Ultrasound bladder wall thickness and detrusor overactivity: a multicentre test accuracy study

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.

Pathophysiological Mechanisms Involved in Overactive Bladder/Detrusor Overactivity

Purpose of Review

To examine the latest published findings on the pathophysiological mechanisms involved in the development of overactive bladder (OAB) and detrusor overactivity (DO), and to identify common pathways linked to the risk factors associated with these conditions.

Recent Findings

Evidence is accumulating, both clinical and experimental, that many of the factors linked to the development of OAB/DO, including ageing, bladder outlet obstruction, psychological stress, and obesity are associated with reduced bladder blood flow. This induces local tissue inflammation with cytokine release and enhanced oxidative stress, ultimately resulting in altered detrusor sensitivity, detrusor hypertrophy and fibrosis, together with afferent hypersensitivity. These mechanisms would explain the symptoms of urgency and frequency observed in OAB patients. Although not a characteristic of OAB, undetected low level bacterial infections of the bladder have been proposed to explain the OAB symptoms in patients resistant to standard treatments. In this condition, inflammatory responses without reductions in perfusion activate the inflammatory pathways.

Summary

Evidence is mounting that poor bladder perfusion and local inflammatory responses are central mechanisms involved in the development of OAB/DO. As our understanding of these pathophysiological mechanisms advances, new avenues for drug development will be identified and ultimately treatment may become more individualized depending on the particular pathway involved and the drugs available.

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.

Correlations between bladder wall thickness and clinical manifestations in female patients with detrusor underactivity and detrusor overactivity-with-detrusor underactivity

BACKGROUND

Among female patients with lower urinary tract symptoms, detrusor underactivity (DU), and detrusor overactivity-with-detrusor underactivity (DO-DU) are two common diagnoses. Here, we investigated the correlations between bladder wall thickness (BWT) and clinical manifestations of the two diagnoses.

METHODS

From 2011 to 2016, female patients with DU or DO-DU, diagnosed at our institute, were recruited. We analyzed their urodynamic parameters and collected three questionnaires (IPSS, UDI-6, OABSS). Using transabdominal sonography, the BWT was recorded. DU was defined as follows: maximum free flow rate (Qmax) ≤ 15 cc/s; detrusor pressure at maximum flow (PdetQmax) ≤ 20 cmH2O; bladder capacity > 150 cc. DO-DU was defined as follows: Qmax ≤ 15 cc/s; PdetQmax ≤ 20 cmH2O; bladder capacity ≤ 150 cc. The BWTs of the two groups were compared using the Mann-Whitney U test; the correlations among the BWTs and the results of three questionnaires were analyzed using Spearman's rank correlation coefficient.

RESULTS

Forty-eight female patients with DU and 13 with DO-DU were recruited. Demographic data revealed no differences between the two groups. The mean BWT of the DO-DU patients was significantly larger than that of the DU patients (4.11 vs 3.42 mm; p = 0.001). In the DO-DU group, a high correlation existed between the BWT and some of the UDI-6 items (urgency incontinence: r = 0.831, p = 0.006; incontinence related to activity: r = 0.884, p = 0.002; small amounts of leakage: r = 0.809, p = 0.008). The BWT of the DO-DU patients also exhibited a moderate correlation with the urgency incontinence from the OABSS questionnaire (r = 0.679; p = 0.044). No correlations existed between the BWT of the DU patients and any of the data from the three questionnaires.

CONCLUSION

The BWT in the DO-DU patients was significantly thicker than that in the DU patients. The DO-DU patients with thicker bladder walls also had higher UDI-6 scores for both urgency and urgency incontinence.

Ultrasonographic Imaging of the Pelvic Floor

This article discusses various pelvic floor ultrasonographic modalities and the clinical applications of ultrasonography of the pelvic floor. Ultrasonography provides a detailed anatomic assessment of the muscles and surrounding organs of the pelvic floor. Different anatomic variabilities and pathologic conditions, such as prolapse, fecal incontinence, urinary symptoms, vaginal wall cysts, synthetic implanted material, and pelvic pain, are assessed with pelvic floor ultrasonography. This imaging modality is an important adjunct to the evaluation and diagnosis of pelvic floor disorders.

Intravaginal 6.5 mg prasterone administration in postmenopausal women with overactive bladder syndrome: A pilot study

OBJECTIVE

The aim of this study was to evaluate the impact of vaginally prasterone administration on postmenopausal women with genitourinary syndrome of menopause (GSM) affected by overactive bladder syndrome (OAB). A secondary aim of this study was to assess the efficacy of prasterone on VVA and quality of life (QoL).

STUDY DESIGN

Thirty-two postmenopausal women with GSM and referred OAB symptoms received treatment with daily intravaginal prasterone 6.5 mg. We assessed urinary symptoms through approved ICIQ-OAB and ICIQ-UI questionnaires on incontinence. Women were also screened by the Vaginal Health Index (VHI) to investigate the vulvovaginal atrophy (VVA). Quality of life (QoL) was assessed by the SF-12 Health Survey. Each questionnaire was administrated at baseline (T0) and after a 12-week treatment (T1).

RESULTS

Incontinence questionnaires showed improvement at T1 (from 7.8 ± 2.7 to 2.7 ± 2.2, p < 0.001). Even if women referred an improvement of daily urine although the women reported improvement in daily urine leaks, their urine leak amount did not improve statistically significant [T0 (28.6%) Vs T1 (14.3%), p < 0.16]. Prasterone therapy improved significantly the VHI [T1(21 ± 3.7) Vs T0 (10.8 ± 4.1), p < 0.001]. Finally, women had a statistically significant improvement both in Mental [T1(49.9 ± 11.2) Vs T0 (42 ± 9.2), p < 0.009],) and Physical Health [T1(47.1 ± 9.1) Vs T0 (38.6 ± 8.4), p < 0.006], domains of the SF-12 questionnaire. No women referred side effects.

CONCLUSION

Prasterone is an inactive precursor converted into estrogens and androgens into vaginal tissue. It leads to positive effects on VVA through the activation of the vaginal androgen and estrogen receptors. Empirical evidence in this study suggests that intravaginal 6.5 mg prasterone administration could be an effective treatment for postmenopausal women with GMS affected by OAB.

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

Conventional assessment of overactive bladder syndrome uses invasive pressure-measuring catheters to detect bladder contractions (urodynamics). We hypothesised that bladder shape changes detected and measured using transabdominal ultrasound scan could provide a non-invasive and clinically useful alternative investigation of bladder contractions. This feasibility study evaluated a novel transabdominal ultrasound scan bladder shape test during conventional urodynamics and physiological bladder filling. The aim was to initially evaluate and refine a non-invasive approach for detecting and quantifying bladder shape changes associated with involuntary bladder contractions. To develop measurement techniques and characterise bladder shape changes during bladder filling, healthy female volunteers (n=20) and women with overactive bladder symptoms who had previously undergone urodynamics (n=30) completed symptom questionnaires and bladder diaries. The bladder shape test protocol included consumption of 1 l water before undergoing serial transabdominal ultrasound scan imaging of the bladder during physiological bladder filling and during episodes of urgency. In a further group of women with overactive bladder (n=22), serial transabdominal ultrasound scan images were captured during urodynamics so that shape changes occurring with bladder contractions could be characterised. In both healthy volunteers and women with overactive bladder, the transverse view of the bladder provided the most reliable plane to characterise and measure bladder shape changes. A sphericity index derived from the ratio between maximum inscribed and minimum circumscribed ellipses (πac^2(inner)/πac^2(outer)) offered a reliable and reproducible measurement system. Of participants undergoing transabdominal ultrasound scan during urodynamics, there were significant measurable differences in sphericity index between patients with bladder contractions (n=12) and patients with acontractile bladders (p < 0.001). Bladder shape changes detected during physiological filling and urodynamics have provided preliminary evidence to support further research into bladder shape test as a non-invasive diagnostic tool to identify involuntary bladder contractions in patients with overactive bladder syndrome.

Comparison of vascularization and overall perfusion of the bladder wall between women with and without overactive bladder syndrome

The pathophysiology of female overactive bleeder syndrome (OAB) remains undetermined. Our aim is to elucidate the role of vacularization and overall perfusion of the bladder wall in women with OAB. Between 2010 and 2016, women with OAB and the asymptomatic controls were enrolled. Women with OAB were treated with tolterodine. Women with OAB (n = 40) had higher vascularization index (0.40 ± 0.57 versus 0.17 ± 0.22, p = 0.003), vascularization-flow index (0.15 ± 0.28 versus 0.05 ± 0.08, p = 0.003) and thicker trigone (0.56 ± 0.13 cm versus 0.47 ± 0.11 cm, p = 0.004), compared with the controls (n = 34). The following optimum cut-off values to predict OAB were determined: (1) vascularization index (%) ≥ 0.16, (2) vascularization-flow index ≥ 0.032, and (3) trigone bladder wall thickness ≥ 0.47 cm with an area under the curve of 0.71, 0.71 and 0.70, respectively. Correlation analysis showed that a significant correlation between urgency and vascularization index/vascularization-flow index (Spearman’s rho = 0.34 and 0.35, respectively, all p < 0.01). However, after 12 weeks of tolterodine treatment, the vascularization index, flow index and vascularization-flow index did not differ between baseline and after treatment. In conclusion, women with OAB have higher vascularization and overall perfusion of the bladder wall, compared women without OAB. However, vascularization and overall perfusion did not change after antimuscarinic treatment.

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.

Validation study of ultrasound bladder wall thickness measurements

INTRODUCTION AND HYPOTHESIS

The aim was to validate ultrasound bladder wall thickness measurements. We scanned at three frequencies (5 MHz, 7 MHz and 9 MHz), using two techniques described in clinical practice and compared them with direct micrometre calliper measurements.

METHODS

Bladder dome cadaver specimens were dissected from male and female cadavers. The direct micrometre calliper measurement under direct vision was used as the gold standard. We imaged using a Voluson E8 ultrasound scanner at three frequencies, using three probes: AB27D (2-7 MHz), RAB25D (2-5 MHz) and RIC50D (5-9 MHz). The specimens were scanned on two different occasions for intra-observer variability. A second operator, measured the samples again independently for the interobserver agreement. The specimens were gently placed onto a sheathed and gelled probe to avoid deformation. The method of scanning was the same for all the specimens, probes and operators.

RESULTS

Twenty-five bladder dome specimens were assessed. The correlation of the ultrasound measurement to the direct measurement improved at higher ultrasound frequencies. Measuring from the inside of the serosal hyperechogenicity also increased the accuracy correlation with the direct measurement for all the frequencies tested.

CONCLUSIONS

This is the first study validating BWT ultrasound measurements against cadaveric bladder wall calliper measurements. Technology and technique affect accuracy, which is important in clinical practice. The use of 5-MHz probes is not recommended. The most accurate measurement was obtained using high-frequency ultrasound, where the measurement did not include the serosal brightness. These data suggest that high-frequency ultrasound should be used to assess BWT.