Continuous Monitoring of Bladder Dysfunction in People With Multiple Sclerosis: Wearables for the Bladder

ABSTRACT

Background

Bladder dysfunction affects over 85% of people with multiple sclerosis (PwMS), yet current assessment methods are limited to periodic in‐clinic evaluations or subjective patient reports, failing to capture real‐world symptom fluctuations.

Objectives

To evaluate the feasibility and validity of using a novel remote bladder ultrasound device for home monitoring of bladder dysfunction in PwMS, comparing remote measurements with standard clinical assessments.

Methods

Twenty‐two women with MS participated in this 3‐month pilot study. Participants were asked to use the wearable ultrasound device at home for at least 3–5 days a month. Remote device measurements were compared with standard clinical data for post‐void residual (rPVR vs. cPVR) and urinary frequency (rFrequency vs. 3‐day bladder diary frequency). Agreement between measures was assessed using Bland–Altman analyses and correlation coefficients.

Results

Participants were middle‐aged (mean 51.5 years; SD 9.3) with mild–moderate disability (median EDSS 4.0) and mostly relapsing MS (72.7%). Study retention was high (86.4%; 19/22), with mean device utilization of 14.1 days. Good agreement was seen between rPVR and cPVR (mean difference = 32.1 mL, SD = 38.6; 95% limits of agreement: −43.6, 107.9). The rFrequency measure also demonstrated a strong correlation with patient‐reported frequency (ICC = 0.81, Pearson's r = 0.793, p = 0.002). Visualization of remote monitoring data revealed substantial day‐to‐day variability in bladder symptoms not captured by traditional assessments.

Conclusion

This pilot study demonstrates the feasibility and preliminary validity of using wearable ultrasound technology for remote monitoring of bladder dysfunction in PwMS. The ability to capture real‐world symptom variations could transform assessment and management approaches, enabling more personalized and responsive care strategies.

1. Introduction

Over 85% of people with multiple sclerosis (MS) experience bladder dysfunction (including storage, voiding, and emptying symptoms) that significantly impacts daily life [1, 2]. Bladder dysfunction usually manifests within a decade of MS diagnosis, with symptoms such as urgency, frequency, nocturia, urinary incontinence—as well as incomplete bladder emptying (retention) [3, 4]. Beyond the primary symptoms, bladder dysfunction in people with MS (PwMS) precipitates a cascade of secondary consequences, notably compromising physical activity levels, exacerbating fatigue, and increasing fall risk. These secondary manifestations can substantially amplify the overall disease burden. In addition, bladder dysfunction increases hospitalizations due to urinary tract infections (UTIs) [5].

Despite its significant impact, bladder dysfunction in PwMS remains under‐researched. Current assessments of urinary retention and frequency are limited to periodic in‐person, in‐clinic evaluations, including post‐void residual (PVR) measurements and invasive urodynamic testing, or rely on subjective patient‐reported outcomes (PROs). These traditional approaches fail to capture the dynamic, real‐world fluctuations in symptom severity that characterize this condition [6, 7].

Integrating wearable neurotechnology with PROs for remote monitoring of bladder dysfunction presents a promising approach to address the current gaps in care. To explore this, a pilot study was conducted, informed by inter‐professional stakeholder input—including experts in pelvic health physical therapy, urology, neurology, and PwMS—who evaluated commercially available bladder wearables for feasibility and ease of use in home settings [8]. This human‐centered design process culminated in the development of the “Wearables for the Bladder” (WeB) toolkit, including the DFree wearable bladder ultrasound, which provides real‐time bladder fullness data via a Bluetooth‐connected smartphone app.

The current pilot study assessed the feasibility of using the novel remote bladder ultrasound device (DFree) at home for 3 months in PwMS and compared standard urinary retention (PVR) and the frequency measure from a traditional bladder diary with those derived from the device.

2. Methods

2.1. Participants

Twenty‐two adults (≥ 18 years old) with either relapsing or progressive MS (per 2017 McDonald criteria [9]) were recruited from either the University of California San Francisco (UCSF) MS and Neuroinflammation Center or the UCSF Urology clinic. In an effort to reduce anatomical variations for the current pilot, only females were included since they comprise three‐quarters of all PwMS. Other eligibility criteria required participants to have at least early/mild bladder dysfunction symptoms (Bladder/Bowel Functional System Score [B/B FS] > 1 or Bladder Control Scale [BLCS] > 0) and to be California residents with access to Wi‐Fi. Participants were excluded if they had a clinical relapse or steroid use within 30 days of study baseline, or if there were severe cognitive, dexterity, or visual impairments precluding the use of the neurotechnology tool or smartphone. Individuals with mild/moderate impairments were not excluded.

2.2. Recruitment

Participants were identified through routine clinical visits or chart reviews of recent (< 30 days) Expanded Disability Status Scale (EDSS [10]) assessments with functional system scores. During recruitment, eligible individuals were invited to participate in this pilot study. The study design was approved by the UCSF Institutional Review Board, and all participants provided written informed consent.

2.3. Data Collection

At baseline, participants underwent a comprehensive neurological assessment as part of their routine clinical care, including disability status score, EDSS. Participants recruited from the neuro‐urology clinic were sent a validated, online assessment of disability (electronic patient‐reported EDSS; ePR‐EDSS) via secure REDCap [11] email. MS and bladder dysfunction history, as well as demographic data were obtained from the electronic health record.

2.4. Bladder Assessments

2.4.1. Bladder Ultrasound

A standard clinic PVR (cPVR) [12, 13] was performed by a registered nurse, medical assistant, or trained member of the study team three times within 5 min. The average of three (3) PVRs was used for analysis.

2.4.2. Wearable Device

Participants were provided with a DFree kit. This included the wearable ultrasound device, patches, and hypoallergenic tape to attach the device to the lower abdomen—over the bladder—and ultrasound gel. They received training on its use, placement, and basic troubleshooting, as well as device maintenance (Table S1). They were asked to use the device for a minimum of 3–5 days a month at home for a 3‐month period.

2.5. Data Extraction

DFree raw data are reported on a 0–100 scale, with recordings ~every minute. Two de novo outcomes were generated (Table 1).

TABLE 1.

Overview of bladder assessments.

Outcome	Remote	Clinic	Patient‐reported (exploratory)
Urinary retention	RemotePVR (rPVR) To generate a measure of retention, the last measure of urine volume before urination (pre‐void) and the first valid measure after urination (i.e., “bout”) were used to determine the residual urine.	Average of the 3 standard clinic Post‐Void Residuals (cPVR) obtained in clinic was used for analysis.	Neurogenic Bladder Symptom Score—Short Form (NBSS‐SF) [14] Assess the severity of lower urinary tract symptoms in individuals with neurogenic bladder conditions. Higher scores indicate a greater symptom burden, that is, incontinence, storage problems, and voiding difficulties, along with the negative consequences these symptoms have on quality of life
Urinary frequency	RemoteFrequency (rFrequency) The number of recorded voids per day was summated over the same days the 3‐day Bladder Diary was completed for comparative analysis	3‐day bladder diary [15]—a validated survey asking patients to record how often they urinate (frequency), if there was any leakage or urgency related, and amount and type of fluid intake over 3 days.	Overactive Bladder Symptom Survey (OABSS) [16] A validated self‐assessment questionnaire consisting of four questions assessing overactive bladder symptoms (bladder symptoms) during the previous week. Total score ranges from 0 to 15, with higher scores indicating more severe symptoms.

2.5.1. RemotePVR (rPVR)

The last measure of urine volume before urination (pre‐void) and the first valid measure after urination (i.e., “bout,” post‐void) were used to determine the residual urine.

2.5.2. RemoteFrequency (rFrequency)

The number of recorded voids per day was summed over the same days the 3‐day Bladder Diary was completed.

2.5.3. Patient Surveys

Participants were asked to complete a standard paper 3‐day Bladder diary [15]—a validated survey asking patients to record how often they urinate (frequency), if there was any leakage or urgency related, and amount and type of fluid intake over 3 consecutive days.

2.5.4. Other Assessments

Directly following the baseline visit, additional bladder questionnaires (including the Neurogenic Bladder Symptom Score—Short Form [NBSS‐SF] [14] and the Overactive Bladder Symptom Survey [OABSS]) [16] were sent to participants via secure REDCap emails (detailed in Table 1) and completed within 1 week.

2.6. Study Feedback

Participants participated in a short Zoom interview led by the study PI (VB) to elicit quantitative and qualitative feedback after completion or withdraw from the study. These included open‐ended questions about the benefits and disadvantages of using the device, the study timeline and interaction with the study team.

At study completion, questions adapted from the Health IT Usability Evaluation Survey (Health ITUES) were completed via secure REDCap email [17]. These asked about “impact,” “perceived usefulness,” and “perceived ease of use” of using the remote wearable ultrasound device.

The University of California San Francisco Institutional Review Board granted approval for the study protocol, and all participants provided written informed consent.

2.7. Statistical Analyses

Demographic and clinical characteristics are presented as mean ± standard deviation, number (percentages), or median (interquartile range), as appropriate.

To evaluate the feasibility of deploying the remote wearable device for home use, the percentage of participants completing the study was calculated. Reasons for lower adherence were explored through exit surveys and classified according to thematic domains (barriers or facilitators) to adherence which can be addressed.

Face validity was assessed by plotting remote post‐void volumes (remotePVR; rPVR) against bladder volumes measured immediately before voiding, pre‐void volumes. Bland–Altman plots were used to visually assess the agreement between the two measurement methods: remote (using all available data over the 3‐months, and separately, over the first 7‐days of the study) and clinical PVR measures, by plotting their mean against the difference, identifying bias and limits of agreement.

The face validity of urinary frequency was assessed by plotting rFrequency against the urinary frequency reported by patients in the 3‐day bladder diary. To compare patient‐reported and remote urinary frequency, Interclass Correlation Coefficients (ICC), and Pearson's correlations were used given that these measures were continuous and approximately normally distributed. Spearman's (rho) was used to assess correlations between remote metrics and patient‐reported outcomes as these measures non‐normally distributed. Analysis was carried out using STATA 18 software (StataCorp, College Station, TX, USA) and JMP Pro 17 [18, 19] (SAS Institute Inc.) with significance set at p < 0.05.

3. Results

Twenty‐two women with MS were enrolled; mean age was 51.5 years (SD 9.3). Disability was moderate (median EDSS 4.0; range 2.5–6.0); 72.7% had relapsing disease (Table 2).

TABLE 2.

Demographics information (N = 22 females).

Age, years (mean, SD)	51.5 (9.3)
BMI, kg/m2 (mean, SD)	25.6 (5.5)
Parity, yes (N, %)	14 (63.6%)
0 births (N)	8
1 birth (N)	2
2 births (N)	9
3 births (N)	2
4 births (N)	1
Bladder medication (% receiving)	32%
Bladder botulinum injection	N = 2
Solifenacin	N = 1
Beta‐3 adrenergic agonist	N = 1
Baseline prEDSS (median, range)	4.0 (2.5–6.0)
Disease duration, years (median, IQR)	16.5 (13.8)
Disease type, relapsing (N, %)	16 (72.7%)
DMT, B‐cell depleting, anti‐CD20 (N, %)	10 (45.5%)

Abbreviations: BMI = body mass index, DMT = disease modifying therapy, IQR = interquartile range, N = number, prEDSS = patient‐reported expanded disability status scale, SD = standard deviation.

3.1. Feasibility of Remote Tools

Study retention was high; 86.4% (19/22) completed the 3‐month study. Additionally, device utilization was on target, with an average of 14 days use (target: 9–15 days, mean use: 14.1 days).

Reasons for device use/study discontinuation (n = 3) were: (1) possible Bluetooth interference with baclofen pump—also located in the abdominal region, (2) device positioned on the lower abdomen triggered concerns about body weight (although the individual continued to complete PROs), and (3) considerable life events—including a clinical MS relapse—during the first week of the study.

3.2. Agreement Between Remote and In‐Clinic Bladder Assessments

3.2.1. Urinary Retention

3.2.1.1. Face Validity

To initially verify the face validity of the results, the rPVR values were plotted against the bladder volumes measured immediately before a void. As illustrated in Figure 1, there was a clear decrease in volumes after a void. Furthermore, the rPVR was able to capture day‐to‐day variability in symptoms not appreciated using single clinic snapshots. For example, Figure 1B shows the “residual” (urine remaining after a void) for three separate voids for the same patient over the same day.

FIGURE 1.

(A, B) Remotely acquired pre‐ and post‐void residual measures highlighting bladder symptom variability. (A) Example of the pre‐void DFree measure and a post‐void measure (remotePVR) for all patients over the entire study, and (B) highlighting daily rPVR variability over three separate voids in 1 day, for one patient. Pre‐void bladder volume is in green, post‐void in purple.

3.2.1.2. Concurrent Validity

When compared with the standard in‐clinic residual urine volume (cPVR), the remotely measured residual urine volume (rPVR), collected over the first 7 days, showed good agreement (mean difference = 32.1, SD 38.6; 95% limits of agreement: −43.6, 107.9). The agreement was similar, albeit slightly worse, when utilizing all rPVR data for the entire 3‐month period (mean difference between the measures = 40.2, SD 44.1; 95% limits of agreement: −46.3, 126.6). Bland–Altman plots showed no systematic bias between measures; 1 individual was on the 95% limits of agreement (Figure 2; green lines).

FIGURE 2.

Bland–Altman showing good agreement between remote and in‐clinic post‐void residual measures. A Bland–Altman plot visually assesses agreement between two measurement methods by plotting their mean against the difference, identifying bias and limits of agreement. Y‐axis: difference between clinical post‐void residual (cPVR) and remote post‐void residual (rPVR). X‐axis: mean of cPVR and rPVR. The circles represent each individual, with the dotted line representing the mean difference and the solid lines showing where the 95% limits of agreement lie.

Furthermore, the rPVR values were moderately correlated with patient‐reported voiding difficulties, as measured by the voiding portion of the NBSS‐SF (Pearson r = 0.537, 95% CI: 0.094–0.803, p = 0.022). The model explained 28.9% of the variance (R ² = 0.289, adjusted R ² = 0.244), with an estimate of 9.982.

3.2.2. Remote Urinary Frequency

3.2.2.1. Concurrent Validity

The remote measure of urinary frequency (rFrequency) was comparable with the traditional patient‐reported outcome (3‐day bladder diary) (Figure 3A). Indeed, the ICC between the two variables was good (0.81) (Figure 3B), and Pearson's correlation (0.793 [lower 95% 0.404—upper 95% 0.940] p = 0.0021. R ² = 0.630, R ² adj = 0.593) indicated a strong linear relationship between them.

FIGURE 3.

(A, B) Comparing urinary frequency measured via standard and remote wearable outcomes. (A) Per individual, remote urinary frequency (rFrequency; orange) was similar to the patient‐reported 3‐day bladder diary urinary frequency (green) over the same 3‐day epoch. (B) Box plots illustrate the comparison between the patient‐reported and remotely acquired urinary frequency over 3 days.

Additionally, the rFrequency measure correlated with patient‐reported overactive bladder symptoms, as assessed by the OABSS combined measure (Daytime frequency, Nighttime frequency, Urgency, Urge incontinence; p = 0.029; corr 0.627 [0.083–0.883], R ² = 0.393, R ² adj = 0.332).

3.2.3. Illustration of Augmented Value Provided by Remote Monitoring: Symptom Variability and Granularity

Having evaluated the initial validity of the remotely collected measures of urinary retention (rPVR) and frequency (rFrequency), the study further sought to understand the added value provided by longitudinal remote measures beyond an initial objective assessment of symptoms.

As demonstrated in Figure 4A, the range of rPVRs collected over the course of the study, while showing good agreement with in‐clinic PVR, also varied substantially, providing additional granularity into the dramatic day‐to‐day variability in bladder symptoms, previously un‐addressed through traditional measures. Figure 4B clearly illustrates that day‐to‐day variability in bladder symptoms is reflected in fluctuating daily urination frequency (rFrequency).

FIGURE 4.

(A, B) Box‐plots illustrating the wide variability within individual participants in urinary retention (A) and frequency (B) as measured via remote monitoring. Left X‐axis: shows the volume of urine measured (from 0 to 100 [maximum]) by the wearable ultrasound after a “void”—indicating the rPVR. Blue box plots indicate all available rPVR measures over the study. Right X‐axis: shows the average clinical post‐void residual. Red (×) shows the average of three cPVR measures, all taken within 5‐min, directly after participant was asked to fully void. (B) Average number of voids per day, with the mean, standard deviation (SD), and total number displayed on the bottom of the graph.

To illustrate the additional granularity afforded by the remote metrics for the purposes of symptomatic and rehabilitative interventions, one participant's voids and bladder measurements are depicted in Figure 5. Patient awareness of bladder patterns and behaviors can offer meaningful opportunities for behavior modification interventions; the remotely collected data illustrate many opportunities through which the clinical rehabilitation professionals could query daytime function to provide education and recommend tailored behavioral modifications based on individual symptom presentation, including dayto‐day fluctuations in bladder dysfunction. Interventions may include strategies such as bladder emptying techniques when rPVR is high or urge suppression techniques when rFrequency is high and rPVR is low (indicating appropriate bladder evacuation).

FIGURE 5.

Remote bladder monitoring reveals opportunities for personalized symptom management in multiple sclerosis. Blue shaded areas: nighttime periods, Peach shaded areas: daytime periods, Red dots: voiding events. This graph illustrates remote bladder monitoring data from a single participant, highlighting fluctuations in remote post‐void residual volume (rPVR) across the day and night. The remotely collected data demonstrate the potential for targeted behavioral interventions based on real‐time bladder patterns.

3.3. Qualitative Participant Feedback

All 22 participants completed study exit (n = 19)/discontinuation (n = 3) interviews.

3.3.1. Health ITUES Summary

Participant feedback revealed excellent impact, usefulness and ease of use. 66% agreed/strongly agreed that the device would be a positive addition for people living with MS, > 50% agreed/strongly agreed that the device was easy to use and would improve quality of life for PwMS. Participants (61.1%) agreed/strongly agreed that the device was useful for self‐management of MS‐related bladder symptoms, 44% agreed/strongly agreed that the device would increase their ability to self‐manage their MS‐related bladder symptoms, and 38.9% agreed/strongly agreed with the statement “I am satisfied with the [device] tools for self‐management of MS‐related bladder symptoms.”

3.3.2. Technical Feedback

During the exit interviews, five participants mentioned that the device could have been more accurate, with 87% suggesting that the placement holder could be better designed. 16% (3/19) of the participants reported a desire for additional device training from the study team. Additional concerns/suggestions included the minimal discomfort and redness from using the adhesive tape, as well as the burden of charging the device every 36 h.

3.3.3. Clinically Informative Feedback

Respondents provided a range of self‐management uses for the wearable based on their initial period of use.

1. Reducing leakage frequency: Of nine participants who reported > 5 leakage episodes daily at baseline, 56% reported a significant (to them) reduction in leaks—with 33% indicating zero leaks at 1 month following the study exit (via email or personal communication to the study PI [VB]).

2. Self‐management: One participant noted that prior to the study, while working, she would “forget or not feel the urge to urinate until standing…” resulting in leakage before reaching the bathroom. The DFree App allows the user to set a level (from 0 to 10) where a smartphone notification to “Find a restroom soon” will appear. During the exit interview, it was noted that by setting the level below where the level where a leak was experienced, leakage episodes were reduced by half.

3. Motivation for further treatment: Two participants noted that the biofeedback/visual data made them aware of incomplete emptying, motivating them to final schedule pelvic health PT (despite this having been a recommendation for some time).

4. Planning activities: Three participants reported using the wearable ultrasound monitor bladder fullness before running errands, rather than having to restrict their activities so they occur between timed voids (the usual clinical recommendation).

4. Discussion

To our knowledge, this is the first study to investigate the potential utility of commercially available, wearable bladder ultrasound devices in PwMS. The results demonstrate the feasibility and validity of this innovative technology and provide detailed insights into urinary retention and frequency, establishing a non‐invasive, novel approach for monitoring bladder dysfunction. High adherence rates (86.4%) and participant‐reported benefits further emphasize the potential for these technologies to transform self‐management strategies for bladder dysfunction in PwMS.

Our findings demonstrate robust face validity between remote bladder volume measurements and clinical post‐void residual (cPVR), with Bland–Altman analyses confirming this agreement. The strong correlations between remotely measured frequency (rFrequency) and traditional patient‐reported bladder diary measures further establish concurrent validity. These initial validation steps support the potential of wearable devices as an objective complement to existing subjective measures of bladder dysfunction.

A key novel finding was the significant day‐to‐day variability in bladder metrics, including for retention (rPVR) and voiding frequency (rFrequency). This variability, typically undetected by conventional in‐clinic assessments at isolated timepoints, reveals the dynamic nature of bladder dysfunction in MS. The capacity for continuous, home‐based monitoring enables a more nuanced understanding of symptom patterns and could revolutionize treatment approaches. This longitudinal data collection creates opportunities for healthcare providers, particularly pelvic health PTs and urologists, to implement closed‐loop treatment strategies. For instance, clinicians could track treatment responses to pharmacological interventions or monitor potential complications, such as increased retention following bladder Botox administration, enabling more responsive and personalized care approaches.

Our comparative analysis of Bland–Altman results between the full 3‐month period and the initial 7 days suggests that a week‐long monitoring period may suffice for establishing baseline retention metrics. However, determining optimal monitoring durations for longitudinal assessment requires further investigation, particularly to balance comprehensive symptom tracking with patient burden. rPVR was moderately correlated with PROs (r = 0.54), but explained only 28.9% of variance, indicating other contributing factors that should be explored. Future research should explore the integration of additional metrics beyond PVR and frequency to develop a more comprehensive understanding of bladder dysfunction dynamics and treatment efficacy.

Several limitations warrant consideration. While our study demonstrated feasibility and preliminary validity, successful self‐management may require specialized training from pelvic health professionals. Here, self‐management benefits were participant‐identified. A larger trial with predefined behavioral targets is planned to evaluate efficacy more rigorously. The absence of established minimal clinically important difference (MCID) thresholds for remote bladder dysfunction metrics presents another challenge for clinical implementation. Our pilot study's generalizability is constrained by its small, female‐only cohort and reliance on single in‐clinic PVR validation measurements. There are few studies in any population—male or female—on the use of remote bladder ultrasound wearables. Rigorous research is needed to identify their limitations and explore potential sex differences. Prior studies have established that remote research can be cost‐effective, considering the savings in costs to participants (both direct costs, such as travel and parking, and opportunity costs, such as time missing work) and to researchers and clinicians [19]. In the current study, no formal cost analysis was performed. Future prospective work will have to factor in the cost of commercially available wearable ultrasounds (~$399 per unit) as part of a formal cost analysis to better inform large‐scale implementation and adoption. Future research should address these limitations by incorporating larger, more diverse cohorts, longer study durations, and broader metric collection—including Ecological Momentary Assessments that would indicate time‐to‐urge threshold for urgency and urge incontinence, as well as assessments of leakage severity.

This study provides compelling preliminary evidence supporting the feasibility and validity of remote bladder monitoring in PwMS using wearable technology. The ability to capture real‐world data on urinary retention and frequency represents a significant advance in bladder dysfunction assessment and management, potentially enabling more proactive and personalized care approaches. This technology could mark a paradigm shift in how we understand and treat bladder dysfunction in this population.

Author Contributions

V.J.B. conceptualized, designed the study, collected and curated the data, wrote the first draft – and acquired funding. R.B. provided supervision, and conceptualized, designed the study. S.P. curated the data, and conducted formal analyses. N.S. and C.P. collected and curated the data. L.M., M.V.K. and A.M.S. data collection and study design. G.J. conducted formal analyses. All authors contributed to review and editing.

Conflicts of Interest

Dr. Block is funded by the National MS Society Career Transition Award. Mr. Poole, Dr. McIntyre, Ms. Sisodia, Ms. Park, Dr. Joseph, Dr. Van Kuiken report not relevant conflicts of interest. Dr. Suskind is a paid consultant on an AHRQ grant and for FLUME catheters. Dr. Bove is funded by the NMSS Harry Weaver Award, NIH, DOD, NSF as well as Biogen, Novartis, and Roche Genentech. She has received personal fees for consulting from Alexion, EMD Serono, Horizon, Jansen, Genzyme Sanofi, and TG Therapeutics.

Supporting information

Table S1.

Funding Statement

This work was funded by National Multiple Sclerosis Society grant TA‐2006‐36695.

Data Availability Statement

The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.