According to the current AUA guidelines on the medical management of kidney stones, “Clinicians should recommend to all stone formers a fluid intake that will achieve a urine volume of at least 2.5 liters daily.”¹ These recommendations were established based on numerous studies demonstrating a dose dependent relationship between increased water intake and decreased stone formation.² However, despite objective data on the benefits of drinking more fluids, adherence to these recommendations has proven to be challenging for patients with compliance rates of 50% or less, presumably due to lifestyle and motivational factors.³ With the rapid adoption of emerging technologies into the realm of digital health, it is conceivable that some of these tools may be beneficial for patients to achieve their fluid intake recommendations.

Interestingly, with over 300,000 mobile health apps currently available, a systematic evaluation of all smart phone apps for the medical management of nephrolithiasis identified only 31 apps, 18 of which focused on fluid management;⁴ in this study, while fluid management apps outperformed dietary apps, they were limited to user-entered fluid intake data, which imposes a burden on users for effective tracking. By the same token, studies have shown that patients with a history of kidney stones have expressed interest in using smart technology to improve adherence to fluid intake recommendations.⁵ Fortunately, there are several smart devices in the market to assist with fluid intake, and while it is difficult to ascertain the effectiveness of such devices, it has been shown that smart water bottles can accurately measure daily fluid intake when compared to manual hand measurement.⁶ But as attractive as these seem, do apps and devices really help patients with chronic disease management?

Indeed, it has been shown with other chronic disease conditions that the utilization of smart technology can improve patient adherence. For example, clinical trials in hypertensive patients have shown sustainable changes in patient adherence with improved blood pressure control with the use of smartphone app monitoring with feedback vs counseling alone.⁷ Accordingly, the incorporation of mobile health technology towards helping our kidney stone patients achieving their fluid intake goal is an attractive and logical step into the future.

Based on these insights and a paucity in the literature on this topic, we conducted a 3-arm prospective trial to evaluate whether a smart water bottle (HydraCoach™) or smartphone app (Aqualert™) could improve patient adherence and augment fluid intake when compared to standard counseling alone.⁸ We randomized 111 patients (37 per group), and found that in the 12-month followup period, the control group patients were the most likely to adhere to follow up. Overall, the mean urine output increased by 0.4 L in each of the 3 groups (p <0.05), with no significant difference between groups (p >0.05) in mean 24-hour urine output at baseline (1.6 L) or at 12 months (2.0 L). Although it was disappointing that our hypothesis was disproven–that the use of smart technology did not further increase urine output or patient adherence–this study does underscore the importance of dietary and medical counselling for kidney stone prevention. Furthermore, we can infer that technology driven self-monitoring alone may not be enough to yield sustainable behavioral change in chronic disease states such as nephrolithiasis. We did acknowledge some limitations in our study, notably that it consisted of patients from a single tertiary care academic setting with predominantly White patients.

To this end, 2 additional clinical trials are currently underway to further our understanding of this issue. One of these, similar to our study discussed above, investigates whether using a smart water bottle (HidrateSpark™) improves adherence to recommended increases in hydration compared to standard techniques such as education and reading materials.⁹ The investigators completed their target enrollment of 85 participants in January 2021, and presumably the results of this trial are forthcoming. The critical study, however, is a large-scale, multicentered clinical trial, the Prevention of Urinary Stones with Hydration (PUSH) study, funded by the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), which began in September 2017 and is nearing the end of patient recruitment. The primary aim of this trial is to determine whether a multi-component program of behavioural interventions to increase fluid intake, including that of a smart water bottle (HidrateSpark™) and mobile health app (Hidrate Inc™), will result in reduced risk of stone progression¹⁰. While this will be the largest clinical trial to date on kidney stone prevention with a pragmatic design incorporating smart technology, adaptable intervention and active patient engagement, a unique feature of this study lies in evaluating how active coaching further enhances the smart technology.

Despite the challenges we face in helping our patients meet their hydration goals, it is reassuring to know we may soon have a definitive evidence-based answer to this conundrum–whether technology can truly augment fluid intake behaviours in our patients.