Factors influencing fluid intake behavior among kidney stone formers

Urges to Drink Predict Urine Output Volume in Patients with Kidney Stones

OBJECTIVE

To evaluate the hypotheses that 24-hour urine output volume would be associated with (a) cognitive evaluations of unflavored water and (b) urges to drink.

METHODS

Patients (N=380, 60% female) with a history of kidney stones completed a baseline questionnaire and a 24-hour urine collection.

RESULTS

Non-thirst-related urges to drink unflavored water were positively associated with daily urine volume (b = 0.15, p <.01), but non-thirst-related urges to drink flavored drinks were not associated with daily urine volume. Cognitive evaluations of unflavored water were not associated with daily urine volume.

CONCLUSIONS

These findings highlight the importance of affective over cognitive processes for motivating non-thirst-related fluid intake. Non-thirst-related urges to drink unflavored water are a potential target for promoting urine output in patients at risk for kidney stone recurrence and may be potentially used to identify those patients at higher risk in absence of a 24-hour urine volume.

DATA AVAILABILITY

A de-identified dataset is available upon request from the corresponding author.

Cognitive evaluations of water, urges to drink, and fluid intake in patients with kidney stones

Increasing fluid intake is a core recommendation for reducing risk of kidney stone recurrence. Thirst is often insufficient to motivate the volume of intake recommended to reduce risk, so this study examined cognitive and affective processes that support fluid intake (water and flavored beverages). Patients (N = 230) with a history of kidney stones identified from medical records were recruited to complete an online survey. Participants who associated unflavored water with favorable bodily consequences and positive hedonic experiences were likely to have stronger non-thirst-related urges to drink unflavored water, and those who associated unflavored water with negative hedonic experiences were likely to have stronger non-thirst-related urges to drink flavored drinks. Non-thirst-related urges to drink unflavored water were positively associated with water intake volume, but non-thirst-related urges to drink flavored drinks were negatively associated with water intake volume. These findings establish the importance of affective processing as a target for promoting fluid intake in cases where thirst is not sufficient.

Can the Total Body Water and Total Fat Mass Predict Kidney Stone Recurrence in Overweight and Obese Patients?

Background Urolithiasis prophylaxis is a cornerstone for kidney stone formers. Obesity is a well-known risk factor for kidney stone recurrence. The objectives of this research were to highlight the correlations between the mean water intake and free water deficit (FWD) depending on plasma Na and weight. Methods Anthropometric and nutritional analysis was performed using a body analyzer with magnetic bioimpedance ankle-to-foot, which determined the total percentage of water in the body. Results The mean age was 52.19 years old and the mean body mass index (BMI) was 33.68 km/m2. About 58.23% (n=46) of patients declared at least one episode of urolithiasis in their pathological antecedents. The patients were counseled by a dietician and lost weight. After losing weight, the total body water (TBW) percentage increased (average=41.37%), while the total fat percentage decreased (average=33.52%). Urinary volume increased, but the water did not accumulate for proper hydration. This may explain the recurrence of urinary stones despite large amounts of water intake. Conclusions The present study indicates an inverse-proportional relationship between TBW and fat mass (FM). Obese patients with lithiasis should lose weight due to total FM, not TBW.

Risk for hypertension and heart failure linked to high normal serum sodium and tonicity in electronic medical records

Background and Aims

Population aging is fueling an epidemic of age-related chronic diseases. Managing risk factors and lifestyle interventions have proven effective in disease prevention. Epidemiological studies have linked markers of poor hydration with higher risk of chronic diseases and premature mortality. Many individuals do not adhere to recommended hydration levels and could benefit from improved hydration habits. Our study evaluates the use of electronic medical records to confirm the relationship between inadequate hydration and the risk of chronic diseases, which may inform hydration-focused interventions in general healthcare.

Methods

We analyzed 20-year electronic medical records for 411,029 adults from Israel's Leumit Healthcare Services. Hydration status was assessed using serum sodium and tonicity. We included adults without significant chronic diseases or water balance issues, defined as having normal serum sodium (135-146 mmol/l) and no diagnosis of diabetes. We used Cox proportional hazards models, adjusted for age, to assess the risk of developing hypertension and heart failure.

Results

Our findings showed an increased risk of hypertension with elevated serum sodium levels: a 12% rise for the 140-142 mmol/l group and 30% for levels above 143 mmol/l (HR1.30, 95%CI:1.26-1.34). Tonicity over 287 mosmol/kg was associated with a 19% increased risk of hypertension (HR1.19, 95%CI:1.17-1.22). The risk of heart failure also increased, reaching 20% for sodium levels above 143 mmol/l (HR1.20,95%CI:1.12-1.29) and 16% for tonicity above 289 mosmol/kg (HR1.16, 95%CI: 1.10-1.22). The association between sodium and hypertension was observed across genders, while the risk of heart failure was more pronounced in females. Within the healthy Leumit cohort, 19% had serum sodium levels within the 143-146 mmol/l range, and 39% were in the 140-142 mmol/l range.

Conclusions

Data analysis from electronic medical records identified a link between serum sodium of 140 mmol/l and above and increased risk of hypertension and heart failure in the general Israeli population. Identifying individuals with high-normal sodium values in healthcare records could guide improvements in hydration habits, potentially leading to better health outcomes.

Long-term health outcomes associated with hydration status

Body water balance is determined by fundamental homeostatic mechanisms that maintain stable volume, osmolality and the composition of extracellular and intracellular fluids. Water balance is maintained by multiple mechanisms that continuously match water losses through urine, the skin, the gastrointestinal tract and respiration with water gains achieved through drinking, eating and metabolic water production. Hydration status is determined by the state of the water balance. Underhydration occurs when a decrease in body water availability, due to high losses or low gains, stimulates adaptive responses within the water balance network that are aimed at decreasing losses and increasing gains. This stimulation is also accompanied by cardiovascular adjustments. Epidemiological and experimental studies have linked markers of low fluid intake and underhydration - such as increased plasma concentration of vasopressin and sodium, as well as elevated urine osmolality - with an increased risk of new-onset chronic diseases, accelerated aging and premature mortality, suggesting that persistent activation of adaptive responses may be detrimental to long-term health outcomes. The causative nature of these associations is currently being tested in interventional trials. Understanding of the physiological responses to underhydration may help to identify possible mechanisms that underlie potential adverse, long-term effects of underhydration and inform future research to develop preventative and treatment approaches to the optimization of hydration status.

Every sip counts: Understanding hydration behaviors and user-acceptability of digital tools to promote adequate intake during early and late pregnancy

Maintaining adequate hydration over the course of pregnancy is critical for maternal and fetal health and reducing risks for adverse pregnancy outcomes (e.g., preeclampsia, low placental and amniotic fluid volume). Recent evidence suggests that women may be at risk for under-hydration in the second and third trimesters when water needs begin to increase. Scant research has examined pregnant women's knowledge of hydration recommendations, water intake behaviors, and willingness to use digital tools to promote water intake. This study aimed to: 1) describe hydration recommendation knowledge and behaviors by the overall sample and early vs late pregnancy, and 2) identify habits and barriers of using digital tools. Pregnant women (N = 137; M age = 30.9 years; M gestational age = 20.9) completed a one-time, 45-minute online survey. Descriptive statistics quantified women's knowledge of hydration recommendations, behaviors, and attitudes about utilizing digital tools to promote adequate intake, and Mann-Whitney U and chi-squared tests were used to determine group differences. Most women lacked knowledge of and were not meeting hydration recommendations (63%, 67%, respectively) and were not tracking their fluid consumption (59%). Knowledge of hydration recommendations differed by time of pregnancy, such that women in later pregnancy reported 82 ounces compared to women in early pregnancy (49 ounces). Common barriers included: forgetting to drink (47%), not feeling thirsty (47%), and increased urination (33%). Most were willing to use digital tools (69%) and believed a smart water bottle would help them achieve daily fluid recommendations (67%). These initial findings suggest that pregnant women may benefit from useful strategies to increase knowledge, decrease barriers, and maintain adequate hydration, specifically earlier in pregnancy. These findings will inform the design of a behavioral intervention incorporating smart connected water bottles, wearables for gesture detection, and behavior modification strategies to overcome barriers, promote proper hydration and examine its impact on maternal and infant health outcomes.

Promoting fluid intake to increase urine volume for kidney stone prevention: Protocol for a randomized controlled efficacy trial of the sipIT intervention

BACKGROUND

Risk of kidney stone recurrence can be reduced by increasing fluid intake and urine production but most patients fail to adhere to recommended clinical guidelines. Patients have indicated that common barriers to fluid intake include a lack of thirst, forgetting to drink, and not having access to water. We developed the sipIT intervention to support patients' fluid intake with semi-automated tracking (via a mobile app, connected water bottle and a smartwatch clockface that detects drinking gestures) and provision of just-in-time text message reminders to drink when they do not meet the hourly fluid intake goal needed to achieve the recommended volume. This trial evaluates the efficacy of sipIT for increasing urine output in patients at risk for recurrence of kidney stones.

METHOD/DESIGN

Adults with a history of kidney stones and lab-verified low urine production (<2 L/day) will be randomly assigned to receive either usual care (education and encouragement to meet fluid intake guidelines) or usual care plus the sipIT intervention. The primary outcome is 24-h urine volume; secondary outcomes include urinary supersaturations, past week fluid intake, and experienced automaticity of fluid intake. Outcomes will be assessed at baseline, 1 month, 3 months, and 12 months.

CONCLUSIONS

The sipIT intervention is the first to prompt periodic fluid intake through integration of just-in-time notifications and semi-automated tracking. If sipIT is more efficacious than usual care, this intervention provides an innovative treatment option for patients needing support in meeting fluid intake guidelines for kidney stone prevention.

Hydration for Adult Patients with Nephrolithiasis: Specificities and Current Recommendations

Nephrolithiasis affects around 10% of the population and is frequently associated with impaired dietary factors. The first one is insufficient fluid intake inducing reduced urine volume, urine supersaturation, and subsequently urinary lithiasis. Kidneys regulate 24 h urine volume, which, under physiological conditions, approximately reflects daily fluid intake. The aim of this study is to synthesize and highlight the role of hydration in the treatment of nephrolithiasis. Increasing fluid intake has a preventive effect on the risk of developing a first kidney stone (primary prevention) and also decreases the risk of stone recurrence (secondary prevention). Current guidelines recommend increasing fluid intake to at least at 2.5 L/day to prevent stone formation, and even to 3.5-4 L in some severe forms of nephrolithiasis (primary or enteric hyperoxaluria or cystinuria). Fluid intake must also be balanced between day and night, to avoid urinary supersaturation during the night. Patients should be informed and supported in this difficult process of increasing urine dilution, with practical ways and daily routines to increase their fluid intake. The liquid of choice is water, which should be chosen depending on its composition (such as calcium, bicarbonate, or magnesium content). Finally, some additional advice has to be given to avoid certain beverages such as those containing fructose or phosphoric acid, which are susceptible to increase the risk of nephrolithiasis.

Stone diet and dietary change: understanding determinants for dietary change behaviour in patients following urinary stones

BACKGROUND

Dietary habit is one of the most important methods to prevent and treat urinary stones. However, only limited evidence of the experiences of dietary management among urinary stone patients in Malaysia is available. This study aimed to explore participants' current dietary practices after the diagnosis of urinary stones and to identify the factors that facilitate their dietary changes.

METHODS

A qualitative study with purposive sampling was conducted using face-to-face semistructured interviews. A total of 20 participants from a tertiary general hospital in Kuantan, Malaysia, were recruited in this study. Data were analysed using framework analysis.

RESULTS

Two themes emerged from the analysis. The first theme explained the changes in the dietary practice of the participants postdiagnosis. The second theme revealed that the participants' dietary changes were greatly influenced by personal factors and external support from professionals, family and peers.

CONCLUSIONS

Urinary stone patients highlighted the fear of complications, self-determination and knowledge of nutrition as the main drivers of their dietary change postdiagnosis. Emphasising proper nutritional care by assessing and evaluating dietary self-management among patients can facilitate effective self-care in stone prevention management.

'Like a ticking time bomb': A qualitative study exploring the illness experiences of adults with kidney stone disease

OBJECTIVE

Kidney stone disease (KSD) is a common, complex and painful urological condition, but how patients make sense of and respond to the challenges of KSD is poorly understood. Using the common-sense model of illness self-regulation (CSM-SR), we aimed to explore the illness experiences of individuals with KSD.

DESIGN

A qualitative design using individual semi-structured interviews.

METHODS

Thirty-three patients with KSD attending outpatient urology services participated in interviews informed by the CSM-SR. Data were analysed using reflexive thematic analysis. Themes were mapped onto the domains of the CSM-SR.

RESULTS

Five main themes were generated, broadly echoing domains within the CSM-SR: (1) making sense of KSD, (2) normality paused, (3) the psychological burden of KSD, (4) the tensions of managing KSD, and (5) improving understanding of KSD. Additionally, findings suggested that partners' perceptions of KSD were an additional contextual factor that informed patients' own perceptions and management of KSD. Participants appraised initial KSD symptoms as indicative of a serious health threat. Diagnosis brought some relief, however, KSD wielded multi-dimensional impacts on patients' perceptions, self-management and well-being. Anxiety, including fear of KSD recurrence, and low mood were common psychological burdens across narratives.

CONCLUSION

The majority of the themes identified were commensurate with an extended CSM-SR. This model has utility in informing how patients perceive and manage KSD. Examining patients' KSD representations and routinely assessing for psychological distress may be of benefit to improve health outcomes for this patient group.

Feasibility of Mini sipIT Behavioral Intervention to Increase Urine Volume in Patients With Kidney Stones

OBJECTIVE

To determine the feasibility and acceptability of mini sipIT, a context-sensitive reminder system that incorporates a connected water bottle and mobile app with text messaging, for kidney stone patients who have poor adherence to increasing fluid intake for prevention.

METHODS

Patients with a history of kidney stones and urine volume <2L/d participated in a 1-month single-group feasibility trial. Patients used a connected water bottle and received text message reminders when fluid intake goals weren't met. Perceptions of drinking behavior, intervention acceptability, and 24-hour urine volumes were obtained at baseline and 1-month.

RESULTS

Patients with a history of kidney stones were enrolled (n = 26, 77% female, age=50.4 ± 14.2years). Over 90% of patients used the bottle or app daily. Most patients perceived that mini sipIT intervention helped them to increase their fluid intake (85%) and reach their fluid intake goals (65%). There was a significant increase in average 24-hour urine volume after the 1-month intervention compared to baseline (2006.5 ± 980.8 mL vs 1352.7 ± 449.9 mL, t (25)= 3.66, P = .001, g= 0.78), with 73% of patients having higher 24-hour urine volumes at the end of the trial.

CONCLUSION

Mini sipIT behavioral intervention and outcome assessments are feasible for patients and may lead to significant increases in 24-hour urine volume. Digital tools in combination with behavioral science may improve adherence to fluid intake recommendations for kidney stone prevention, however, rigorous efficacy trials are necessary.

Patient compliance to dietary recommendations: tips and tricks to improve compliance rates

Urinary stone disease continues to be a public health problem with growing incidence and recurrences. Recurrence is nearly detected in 50% of the patients within 5 years after the first episode. However, stone recurrence rates can be reduced to a certain extent. The American Urological Association (AUA) and the European Urological Association (EAU) guidelines advice dietary, fluid intake, and medical treatment to prevent or minimize stone recurrence. However, studies have shown that compliance to dietary and fluid intake recommendations is low. Beside this, nutritional evaluation of the patients is sufficient. Using food frequency questionnaires (FFQs), 24 h recall methods (short, individual-oriented, and easily applicable) or mobile apps can be used. In addition, cooperation with registered dietitians (RD) and planning tailored dietary programmes may have positive effect on compliance. Providers who give dietary advices should improve their knowledge about the topic and communication skills to create a patient-provider trust relationship. Simplifying the advices (shorter lists, applicable advices), spending more time, and giving education until being sure for patients' understanding with regular remindings may improve adherence. Moreover, patients increased awareness and knowledge about dietary advices are beneficial. Smart devices for fluid uptake or urine pH monitoring, mobile apps or web-based portals, and telemedicine applications can be used to maintain the compliance on dietary advices. Compliance with dietary modifications and fluid intake recommendations can be well achieved by individualized evaluation/close follow-up and the elimination of the problems limiting the patient compliance.

Just-in-time adaptive intervention to promote fluid consumption in patients with kidney stones

OBJECTIVE

Kidney stones are painful and costly. Prevention guidelines emphasize a simple behavior change: increasing fluid intake and urine output. Unfortunately, adherence to those prevention guidelines is limited, and patients report forgetting or not being thirsty enough. This study evaluated the acceptability of using semiautomated tracking of fluid consumption to trigger just-in-time reminders to drink and increase the experienced automaticity of fluid intake.

METHOD

In a single-group trial, participants with a history of kidney stones (n = 31) used the sip^IT digital tools (H2OPal connected water bottle, H2OPal mobile app for self-tracking, Fitbit smartwatch app for gesture detection) for 3 months.

RESULTS

The semiautomated monitoring system detected 46,654 drinking events. From baseline to 1-month follow-up, the experienced automaticity of fluid intake increased significantly (d = 0.50) and remained elevated at 3-month follow-up (d = 0.64). A major barrier to adherence (lack of thirst) decreased from baseline to follow-ups. Retention rates and participant feedback indicated that this digital tool was acceptable to patients.

CONCLUSION

Semiautomated tracking of fluid consumption can be used to trigger just-in-time reminders. Based on this demonstration, the sip^IT tools are ready for testing in a rigorous Phase II trial to evaluate efficacy for increasing fluid consumption and urine output as recommended for preventing the recurrence of kidney stones. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Prevention of Urinary Stones With Hydration (PUSH): Design and Rationale of a Clinical Trial

RATIONALE & OBJECTIVE

Although maintaining high fluid intake is an effective low-risk intervention for the secondary prevention of urinary stone disease, many patients with stones do not increase their fluid intake.

STUDY DESIGN

We describe the rationale and design of the Prevention of Urinary Stones With Hydration (PUSH) Study, a randomized trial of a multicomponent behavioral intervention program to increase and maintain high fluid intake. Participants are randomly assigned (1:1 ratio) to the intervention or control arm. The target sample size is 1,642 participants.

SETTING & PARTICIPANTS

Adults and adolescents 12 years and older with a symptomatic stone history and low urine volume are eligible. Exclusion criteria include infectious or monogenic causes of urinary stone disease and comorbid conditions precluding increased fluid intake.

INTERVENTIONS

All participants receive usual care and a smart water bottle with smartphone application. Participants in the intervention arm receive a fluid intake prescription and an adaptive program of behavioral interventions, including financial incentives, structured problem solving, and other automated adherence interventions. Control arm participants receive guideline-based fluid instructions.

OUTCOMES

The primary end point is recurrence of a symptomatic stone during 24 months of follow-up. Secondary end points include changes in radiographic stone burden, 24-hour urine output, and urinary symptoms.

LIMITATIONS

Periodic 24-hour urine volumes may not fully reflect daily behavior.

CONCLUSIONS

With its highly novel features, the PUSH Study will address an important health care problem.

FUNDING

National Institute of Diabetes and Digestive and Kidney Diseases.

TRIAL REGISTRATION

Registered at ClinicalTrials.gov with study number NCT03244189.

Hydration for health hypothesis: a narrative review of supporting evidence

PURPOSE

An increasing body of evidence suggests that excreting a generous volume of diluted urine is associated with short- and long-term beneficial health effects, especially for kidney and metabolic function. However, water intake and hydration remain under-investigated and optimal hydration is poorly and inconsistently defined. This review tests the hypothesis that optimal chronic water intake positively impacts various aspects of health and proposes an evidence-based definition of optimal hydration.

METHODS

Search strategy included PubMed and Google Scholar using relevant keywords for each health outcome, complemented by manual search of article reference lists and the expertise of relevant practitioners for each area studied.

RESULTS

The available literature suggest the effects of increased water intake on health may be direct, due to increased urine flow or urine dilution, or indirect, mediated by a reduction in osmotically -stimulated vasopressin (AVP). Urine flow affects the formation of kidney stones and recurrence of urinary tract infection, while increased circulating AVP is implicated in metabolic disease, chronic kidney disease, and autosomal dominant polycystic kidney disease.

CONCLUSION

In order to ensure optimal hydration, it is proposed that optimal total water intake should approach 2.5 to 3.5 L day^-1 to allow for the daily excretion of 2 to 3 L of dilute (< 500 mOsm kg^-1) urine. Simple urinary markers of hydration such as urine color or void frequency may be used to monitor and adjust intake.

Distinguishing Low and High Water Consumers-A Paradigm of Disease Risk

A long-standing body of clinical observations associates low 24-h total water intake (TWI = water + beverages + food moisture) with acute renal disorders such as kidney stones and urinary tract infections. These findings prompted observational studies and experimental interventions comparing habitual low volume (LOW) and high volume (HIGH) drinkers. Investigators have learned that the TWI of LOW and HIGH differ by 1-2 L·d-1, their hematological values (e.g., plasma osmolality, plasma sodium) are similar and lie within the laboratory reference ranges of healthy adults and both groups appear to successfully maintain water-electrolyte homeostasis. However, LOW differs from HIGH in urinary biomarkers (e.g., reduced urine volume and increased osmolality or specific gravity), as well as higher plasma concentrations of arginine vasopressin (AVP) and cortisol. Further, evidence suggests that both a low daily TWI and/or elevated plasma AVP influence the development and progression of metabolic syndrome, diabetes, obesity, chronic kidney disease, hypertension and cardiovascular disease. Based on these studies, we propose a theory of increased disease risk in LOW that involves chronic release of fluid-electrolyte (i.e., AVP) and stress (i.e., cortisol) hormones. This narrative review describes small but important differences between LOW and HIGH, advises future investigations and provides practical dietary recommendations for LOW that are intended to decrease their risk of chronic diseases.

Association Between Daily Water Intake and 24-hour Urine Volume Among Adolescents With Kidney Stones

OBJECTIVE

To determine the association between daily water intake and 24-hour urine volume among adolescents with nephrolithiasis in order to estimate a "fluid prescription," the additional water intake needed to increase urine volume to a target goal.

METHODS

We conducted a secondary analysis of an ecological momentary assessment study that prospectively measured daily water intake of 25 adolescents with nephrolithiasis over 7 days. We identified 24-hour urine volumes obtained for clinical care within 12 months of water intake assessment. A linear regression model was fit to estimate the magnitude of the association between daily water intake and 24-hour urine volume, adjusting for age, sex, race, and daily temperature.

RESULTS

Twenty-two participants completed fifty-seven 24-hour urine collections within 12 months of the study period. Median daily water intake was 1.4 L (IQR 0.67-1.94). Median 24-hour urine volume was 2.01 L (IQR 1.20-2.73). A 1 L increase in daily water intake was associated with a 710 mL increase in 24-hour urine output (95%CI 0.55-0.87). Using the model output, the equation was generated to estimate the additional fluid intake needed fluid prescription (FP) to produce the desired increase in urine output (dUOP): FP = dUOP/0.71.

CONCLUSION

The FP equation (FP = dUOP)/0.71), which reflects the relationship between water intake and urine volume, could be used to help adolescents with nephrolithiasis achieve urine output goals to decrease stone recurrence.

Ecological Momentary Assessment of Factors Associated with Water Intake among Adolescents with Kidney Stone Disease

PURPOSE

Maintaining high water intake decreases kidney stone recurrence but is difficult to do. Strategies to reduce stone recurrence among adolescents are lacking. We conducted an ecological momentary assessment study to identify factors associated with water intake in adolescents with nephrolithiasis.

MATERIALS AND METHODS

The study population consisted of 15 female and 10 male patients 12 to 18 years old with at least 1 prior kidney stone. For 7 days participants used "smart" bottles to self-monitor water intake and received questionnaires randomly 4 times daily, which were completed in real time on mobile devices. The questionnaires ascertained awareness of water intake volume, awareness of water intake goals, perceived need to drink, access to water, alternative beverage consumption and attitudes toward bathrooms. Linear mixed effects models were fit to estimate the association between momentary responses and daily water intake.

RESULTS

During 175 person-days 595 assessments (85%) were completed. Median daily water intake was 1,304 ml (IQR 848-1,832) and 20% of participants met their intake goal for 4 days or more. Unawareness of water intake volume was associated with drinking 690 ml less water per day (p = 0.04). A strong self-perceived need to drink more was associated with drinking 1,954 ml less water each day compared to no self-perceived need to drink more (p <0.01). Unawareness of intake goals was weakly associated with drinking 1,129 ml less water each day (p = 0.1). Access to water, alternative beverage consumption and bathroom aversion were not associated with water intake.

CONCLUSIONS

Unawareness of water volume consumed and low responsiveness to perceived need to drink more were associated with low water intake. Interventions that help adolescents recognize when and identify how to increase water intake may be effective in decreasing stone recurrence.

The Urological Association of Asia clinical guideline for urinary stone disease

The Urological Association of Asia, consisting of 25 member associations and one affiliated member since its foundation in 1990, has planned to develop Asian guidelines for all urological fields. The field of stone diseases is the third of its guideline projects. Because of the different climates, and social, economic and ethnic environments, the clinical practice for urinary stone diseases widely varies among the Asian countries. The committee members of the Urological Association of Asia on the clinical guidelines for urinary stone disease carried out a surveillance study to better understand the diversity of the treatment strategy among different regions and subsequent systematic literature review through PubMed and MEDLINE database between 1966 and 2017. Levels of evidence and grades of recommendation for each management were decided according to the relevant strategy. Each clinical question and answer were thoroughly reviewed and discussed by all committee members and their colleagues, with suggestions from expert representatives of the American Urological Association and European Association of Urology. However, we focused on the pragmatic care of patients and our own evidence throughout Asia, which included recent surgical trends, such as miniaturized percutaneous nephrolithotomy and endoscopic combined intrarenal surgery. This guideline covers all fields of stone diseases, from etiology to recurrence prevention. Here, we present a short summary of the first version of the guideline - consisting 43 clinical questions - and overview its key practical issues.

Examining the links between hydration knowledge, attitudes and behavior

PURPOSE

This study aimed to examine the psychological factors (knowledge, barriers and facilitators) that can contribute to hydration-related behaviors (i.e., fluid intake) in the general population and how these relate to physical health.

METHODS

A structured survey was developed to examine the links between hydration knowledge (29 items), attitudes about hydration (80 items), and fluid intake behavior (8 items) among US adults. Survey data from Phase 1 (n =301, US adults) psychometrically evaluated the items via item analysis (knowledge and fluid behavior) and factor analysis (attitudes). Phase 2 survey data (n =389, US adults and college students) refined and validated the new 16-item hydration knowledge measure, 4-item fluid intake behavior index, and 18-item attitude measure (barriers and facilitators of hydration-related behaviors) alongside indices of physical health (BMI and exercise behaviors).

RESULTS

Participants had a moderate level of hydration knowledge (Phase 1: 10.91 ± 3.10; Phase 2: 10.87 ± 2.47). A five-factor measure of attitudes which assessed both facilitators (social pressure and attention to monitoring) and barriers (lack of effort, physical barriers and lack of a fluid container) to hydration demonstrated strong internal consistency (αs from 0.75 to 0.90). Attitudes about hydration-most notably barriers to hydration-were associated with indicators of health and with fluid intake behaviors, whereas hydration knowledge was not.

CONCLUSIONS

Increasing hydration knowledge may be necessary for people who hold inaccurate information about hydration, but attitudes about hydration are likely to have a larger impact on fluid intake behaviors and health-related outcomes.

Impact of LUTS on urine volume in stone formers The impact of lower urinary tract symptomatology on urine volumes in stone formers

INTRODUCTION

We aimed to determine if there is a correlation between International Prostate Symptom scores (IPSS) and 24-hour urine collection volumes, as patients experiencing lower urinary tract symptoms (LUTS) may have impaired ability to increase fluid intake for stone prevention.

METHODS

We conducted a single-centre, retrospective review was performed of stone-formers presenting from 2014-2016. Inclusion criteria were completion of an IPSS questionnaire and a 24-hour urine collection. Exclusion criteria included symptomatic stone or urinary tract infection at time of IPSS completion, inadequate 24-hour collection, or incomplete IPSS questionnaire.

RESULTS

A total of 131 patients met inclusion criteria. Stratification by IPSS severity into mild (0-7), moderate (8-19), and severe (20-35) yielded groups of n=96, 28, and 7, respectively. Linear regression modelling did not reveal a correlation between IPSS score and volume (p=0.10). When compared to those with adequate urine volumes (>2 L/day, n=65), low-volume patients (<1 L/day, n=10) had a significantly higher total IPSS (11.7 vs. 6.1; p=0.036). These groups showed significant differences in their responses to questions about incomplete emptying (p=0.031), intermittency (p=0.011), and stranguria (p=0.0020), with higher scores noted in the low urine output group.

CONCLUSIONS

This study is the first to examine the correlation between IPSS and 24-hour urine volume. Though our data does not show a linear relationship between urine output and IPSS, those with lower urine volumes appear to have worse self-reported voiding symptoms when compared to those with adequate volumes (>2 L/day) for stone prevention. The overall number of patients in our study is relatively small, which may account for the lack of a relationship between IPSS and 24-hour urine volumes.

Acceptability of Mobile Health Technology for Promoting Fluid Consumption in Patients With Nephrolithiasis

OBJECTIVE

To evaluate kidney stone patients' interest in lifestyle behavior modification and a variety of mobile health (mHealth) technologies to improve adherence to fluid consumption recommendations for the prevention of nephrolithiasis. Of particular interest was the acceptability of various intervention components for the design of a stone-specific mHealth technology.

MATERIALS AND METHODS

Using a cross-sectional design, adult patients with a diagnosis of kidney stones (n = 94) were recruited from outpatient clinics to complete a three-part questionnaire.

RESULTS

Patients reported being willing to make lifestyle changes to prevent kidney stones (97%). The majority of the patients recalled the recommendation to increase fluid intake (93%) but few monitored their daily fluid intake (30%). Most patients had never installed an app (95%) or owned a device (100%) to help with increasing fluid consumption, but believed an app or device could improve their adherence (72%) and would be interested in using an app or device (86%). The mHealth intervention components most widely perceived as useful included automated lapse detection with notifications, educational materials, self-monitoring tools, scheduler with prompts and/or reminders and/or notifications, connected water bottles and text message reminders to drink.

CONCLUSION

Patients are interested in lifestyle behavior change to prevent stones but technology has not been widely adopted to improve adherence to fluid intake recommendations for stone prevention. This study identified a number of viable mHealth intervention components that should be considered when designing a stone-specific mHealth technology to support adherence to increased fluid consumption recommendations.

Randomised controlled trial to determine the efficacy and safety of prescribed water intake to prevent kidney failure due to autosomal dominant polycystic kidney disease (PREVENT-ADPKD)

INTRODUCTION

Maintaining fluid intake sufficient to reduce arginine vasopressin (AVP) secretion has been hypothesised to slow kidney cyst growth in autosomal dominant polycystic kidney disease (ADPKD). However, evidence to support this as a clinical practice recommendation is of poor quality. The aim of the present study is to determine the long-term efficacy and safety of prescribed water intake to prevent the progression of height-adjusted total kidney volume (ht-TKV) in patients with chronic kidney disease (stages 1-3) due to ADPKD.

METHODS AND ANALYSIS

A multicentre, prospective, parallel-group, open-label, randomised controlled trial will be conducted. Patients with ADPKD (n=180; age ≤65 years, estimated glomerular filtration rate (eGFR) ≥30 mL/min/1.73 m²) will be randomised (1:1) to either the control (standard treatment+usual fluid intake) or intervention (standard treatment+prescribed fluid intake) group. Participants in the intervention arm will be prescribed an individualised daily fluid intake to reduce urine osmolality to ≤270 mOsmol/kg, and supported with structured clinic and telephonic dietetic review, self-monitoring of urine-specific gravity, short message service text reminders and internet-based tools. All participants will have 6-monthly follow-up visits, and ht-TKV will be measured by MRI at 0, 18 and 36 months. The primary end point is the annual rate of change in ht-TKV as determined by serial renal MRI in control vs intervention groups, from baseline to 3 years. The secondary end points are differences between the two groups in systemic AVP activity, renal disease (eGFR, blood pressure, renal pain), patient adherence, acceptability and safety.

ETHICS AND DISSEMINATION

The trial was approved by the Human Research Ethics Committee, Western Sydney Local Health District. The results will inform clinicians, patients and policy-makers regarding the long-term safety, efficacy and feasibility of prescribed fluid intake as an approach to reduce kidney cyst growth in patients with ADPKD.

TRIAL REGISTRATION NUMBER

ANZCTR12614001216606.

Effectiveness of Treatment Modalities on Kidney Stone Recurrence

Nephrolithiasis is highly prevalent across all demographic groups in the Western world and beyond, and its incidence rates are rising. In addition to the morbidity of the acute event, stone disease often becomes a lifelong problem that requires preventative therapy to diminish ongoing morbidity. Across the majority of stone types, increased fluid intake and targeted dietary modifications are mainstays of therapy. Specific dietary interventions associated with reduced calcium stone risk include adequate dietary calcium intake and restriction of sodium, protein, and oxalate intake, among others. Pharmaceutical therapy may be required if lifestyle changes are insufficient to minimize risk of stone recurrence, and must be targeted to the specific metabolic abnormalities portending risk for a given patient. Therapeutic options for idiopathic calcium stone disease include thiazides, citrate salts, and uric acid-lowering agents. Alkali salts are also the treatment of choice for uric acid stone disease. Management of struvite stone disease is largely surgical, but acetohydroxamic acid is a proven second line therapy. Cystinuria requires lifestyle modifications and may call for thiol-binding agents. Significant heterogeneity of the clinical population with stone disease has previously limited opportunities for large randomized controlled trials. However, as clinical phenotypes and genotypes are increasingly clarified, there are mounting opportunities for targeted randomized controlled trials in stone prevention. In the meantime, the currently available evidence for both lifestyle and pharmacologic interventions is reviewed herein.

Factors Associated with Compliance to Increased Fluid Intake and Urine Volume Following Dietary Counseling in First-Time Kidney Stone Patients

OBJECTIVE

Increasing fluid intake to achieve a urine volume (UV) of >2.5 L/day decreases stone events. We assessed compliance rates and demographic and clinical variables associated with increased fluid intake and UV in patients with urolithiasis following dietary counseling.

MATERIALS AND METHODS

In a retrospective study, patients with a low baseline UV (<2.5 L/day) on an initial 24-hour urine collection during metabolic stone evaluation were identified between 2010 and 2015. Patients received detailed standardized dietary counseling, including increasing fluid intake to >3 L/day and titrating it to achieve UV >2.5 L/day. A follow-up 24-hour urine collection was performed at 6 months (FU1) and 18 months (FU2) to assess compliance (UV >2.5 L/day) and predictors associated with it.

RESULTS

Our cohort contained 363 patients, 53.4% men and 46.6% women. The mean UV of baseline, FU1, and FU2 urine collections was 1.63, 2.52, and 2.48 L, respectively. The compliance rate of obtaining UV of >2.5 L was 50.1% at 6 months. On logistic regression, male sex (odds ratio [OR] 3.27, 95% confidence interval [CI] 1.94, 5.52, p < 0.001), urolithiasis-related procedures such as ureteroscopy (OR 2.31, 95% CI 1.20, 4.42, p = 0.01) or percutaneous nephrolithotomy (OR 3.48, 95% CI 1.58, 7.63, p = 0.002), and baseline 24-hour UV >1 L (OR 3.00, 95% CI 1.02, 8.76, p = 0.04) were associated with greater odds of compliance. Age >58 years (OR 0.39, 95% CI 0.20, 0.75, p = 0.005) and presence of lower urinary tract symptoms (OR 0.50, 95% CI 0.26, 0.95, p = 0.03) were associated with lower odds of compliance. Ethnicity, body mass index, renal function, marital status, renal stone burden, stone type, and household income were not associated with compliance.

CONCLUSIONS

In stone formers, compliance to fluid intake recommendations as measured by 24-hour UV is roughly 50%. Understanding risk factors for noncompliance, especially in at risk patients, can be used for quality improvement initiatives and reducing stone events.

Water and other fluids in nephrolithiasis: State of the art and future challenges

Adequate hydration, as to maintain urinary volume over 2 L/day, has long been considered as the cornerstone medical prescription for preventing nephrolithiasis. However, scientific evidence about what kind of water stone formers should drink and about the effects of other beverages on urinary stone risk factors is sometimes unclear. Moreover, the recommendation that water therapy prevents kidney stone recurrence relies on only one randomized controlled trial, even if more epidemiologic and basic science studies seem to support this assumption. Therefore, in this review we analyze current evidence that support water therapy in nephrolithiasis and we highlight the possible effects of different types of water and other beverages on lithogenic risk, giving some practical recommendations for what stone formers should be advised to prevent recurrence.

Experiences and Perspectives of Polycystic Kidney Disease Patients following a Diet of Reduced Osmoles, Protein, and Acid Precursors Supplemented with Water: A Qualitative Study

BACKGROUND

Salt, protein, acid precursors, and fluid intake have been identified as factors that influence cyst growth in ADPKD. Unfortunately, the feasibility of following these dietary restrictions/enhancements from a patient's point-of-view has yet to be studied. The purpose of this study is to understand better the experiences of patients following a relatively complex dietary prescription targeting these factors.

METHODS

Twelve adults with ADPKD and kidney function >30ml/min/1.73m2 were recruited from the University of Kansas Medical Center Polycystic Kidney Disease clinic. In a qualitative design, semi-structured interviews of participants were conducted following a four week dietary intervention (experimental diet lower in sodium, protein, and acid precursors, and supplemented with water) either face-to-face or by telephone. All interviews were recorded, transcribed verbatim, and checked for accuracy. Transcripts were analyzed thematically for emerging themes.

RESULTS

Participants reported that eating less meat and more fruits and vegetables were the easiest components of the diet, whereas reaching the daily goal amount of fruits and vegetables and tracking the diet constantly were the most difficult components. Participants had little difficulty with fluid intake and reported the prescribed fluid goal as achievable. The tracking system for fruits and vegetables and protein was reported to be both helpful and intuitive, but tracking their intake on paper was tedious. Eating out was the most significant barrier to following the diet with some individuals avoiding restaurants in order to comply with the dietary prescription.

CONCLUSION

Participants on the experimental diet heightened their awareness of the consumption of dietary salt, protein, acid precursors, and fluid intake. Additionally, most participants believed adherence to the prescribed diet was feasible. However, participants wanted less cumbersome ways to track and monitor the diet, especially given that the prescribed diet is designed for lifelong adherence. Future studies should focus on targeting these specific dietary factors in larger groups of more ethnically and culturally diverse populations to help inform clinicians and how best to help diverse populations adhere to the dietary intervention.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01810614.

Increased Hydration Can Be Associated with Weight Loss

This mini-review develops the hypothesis that increased hydration leads to body weight loss, mainly through a decrease in feeding, and a loss of fat, through increased lipolysis. The publications cited come from animal, mainly rodent, studies where manipulations of the central and/or the peripheral renin–angiotensin system lead to an increased drinking response and a decrease in body weight. This hypothesis derives from a broader association between chronic hypohydration (extracellular dehydration) and raised levels of the hormone angiotensin II (AngII) associated with many chronic diseases, such as obesity, diabetes, cancer, and cardiovascular disease. Proposed mechanisms to explain these effects involve an increase in metabolism due to hydration expanding cell volume. The results of these animal studies often can be applied to the humans. Human studies are consistent with this hypothesis for weight loss and for reducing the risk factors in the development of obesity and type 2 diabetes.

Diet and polycystic kidney disease: A pilot intervention study

BACKGROUND & AIMS

Dietary sodium, protein, acid precursors, and water have been linked to cyst growth in polycystic kidney disease; yet, no studies in patients have examined the feasibility of using a dietary intervention that controls all of these factors. The aim of this study was to determine if a diet, appropriate for persons of most ages, reduces the excretion of sodium, urea, acid, and decreases mean urine osmolality while gaining acceptance by patients with autosomal dominant polycystic kidney disease (ADPKD).

METHODS

Twelve adults with ADPKD enrolled in a pre-post pilot feasibility study and served as their own controls. Individuals consumed their usual diet for one week then for four weeks followed an isocaloric diet lower in sodium and protein and higher in fruits, vegetables, and water. Three-day diet records and two 24-h urine samples were collected at baseline, week 2, and week 4 visits; blood pressure, weight, and serum were obtained at all three visits. A modified nutrition hassles questionnaire was completed on the last visit.

RESULTS

During the dietary intervention, subjects (n = 11) consumed less sodium, protein, and dietary acid precursors 36%, 28%, and 99%, respectively, and increased fluid intake by 42%. Urinary sodium, urea, net acid excretion, osmoles, and osmolality decreased 20%, 28%, 20%, 37%, and 15%, respectively; volume increased 35%. Urine changes were in accord with the diet record. Ninety-one percent of participants reported that none of the hassles were worse than "somewhat severe", and most participants felt "somewhat confident" or "very confident" that they could manage the new diet.

CONCLUSIONS

A majority of adult patients with ADPKD successfully prepared and followed a composite diet prescription with decreased sodium, protein, acid precursors, and increased fluid intake. This trail was registered at ClinicalTrials.gov (NCT01810614).

Opportunities for intervention strategies for weight management: global actions on fluid intake patterns

Water is an essential nutrient for all physiological functions and particularly important for thermoregulation. About 60% of our body weight is made of water. Under standard conditions (18-20 °C and moderate activity), water balance is regulated within 0.2 % of body weight over a 24-hour period. Water requirement varies between individuals and according to environmental conditions. Concerning considerations related to obesity, the health impact of fluid intake is commonly overlooked. Fluid intake advices are missing in most of food pyramids offered to the public, and water requirements and hydration challenges remain often neglected. The purpose of this paper is to emphasize and discuss the role of water consumption in the context of other important public health measures for weight management. Attention will be focused on fluid intake patterns and hydration-related questions in the context of global interventions and/or physical activity programs settled in weight management protocols.

The efficacy of antioxidant therapy against oxidative stress and androgen rise in ethylene glycol induced nephrolithiasis in Wistar rats

Administration of natural antioxidants has been used to protect against nephrolithiasis. Urolithiasis was induced by ethylene glycol (EG) in Wistar rats. For 4 weeks, group 1 (control) was fed with a standard commercial diet. Group 2 received the same diet with 0.75% of EG. Group 3 received EG plus the diet and water added with antioxidant nutrients and lime juice as the dietary source of citrate (EG + AX). Group 4 same as group 3 with no EG in water. For 8 weeks, group 5 was fed the standard diet with EG in water for the first 28 days, followed by no EG. Group 6 received the diet with EG for the first 28 days, followed by discontinuation of EG and addition of antioxidant nutrients. Group 7 were provided the diet with antioxidant nutrients for 8 weeks. Group 8 received the diet with antioxidant nutrients for 4 weeks, followed by antioxidant nutrients with EG for the next 4 weeks. Blood samples were collected and kidneys were removed. The size and the mean number of crystal deposits in EG-treated groups was significantly higher than the EG-treated groups, added with antioxidant nutrients and lime juice. After 4 weeks, the mean concentration of malondialdehyde in group 2 was higher than the group 3, and significantly lower in group 4; and in groups 7 after 8 weeks, as well. After 8 weeks, supplementation developed less mean number of deposits in group 6 as compared to group 5; and in group 8, the crystal deposits was substantially less than either group 2 or group 5 (EG-treated rats). Elevated concentration of androgens (as promoters of the formation of renal calculi) as a result of EG consumption decreased following antioxidant supplementations. Results showed a beneficial effect of antioxidant and provided superior renal protection on treating and preventing stone deposition in the rat kidney.

Are we being drowned in hydration advice? Thirsty for more?

Hydration pertains simplistically to body water volume. Functionally, however, hydration is one aspect of fluid regulation that is far more complex, as it involves the homeostatic regulation of total body fluid volume, composition and distribution. Deliberate or pathological alteration of these regulated factors can be disabling or fatal, whereas they are impacted by exercise and by all environmental stressors (e.g. heat, immersion, gravity) both acutely and chronically. For example, dehydration during exercising and environmental heat stress reduces water volume more than electrolyte content, causing hyperosmotic hypohydration. If exercise continues for many hours with access to food and water, composition returns to normal but extracellular volume increases well above baseline (if exercising upright and at low altitude). Repeating bouts of exercise or heat stress does likewise. Dehydration due to physical activity or environmental heat is a routine fluid-regulatory stress. How to gauge such dehydration and - more importantly-what to do about it, are contested heavily within sports medicine and nutrition. Drinking to limit changes in body mass is commonly advocated (to maintain ≤2% reduction), rather than relying on behavioural cues (mainly thirst) because the latter has been deemed too insensitive. This review, as part of the series on moving in extreme environments, critiques the validity, problems and merits of externally versus autonomously controlled fluid-regulatory behaviours, both acutely and chronically. Our contention is that externally advocated hydration policies (especially based on change in body mass with exercise in healthy individuals) have limited merit and are extrapolated and imposed too widely upon society, at the expense of autonomy. More research is warranted to examine whether ad libitum versus avid drinking is beneficial, detrimental or neither in: acute settings; adapting for obligatory dehydration (e.g. elite endurance competition in the heat), and; development of chronic diseases that are associated with an extreme lack of environmental stress.

Therapy modifies cystine kidney stones at the macroscopic scale. Do such alterations exist at the mesoscopic and nanometre scale?

With an incidence of 1:7000 births, cystinuria, the most frequent cause of stone formation among genetic diseases, represents a major medical problem. Twenty-five cystine stones randomly selected from cystinuric patients were investigated. From a crystallographic point of view, cystine stones are composed of micrometre size crystallites, which are made up of an aggregation of nanocrystals. Through scanning electron microscopy, the morphology and size of the crystallites have been described, while the size of the nanocrystals was investigated by means of powder neutron diffraction. Powder neutron diffraction analysis and/or scanning electron microscopy examination of cystine stones provide evidence that usual alkalinization by sodium bicarbonate associated with high diuresis significantly reduces the size of both nanocrystals and crystallites, while for other treatments, including alkalinizing drugs and thiol derivatives, the data suggest mainly changes in the topology of crystallites. Alkalinization with sodium bicarbonate affects cystine kidney stones at the mesoscopic and nanoscopic scales, while other medical treatments only alter their surface. Such an approach may help to assess the interaction between drugs and cystine stones in cystinuric patients.

Novel hydration assessment techniques employing thirst and a water intake challenge in healthy men

Exploring novel hydration indices is important because no human biomarker has been shown to be incontrovertibly valid in all life situations. The present investigation was designed to identify inexpensive, nontechnical methods to use when self-assessing hydration status. This investigation evaluated the validity and efficacy of 2 novel techniques (i.e., thirst sensation and urine volume) to assess hydration state of 29 active men (mean ± SD; age, 23 ± 4 years; body mass, 76.02 ± 11.94 kg) at rest. Eight combinations of 4 water challenges (4.8, 9.3, 11.0, or 14 mL·kg−1) and 2 hydration states (mildly hypohydrated (HY), –2.0%; euhydrated (EU), –0.2% body mass) were employed. First, thirst was linearly related to body water loss, and ratings of thirst distinguished HY from EU (p < 0.001) subsequent to 19 h of controlled food and fluid intake. Second, measurements of urine volume 60 min after consuming a water bolus (11.0 or 14 mL·kg−1) were strongly and inversely correlated with entering hydration state, assessed by urine specific gravity (r2 = 0.76, p < 0.0001) and urine osmolality (r2 = 0.77, p < 0.0001). We concluded that healthy men can employ simple measurements of morning thirst sensation and urine volume to identify the presence of mild hypohydration and to guide fluid replacement. These 2 techniques are relevant because HY (–2% body mass) is the approximate threshold for the onset of thirst, reduced endurance exercise performance, and decrements of working memory and mood.

The chronic kidney disease Water Intake Trial (WIT): results from the pilot randomised controlled trial

BACKGROUND AND OBJECTIVES

Increased water intake may benefit kidney function. Prior to initiating a larger randomised controlled trial (RCT), we examined the safety and feasibility of asking adults with chronic kidney disease (CKD) to increase their water intake.

DESIGN, SETTING, PARTICIPANTS AND MEASUREMENTS

Beginning in October 2012, we randomly assigned 29 adults with stage 3 CKD (estimated glomerular filtration rate (eGFR) 30-60 mL/min/1.73 m(2) and albuminuria) to one of the two groups of water intake: hydration (n=18) or standard (n=11). We asked the hydration group to increase their water intake by 1.0-1.5 L/day (in addition to usual intake, depending on sex and weight) for 6 weeks, while the control group carried on with their usual intake. Participants collected a 24 h urine sample at baseline and at 2 and 6 weeks after randomisation. Our primary outcome was the between-group difference in change in 24 h urine volume from baseline to 6 weeks.

RESULTS

(63%)of participants were men, 81% were Caucasians and the average age was 61 years (SD 14 years). The average baseline eGFR was 40 mL/min/1.73 m(2) (SD 11 mL/min/1.73 m(2)); the median albumin to creatinine ratio was 19 mg/mmol (IQR 6-74 mg/mmol). Between baseline and 6-week follow-up, the hydration group's average 24 h urine volume increased by 0.7 L/day (from 2.3 to 3.0 L/day) and the control group's 24 h urine decreased by 0.3 L/day (from 2.0 to 1.7 L/day; between-group difference in change: 0.9 L/day (95% CI 0.4 to 1.5; p=0.002)). We found no significant changes in urine, serum osmolality or electrolyte concentrations, or eGFR. No serious adverse events or changes in quality of life were reported.

CONCLUSIONS

A pilot RCT indicates adults with stage 3 CKD can successfully and safely increase water intake by up to 0.7 L/day in addition to usual fluid intake. TRIAL REGISTRATION REGISTERED WITH CLINICAL TRIALSGOVERNMENT IDENTIFIER: NCT01753466.

Update on the evaluation of repeated stone formers

Office management of stone disease is an important component of a urologist's practice. Evaluation should include analysis of stone composition, 24-hour urine studies, identification of modifiable risk factors, and targeted dietary, lifestyle, and/or medical therapy. A sizeable portion of investigated etiologies and risk factors for stone disease have centered on the complex interplay between obesity, diabetes, and other disease states that comprise the metabolic syndrome. Alternatives to traditional preventive therapy, such as probiotics and various fruit juices, are still being studied but may prove useful adjuncts to traditional preventive therapy, where the mainstays remain increased fluid intake, dietary modification, and pharmacologic therapy. Future studies on preventive therapy of urolithiasis are likely to focus on strategies to increase compliance, cost-effectiveness, and systems-based implementation.

Increased water intake as a prevention strategy for recurrent urolithiasis: major impact of compliance on cost-effectiveness

PURPOSE

We evaluated the economic impact of preventing recurrent stones using a strategy of increased water intake and determined the impact of compliance on cost-effectiveness for the French health care system.

MATERIALS AND METHODS

A Markov model was constructed to compare costs and outcomes for recurrent kidney stone formers with less than 2 L vs 2 L or more daily fluid intake. Model assumptions included an annual prevalence of 120,000 stone episodes in France, 14.4% annual risk of stone recurrence and a 55% risk reduction in subjects with adequate water intake. Costs were based on resource use as estimated by a panel of experts and official national price lists. Outcomes were from the perspective of the public health payer, and encompassed direct and indirect costs.

RESULTS

The total cost of an episode of urolithiasis was estimated at €4,267 including the cost of treatment and complications. This corresponds to an annual budget impact of €88 million for recurrent stones based on 21,000 stone events. Assuming 100% compliance with fluid intake recommendations of 2 L daily, 11,572 new stones might be prevented, resulting in a cost savings of €49 million. Compliance with water intake in only 25% of patients would still result in 2,893 fewer stones and a cost savings of €10 million. Varying the costs of managing stones had a smaller impact on outcomes since in many patients stones do not form. Varying the incidence of complications did not change the incidence of stones and had a negligible effect on overall cost.

CONCLUSIONS

Preventing recurrent urolithiasis has a significant cost savings potential for a payer as a result of a reduced stone burden. However, compliance is an important factor in determining cost-effectiveness.