The digital bladder diary

In the early years of the BeDRY digital bladder diary, all users had was an automated statistical summary. The users were primarily parents of children with incontinence, mostly bedwetting. If those parents needed more insight into what this summary meant in real life, they had to schedule a doctor's appointment. As a doctor, during the outpatient visit, I would explain that the bladder diary is the first and the most important diagnostic tool in patients with lower urinary tract symptoms, which doctors abbreviate as LUTS, covering all symptoms of bladder dysfunction. Another important term is LUTD — lower urinary tract disorder — which I will also use in this text to refer to any condition that causes LUTS.

To understand why the diary is a diagnostic tool, you need to know what the bladder actually does. It has two jobs: store urine, and empty itself — storage and emptying. A healthy bladder fills to the expected capacity for the child's age, fills without premature contractions, produces no involuntary leaks, empties at a normal frequency (roughly four to seven times a day), and empties completely, with no urine left behind. If bladder function is abnormal, lower urinary tract symptoms will manifest. A careful medical history can distinguish which function — storage or emptying — is disordered, so that a rational diagnostic evaluation and therapy can be prescribed. But sometimes, taking a medical history needs a little push so it can collect patient data correctly, reliably, and objectively. The bladder diary is that little push.

The main problem in the outpatient clinic during history-taking, especially with children, is that these symptoms are sometimes hard to report and hard to differentiate. Take urgency, for example. It is a sudden urge to void; it may end with urge incontinence. It is an obligatory symptom of overactive bladder — one of the most common LUTD in children, adolescents, and adults. The main problem with urgency, especially in children, is its subjective nature. Only the patient can report urgency. Parents, caregivers, and medical personnel can see some signs of urgency, but we cannot reliably estimate the level of it. Parents usually report that a child with urgency holds urine for too long and then runs to the toilet. Sometimes the child doesn't make it on time, and urge incontinence happens. But children are playful, too — going to the toilet to pee is the last thing on their list of activities, way behind play, their favourite cartoon, or a stream on a tablet. A child may have urgency with incontinence because of an overfilled bladder, or, on the other hand, because of a premature, uncontrolled bladder contraction as in overactive bladder. To distinguish between these, I usually ask whether the child is peeing large volumes when running to the toilet, or only small, or sometimes small and sometimes large — the last would point to overactive bladder. You probably want to ask how a diary helps to make these symptoms more objective.

Parents are instructed to log every urination volume for at least two days. They also log all drinking volumes, incontinence events, and stool type. By reading the recorded data, a doctor can interpret the storage symptoms such as urgency, daytime and nighttime incontinence, and urination count. From the diary we can learn total urinations per day (too many, above seven, or too few, below four), the maximum voided volume (which tells us if the bladder is small for age), the type of incontinence events, signs of constipation — a hidden cause of lower-tract symptoms, and advanced metrics such as the Overactivity Index. Checking these metrics, we can see if the child holds urine for too long, has a small or overactive bladder, produces too much urine during the night, doesn't drink enough during the day, and much more. Symptoms which are hard to tell apart, such as different types of incontinence, are accurately reported and show correlation with other corresponding metrics. Urge incontinence happens because the child did not make it on time to the toilet, and is accompanied by a high Overactivity Index; post-void dribble happens right after peeing, with a usually normal urge to urinate. A bladder diary contains a wealth of valuable information, and keeping it takes effort. However, interpreting the data is not always straightforward and requires careful analysis, as important patterns may otherwise be overlooked. Since I started working in bladder clinics, I learned that a standardized and accurate diary analysis is a major skill.

During the five-year period from 2018 to 2022, I ran an intervention study examining biomarkers in overactive bladder (OAB) in children. What puzzled me about overactive bladder was that it presents identically to an acute lower urinary tract infection — urgency, incontinence, frequent urination — but the urine culture comes back clean. So if it is not of microbial origin, what is driving it? Beyond the unknown origins, I needed an answer to a different question: how can we diagnose and follow its severity in a noninvasive, objective, and reliable manner? The clinical study I started was demanding, and most of the children went through multiple diagnostic evaluations, including invasive ones such as the urodynamic study, abbreviated as UDS. UDS investigates both the storage and the voiding phase of bladder function, and requires placing an indwelling urodynamic catheter to monitor pressures inside the bladder in real time. The protocol was peer-reviewed and approved by the Ethical Board before I received the grant that covered the PhD student's salary and all the study materials.

Some published papers reported the role of neurotrophins — molecules released from the bladder wall when it is full, which actively stimulate bladder contraction. I started investigating the concentrations of these molecules in the urine of patients and controls. I did this alongside other biomarkers: inflammatory cytokines in urine, ultrasound markers such as bladder wall thickness, and uroflow output (the test that examines the voiding phase of bladder function). All the measured data was compared against validated questionnaires for overactive bladder (OABSS) and UDS metrics, primarily maximum cystometric capacity. All patients filled in a bladder diary for two days. At that point I didn't have a digital version, so parents recorded data in frequency-voiding charts — tables with dates and hours. I also came up with something I named the “continence diary.” I created a table with seven columns, one for each day of the week, and 24 rows to represent each hour of the day. Parents were instructed to record all urge, urge-incontinence, incontinence-without-urge, and normal-urination events during each of the seven days. They also marked when the child went to sleep and when they woke up, so I could distinguish daytime and nighttime symptoms (such as bedwetting or nocturia — waking up to pee without leaking). This continence diary was strenuous, but it provided robust data with total counts of urgency and incontinence incidents for the period of diary-keeping.

Eventually, the neurotrophins came out as a huge disappointment because I couldn't measure any levels in the urine. What I felt back then was immeasurable: the primary hypothesis, and the idea of developing simple urine tests, were gone. As any diligent researcher, I wanted to find out what went wrong, and I had a plan for how to find out. First, my PhD student and I checked our cold-chain of urine collection and storage; then the lab kits we used to measure the levels; next we changed the whole measuring methodology twice; and finally we contacted colleagues we knew were doing similar research. They also confirmed our findings but were reluctant to publish, because of the negative results. I published the lack of success with neurotrophins — you can find the details of our efforts in the paper. Fortunately, the story with biochemical markers in urine did not end there, and we had promising results with inflammatory markers, which is a story for another time.

Of all the markers I measured in this study, the most useful one to diagnose and follow up OAB came from the least expected tool: data derived from the bladder diary. This new metric correlated strongly with urgency counts and with the most reliable UDS metric — maximum cystometric capacity — the gold standard for clinical investigations. The bladder diary: the simplest and free diagnostic tool produced the most useful data. After five years of research, I thought I finally had an answer — at least one.

The new metric I called the Overactivity Index (OI) — a median of recorded urination volumes normalized to expected bladder capacity for age. It gave the best results on multivariate binary logistic regression in diagnosing overactive bladder, with a score of 23 and above as the cut-off value for the diagnosis of OAB. What did that mean in clinical practice? If a patient with urgency or incontinence came to my office, checking their bladder diary data and calculating the OI could give me reliable data to start pharmacotherapy for OAB. On the other hand, values below 23 were indicative of clinical success, and probably an indication for safe cessation of pharmacotherapy with minimal risk of the condition returning. The last hypothesis still needs to be evaluated in a clinical setting, but my experience from the outpatient clinic suggests exactly that. If proven, this will be useful, because there is more than a 40% risk of OAB recurrence when stopping medication once complete success has been achieved.

Immediately after publishing my Overactivity Index paper, I incorporated it into my clinical workflow. Parents sent me photos or scans of their bladder diaries by email, and I manually entered the data into an Excel sheet that calculated the OI. I still have the file — overactivity-index.xlsx. It was a good file, with a report, charts, even trends if I entered data from multiple diaries. But I started thinking about a digital bladder diary where parents would collect data that could be shared with me, while the OI and other variables would be calculated automatically. That is exactly how the idea of BeDRY was born.

The path from idea to realization was not a simple overnight task. I went through three developers, and finally settled with Kristijan, with whom I still have a great and ongoing collaboration. We managed to release BeDRY as a web application at https://bedry.app in 2022. To fund the development of this minimal viable version of the BeDRY app, I sold my Honda CRV — an automatic diesel, four-wheel drive. I loved that car. It was reliable, didn't have many kilometers on it, looked like it had just come off the production line, in perfect shape. I sold it to an older gentleman for 22,000 euros — too cheap, when I think about it now. The last time I saw the car, I hugged its rear, so no one could see what I was doing; I am sure there was a drop of tear in my eyes. Now it was me, in charge of managing my own dreams and wishes, so I had to make the right choices on my own. At that time my wife and I were blessed with our third child, and I had a good reason to think about a bigger vehicle and financial plans for my growing family.

The app turned out to be very useful for me and the few colleagues who adopted it. The most important thing was that parents adopted this new diary immediately, and never thought of going back to the paper version. The digital diary started, and continued, as a free tool available to all, and the impact on helping families and children with treatment was what mattered most. But I wanted to develop the app further. I had a lot of ideas for how to upgrade it — some of them useful, such as including a stool diary using the validated Bristol Stool Scale, and incorporating the continence diary that could actually discriminate between different types of urinary incontinence. Some of the ideas never saw the light of day, and still linger in Trello boards.

After the initial release, I needed more money to fund this project of mine, and I started looking for grants. I quickly realized that if I didn't found a startup company and have a sustainable business plan, no grant would ever come through. Since I had a web application running, and substantial traction, I applied for a non-refundable 10,000-euro grant and a pre-accelerator program called “Start Something of Your Own.” This was the second time I applied for this grant. The first time I only had the idea without the product to relase and test. Then I realized that an idea has no value until it is brought to life — and for my second try I was ready. Winning this grant was a huge leap forward, because I met the right people and polished the future app's development. That soon led to a proof-of-concept grant of 56,000 euros from the Ministry of Science, to develop the bladder training concept.

A free digital diary was useful, but as families used it I noticed something. They did not need a tool to tell them that their child's leaks were caused by an overactive bladder, and that these urine leaks are called urge incontinence. They already knew their child could not control the bladder. What they wanted was therapy — something to do about it — and, if available, a reliable remote tool. The right path seemed to be to offer remote, personalized, digital therapy for LUTS, based on the data recorded by the bladder diary.