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.

A porcine bladder model of pre-clinical urodynamics demonstrates increased afferent nerve activity during filling.

INTRODUCTION AND OBJECTIVES: Urodynamics are the accepted gold standard for the evaluation of multiple forms of voiding dysfunction. However, the tests are expensive, invasive, poorly reproducible, and often prone to artifacts. Therefore, there is a pressing need to develop next-generation urodynamics. The purpose of this study was to develop a novel ex vivo porcine bladder urodynamics model with afferent pelvic nerve signaling that can be used as a preclinical surrogate for bladder sensation. METHODS: Porcine bladders including the ureters and vascular supply were harvested from local abattoirs using an established protocol in both male and female animals. Ex vivo bladder perfusion was performed using physiologic MOPS (3-(N-morpholino) propanesulfonic acid) buffer solution. The pelvic nerve adjacent to the bladder was grasped with micro-hook electrodes and electroneurogram (ENG) signals recorded at 20 kHz. Bladders were filled with saline at a nonphysiologic rate (100 mL/min) to a volume of 1 L using standard urodynamics equipment to simultaneously record intravesical pressure. ENG amplitude was calculated as the area under the curve for each minute, and ENG firing rate was calculated as number of spikes (above baseline threshold) per minute. At the conclusion of the experiment, representative nerve samples were removed and processed for nerve histology by a pathologist (hematoxylin and eosin and S100 stains). RESULTS: A total of 10 pig bladders were used, and nerve histology confirmed the presence of nerve in all adequately processed samples. Vesical pressure, ENG firing rate, and ENG amplitude all increased as a function of filling. During filling tertiles (low fill: min 1-3, med fill: min 4-6, and high fill: min 7-10), normalized pressures were 0.22 ± 0.04, 0.38 ± 0.05, and 0.72 ± 0.07 (cmH2O). Similarly, normalized ENG firing rates were 0.08 ± 0.03, 0.31 ± 0.06, and 0.43 ± 0.04 spikes/minute, respectively, and normalized nerve amplitudes were 0.11 ± 0.06, 0.39 ± 0.06, and 0.56 ± 0.14) µV, respectively. Strong relationships between average normalized pressure values and averaged normalized ENG firing rate (r2 = 0.66) and average normalized ENG amplitude (r2 = 0.8) were identified. CONCLUSIONS: The ex vivo perfused porcine bladder can be used as a preclinical model for the development of next-generation urodynamics technologies. Importantly, the model includes a reproducible method to measure afferent nerve activity that directly correlates with intravesical pressure during filling and could potentially be used as a surrogate measure of bladder sensation.

Repeatability of Ultrasound-Defined Bladder Shape Metrics in Healthy Volunteers.

Purpose: Recent studies demonstrate the potential value of using non-invasive abdominal ultrasound to quantify bladder shape and its association with disorders of bladder filling and voiding. The aim of the present study was to assess the repeatability of ultrasound-defined bladder shape metrics within the same individual from multiple bladder fills and study visits. Patients and Methods: Healthy volunteers completed an oral hydration protocol with two weekly visits, each with two consecutive bladder fill-void cycles, providing four total fills per participant. Throughout filling, 3-dimensional (3-D) ultrasound images were recorded at 5-minute intervals. Perimeters were manually traced in six cross-sectional planes 30° apart using GE 4D-View software. Diameters, perimeters and cross-sectional areas for the transverse, sagittal and coronal planes were interpolated at three standard bladder volumes of 200, 300, and 400mL. To quantify repeatability, intraclass correlation coefficients (ICCs) and normalized mean absolute differences were calculated for each metric at each standard volume. Moderate and good repeatability were defined as ICC ≥0.5 and ICC ≥0.75, respectively. Results: Data from 16 healthy volunteers (9 females, 7 males) were analyzed. ICCs for the transverse vertical and horizontal diameters showed good repeatability, and five of nine perimeter ICCs showed moderate or good repeatability. The mean absolute difference/mean ratio was ≤4% for all perimeter measurements, indicating repeatability was consistent for multiple fills and visits. Conclusion: Initial evidence indicates that bladder shape metrics are relatively repeatable and therefore feasible to pursue as a non-invasive tool for potential evaluation of bladder function.

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.

Regulation of bladder dynamic elasticity: a novel method to increase bladder capacity and reduce pressure using pulsatile external compressive exercises in a porcine model.

PURPOSE: Dynamic elasticity is a biomechanical property of the bladder in which muscle compliance can be acutely adjusted through passive stretches and reversed with active contractions. The aim of this study was to determine if manipulating dynamic elasticity using external compression could be used as a novel method to acutely increase bladder capacity and reduce bladder pressure in a porcine model. METHODS: Ex vivo experiment: bladders underwent continuous or pulsatile compression after establishing a reference pressure at bladder capacity. Bladders were then filled back to the reference pressure to determine if capacity could be acutely increased. In-vivo experiments: bladders underwent five cycles of pulsatile external compression with ultrasound confirmation. Pre and post-compression pressures were measured, and pressure was measured again 10 min post-compression. RESULTS: Ex vivo experiment: pulsatile compression demonstrated increased bladder capacity by 16% (p = 0.01). Continuous compression demonstrated increased capacity by 9% (p < 0.03). Comparison of pulsatile to continuous compression showed that the pulsatile method was superior (p = 0.03). In-vivo experiments: pulsatile external compression reduced bladder pressure by 19% (p < 0.00001) with a return to baseline 10 min post-compression. CONCLUSIONS: These results suggest that regulation of bladder dynamic elasticity achieved with external compression can acutely decrease bladder pressure and increase bladder capacity. Pulsatile compression was found to be more effective as compared to continuous compression. These results highlight the clinical potential for use of non-invasive pulsatile compression as a therapeutic technique to increase bladder capacity, decrease bladder pressure, and reduce the symptoms of urinary urgency.

A preliminary study of bilateral color mapping of pig bladder vasculature demonstrates potential for acute hemi-ischemic events.

BACKGROUND: Chronic ischemia is a known risk factor for the development of lower urinary tract symptoms (LUTS) and bladder hypocontractility. Less is known, however, about the impact of acute ischemia. Classic teaching suggests that collateral circulation is robust in the bladder and, therefore, loss of a single source of blood flow should have no deleterious effect. This study aims to provide visual evidence that segmental vascular supply is critical for maintaining adequate perfusion to the bladder. METHODS: Ex vivo pig bladders were cannulated bilaterally in the superior vesical arteries and perfused using contrasting red and green dye. Images were collected at each step of the perfusion dyeing process and these images were analyzed using a custom program to calculate the average hue of each side. Statistical analysis was performed using Student's t-test. RESULTS: The two halves being perfused by separate arteries showed a statistically significant difference when compared (P<0.05) on both the outer wall (n=9) and in the mucosal layer (n=4). On the outside wall, the average normalized hue of the green halves was 27.5°±14.3°, while the average normalized hue of the red halves was -58.7°±3.1°. In the mucosa, the average normalized hue of the green halves was 34.5°±17.4°, while the average normalized hue of the red halves was -51.5°±3.5°. CONCLUSIONS: This study identified a novel color mapping method to study pig bladder vascular supply. The results demonstrated a lack of collateral blood flow, highlighting the possibly of acute hemi-ischemic event. However, further research in the effect of acute ischemia on bladder function is necessary.

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.

Incidence and OR team awareness of "near-miss" and retained surgical sharps: a national survey on United States operating rooms.

INTRODUCTION: A retained surgical sharp (RSS) is a never event and defined as a lost sharp (needle, blade, instrument, guidewire, metal fragment) that is not recovered prior to the patient leaving the operating room. A "near-miss" sharp (NMS) is an intraoperative event where there is a lost surgical sharp that is recovered prior to the patient leaving the operating room. With underreporting of such incidents, it is unrealistic to expect aggressive development of new prevention and detection strategies. Moreover, awareness about the issue of "near-miss" or retained surgical sharps remains limited. The aim of this large-scale national survey-based study was to estimate the incidence of these events and to identify the challenges surrounding the use of surgical sharps in daily practice. METHODS: We hypothesized that there was a larger number of RSS and NMS events than what was being reported. We survived the different OR team members to determine if there would be discordance in reported incidence between groups and to also evaluate for user bias. An electronic survey was distributed to OR staff between December 2019 and April 2020. Respondents included those practicing within the United States from both private and academic institutions. Participants were initially obtained by designating three points of contact who identified participants at their respective academic institutions and while attending specialty specific medical conferences. Together, these efforts totaled 197 responses. To increase the number of respondents, additional emails were sent to online member registries. Approximately 2650 emails were sent resulting in an additional 250 responses (9.4% response rate). No follow up reminders were sent. In total, there were 447 survey responses, in which 411 were used for further analysis. Thirty-six responses were removed due to incomplete respondent data. Those who did not meet the definition of one of the three categories of respondents were also excluded. The 411 were then categorized by group to include 94 (22.9%) from anesthesiologist, 132 (32.1%) from resident/fellow/attending surgeon and 185 (45%) from surgical nurse and technologist. SURVEY: The survey was anonymous. Participants were asked to answer three demographic questions as well as eight questions related to their personal perception of NMS and RSS (Fig. 1). Demographic questions were asked with care to ensure no identifiable information was obtained and therefore unable to be traced back to a specific respondent or institution. Perception questions 4-6 and 11 were designed to understand the incidence of various sharp events (e.g. lost, retained, miscounted). Questions 7 and 10 were dedicated to understanding time spent managing sharps and questions 8 and 9 were dedicated to understanding the use x-ray and its effectiveness. RESULTS: Overall, most of each respondent group reported 1-5 lost sharp events over the last year. Roughly 20% of surgeons believed they never had a miscounted sharp over the last year, where only 5.3% of anesthesiologist reported the same (p = 0.002). Each group agreed that roughly 4 lost events occur every 1000 surgeries, but a significant difference was found between the three groups regarding the number of lost sharps not recovered per 10,000 surgeries with anesthesiologist, surgeon and nurse/technologist groups estimating 2.37, 2.56 and 2.94 respectively (p = 0.001). All groups noted x-ray to offer poor effectiveness at 26-50% with 31-40 min added for each time x-ray was used. More than half (56.8%) of surgeons reported using x-ray 100% of the time when managing a lost sharp whereas anesthesiologists and nurses/technologists believe it is closer to 1/3 of the time. An average of 21-30 min is spent managing each NMS, making a lost sharp event result in up to 70 min of added OR time. CONCLUSIONS: "Near-miss" and RSS are more prevalent than what is reported in current literature. Surgeons perceive a higher rate of success in retrieving the RSS when compared to anesthesiologists and OR nurses/technologists. We recognize several challenges surrounding "near-miss" and never events as contributing factors to their underreported nature and the higher degree of surgeon recall bias associated with these events. Additionally, we highlight that current methods for prevention are costly in time and resources without improvement in patient safety. As NMS and RSS have significant health system implications, a strong understanding of these implications is important as we strive to improve patient safety.

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.

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.

Phases of decompensation during acute ischemia demonstrated in an ex vivo porcine bladder model.

BACKGROUND: The aim of this project was to develop an ex-vivo porcine bladder model to test the effects of increasing durations of acute ischemia on detrusor function. METHODS: Porcine bladders were perfused through bilateral vesical arteries at physiologic flow (4 mL/min) and filled through a urethral catheter. Intravesical pressures were continuously recorded using standard urodynamics equipment. Bladder contractions, with simulated voiding, were induced by arterial infusion of KCl at 250 mL. Total, passive, and active pressures were recorded for each contraction and data were normalized to the control fill. Bladders underwent the following perfusion protocol by adjusting the arterial flow rates: Equilibration (4 mL/min), control (4 mL/min), partial ischemia (2 mL/min), global ischemia (0 mL/min) and reperfusion (4 mL/min). Perfusion periods were held for 15 min for one group and 30 min for another group of bladders. RESULTS: Porcine bladders (N=19) including 8 (15 min group) and 11 (30 min group) were used. With 15 min ischemia, passive pressure increased 39% (P=0.03) and the active pressure decreased 23% (P=0.002). Total pressure remained constant, identifying a compensated phase. Values returned to baseline with reperfusion. With 30 min ischemia, passive pressure remained unchanged. However, there was a decrease in total pressure 34% (P<0.001) and active pressure 61% (P<0.001), which incompletely recovered to baseline values, identifying a decompensated phase with incomplete recovery upon reperfusion. CONCLUSION: In the porcine bladder, 15 min ischemia resulted in a compensated phase and 30 min ischemia resulted in a decompensated phase of detrusor function. This study provides mechanistic insight into the natural history of ischemia-mediated voiding dysfunction.

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.

Are oxidative stress and ischemia significant causes of bladder damage leading to lower urinary tract dysfunction? Report from the ICI-RS 2019.

Several studies indicate that pelvic ischemia and oxidative stress may play a significant role in lower urinary tract dysfunction (LUTD), including detrusor overactivity (DO)/overactive bladder (OAB) and detrusor underactivity (DU)/underactive bladder (UAB). The present article addresses proposal 1: "Are oxidative stress and ischemia significant causes of bladder damage leading to LUTD?" from the 2019 International Consultation on Incontinence-Research Society (ICI-RS) meeting. Bladder ischemia in animals and humans is briefly described, along with the proposed progression from ischemia to LUTD. Bladder ischemia is compared with ischemia of other organs, and the ongoing development of pelvic ischemia animal models is discussed. In addition, the distribution of blood within the bladder during filling and voiding and the challenges of quantification of blood flow in vivo are described. Furthermore, oxidative stress, including potential biomarkers and treatments, and challenges regarding antioxidant therapy for the treatment of LUTD are discussed. Finally, seven critical research questions and proposed studies to answer those questions were identified as priorities that would lead to major advances in the understanding and treatment of lower urinary tract symptoms (LUTS)/LUTD associated with pelvic ischemia and oxidative stress.

What developments are needed to achieve less-invasive urodynamics? ICI-RS 2019.

AIMS: To assess the state of technologies for urodynamics that are less invasive than standard cystometry and pressure-flow studies and to suggest areas needing research to improve this. METHODS: A summary of a Think Tank debate held at the 2019 meeting of the International Consultation on Incontinence Research Society is provided, with subsequent analysis by the authors. Less-invasive techniques were summarized, classified by method, and possible developments considered. Discussions and recommendations were summarized by the co-chairs and edited into the form of this paper by all authors. RESULTS: There is a full spectrum of technologies available for less-invasive assessment, ranging from simple uroflowmetry through imaging techniques to emerging complex technologies. Less-invasive diagnostics will not necessarily need to replace diagnosis by, or even provide the same level of diagnostic accuracy as, invasive urodynamics. Rather than aiming for a technique that is merely less invasive, the priority is to develop methods that are either as accurate as current invasive methods, or spare patients from the necessity of invasive methods by improving early triaging. CONCLUSIONS: Technologies offering less-invasive urodynamic measurement of specific elements of function can be potentially beneficial. Less-invasive techniques may sometimes be useful as an adjunct to invasive urodynamics. The potential for current less-invasive tests to completely replace invasive urodynamic testing is considered, however, to be low. Less-invasive techniques must, therefore, be tested as screening/triaging tools, with the aim to spare some patients from invasive urodynamics early in the treatment pathway.

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 (Pves ) 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 Pves during filling after strain softening and restored Pves 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.

An external compress-release protocol induces dynamic elasticity in the porcine bladder: A novel technique for the treatment of overactive bladder?

INTRODUCTION: Dynamic elasticity is an acutely regulated bladder material property through which filling and passive emptying produce strain softening, and active voiding restores baseline pressure. The aim of this study was to test the hypothesis that strain softening produced by filling-passive emptying is equivalent to that produced by compression-release in a porcine bladder model. METHODS/MATERIALS: Latex balloons and ex vivo perfused pig bladders were used for a series of alternating fill-passive emptying ("Fill") and external compress-release ("Press") protocols. For the Fill protocol balloons/bladders were (1) filled to defined volumes (prestrain softening), (2) filled to capacity to strain soften (reference), and (3) passively emptied to the original volume (poststrain softening). For the Press protocol, balloons/bladders were (1) filled to defined volumes (prestrain softening), (2) externally compressed to reference pressure and then released for five cycles (poststrain softening). After each protocol, bladders were voided with high-KCl buffer to induce "active" voiding. RESULTS: In both balloons and porcine bladder, both the Fill and Press protocols produced significant strain softening (P < 0.05) and poststrain softening pressures were not different for Fill and Press protocols (P > 0.05), indicating a similar degree of strain softening with both methods. CONCLUSIONS: Repeated external compression can induce bladder strain softening similar to filling and passive emptying. This technique may represent a means to acutely regulate bladder compliance and potentially be used as a mechanical treatment for urinary urgency.

Bladder attack: transient bladder ischemia leads to a reversible decrease in detrusor compliance.

BACKGROUND: The deleterious effects of chronic ischemia on bladder function have been extensively studied; however, evaluation and characterization of the effects of acute ischemia and hypoxia are lacking. The present study examined pig and human detrusor smooth muscle (DSM) strips, in combination with an isolated perfused working pig bladder model to evaluate the relationship between transient ischemia and bladder function. METHODS: Organ bath and myographic studies were performed using pig and human DSM strips exposed to starvation/hypoxia conditions. Analogous conditions were then recreated in the ex vivo bladder preparation. Filled bladders were then treated with intravascular carbachol to induce contraction and subsequent void. An intravesical transducer continuously monitored changes in bladder pressure, while a tissue pO2 monitor analyzed changes in oxygenation. RESULTS: After 120 min in starved/hypoxic conditions, both pig and human DSM strips demonstrated significantly increased resting tone, with a greater than two-fold increase in force over control. This was effectively blocked with atropine. DSM strips also demonstrated significantly weaker contractions; however, contractile force was nearly recovered following 15-min exposure to replete/oxygenated buffer. In the ex vivo bladder preparation, filling under ischemic conditions yielded a 225% increase in end-fill vesical pressures (Pves) compared to controls. End-fill Pves returned to baseline with reperfusion during a subsequent filling cycle. CONCLUSIONS: Transient ischemia/hypoxia leads to an acute increase in tone in both DSM strips and ex vivo pig bladder. Remarkably, the effect is reversible with re-perfusion and may be blocked with anticholinergics, suggesting a relationship between acute ischemia and increased local acetylcholine release.