Clinical usefulness of ultrasound assessment of detrusor wall thickness in patients with neurogenic lower urinary tract dysfunction due to spinal cord injury: urodynamics made easy?

The Utility of Urodynamic Studies in Neuro-Urological Patients

INTRODUCTION

The utility of a clinical tool lies in its clinical performance evaluation and describes the relevance and usefulness of that tool in a medical setting. The utility of urodynamic and video-urodynamic studies in the management of specific urodynamic profiles in the diagnosis, treatment, and prognostic approach in neuro-urological patients is the focus of the current review.

METHODS

For this narrative review, a PubMed^® search was performed by cross-referencing the keywords "urodynamics", "neurogenic bladder", "utility", "clinical utility" and "clinical performance" with various terms related to the management of neurogenic lower urinary tract dysfunction. Clinical practice guidelines and landmark reviews from the most renowned experts in the field were also used.

ANALYSIS

Assessment of the utility of urodynamic study was performed during the diagnostic, therapeutic and prognostic steps of the neuro-urological patients' management. We focused on its clinical performance in the identification and evaluation of several unfavorable events, such as neurogenic detrusor overactivity, detrusor-sphincter dyssynergia, elevated detrusor leak point pressure and the presence of vesico-ureteral reflux, which may be indicators for a higher risk for the development of urological comorbidities.

CONCLUSION

Despite the paucity of existing literature assessing the utility of urodynamic study-specifically video-urodynamic study-in neuro-urological patients, it does remain the gold standard to assess lower urinary tract function precisely in this patient category. With regard to its utility, it is associated with high clinical performance at every step of management. The feedback on possible unfavorable events allows for prognostic assessment and may lead us to question current recommendations.

Can ultrasound measurement of bladder wall thickness be a useful adjunct for regular urodynamics in children with spina bifida?

INTRODUCTION

Spina bifida is a major cause of neurologic bladder dysfunction among children. The goal of neurogenic bladder treatment is to preserve renal function. Close follow-up is essential, as lower urinary tract functions can change with patient growth. Presently, invasive urodynamics is the gold standard for precisely assessing lower urinary tract function. Ultrasound is a low-cost, non-invasive, uncomplicated examination that can be easily repeated. Bladder wall thickness (BWT) measurement by ultrasound has been proposed as a non-invasive alternative for identifying lower urinary tract dysfunctions.

OBJECTIVE

Currently there are few reports on BWT in children with spina bifida, and BWT assessment methodology has yet to be defined. The present study aim was to investigate whether BWT could be a useful adjunct for regular urodynamics in children with spina bifida. We especially focused on the precise bladder volume during BWT measurements that were simultaneously performed with urodynamics.

STUDY DESIGN

This prospective observational study investigated 33 patients with spina bifida who underwent video urodynamics. We assessed BWT measurements using ultrasound simultaneously performed with video urodynamics. BWT was calculated for the ventral and dorsal walls at 0%, 20%, 40%, 60%, 80%, and 100% of the expected bladder capacity.

RESULTS

Median of bladder capacity was 240 mL, and bladder compliance was 19.2 mL/cmH₂O. Detrusor overactivity was present in 66.7% and vesicoureteral reflux was present in 27.3% of the patients. BWT of the ventral wall was significantly lower than the dorsal wall. During increases in the bladder volume, both the ventral and dorsal walls exhibited proportional thinning (p < 0.05). There were no significant differences for BWT between males and females. Although there was a higher statistical tendency for detrusor overactivity versus without detrusor overactivity (p = 0.085), there were no significant differences found between patients with and without detrusor overactivity.

DISCUSSION

This is the first report where multiple BWT measurements points with video urodynamics were simultaneously performed. Selection of bladder volumes for BWT measurements is critical. Our current study measured six points for each patient during urodynamics. However, available data was not sufficient for detecting bladder function. Until now, there has been no valid standard condition defined for measuring BWT and thus, lack of a standardized method has resulted in discrepancies among studies.

CONCLUSION

Our measurement conditions showed BWT may not correlate with the degree of bladder detrusor dysfunction. As BWT ultrasound cannot identify bladder dysfunction of children with spina bifida, this cannot be used as a substitute for invasive urodynamics.

Incidence of Renal Tract Abnormalities on Ultrasonography in Patients with Spinal Cord Injury: A Retrospective Pilot Study of a Military Cohort Undergoing Long-Term Institutional Rehabilitation

Study Design

Retrospective pilot study.

Purpose

To assess the incidence of renal tract abnormalities using ultrasonography (US) in a military cohort with traumatic spinal cord injury (TSCI) at a tertiary level spinal cord injury center.

Overview of Literature

Neurogenic bladder in TSCI patients results in significant urological morbidity. There is lack of data for these patients during the first 18 months of long-term rehabilitation in an institutional setting.

Methods

We retrospectively reviewed patient records to collect data on demographic characteristics, injury level, injury severity, time since injury, bladder management methods (such as an indwelling catheter [IC], clean intermittent catheterization [CIC], or self-voiding [S]); we correlated these data with the findings of the renal tract US.

Results

The study included 73 out of 81 male participants. The mean patient age was 29.99 years; the study group included 34.2% tetraplegics and 65.8% people with paraplegia. The time since injury was 6–12 months for 42.5% of the subjects and 12–18 months for 57.5% of the subjects. A normal US scan was recorded in 65.7% patients, and bladder trabeculation was the commonest finding in 15.1% of the subjects, followed by hydronephrosis (HDN) in 12.3%, and renal calculus and atrophy in 1.3% participants each. We found 22.22% of the IC group participants had higher US abnormalities than those in the reflex voiding group (statistically non-significant difference, p=0.7). Trabeculations (21.4%) and HDN (19%) were more common in those who had sustained the injury 12–18 months previously as compared to that in those who had injured themselves 6–12 months previously (p=0.04). The proportion of patients who had a normal US scan was higher in the group who sustained the injury 6–12 months previously versus those who had sustained the injury 12–18 months previously; the difference was statistically significant (p=0.02). There was no significant (p=0.72) correlation in the bladder management method, injury level, and renal tract abnormalities between the groups.

Conclusions

This retrospective study shows that 65% of TSCI participants had no renal tract abnormality on US scan and bladder trabeculation ruled out as the most common finding. Long-term supervised rehabilitation may help achieve good renal quality of life; however, further prospective trials are required on this subject.

ACR Appropriateness Criteria® Renal Failure

Renal failure can be divided into acute kidney injury and chronic kidney disease. Both are common and result in increased patient morbidity and mortality. The etiology is multifactorial and differentiation of acute kidney injury from chronic kidney disease includes clinical evaluation, laboratory tests, and imaging. The main role of imaging is to detect treatable causes of renal failure such as ureteral obstruction or renovascular disease and to evaluate renal size and morphology. Ultrasound is the modality of choice for initial imaging, with duplex Doppler reserved for suspected renal artery stenosis or thrombosis. CT and MRI may be appropriate, particularly for urinary tract obstruction. However, the use of iodinated and gadolinium-based contrast should be evaluated critically depending on specific patient factors and cost-benefit ratio. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Sonographic evaluation of bladder wall thickness in women with lower urinary tract dysfunction

Objective

To investigate the correlation between bladder wall thickness (BWT) measured by ultrasonography and lower urinary tract dysfunction (LUTD) in patients with lower urinary tract symptoms (LUTS).

Methods

Forty-eight women with LUTS who underwent urodynamic study and BWT by ultrasonography as outpatients were studied. We assessed LUTS during a medical examination by interview. The thinnest part of the bladder wall was measured by a transabdominal ultrasonography. We excluded patients who had visited another hospital previously because we did not know what treatment they had received, including medications, behavioral therapy, or other treatments. We constructed receiver operating characteristic (ROC) curves for diagnosis of LUTD and also determined reliable BWT criteria by calculating the area under the curve. Statistical analyses were performed using the Kolmogorov-Smirnov method and Student's t-test.

Results

The mean age, body mass index, and duration of symptoms were 59.9±9.7 years, 26.06±3.4 kg/m², and 53.4±38.2 months, respectively. Urodynamic study parameters (Valsalva leak point pressure, maximal urethral closure pressure, functional length, and postvoid residual volume) were lower in patients with BWT <3 mm; however, these differences were not significant. Patients with BWT ≥3 mm developed a hypoactive bladder (P=0.009) and intrinsic sphincter deficiency (ISD) (P=0.001) at a significantly higher rate. According to the ROC analysis, the best BWT cut-off value was 3 mm for overactive bladder diagnosis.

Conclusions

Women with LUTD showed higher BWT values (≥3 mm), especially patients with hypoactive bladder and ISD. Sonographic evaluation of BWT is an easy, fast, and noninvasive method for possible diagnostic tool for LUTD.

Reproducibility of the transvaginal sonographic assessment of bladder wall thickness

OBJECTIVE

To assess whether transvaginal sonographic measurements of bladder wall thickness (BWT) have adequate reproducibility to detect differences in BWT potentially indicative of detrusor overactivity in women with overactive bladder.

STUDY DESIGN

Three reproducibility studies were undertaken to assess (A) total measurement error, (B) intra-observer variability and (C) inter-observer measurement in the interpretation of scans. Women recruited to the Bladder Ultrasound Study underwent a transvaginal ultrasound scan to obtain a measurement of BWT. When a second observer was available, women who agreed to have two transvaginal scans by different operators were recruited into study A. For study B the first observer reassessed a sample of the recorded images at a later date whilst for study C, a random selection of BWT images were read by a second assessor. Analytical variability, percentage of variability attributable to measurement error, within-person variation and the smallest real difference detectable were estimated.

RESULTS

One hundred and twenty-one women took part: 27 had repeat scans, 37 had scans re-read by the same observer, and 57 had scans read by two observers. In study A, 39% of the total variability in measurements was explained by measurement error (the remainder to within person change); the standard deviation (SD) of measurement error was 0.76mm and the smallest detectable clinical difference was 2.1mm. The SD of measurement error from scan interpretation was 0.42mm within observers (study B) and 0.35mm between observers (studyC).

CONCLUSION

The high levels of measurement error for a small measurement of BWT means it is unlikely Transvaginal ultrasound measurements have insufficient reliability and reproducibility to be an accurate diagnostic test.

Bladder ultrasonography for diagnosing detrusor overactivity: test accuracy study and economic evaluation

BACKGROUND

Urodynamics (UDS) has been considered the gold standard test for detrusor overactivity (DO) in women with an overactive bladder (OAB). Bladder ultrasonography to measure bladder wall thickness (BWT) is less invasive and has been proposed as an alternative test.

OBJECTIVES

To estimate the reliability, reproducibility, accuracy and acceptability of BWT in women with OAB, measured by ultrasonography, in the diagnosis of DO; to explore the role of UDS and its impact on treatment outcomes; and to conduct an economic evaluation of alternative care pathways.

DESIGN

A cross-sectional test accuracy study.

SETTING

22 UK hospitals.

PARTICIPANTS

687 women with OAB.

METHODS

BWT was measured using transvaginal ultrasonography, and DO was assessed using UDS, which was performed blind to ultrasonographic findings. Intraobserver and interobserver reproducibility were assessed by repeated measurements from scans in 37 and 57 women, respectively, and by repeated scans in 27 women. Sensitivity and specificity were computed at pre-specified thresholds. The smallest real differences detectable of BWT were estimated using one-way analysis of variance. The pain and acceptability of both tests were evaluated by a questionnaire. Patient symptoms were measured before testing and after 6 and 12 months using the International Consultation on Incontinence modular Questionnaire Overactive Bladder (short form) (ICIQ-OAB) questionnaire and a global impression of improvement elicited at 12 months. Interventions and patient outcomes were analysed according to urodynamic diagnoses and BWT measurements. A decision-analytic model compared the cost-effectiveness of care strategies using UDS, ultrasonography or clinical history, estimating the cost per woman successfully treated and the cost per quality-adjusted life-year (QALY).

RESULTS

BWT showed very low sensitivity and specificity at all pre-specified cut-off points, and there was no evidence of discrimination at any threshold (p = 0.25). Extensive sensitivity and subgroup analyses did not alter the interpretation of these findings. The smallest detectable difference in BWT was estimated to be 2 mm. Pain levels following both tests appeared relatively low. The proportion of women who found the test 'totally acceptable' was significantly higher with ultrasonography than UDS (81% vs. 56%; p < 0.001). Overall, subsequent treatment was highly associated with urodynamic diagnosis (p < 0.0001). There was no evidence that BWT had any relationship with the global impression of improvement responses at 20 months (p = 0.4). Bladder ultrasonography was more costly and less effective than the other strategies. The incremental cost-effectiveness ratio (ICER) of basing treatment on the primary clinical presentation compared with UDS was £491,500 per woman successfully treated and £60,200 per QALY. Performing a UDS in those women with a clinical history of mixed urinary incontinence had an ICER of £19,500 per woman successfully treated and £12,700 per QALY compared with the provision of urodynamic to all women. For DO cases detected, UDS was the most cost-effective strategy.

CONCLUSION

There was no evidence that BWT had any relationship with DO, regardless of the cut-off point, nor any relationship to symptoms as measured by the ICIQ-OAB. Bladder ultrasonography has no diagnostic or prognostic value as a test in this condition. Furthermore, despite its greater acceptability, BWT measurement was not sufficiently reliable or reproducible.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN46820623.

FUNDING

This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 20, No. 7. See the NIHR Journals Library website for further project information.

Neurogenic lower urinary tract dysfunction: how, when, and with which patients do we use urodynamics?

Neurogenic lower urinary tract dysfunction (NLUTD) affects many patients and requires close monitoring. Initial studies establishing patients at risk for upper tract disease revealed that high detrusor leak point pressures were predictive of upper tract disease. Urodynamics in patients with NLUTD have specific challenges. Initial studies in patients after an acute injury should be delayed until after the spinal shock phase. In children with spinal dysraphism, studies should be done early to established potential risk. The goals are maintaining low bladder pressures, decreasing risk of infection, and maintaining continence.

Association between the bladder wall thickness and urodynamic findings in patients with spinal cord injury

PURPOSE

To investigate whether ultrasonographic bladder wall thickness (BWT) correlates with urodynamic parameters in patients with spinal cord injury (SCI).

METHODS

Two hundred and seventy-two patients with SCI were enrolled in the study. All of the patients underwent bladder ultrasonography and urodynamic study. The anterior bladder wall was measured and compared to urodynamic data.

RESULTS

The mean age of the patients was 37.4 years. The mean BWT was 3.9 mm. BWT was significantly higher in the patients with neurogenic detrusor overactivity associated with detrusor sphincter dyssynergia (NDO/DSD) compared to those without sphincter dyssynergia (4.2 vs. 3.6 mm, respectively, p < 0.001) and in those with compliance <20 ml/cm H2O. Nevertheless, ROC curve analysis [ROC = 0.624, 95 % CI (0.530, 0.718), p = 0.011] showed that no meaningful BWT measurement cutoff could be made to predict an elevated detrusor pressure in the storage phase.

CONCLUSIONS

Increased BWT was present in patients with low bladder compliance and NDO/DSD. No BWT cutoff value to predict an elevated detrusor pressure was found. Therefore, the measurement of BWT has no clinical role in patients with SCI and cannot replace urodynamic evaluation.