Andrew Colhoun

A pilot study to measure dynamic elasticity of the bladder during urodynamics

Previous studies using isolated strips of human detrusor muscle identified adjustable preload tension, a novel mechanism that acutely regulates detrusor wall tension. The purpose of this investigation was to develop a method to identify a correlate measure of adjustable preload tension during urodynamics.

Acute length adaptation and adjustable preload in the human detrusor

The biomechanical properties of length adaptation and adjustable preload have been previously identified in detrusor smooth muscle in animal models. This in vitro study aims to show that human detrusor smooth muscle exhibits length adaptation and adjustable preload tension which could play an important role in both overactive bladder and detrusor underactivity.

Long-Term Outcomes After Repair of Transurethral Perforation of Midurethral Sling.

Objectives The literature lacks long-term evaluation of outcomes after repair of transurethral midurethral sling (MUS) perforation. Methods We prospectively followed 5 patients undergoing repair of urethral perforation (International Continence Society–International Urogynecological Association classification 4B) after MUS (mean follow-up, 54 months). Outcomes assessment was composed of validated measures of urinary (International Consultation on Incontinence Questionnaire [ICIQ]-Female Lower Urinary Tract Symptoms), vaginal (ICIQ-Vaginal Symptoms), and quality of life (Incontinence Impact Questionnaire, Short Form) symptoms. Results Five patients underwent MUS (4 transobturator, 1 retropubic) with a mean of 41 months before referral. Primary referring complaints composed of hematuria (2), weak stream (2), and urgency (1). All but 1 patient reported transient urinary retention requiring catheterization after initial sling placement. Each patient underwent transvaginal sling excision and repair of urethral injury. Four of 5 patients experienced persistent postoperative stress urinary incontinence. Before final assessment, further treatment included observation, physical therapy, and autologous fascial sling in 1, 2, and 2 patients, respectively. ICIQ-Female Lower Urinary Tract Symptoms, ICIQ-Vaginal Symptoms, and Incontinence Impact Questionnaire, Short Form, assessment failed to demonstrate statistically significant improvements in comparison of baseline and multiple time point (6-week, 12-month, 54-month) assessments during long-term follow-up (P > 0.05). Conclusions Urethral perforation represents a significant complication after MUS placement. Many patients continue to have incontinence despite the use of physical therapy/salvage sling placement. Furthermore, subjective outcomes and quality of life do not seem to improve over time. Because of the rarity of urethral perforation, our small series is notable given the absence of reported data that include prospective, long-term follow-up with validated questionnaire evaluation.

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.

Automated quantification of low amplitude rhythmic contractions (LARC) during real-world urodynamics identifies a potential detrusor overactivity subgroup

Objectives Detrusor overactivity (DO) is characterized by non-voiding detrusor smooth muscle contractions during the bladder filling phase and often contributes to overactive bladder. In some patients DO is observed as isolated or sporadic contractions, while in others DO is manifested as low amplitude rhythmic contractions (LARC). The aim of this study was to develop an objective method to quantify LARC frequencies and amplitudes in urodynamic studies (UDS) and identify a subgroup DO of patients with LARC. Methods An automated Fast Fourier Transform (FFT) algorithm was developed to analyze a 205-second region of interest of retrospectively collected “real-world” UDS ending 30 seconds before voiding. The algorithm was designed to identify the three largest rhythmic amplitude peaks in vesical pressure (Pves) in the 1.75–6 cycle/minute frequency range. These peak Pves amplitudes were analyzed to determine whether they were 1) significant (above baseline Pves activity) and 2) independent (distinct from any in abdominal pressure (Pabd) rhythm). Results 95 UDS met criteria for inclusion and were analyzed with the FFT algorithm. During a blinded visual analysis, a neurourologist/urodynamicist identified 52/95 (55%) patients as having DO. The FFT algorithm identified significant and independent (S&I) LARC in 14/52 (27%) patients with DO and 0/43 patients (0%) without DO, resulting in 100% specificity and a significant association (Fischer’s exact test, p<0.0001). The average slowest S&I LARC frequency in this DO subgroup was 3.20±0.34 cycles/min with an amplitude of 8.40±1.30 cm-H2O. This algorithm can analyze individual UDS in under 5 seconds, allowing real-time interpretation. Conclusions An FFT algorithm can be applied to “real-world” UDS to automatically characterize the frequency and amplitude of underlying LARC. This algorithm identified a potential subgroup of DO patients with LARC.

Potential vascular mechanisms in an ex vivo functional pig bladder model

Chronic ischemia is a recognized factor in the pathophysiology of underactive bladder (UAB). Although relative ischemia (ie, low blood flow) is known to occur during filling, little is known regarding the pathophysiology that leads to UAB. Therefore, we developed an ex vivo functional porcine model to investigate the role of transient ischemia and whether autoregulation, a mechanism that maintains tissue oxygenation in certain vital organs, also exists in the bladder.

Providing Access to Care through a 24-Hour Dedicated Stone Line

Introduction: Many patients with urolithiasis are seen acutely in the emergency department for initial treatment. In an effort to improve cost and quality of care increasing focus has been placed on shifting management of low acuity conditions from emergency departments to outpatient settings. One barrier to such initiatives is timely access to outpatient services. We established a telephone stone line to provide access to outpatient urological care of kidney stones and we report our initial experience. Methods: A 24‐hour dedicated telephone stone line was created with calls answered by dedicated staff. A computer program was created to track stone line calls and post‐call care. We retrospectively analyzed all stone line calls received in a 4‐year period with the focus on utilization and cost. An e‐mail survey was performed to assess patient satisfaction. Results: Between January 2009 and July 2013 the mean call volume was 2,107 per year. A significant distribution of calls was seen across all days and hours. Duration was less than 15 minutes in 7,761 calls (82%). Patients or family members placed 77% of calls and physicians placed 16%. As a result of a stone line call, 4,173 patients (76%) were seen by a urologist within 48 hours. Of the patients 88% reported satisfaction with the stone line. The mean annual cost of providing the telephone stone line was

MP63-07 CHARACTERIZATION OF LOW AMPLITUDE RHYTHMIC CONTRACTIONS DURING URODYNAMICS

51,873. Conclusions: Our experience demonstrates sustained utilization of and satisfaction with the telephone stone line. Further, stone line use results in timely outpatient evaluation in the majority of patients. Further analysis to assess for a cost benefit is ongoing.

AB282. SPR-09 A method to quantify of bladder wall biomechanics using ultrasound imaging in conjunction with urodynamics

INTRODUCTION AND OBJECTIVES: Human detrusor smooth muscle (DSM) can exhibit low amplitude rhythmic contractions (LARC) which may contribute to overactive bladder (OAB) in some patients. The aim of this study was to develop an objective method to identify LARC during urodynamics (UD), categorize patients with significant LARC, and potentially begin to characterize a LARC-mediated OAB/detrusor overactivity subtype. METHODS: An algorithm was developed to analyze UD filling data in low volume (1st 410 seconds) and high volume (final 410s) regions. Fast Fourier Transform (FFT) analysis identified the frequency (F) in the 1-6 cycle/min range associated with the maximum amplitude of the vesical pressure (Pves) in each region (Fig 1). A patient-specific range of interest corresponding to F 0.5 cycles/min was determined. Pves and Pabd amplitudes were analyzed separately to identify both significant (higher than average) and independent (distinct from Pabd) Pves signals. To be significant, Pves amplitude must be > 1.35 standard deviations (SD) above average Pves amplitude. To be independent, the Pabd amplitude must be < 1.35 SD above the average Pabd amplitude. SD of 1.35 was chosen using an iterative process in 0.05 SD increments to identify the maximum number of significant and independent signals. RESULTS: This algorithm was used to retrospectively analyze 43 consecutive UD studies which included 25 (14 neurogenic, 11 idiopathic) with detrusor overactivity (58%). The average age of the entire group was 55 2 years and included 14 men and 29 women. FFT analysis identified a significant and independent Pves signal in 12/43 patients (28%) of which 8/12 (67%, 5 neurogenic, 3 idiopathic) had detrusor overactivity. The average age of patients with significant and independent signals was 54 5 years and included 6 men and 6 women. CONCLUSIONS: Analysis of LARC during UD testing identified a subset of patients with a significant and independent slow wave frequency in Pves. Further refinements of this technique may help identify subsets of individuals with LARC-mediated OAB/detrusor overactivity.

MP77-04 SENSATION DURING FILLING CYSTOMETRY CORRELATES WITH DETRUSOR WALL TENSION IN PATIENTS WITH OVERACTIVE BLADDER

Objective Overactive bladder (OAB) is often associated with detrusor over-activity which is characterized by biomechanical changes in the smooth muscle of the bladder wall, but there is no established method to measure these changes in vivo. This study’s goal was to develop a novel method to determine detrusor wall biomechanical parameters during urodynamics through the incorporation of abdominal ultrasound imaging. Methods Individuals with OAB underwent ultrasound imaging during filling. Fill rate was 10% cystometric capacity (CCap) as determined by an initial fill. Ultrasound images were obtained using a Philips Epiq 7 machine with a 1–5 MHz abdominal probe to capture midsagittal and transverse images at 1 min intervals. Using image data and vesical pressure (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% CCap. Elastic modulus was calculated as stress/strain in each direction. Patient-reported fullness sensation was continuously recorded. Results Data from five individuals with OAB showed that detrusor wall tension, volume, and strain had the highest correlation to continuous bladder sensation of all quantities measured. This finding demonstrates that Pves and Pdet measurements during urodynamics may not necessarily reflect the underlying state of detrusor wall tension. Conclusions This study demonstrates that detrusor wall tension, stress, strain, and elastic modulus can be calculated by adding ultrasound imaging to standard urodynamics. This technique may be useful in better understanding the biomechanics involved in OAB and other bladder disorders. Funding Source(s) Research funding for this study was provided by the Virginia Commonwealth University Presidential Research Quest Fund and NIH grant R01DK101719.