Evaluation of bladder shape using transabdominal ultrasound: Feasibility of a novel approach for the detection of involuntary detrusor contractions

Can we use machine learning to improve the interpretation and application of urodynamic data?: ICI-RS 2023

INTRODUCTION

A "Think Tank" at the International Consultation on Incontinence-Research Society meeting held in Bristol, United Kingdom in June 2023 considered the progress and promise of machine learning (ML) applied to urodynamic data.

METHODS

Examples of the use of ML applied to data from uroflowmetry, pressure flow studies and imaging were presented. The advantages and limitations of ML were considered. Recommendations made during the subsequent debate for research studies were recorded.

RESULTS

ML analysis holds great promise for the kind of data generated in urodynamic studies. To date, ML techniques have not yet achieved sufficient accuracy for routine diagnostic application. Potential approaches that can improve the use of ML were agreed and research questions were proposed.

CONCLUSIONS

ML is well suited to the analysis of urodynamic data, but results to date have not achieved clinical utility. It is considered likely that further research can improve the analysis of the large, multifactorial data sets generated by urodynamic clinics, and improve to some extent data pattern recognition that is currently subject to observer error and artefactual noise.

Ultrasound Urodynamics: A Review of Ultrasound Imaging Techniques for Enhanced Bladder Functional Diagnostics

Purpose of Review

Invasive urodynamics are currently used to diagnose disorders of bladder function. However, due to patient discomfort as well as artifacts induced by catheters and non-physiologic filling, less invasive screening tools that can improve diagnostic information, such as ultrasound are required. The purpose of this review is to assess different modalities of ultrasound as applied to functional bladder imaging. This information will help guide future studies in the use of ultrasound during urodynamics.

Recent Findings

Recently, multiple studies have employed ultrasound to evaluate bladder volume, wall thickness, shape, vibrometry, elastography, compliance, biomechanics, and micromotion during urodynamics. These new techniques have used both 2D and 3D ultrasound techniques to evaluate bladder changes during filling. Continued research is needed to confirm ongoing findings prior to widespread incorporation into clinical practice.

Summary

This review demonstrates the potential use of ultrasound as an adjunct to urodynamics for the diagnostic evaluation of functional bladder disorders.

Research priorities for diagnostic instrumentation in urinary incontinence

The International Consultation on Incontinence (ICI) captures current evidence on incontinence. The conference 'Incontinence: The Engineering Challenge XIII' in November 2021 heard an update on the most recent ICI summary on urodynamic testing. This paper summarises the ICI recommendations for future research in urodynamics, with a view to informing engineers of issues and challenges that could benefit from engineering solutions. Engineers are encouraged to contribute to the following areas of research, which will have a direct and positive effect on patients' quality of life and overall health: (a) Urine flow measurement: home- and app-based devices, machine learning analysis of flow shape, (b) Pressure measurement: normal values for and validation of new technologies, including air-filled, non-invasive and urethral pressure reflectometry, (c) Ultrasound imaging: bladder wall biomechanics, bladder shape analysis, (d) Assess normal and abnormal value ranges, and diagnostic performance and (e) Specific trials in understudied patient groups including those with symptoms resistant to treatment, children and the frail elderly.

Repeatability of Ultrasound-Defined Bladder Shape Metrics in Healthy Volunteers

Purpose

Patients and Methods

Results

Conclusion

Detrusor overactivity assessment using ultrasound bladder vibrometry

Objective. Detrusor overactivity (DO) is a urodynamic observation characterized by fluctuations in detrusor pressure (Pdet) of the bladder. Although detecting DO is important for the management of bladder symptoms, the invasive nature of urodynamic studies (UDS) makes it a source of discomfort and morbidity for patients. Ultrasound bladder vibrometry (UBV) could provide a direct and noninvasive means of detecting DO, due to its sensitivity to changes in elasticity and load in the bladder wall. In this study, we investigated the feasibility and applying UBV toward detecting DO.Approach. UBV and urodynamic study (UDS) measurements were collected in 76 neurogenic bladder patients (23 with DO). Timestamped group velocity squared (cg2) data series were collected from UBV measurements. ConcurrentPdetdata series were identically analyzed for comparison and validation. A processing approach is developed to separate transient fluctuations in the data series from the larger trend of the data and a DO index is proposed for characterizing the transient peaks observed in the data.Main Results.Applying the DO index as a classifier for DO produced sensitivities and specificities of 0.70 and 0.75 forcg2data series and 0.70 and 0.83 forPdetdata series respectively.Significance. It was found that DO can be feasibly detected from data series of timestamped UBV measurements. Collectively, these initial results are promising, and further refinement to the UBV measurement process is likely to improve and clarify its capabilities for noninvasive detection of DO.

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.

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.

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.