Non-invasive bladder volume measurement for the prevention of postoperative urinary retention: validation of two ultrasound devices in a clinical setting

Proof-of-Concept of Microwave-Based Bladder State Detection Using Realistic Pelvic Models

Goal: Urinary incontinence (UI) affects a significant proportion of the population and is associated with negative physical and psychological side-effects. Microwave-based technologies may have the potential to monitor bladder volume, providing a proactive, low-cost and non-invasive tool to support individuals with UI. Methods: Studies to date on microwave bladder monitoring have been limited to highly simplified computational and experimental scenarios. In this work, we study the most realistic models to date (both male and female), which incorporate dielectrically and anatomically representative tissues of the pelvic region. Results: We examine the ability of detecting bladder fullness through both reflection and transmission-based parameters and, for the first time, study the effect of urine permittivity. As a proof-of-concept of bladder state detection, we further investigate reconstructing differential radar images of the bladder with two different volumes of urine. Conclusions: The results indicate that there is strong potential for monitoring and detecting the bladder state using microwave measurements.

Comparative Effectiveness of Two Models of Point-of-Care Ultrasound for Detection of Post-Void Residual Urine during Acute Ischemic Stroke: Preliminary Findings of Real-World Clinical Application

We conducted a comparative study of two models of point-of-care ultrasound devices for measuring post-void residual urine (PVRU). We prospectively enrolled 55 stroke inpatients who underwent both real-time B-mode ultrasound (Device A) and automated three-dimensional (3D) scanning ultrasound (Device B), with a total of 108 measurements. The median PVRU volume of Device B was 40 mL larger than that of Device A. The PVRU difference between the devices was positively and linearly correlated with PVRU. The correlation of PVRU volume between the devices was strong, but the agreement level was only moderate. Measurement deviations were observed in 43 (40%) and 11 (10%) measurements with Device B and Device A, respectively. The PVRU volume was low in spherical bladder shapes but sequentially increased in triangular, undefined, ellipsoid, and cuboid bladder shapes. Further comparison of 60 sets of PVRU without measurement deviations revealed higher agreements between the devices at correction coefficients of 0.52, 0.66, and 0.81 for PVRU volumes of <100, 100-200, and >200 mL, respectively. The automated 3D scanning ultrasound is more convenient for learning and scanning, but it exhibits larger measurement deviations. Real-time B-mode ultrasound accurately visualizes the urinary bladder but tends to underestimate the urinary bladder when the PVRU volume is large. Hence, real-time B-mode ultrasound with automated PVRU-based adjustment of calculation formulas may be a better solution for estimating bladder volume.

A 66-Year-Old Woman with Achondroplasia and Quadriparesis with an Ovarian Cyst Erroneously Diagnosed as Urinary Retention by an Automated Bladder Scan

BACKGROUND Automated bladder scanning has become a principal tool in the assessment and management of chronically debilitated patients residing in skilled nursing facilities, hospices, and acute inpatient settings. To a large extent, the bladder scan, generally performed by nursing staff, has replaced physical examination while addressing the differential diagnoses of anuria or voiding disturbances that require consideration of urinary catheterization. Health care providers can quickly master this easily performed technique, and currently, due to confidence in the bladder scan finding, physical examination with suprapubic palpation and percussion may be carelessly omitted. The case description presented here illustrates how not performing a physical examination can lead to misdiagnosis caused by misinterpretation of bladder scan findings. CASE REPORT A 66-year-old, quadriparetic, chronically ventilated female patient with achondroplasia underwent repeated hospital referrals and bladder catheterizations for presumed flaccid, neurogenic bladder with urinary retention. This postulated diagnosis was based on occasional reports of urinary catheter obstruction as well as on automated bladder scanning indicating a markedly distended bladder. However, the bladder could not be drained by insertion of urinary catheters. Eventually, a proper physical examination excluded the presence of suprapubic fullness compatible with distended bladder and contradicting bladder scan findings, prompting re-examining an overlooked evaluation of computed tomography that reported a huge ovarian cyst. The patient was found to have intact voiding capabilities and is now weaned from the catheter. CONCLUSIONS This case and the literature review underscore drawbacks in automated bladder scanning. This technique should be used as an adjunctive measure rather than a replacement for a physical examination in the evaluation of voiding disturbances, especially when there are discrepancies between bladder scan findings and the volume of urine drained by catheterization.

Accuracy of Multi-organ Point-of-Care Ultrasound for Acute Kidney Injury Etiologies

This study investigated the diagnostic performance of point-of-care ultrasound (POCUS) for acute kidney injury (AKI) etiological subgroups in emergency department (ED) patients. Multi-organ POCUS including kidney, bladder, inferior vena cava (IVC), lung and cardiac examinations were used to identify five AKI subgroups: hypovolemia, reduced cardiac output, systemic vasodilatation and renal vasomodulation, renal and post-renal. One hundred sixty-five AKI patients were included in the study. The most diagnostic parameter in the post-renal group was the presence of any hydronephrosis, with a sensitivity of 93.3% (95% confidence interval [CI]: 68.1-99.8) and specificity of 85.9% (95% CI: 79.3-91.1). For the reduced cardiac output group, the most diagnostic parameter was IVC maximum diameter &gt;17 mm with a sensitivity of 100% (95% CI: 83.2-100) and specificity of 70.2% (95% CI: 61.6-77.7). For the hypovolemia group, the most diagnostic parameter was IVC maximum diameter ≤17.9 mm with a sensitivity of 81.2% (95% CI: 71.2-88.8) and specificity of 56.5% (95% CI: 44-68.4). For the systemic vasodilatation and renal vasomodulation group, the most diagnostic parameter was diffuse ascites with a sensitivity of 56.3% (95% CI: 29.9-80.2) and specificity of 89.9% (95% CI: 83.8-94.2). None of the parameters were significant for the renal group. We concluded that multi-organ POCUS is of diagnostic value for AKI subgroups.

Evaluation of an ultrasound bladder scanner in supine and standing position

PURPOSE

This study examined the performance of a bladder volume measuring device, the BladderScan (BS) BVI9400. The use of the BS offers the possibility of assessing the bladder volume before positioning the patient and performing the daily image-guided radiotherapy procedure. Patients often cannot lie down before entering the treatment vault. Therefore, the BS was also assessed in a standing position.

METHODS

The repeatability precision was first evaluated, which is the variability of immediate repeated measures of the BS with same operator and subject. This was followed by the reproducibility precision of the BS in which the operator and subjects differ. Finally, the trueness was evaluated in terms of fixed and proportional bias of the results by applying weighted least-squares fitting. Note that 53 and 85 patient measurements were carried out in supine and standing position, respectively, each consisting of three repeated BS measurements. These were compared with the computed tomography (CT)-delineated bladder volume.

RESULTS

Repeatability was dependent on measurement value (heteroscedasticity) with σ_{repeatability} (BS) = ±15 cm³  ± 10%. However, the total agreement between BS and CT was low with the 95% limits of agreement (LOAs) exceeding ±200 cm³ due to poor patient reproducibility and presence of fixed and proportional bias. Only in the best case of male patients in the supine position, three BS measurements, and correction for the fixed and proportional bias, 95% LOAs of [-147, +114] cm³ were obtained between CT and BS.

CONCLUSION

The agreement of the BVI9400 BS with CT was found to be too low for radiotherapy applications.

Portable Ultrasound Research System for Use in Automated Bladder Monitoring with Machine-Learning-Based Segmentation

We developed a new mobile ultrasound device for long-term and automated bladder monitoring without user interaction consisting of 32 transmit and receive electronics as well as a 32-element phased array 3 MHz transducer. The device architecture is based on data digitization and rapid transfer to a consumer electronics device (e.g., a tablet) for signal reconstruction (e.g., by means of plane wave compounding algorithms) and further image processing. All reconstruction algorithms are implemented in the GPU, allowing real-time reconstruction and imaging. The system and the beamforming algorithms were evaluated with respect to the imaging performance on standard sonographical phantoms (CIRS multipurpose ultrasound phantom) by analyzing the resolution, the SNR and the CNR. Furthermore, ML-based segmentation algorithms were developed and assessed with respect to their ability to reliably segment human bladders with different filling levels. A corresponding CNN was trained with 253 B-mode data sets and 20 B-mode images were evaluated. The quantitative and qualitative results of the bladder segmentation are presented and compared to the ground truth obtained by manual segmentation.

Novel Three-Dimensional Bladder Reconstruction Model from B-Mode Ultrasound Image to Improve the Accuracy of Bladder Volume Measurement

Traditional bladder volume measurement from B-mode (two-dimensional) ultrasound has been found to produce inaccurate results, and thus in this work we aim to improve the accuracy of measurement from B-mode ultrasound. A total of 75 electronic medical records including ultrasonic images were reviewed retrospectively from 64 patients. We put forward a novel bladder volume measurement method, in which a three-dimensional (3D) reconstruction model was established from conventional two-dimensional (2D) ultrasonic images to estimate the bladder volume. The differences and relationships were analyzed among the actual volume, the traditional estimated volume, and the new reconstruction model estimated volume. We also compared the data in different volume groups from small volume to high volume. The mean actual volume is 531.8 mL and the standard deviation is 268.7 mL; the mean percentage error of traditional estimation is −28%. In our new bladder measurement method, the mean percentage error is −10.18% (N = 2), −4.72% (N = 3), −0.33% (N = 4), and 2.58% (N = 5). There is no significant difference between the actual volume and our new bladder measurement method (N = 4) in all data or the divided four groups. The estimated volumes from the traditional method or our new method are highly correlated with the actual volume. Our data show that the three-dimensional bladder reconstruction model provides an accurate measurement from conventional B-mode ultrasonic images compared with the traditional method. The accuracy is seen across different groups of volume, and thus we can conclude that this is a reliable and economical volume measurement model that can be applied in general software or in apps on mobile devices.

A comprehensive survey on non-invasive wearable bladder volume monitoring systems

Measuring the volume of urine in the bladder is a significant issue in patients who suffer from the lack of bladder fullness sensation or have problems with timeliness getting to the restroom, such as spinal cord injury patients and some of the elderlies. Real-time monitoring of the bladder, therefore, can be highly helpful for urinary incontinence. Bladder volume monitoring technologies can be divided into two distinct categories of invasive and non-invasive. In invasive techniques, a catheter is directly inserted into the urethra to measure the amount of urine accurately. However, it is painful, limits the user's ordinary movements, and may hurt the urinary tract. Current non-invasive techniques measure the volume of the bladder from the skin using different stationary or portable apparatus at health centers. Both techniques have difficulties and are not cost-effective to use for a long period. Recently, both invasive and non-invasive methods have been attempted to be produced in the form of wearable devices utilizing different sensing and communication technologies. Wearable bladder monitoring devices can be easily used by patients with no or few clinical steps, making them much more affordable than non-wearable devices. While wearable devices seem to be a highly convenient and effective solution, they suffer from few drawbacks, such as relatively low precision. Hence, a great number of studies have been conducted to address these issues. In this article, we review and discuss non-invasive and minimally invasive methods for monitoring the bladder volume. We focus on the most practical and state-of-the-art methods employed in wearable devices, classify them by engineering and medical characteristics, and investigate their specifications, architectures, and measurement algorithms. This study aims to introduce the latest advances in this field to practitioners while comparing the advantages and disadvantages of existing approaches. Our study concludes with open problems and future trends in the area of bladder monitoring and measurement systems. Graphical abstract Wearable bladder monitoring system.

Incidence of urinary retention and relations between patient's complaint, physical examination, and bladder ultrasound

OBJECTIVE

To describe the frequency of urinary complaints, bladder globe, and need for bladder relief catheterization according to ultrasound; to investigate the relationship between the urinary volume estimated by ultrasound and the one drained in catheterization; and to describe the relationship of patient's complaints and detection of bladder globe with the diagnosis of urinary retention.

METHOD

A cross-sectional study with clinical patients with suspected urinary retention in a tertiary hospital, conducted from February to September 2018. Urinary volume ≥500 mL in ultrasound was considered urinary retention.

RESULTS

Two hundred and five evaluations were performed in 44 patients. Urinary retention was detected by ultrasound in 33.2% of the evaluations. There was a strong correlation between ultrasound and bladder catheterization. There was a higher frequency of identification of bladder globe in urinary volumes ≥300 mL.

CONCLUSION

The incidence of urinary retention was higher when ultrasound was used for the diagnosis, when compared to patient's complaint and physical examination. Ultrasound showed to be accurate in establishing urinary volume.

Evaluation of a 3-dimensional ultrasound device for noninvasive measurement of urinary bladder volume in dogs

Background

The BladderScan Prime Plus (BPP; Verathon, Bothell, Washington) is an application‐specific, three‐dimensional ultrasound device used for human, point‐of‐care volumetry of the urinary bladder.

Objective

To estimate the BPP's accuracy, repeatability, and optimized settings for assessing urinary bladder volumes in dogs, a variable utilized in assessing micturition disorders.

Animals

Twenty‐four, client‐owned, healthy, male dogs presenting for routine examination.

Methods

Prospective examinations were conducted by an experienced ultrasonographer and a novice, selecting the BPP's “man” or “child” setting, and were compared to urine volume obtained by catheterization.

Results

Mean urine volume significantly varied by operator (P = .05), device setting (P < .001), and weight (P = .01); the “man” setting produced mean volumes nearer to catheterized volumes. The mean difference between BPP's “man” setting and catheterized volume was 0.88 mL, with maximal positive and negative disagreement of +23.2 mL to −55.3 mL (SD 19.0). Percent disagreement between BPP and catheterized volumes demonstrated a mean of −4.5%, with maximal positive and negative disagreement of +58.1% to −74.1% (SD 34.9). The experienced operator recorded volumes significantly (P = .05) higher than the novice, with difference in means of 3.2 mL. In dogs weighing >5.5 kg (n = 18/24), mean difference between BPP's “man” setting and catheterized measurements, regardless of operator, was not significant.

Conclusions

Although small magnitude interuser variability is present in BPP examinations, the device provides accurate, though imprecise quantification of bladder volume in canids weighing >5.5 kg.

Development and evaluation of automated ultrasonographic detection of bladder diameter for estimation of bladder urine volume

Bladder urine volume has been estimated using an ellipsoid method based on triaxial measurements of the bladder extrapolated from two-dimensional ultrasound images. This study aimed to automate this process and to determine the accuracy of the automated estimation method for normal and small amounts of urine. A training set of 81 pairs of transverse and longitudinal ultrasound images were collected from healthy volunteers on a tablet-type ultrasound device, and an automatic detection tool was developed using them. The tool was evaluated using paired transverse/longitudinal ultrasound images from 27 other healthy volunteers. After imaging, the participants voided and their urine volume was measured. For determining accuracy, regression coefficients were calculated between estimated bladder volume and urine volume. Further, sensitivity and specificity for 50 and 100 ml bladder volume thresholds were evaluated. Data from 50 procedures were included. The regression coefficient was very similar between the automatic estimation (β = 0.99, R2 = 0.96) and manual estimation (β = 1.05, R2 = 0.97) methods. The sensitivity and specificity of the automatic estimation method were 88.5% and 100.0%, respectively, for 100 ml and were 94.1% and 100.0%, respectively, for 50 ml. The newly-developed automated tool accurately and reliably estimated bladder volume at two different volume thresholds of approximately 50 ml and 100 ml.