and 3D ultrasound typically underestimate voided volumes. Correction factors enabled more accurate measurements of voided volumes for both 3D ultrasound and BladderScan. Accurate volume measurements will be valuable for the development of non-invasive urodynamics techniques.

Validation of a real-time bladder sensation meter during oral hydration in healthy adults: Repeatability and effects of fill rate and ultrasound probe pressure

OBJECTIVES

A non-invasive protocol was previously developed using three-dimensional ultrasound and a sensation meter to characterize real-time bladder sensation. This study the protocol by measuring the effects of fill rateand ultrasound probe pressure during oral hydration.

METHODS

Healthy volunteers with no urinary symptoms (based on International Consultation on Incontinence Questionnaire on Overactive Bladder surveys) were recruited into an oral hydration study. Throughout two complete fill-void cycles, participants drank 2 L Gatorade G2 (The Gatorade Company, Inc., Chicago, Illinois) and used a touch-screen sensation meter to record real-time bladder sensation (0%-100%). The study was repeated three times, once per week (Visits A, B, and C). In Visits A and B, ultrasound was used to measure bladder volume every 5 minutes. Ultrasound was not used in Visit C except at 100% capacity. Volume data from Visit B were used to estimate volumes throughout the fills in Visit C. Sensation-capacity curves were generated for each fill for comparative analysis.

RESULTS

Ten participants completed three visits (60 total fills). Increased fill rate led to decreased sensation throughout filling, andultrasound probe pressure led to increased sensation. Participants reported higher sensation at low volumes during Fill 1 of Visit A before training with the sensation meter. Sensation curves with intermittent ultrasound showed repeatability for Fill 2 in Visits A and B. Fill rate and ultrasound probe pressure affect real-time bladder sensation during oral hydration.

CONCLUSIONS

This study demonstrated repeatability of real-time bladder sensation during a two-fill oral hydration protocol with ultrasound.

New Diagnostics for Male Lower Urinary Tract Symptoms

PURPOSE OF REVIEW

Lower urinary tract symptoms (LUTS) is a common constellation of symptoms that affect the aging male population with an astonishing prevalence. New technology and new uses of established technology are being used to help further evaluate LUTS in the male population and help guide treatment options. This review focuses on the developments and future directions in diagnostic modalities for evaluation of male LUTS, focusing on evaluation of both the filling and voiding phases of micturition.

RECENT FINDINGS

New techniques in evaluating the voiding phase include penile cuff test, external pressure sensing condom catheter, ultrasound measurement of detrusor wall thickness, ultrasound measurement of intravesical prostatic protrusion, doppler ultrasound and NIRS technology. Evaluation of the filling phase is still undergoing much development and requires additional validation studies. The techniques undergoing evaluation include sensation meters during UDS, assessing bladder micromotion and wall rhythm, assessing detrusor wall biomechanics, ultrasound measurement of detrusor wall thickness, pelvic doppler ultrasound, as well as functional brain imaging including fNIRS and fMRI.

SUMMARY

The development of novel, non-invasive, diagnostic tools have the potential for better evaluation of LUTS with earlier and enhanced treatments. This will likely improve the quality of life for men with LUTS.

An innovative, non-invasive sensation meter allows for a more comprehensive understanding of bladder sensation events: A prospective study in participants with normal bladder function

AIMS

There is currently no standardized method of characterizing changes in bladder sensation during bladder filling outside of the urodynamics laboratory. The purpose of this investigation was to characterize real-time bladder sensation events using a sensation meter during oral hydration in individuals with normal bladder function.

METHODS

Participants enrolled in an accelerated hydration study drank 2 L Gatorade-G2® and utilized a sensation meter to record real-time bladder sensation (0-100%), verbal sensory thresholds, and sensation descriptors of "tense," "pressure," "tingling," "painful," and "other" for two consecutive fill-void cycles.

RESULTS

Data from 21 participants (12 females/9 males) were obtained and demonstrated an average of 8-9 sensation events (significant changes in sensation) per fill with no differences in the total number of sensation events and volume between sensation events (fill 1 vs fill 2). An increased number of sensation events occurred at higher capacity quartiles. Event descriptors of "pressure" and "tingling" were the most commonly chosen descriptors in both fills.

CONCLUSIONS

The innovative sensation meter includes the sensation event descriptors of "tense," "tingling," "pressure," and "painful," to enable a more comprehensive understanding of bladder sensation as well as real-time identification, quantification, and characterization of sensation events. The study demonstrates 8-9 events per fill, acceleration of sensation during filling, and unique sensation event descriptor patterns. This technology may be helpful in the identification of novel sensation patterns associated with overactive bladder (OAB) and aging.

Use of Ultrasound Urodynamics to Identify Differences in Bladder Shape Between Individuals With and Without Overactive Bladder

OBJECTIVES

The objective of this study was to identify differences in bladder shape changes between individuals with overactive bladder (OAB) and unaffected individuals during ultrasound urodynamics.

METHODS

A prospective urodynamic study was performed with concurrent transabdominal ultrasound (ultrasound urodynamics) on individuals with and without OAB based on validated International Consultation on Incontinence Questionnaire - OAB survey scores. Three-dimensional ultrasound images were acquired at 1-minute increments during filling and used to measure bladder diameters in the height, width, and depth orientations. The engineering strain for each diameter was compared between participants with OAB and controls during urodynamic filling. The height-to-width ratio at capacity was used to determine if individuals were shape outliers.

RESULTS

A total of 22 subjects were enrolled, including 11 with OAB and 11 without OAB. During urodynamic filling in both groups, the greatest degree of geometric strain was found in the height orientation, indicating that bladders generally fill in a craniocaudal shape. The mean ± SD height-to-width ratio of the control group was 1.06 ± 0.12 yielding a 95% confidence interval of 0.82 to 1.30. Five (45.5%) of 11 OAB subjects had height-to-width ratios outside this interval as compared with none of the control subjects, identifying a potential shape-mediated subgroup of OAB.

CONCLUSIONS

Three-dimensional ultrasound urodynamics can be used to identify differences in bladder shape comparing individuals with and without OAB. This method may be used to identify a subset of OAB patients with abnormal bladder shapes which may play a role in the pathophysiology of their OAB symptoms.

Methods of assessing and recording bladder sensation: a review of the literature

Introduction and hypothesis

The objective was to review different methods that have been used to assess bladder sensation and to provide an overview of the accuracy and objectivity of the measurement of the subjective perception of the bladder.

Methods

The MEDLINE and PubMed databases were searched to identify articles. References from those articles were also searched. Terms used for the search were: urinary bladder, sensation, cystometry, urodynamics, urinary incontinence and focus group. Eight hundred and fifty abstracts were identified from databases, and 12 from other sources. Twenty-two duplicate articles were removed. Irrelevant articles were excluded after reading their titles. Fifty-four articles were eligible, but 17 were excluded after reading the full text, leaving 37 articles where assessment of bladder sensation was the main aim.

Results

Six different methods of measuring bladder sensation have been described in the literature. Although the most frequently used was cystometry, this is an invasive tool and does not reproduce bladder behaviour during daily life because it records bladder sensation as episodic events. The visual analogue scale using a forced diuresis protocol seemed to be an excellent tool. It was non-invasive and evaluated bladder sensation continuously, from an empty to a full bladder.

Conclusions

In some of the studies, the samples were too small to draw any significant conclusions. There were also conflicting data on which tool was the most accurate, especially as each method of evaluating bladder sensation may influence the way it is described by participants.

Validation of a water-load protocol to define the pattern of bladder sensation

Introduction and hypothesis

The aim of this study was to confirm reliability of a water-load diuresis protocol and to assess the utility of bladder sensation curves.

Methods

For confirmation of fixed diuresis rate (phase 1), 12 volunteers consumed 250–300 ml of water every 15 min and recorded bladder sensation on a visual analogue scale (VAS) every 5 min to maximum sensation over two filling cycles: voids 1 and 2 (V1 and V2). The test was performed twice. For test–retest validation (phase 2), 24 participants underwent the same protocol drinking 300 ml of water every 15 min. Diuresis rates and voided volumes were compared between cycles and across tests.

Results

In phase 1, there was no difference in median void volume (V1 735 ml, V2 678 ml p = 0.433) or median diuresis rates (V2 12.1 ml/min, V3 14.4 ml/min p = 0.136) between cycles. When comparing those who drank 250–300 ml/15 min, there was less variability in those drinking 300-ml aliquots, so this was standardised for later experiments; 95% upper confidence limit of variability of the diuresis rate was calculated as 4.5 ml/min. Any test with a greater difference was rejected as invalid. In phase 2, only 16 participants were analysed. There was no difference in median void volumes between tests [V1 763 ml and 820 ml (p = 0.109) and V2 788 ml and 796 ml (p = 0.266)] or in diuresis rates between test 1 (12.33 ml/min) and 2 (14.40 ml/min) (p = 0.056). Median area under the curve was similar between test 1 404.96 and test 2 418.63.

Conclusions

This refined protocol reliably produced stable diuresis with a water load of 300 ml/15 min, excluding those with a difference in diuresis rate > 4.5 ml/min.

NEW CONCEPTS IN BLADDER SENSATION AND URINARY URGENCY

PURPOSE OF REVIEW

The purpose of this review is to summarize the current state of knowledge regarding the evaluation and measurement of urinary urgency and bladder sensation.

RECENT FINDINGS

New technologies have been developed to improve our diagnostic capabilities in urinary urgency and bladder sensation. Recent developments include MRI-based neuroimaging and novel tablet-based sensation meters that can be used during urodynamics as well as during oral hydration.

SUMMARY

Commonly used metrics for urinary urgency and bladder sensation include the use of validated surveys/void diaries and standardized verbal sensory thresholds during urodynamics. However, these metrics are highly subjective and prone to significant bias. There has been an evolution in evaluation metrics ranging from the use of reflex testing to electrical perception testing to the use of neuroimaging and the development of sensation meters. Neuroimaging allows for mapping of specific brain areas involved in the different phases of voiding and provides an anatomic basis for different forms of overactive bladder. The sensation meter allows for generation of real-time sensation-capacity curves which enables easy and objective comparison between patients as well as potential sub-typing of different forms of overactive bladder. In addition, new research supports the concept of differing forms of urgency and the use of novel patient-derived terminologies for urinary urgency and bladder sensation.

Quantification of bladder wall biomechanics during urodynamics: A methodologic investigation using ultrasound

Overactive bladder is often characterized by biomechanical changes in the bladder wall, but there is no established method to measure these changes in vivo. The goal of this study was to develop a novel method to determine detrusor wall biomechanical parameters during urodynamics through the incorporation of transabdominal ultrasound imaging. Individuals with overactive bladder (OAB) underwent ultrasound imaging during filling. The fill rate was 10% of the cystometric capacity per minute as determined by an initial fill. Transabdominal ultrasound images were captured in the midsagittal and transverse planes at 1min intervals. Using image data and Pves, detrusor wall tension, stress, and compliance were calculated. From each cross-sectional image, luminal and wall areas along with inner perimeters were measured. In the sagittal and transverse planes, wall tension was calculated as Pves∗luminal area, wall stress as tension/wall area, and strain as the change in perimeter normalized to the perimeter at 10% capacity. Elastic modulus was calculated as stress/strain in the medial-lateral and cranial-caudal directions. Patient-reported fullness sensation was continuously recorded. Data from five individuals with OAB showed that detrusor wall tension, volume, and strain had the highest correlations to continuous bladder sensation of all quantities measured. This study demonstrates how detrusor wall tension, stress, strain, and elastic modulus can be quantified by adding ultrasound imaging to standard urodynamics. This technique may be useful in diagnosing and better understanding the biomechanics involved in OAB and other bladder disorders.