Factors that predict relapse of calcium nephrolithiasis during treatment: a prospective study

Low daily water intake profile-is it a contributor to disease?

Few previous review articles have focused on the associations between inadequate daily water intake (LOW) or urinary biomarkers of dehydration (UD; low urine volume or high urine osmolality) and multiple diseases. Accordingly, we conducted manual online searches (47 key words) of the PubMed, Embase, and Google Scholar databases with these inclusion criteria: English language, full-text, peer reviewed, no restriction on research design, and three publications minimum. Initially, 3,903 articles were identified based on their titles and abstracts. Evaluations of full length .pdf versions identified 96 studies that were acceptable for inclusion. We concluded that the evidence is insufficient or conflicting for seven disorders or diseases (i.e. suggesting the need for additional clarifying research) and it is lacking for all-cause mortality. Differential characterizations among women and men have been reported in the results of nine studies involving five diseases. Finally, the evidence for associations of LOW or UD is strong for both kidney stones and type 2 diabetes with hyperglycemia. This suggests that great public health value (i.e. reduced disease risk) may result from increased daily water intake-a simple and cost-effective dietary modification.

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.

Voided volume may not impact stone outcomes: Review of a large institutional nephrolithiasis cohort

Background

Urologic guidelines universally recommend increasing fluid intake for kidney stone prevention. Increased voided volume is thought to help reduce stone recurrence and severity, but supporting evidence is limited.

Patients and Methods

Nephrolithiasis outcomes and 24-h urine data for patients from the Registry for Stones of the Kidney and Ureter (ReSKU), a registry of nephrolithiasis patients collected between 2015 and 2020, were retrospectively analysed. Outcome was stone events, either an office visit where a patient reports symptomatic passage of stones or surgery for stone removal.

Results

We identified 450 stone patients with 24-h urine and kidney stone outcome data. There was no significant difference in 24-h voided volume between patients with one stone event and patients with two or more stone events. On multivariable logistic regression, after controlling for age, gender, BMI, and 24-h sodium and creatinine per kilogram, no significant associations were found between voided volume and stone events. There was a statistically significant negative correlation noted between voided volume and stone events in calcium oxalate dihydrate stone formers (Spearman R = -0.42, p = 0.04), but not others.

Conclusions

Twenty-four-hour voided volume was not associated with stone events in a large institutional cohort, and subset analysis reveals that some stone formers may benefit more from increased voided volume than others; identifying such patients represents a novel precision medicine opportunity.

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.

Breaking the Cycle of Recurrent Calcium Stone Disease

Calcium stones are common and recurrent in nature, yet few therapeutic tools are available for secondary prevention. Personalized approaches for stone prevention have been informed by 24-hour urine testing to guide dietary and medical interventions. However, current evidence is conflicting about whether an approach guided by 24-hour urine testing is more effective than a generic one. The available medications for stone prevention, namely thiazide diuretics, alkali, and allopurinol, are not always prescribed consistently, dosed correctly, or tolerated well by patients. New treatments on the horizon hold the promise of preventing calcium oxalate stones by degrading oxalate in the gut, reprogramming the gut microbiome to reduce oxalate absorption, or knocking down expression of enzymes involved in hepatic oxalate production. New treatments are also needed to target Randall's plaque, the root cause of calcium stone formation.

Secondary oxalate nephropathy and kidney transplantation

PURPOSE OF REVIEW

Secondary hyperoxaluria is associated with poor kidney allograft outcomes after the kidney transplant. Calcium oxalate (CaOx) deposition is common in early allograft biopsies leading to acute tubular necrosis and poor kidney allograft function. Though treatment options for secondary hyperoxaluria are limited, it is crucial to identify patients at increased risk of oxalate nephropathy after the transplant.

RECENT FINDINGS

Recent data suggest that significant changes in renal replacement therapies and dietary modifications in high-risk patients can prevent kidney allograft damage from the calcium oxalate deposition leading to improve allograft outcomes.

SUMMARY

The accurate and timely diagnosis of secondary oxalate nephropathy in kidney transplant recipients is paramount to preserving graft function in the long-term. This review will discuss the incidence, risk factors, prevention, and management of oxalate nephropathy in the kidney allograft.

Temporal Trends of Dietary Risk Factors after a Diagnosis of Kidney Stones

BACKGROUND AND OBJECTIVES

Diet is an important contributor to kidney stone formation, but there are limited data regarding long-term changes in dietary factors after a kidney stone.

DESIGN, SETTING, PARTICIPANTS & MEASUREMENTS

We analyzed data from three longitudinal cohorts, the Health Professionals Follow-Up Study and Nurses' Health Study I and II, comparing changes in dietary factors in participants with and without kidney stones during follow-up. The daily intake of dietary calcium, supplemental calcium, animal protein, caffeine, fructose, potassium, sodium, oxalate, phytate, vitamin D, vitamin C, sugar-sweetened beverages, fluids, net endogenous acid production, and Dietary Approaches to Stop Hypertension score were assessed by repeat food frequency questionnaires and computed as absolute differences; a difference-in-differences approach was used to account for temporal changes using data from participants without kidney stones from the same calendar period.

RESULTS

Included were 184,398 participants with no history of kidney stones, 7095 of whom became confirmed stone formers. Several intakes changed significantly over time in stone formers, with some showing a relative increase up to 8 years later, including caffeine (difference in differences, 8.8 mg/d; 95% confidence interval [95% CI], 3.4 to 14.1), potassium (23.4 mg/d; 95% CI, 4.6 to 42.3), phytate (12.1 mg/d; 95% CI, 2.5 to 21.7), sodium (43.1 mg/d; 95% CI, 19.8 to 66.5), and fluids (47.1 ml/d; 95% CI, 22.7 to 71.5). Other dietary factors showed a significant decrease, such as oxalate (-7.3 mg/d; 95% CI, -11.4 to -3.2), vitamin C (-34.2 mg/d; 95% CI, -48.8 to -19.6), and vitamin D (-18.0 IU/d; 95% CI, -27.9 to -8.0). A significant reduction was observed in sugar-sweetened beverages intake of -0.5 (95% CI, -0.8 to -0.3) and -1.4 (95% CI, -1.8 to -1.0) servings per week and supplemental calcium of -105.1 (95% CI, -135.4 to -74.7) and -69.4 (95% CI, -95.4 to -43.4) mg/d for women from Nurses' Health Study I and II, respectively. Animal protein, dietary calcium, fructose intake, Dietary Approaches to Stop Hypertension score, and net endogenous acid production did not change significantly over time.

CONCLUSIONS

After the first episode of a kidney stone, mild and inconsistent changes were observed concerning dietary factors associated with kidney stone formation.

Essential roles of oncostatin M receptor β signaling in renal crystal formation in mice

Oncostatin M (OSM), a member of the IL-6 family of cytokines, has important roles in renal diseases. The relationship between OSM and kidney stone disease, however, remains unclear. To investigate the roles of OSM in the development of kidney stone disease, we generated a mouse model of renal crystal formation using OSM receptor β (OSMRβ)-deficient mice (OSMRβ^−/− mice). There were fewer renal crystal deposits in OSMRβ^−/− mice than in wild-type (WT) mice. Crystal-binding molecules (osteopontin, annexin A1, and annexin A2), inflammatory cytokines (TNF-α and IL-1β), and fibrosis markers (TGF-β, collagen 1a2, and α-smooth muscle actin) were also decreased in the kidneys of OSMRβ^−/− mice compared with those in WT mice. Immunofluorescence staining showed that OSMRβ was expressed in renal tubular epithelial cells (RTECs) and renal fibroblasts in the model of renal crystal formation. In the cultured RTECs and renal fibroblasts, OSM directly induced the expression of crystal-binding molecules and fibrosis markers. Expressions of inflammatory cytokines were increased by stimulation with OSM in cultured renal fibroblasts. OSM may promote the formation of renal crystal deposits by directly acting on RTECs and renal fibroblasts to produce crystal-binding molecules and inflammatory cytokines.

Patients treated for uric acid stones reoccur more often and within a shorter interval compared to patients treated for calcium stones

INTRODUCTION

We aimed to investigate the association between stone composition and recurrence rate in a well-characterized group of patients.

METHODS

From our prospectively assembled database of 1328 patients undergoing ureteroscopy and percutaneous nephrolithotomy (PCNL) between 2010 and 2015, we identified 457 patients who met the inclusion criteria: a minimum of two years' followup, stone-free status following surgery, normal anatomy, and Fourier transform infrared (FT-IR) stone analysis results. Stone recurrence was identified by kidney-ureter-bladder (KUB) or an ultrasound (US). All symptomatic events were recorded. Kaplan-Meier and Cox proportional hazard regression methods were used to assess the differences in recurrence rates and associated risk factors.

RESULTS

Calcium oxalate (CaOx), uric acid (UA), and struvite stones were found in 298 (65.2%), 99 (21.7%), and 28 (6.1%) patients, respectively. During a median followup of 38 months (interquartile range [IQR] 31-48), stone recurred in 111 (24%) patients. One-year stone-free rates (SFRs) stratified by composition were: CaOx 98%, UA 91.9%, calcium phosphate 90%, struvite 88%, and, cystine 83%; the two-year SFRs were 92.6%, 82.7%, 80%, 73%, and 75%, respectively. On multivariate Cox regression analysis, UA composition, the absence of medical preventive therapy, and preoperative stone burden were associated with a shorter time to recurrence. Secondary intervention for recurrent, symptomatic stones was required in 11 (11.1%) and 22 (7.4%) of patients with UA and CaOx stones, respectively (p=0.02).

CONCLUSIONS

UA stone-formers are more likely to have a recurrence and to undergo surgical intervention in comparison to CaOx stone-formers, regardless of medical preventive treatment. These differences are more prominent during the first year of followup and should be incorporated into the patient's followup protocol.

Water for preventing urinary stones

BACKGROUND

Urinary stone disease is a common condition characterised by increasing prevalence and high rates of recurrence. Observational studies have reported that increased water intake played a role in the prevention of urinary stone formation but with limited strength of evidence.

OBJECTIVES

To compare the effects of increased water intake with standard water intake for the prevention of urinary stone formation in participants with or without a history of urinary stones.

SEARCH METHODS

We performed a systematic search of PubMed (MEDLINE), EMBASE (Ovid) and the Cochrane Library to 15 October 2019. We handsearched review articles, clinical trial registries, and reference lists of retrieved articles. We did not apply any restrictions to publication language or publication status.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and quasi-RCTs looking at the benefits and harms of increased water intake versus standard water intake for the prevention of urinary stone formation in participants with or without a history of urinary stones.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane. Two review authors independently extracted data and assessed the risk of bias of included studies. We pooled dichotomous outcomes (e.g. incidence/recurrence rate of urinary stones; adverse events) using risk ratios (RRs) with 95% confidence intervals (CIs). We calculated hazard ratio (HRs) and corresponding 95% CIs to assess the intervention effect for time-to-event outcomes. We assessed the certainty of the evidence by using the GRADE criteria.

MAIN RESULTS

Our search identified no RCTs investigating the role of increased water intake for the prevention of urinary stone formation in participants with no history of urinary stones (primary prevention). We found one RCT assessing the effects of increased water intake versus standard water intake for the prevention of urinary stone formation in people with a history of urinary stones (secondary prevention). This trial randomised 220 participants (110 participants in the intervention group with increased water intake and 110 in the control group with standard water intake). Increased water intake was defined as achieving a urine volume of at least 2.0 L per day by drinking water. Based on this study, increased water intake may decrease stone recurrences (RR 0.45, 95% CI 0.24 to 0.84; 199 participants; low-certainty evidence); this corresponds to 149 fewer (43 fewer to 205 fewer) stone recurrences per 1000 participants with 270 stone recurrence per 1000 participants over five years in the control group. Increased water intake may also prolong the time to urinary stone recurrence compared to standard water intake (HR 0.40, 95% CI 0.20 to 0.79; 199 participants; low-certainty evidence); based on a stone recurrence rate of 270 per 1000 participants over five years, this corresponds to 152 fewer (209 fewer to 50 fewer) recurrences per 1000 participants. For both outcomes we downgraded the certainty of evidence for study limitations and imprecision. We found no evidence for the outcome of adverse events AUTHORS' CONCLUSIONS: We found no RCT evidence on the role of increased water intake for primary prevention of urinary stones. For secondary prevention, increased water intake achieving a urine volume of at least 2.0 L/day may reduce urinary stone recurrence and prolong time to recurrence for people with a history of urinary stone disease. However, our confidence in these findings is limited. We did not find evidence for adverse events.

Emerging Mobile Platforms to Aid in Stone Management

Nephrolithiasis is an increasingly common condition worldwide and mobile technology is revolutionizing how patients with kidney stone are being diagnosed and managed. Emerging platforms include software applications to increase adherence to stone prevention, mobile compatible hardware, online social media communities, and telemedicine. Applications and hardware specifically relevant to increasing hydration, diet modification, medication adherence, and rapid diagnosis (ie, mobile ultrasound and endoscopy) have the greatest potential to reduce stone recurrence and expedite treatment. Social media and online communities have also been rapidly adopted by patients and providers to promote education and support.

Defining a clinically significant struvite stone: a non-randomized retrospective study

OBJECTIVE

To study the association between a stone's struvite content and clinical outcomes and to determine a clinically significant cutoff for defining struvite stones.

MATERIALS AND METHODS

This was a retrospective study of all patients who underwent ureteroscopy or PCNL at our institution between 2012 and 2017 and had any component of struvite in the stone analysis. Patients were divided into four groups based on percent struvite content: A (1-25%), B (26-50%), C (51-75%), and D (76-100%). Bacterial characteristics were compared between groups. Univariate and multivariate analyses were performed to evaluate the association between struvite content and postoperative SIRS. Log-rank test was used to compare between the four groups' recurrence rates.

RESULTS

A total of 123 patients were included in the study. Positive preoperative urine culture was found in 31%, 81%, 87%, and 90% of patients from group A, B, C, and D, respectively. E. Coli was the most common pathogen in group A (54%), while Proteus was the most common pathogen in groups C (53%) and D (47%). Enterococci isolation rates remained similar between groups A-D, ranging from 23 to 33%. Postoperative SIRS occurred in 2.4%, 21.3%, 26.7%and 47.4% of the patients from groups A, B, C, and D, respectively, and was associated with struvite content and age on multivariate analysis. Increasing struvite content was associated with higher 2-year recurrence rate.

CONCLUSIONS

Higher struvite content is associated with a higher frequency of traditional urea splitting bacteria in urine culture, higher risk for postoperative SIRS, and higher recurrence rate. Struvite content greater than 25% can be used to define a clinically significant struvite stone.

Defining metabolic activity of nephrolithiasis - Appropriate evaluation and follow-up of stone formers

Considering the variation in metabolic evaluation and medical management of kidney stone disease, this consensus review was created to discuss the metabolic activity of nephrolithiasis, define the difference between single and recurrent stone formers, and develop a schema for metabolic and radiologic follow-up. A systematic review of the literature was performed to identify studies of metabolic evaluation and follow-up of patients with nephrolithiasis. Both single and recurrent stone formers share many similarities in metabolic profiles. The study group determined that based on an assessment of risk for stone recurrence and metabolic activity, single and recurrent stone formers should be evaluated comprehensively, including two 24 h urine studies on a random diet. Targeted medication and dietary recommendations are effective for many patients in reducing the risk of stone recurrence. Follow-up of those with stone disease should be obtained depending on the level of metabolic activity of the patient, the risk of chronic kidney disease and the risk of osteoporosis/osteopenia. A standard scheme includes a baseline metabolic profile, a repeat study 3-6 months after initiation of treatment, and then yearly when stable, with abdominal imaging obtained every 1-2 years.

Compliance of the recurrent renal stone former with current best practice guidelines

INTRODUCTION

Patient compliance to best practice guidelines is a significant factor in preventing renal stone recurrence. While patient compliance has been historically poor, there remains a paucity of data in the renal stone setting. We evaluated compliance of the recurrent renal stone former with current Canadian Urological Association (CUA) best practice guidelines.

METHODS

A prospective, cross-sectional study design was used to evaluate patient compliance. Recurrent renal stone former patients were consecutively recruited from McMaster's Institute of Urology and completed a one-time questionnaire developed in accordance with CUA best practice guidelines. Questionnaire sections included: 1) demographics; 2) interaction(s) and satisfaction with their healthcare provider; and 3) knowledge, attitudes, and compliance with best practices.

RESULTS

A total of 300 patients were enrolled in the study; 55.3% were men, 69.5% had a history of stone surgery, while 23.7% had a positive family history. Participants perceived satisfactory education from their urologist and primary care physician 82.7% and 59.7% of the time, respectively (p<0.05). Nearly a quarter of patients (22.8%) perceived their stone disease to be severe and 67.1% of patients believed in the efficacy of preventative stone measures. Overall, 45.8% of patients were compliant with CUA best practice guidelines. The majority of patients (72.6%) complied with high fluid intake, the most critical stone preventative practice.

CONCLUSIONS

Consistent with previous studies, compliance to dietary recommendations in this evaluation of recurrent stone formers was low. Study findings may be attributed to insufficient knowledge translation, lack of perceived disease severity, and/or patient uncertainty in the importance of preventative stone practices.

The Myth of Water and Salt: From Aquaretics to Tenapanor

The impact of water intake has been studied in several renal diseases. For example, increasing water intake is useful to prevent primary and secondary nephrolithiasis. In autosomal dominant polycystic kidney disease, arginine vasopressin (AVP) is involved in the progression of the disease, and water intake could play a therapeutic role by inhibiting the synthesis of AVP, but its efficacy is still controversial. Conversely, the use of aquaretics, which are antagonists of AVP V2 receptors, results in the reduction of the increase rate of total kidney volume with a slower decline of glomerular filtration rate. In chronic kidney disease, AVP contributes to glomerular hyperfiltration, arterial hypertension, and synthesis of renin, resulting in renal sclerosis. Increased water intake could reduce AVP activation determining a potential protective effect on the kidney, but its efficacy has not yet been clearly demonstrated. On the other side, sodium and potassium play an important role in the control of arterial blood pressure and are involved in the development and progression of chronic kidney disease. Reduction of sodium intake and increase of potassium intake determine a decrease of arterial blood pressure with a beneficial effect on the kidney; however, adherence to sodium restriction is very poor. Regarding this, sodium-hydrogen exchanger isoform 3 inhibitors may reduce sodium absorption in the gut. The most recent sodium-hydrogen exchanger isoform 3 inhibitor, known as tenapanor, reduces extracellular fluid volume, left ventricular hypertrophy, albuminuria, and blood pressure in experimental studies and increases fecal loss of sodium in humans.

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.

Citrate salts for preventing and treating calcium containing kidney stones in adults

BACKGROUND

Kidney stones affect people worldwide and have a high rate of recurrence even with treatment. Recurrences are particularly prevalent in people with low urinary citrate levels. These people have a higher incidence of calcium phosphate and calcium oxalate stones. Oral citrate therapy increases the urinary citrate levels, which in turn binds with calcium and inhibits the crystallisation thus reduces stone formation. Despite the widespread use of oral citrate therapy for prevention and treatment of calcium oxalate stones, the evidence to support its clinical efficacy remains uncertain.

OBJECTIVES

The objective of this review was to determine the efficacy and adverse events associated with citrate salts for the treatment and prevention of calcium containing kidney stones.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Specialised Register to 29 July 2015 through contact with the Trials' Search Co-ordinator using search terms relevant to this review.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) that assessed the efficacy and adverse events associated with citrate salts for the treatment and prevention of calcium containing kidney stones in adults treated for a minimum of six months.

DATA COLLECTION AND ANALYSIS

Two authors assessed studies for inclusion in this review. Data were extracted according to predetermined criteria. Summary estimates of effect were obtained using a random-effects model, and results were expressed as risk ratios (RR) and their 95% confidence intervals (CI) for dichotomous outcomes, and mean difference (MD) and 95% CI for continuous outcomes.

MAIN RESULTS

We included seven studies that included a total of 477 participants, most of whom had oxalate stones. Of these, three studies (247 participants) compared potassium citrate with placebo or no intervention; three (166 participants) compared potassium-sodium citrate with no intervention; and one (64 participants) compared potassium-magnesium citrate with placebo. Overall, quality of the reporting of the included studies was considered moderate to poor, and there was a high risk of attrition bias in two studies.Compared with placebo or no intervention, citrate therapy significantly reduced the stone size (4 studies, 160 participants: RR 2.35, 95% CI 1.36 to 4.05). New stone formation was significantly lower with citrate therapy compared to control (7 studies, 324 participants: RR 0.26, 95% CI 0.10 to 0.68). The beneficial effect on stone size stability was also evident (4 studies, 160 participants: RR 1.97, 95% CI 1.19 to 3.26). Adverse events were reported in four studies, with the main side effects being upper gastrointestinal disturbance and one patient reported a rash. There were more gastrointestinal adverse events in the citrate group; however this was not significant (4 studies, 271 participants: RR 2.55, 95% CI 0.71 to 9.16). There were significantly more dropouts due to adverse events with citrate therapy compared to control (4 studies, 271 participants: RR 4.45, 95% CI 1.28 to 15.50). The need for retreatment was significantly less with citrate therapy compared to control (2 studies, 157 participants: RR 0.22, 95% CI 0.06 to 0.89).

AUTHORS' CONCLUSIONS

Citrate salts prevent new stone formation and reduce further stone growth in patients with residual stones that predominantly contain oxalate. The quality of reported literature remains moderate to poor; hence a well-designed statistically powered multi-centre RCT is needed in order to answer relevant questions concerning the efficacy of citrate salts.

Knowledge, attitudes, and practice patterns of recurrent urinary stones prevention in Saudi Arabia

The purpose of this study is to assess the knowledge, attitudes, and practice patterns of urologists in Saudi Arabia regarding prevention of recurrent stone formation and how much they follow preventive stone disease management guidelines. A questionnaire about knowledge, attitudes, and practice patterns of urologists in Saudi Arabia regarding prevention of recurrent stone formation was used. The survey comprised three domains: knowledge, attitudes, and practice patterns. Data about gender, duration of experience and health care sector were also collected. Individual responses were recorded, tabulated and compared using descriptive statistics. The overall response rate was 38.8%. All respondents were male urologists. Most of them (62, 71.3%) had an experience of 5-20 years in management of stone disease patients and the majority (74, 85.1%) belonged to the governmental health care sector. A total of 51% of the respondents answered in concordance with the best practice guidelines in at least half of the questions and 40% in all of the questions. Overall, practice patterns of 58% of the respondents were in concordance with the best practice guidelines in all the questions except for the question of practices regarding stone analysis. As regards to attitude domain, a total of 58.7% respondents expressed their agreement or strong agreement with the questions. Urologists' knowledge of stone recurrence preventive programs is suboptimal. They do not apply effectively the best stone prevention practice guidelines in their daily practice as well. Efforts to increase knowledge and enforce its application in daily practice are strongly warranted.

Treatment effect, adherence, and safety of high fluid intake for the prevention of incident and recurrent kidney stones: a systematic review and meta-analysis

BACKGROUND

The objective of this systematic review and meta-analysis were to evaluate the effectiveness of high fluid intake for the prevention of incident and recurrent kidney stones, as well as its adherence and safety.

METHODS

A literature search was performed encompassing 1980 through July 2014. Studies that reported relative risks, odds ratios, or hazard ratios comparing the risk of kidney stone events in patients with high vs inadequate fluid intake were included. Pooled risk ratios (RRs) and 95 % confidence intervals (CIs) were calculated using a random-effect, generic inverse variance method.

RESULTS

Nine studies [2 randomized controlled trials (RCTs) with 269 patients; 7 observational studies with 273,685 individuals] were included in the meta-analysis. Pooled RRs of kidney stones in individuals with high-fluid intake were 0.40 (95 % CI 0.20-0.79) and 0.49 (0.34-0.71) in RCTs and observational studies, respectively. High fluid intake was significantly associated with reduced risk of recurrent kidney stones: RRs 0.40 (95 % CI 0.20-0.79) and 0.20 (0.09-0.44) in RCTs and observational studies, respectively. Adherence and safety data on high fluid intake treatment were limited; 1 RCT reported no withdrawals due to adverse events.

CONCLUSION

This analysis demonstrated a significantly reduced risk of incident kidney stones among individuals with high fluid consumption. High fluid consumption also reduced the risk of recurrent kidney stones. Furthermore, the magnitude of risk reduction was high. Although increased water intake appears to be safe, future studies on its safety in patients with high risk of volume overload or hyponatremia may be indicated.

Knowledge, attitudes, and practice patterns among healthcare providers in the prevention of recurrent kidney stones in Northern Ontario

INTRODUCTON

Kidney stone recurrence is common. Preventive measures can lead to improved quality of life and costs savings to the individual and healthcare system. Guidelines to prevent recurrent kidney stones are published by various urological societies. Adherence to guidelines amongst healthcare professionals in general is poor, while adherence to preventive management guidelines regarding stone disease is unknown. To understand this issue, we conducted an online study to assess the knowledge, attitudes, and practice patterns of healthcare practitioners in Northern Ontario.

METHODS

We used the database of healthcare providers affiliated with the Northern Ontario School of Medicine, in Sudbury (East Campus) and Thunder Bay (West Campus), Ontario. We designed the survey based on current best practice guidelines for the management of recurrent kidney stones. Questions covered 3 domains: knowledge, attitudes, and practice patterns. Demographic data were also collected. The survey was distributed electronically to all participants.

RESULTS

A total of 68 healthcare providers completed the survey. Of these, most were primary care physicians (72%). To keep uniformity, we analyzed the data of this homogenous group. A total of 70% of the respondents were aware of the current guidelines; however, only 43% applied their knowledge in clinical practice. Most participants lacked confidence while answering most items in the attitude domain.

CONCLUSIONS

Most primary care physician respondents were aware of the appropriate preventive measures for recurrent kidney stones; however, they do not appear to apply this knowledge effectively in clinical practice. A low response rate is a limitation of our study. Further studies involving a larger sample size may lead to information sharing and collaborative care among healthcare providers.

Effects of dietary interventions on incidence and progression of CKD

Traditional strategies for management of patients with chronic kidney disease (CKD) have not resulted in any change in the growing prevalence of CKD worldwide. A historic belief that eating healthily might ameliorate kidney disease still holds credibility in the 21(st) century. Dietary sodium restriction to <2.3 g daily, a diet rich in fruits and vegetables and increased water consumption corresponding to a urine output of 3-4 l daily might slow the progression of early CKD, polycystic kidney disease or recurrent kidney stones. Current evidence suggests that a reduction in dietary net acid load could be beneficial in patients with CKD, but the supremacy of any particular diet has yet to be established. More trials of dietary interventions are needed, especially in diabetic nephropathy, before evidence-based recommendations can be made. In the meantime, nephrologists should discuss healthy dietary habits with their patients and provide individualized care aimed at maximizing the potential benefits of dietary intervention, reducing the incidence of CKD and delaying its progression to end-stage renal disease. Keeping in mind the lack of data on hard outcomes, dietary recommendations should take into account barriers to adherence and be tailored to different cultures, ethnicities and geographical locations.

The ROKS nomogram for predicting a second symptomatic stone episode

Most patients with first-time kidney stones undergo limited evaluations, and few receive preventive therapy. A prediction tool for the risk of a second kidney stone episode is needed to optimize treatment strategies. We identified adult first-time symptomatic stone formers residing in Olmsted County, Minnesota, from 1984 to 2003 and manually reviewed their linked comprehensive medical records through the Rochester Epidemiology Project. Clinical characteristics in the medical record before or up to 90 days after the first stone episode were evaluated as predictors for symptomatic recurrence. A nomogram was developed from a multivariable model based on these characteristics. There were 2239 first-time adult kidney stone formers with evidence of a passed, obstructing, or infected stone causing pain or gross hematuria. Symptomatic recurrence occurred in 707 of these stone formers through 2012 (recurrence rates at 2, 5, 10, and 15 years were 11%, 20%, 31%, and 39%, respectively). A parsimonious model had the following risk factors for recurrence: younger age, male sex, white race, family history of stones, prior asymptomatic stone on imaging, prior suspected stone episode, gross hematuria, nonobstructing (asymptomatic) stone on imaging, symptomatic renal pelvic or lower-pole stone on imaging, no ureterovesicular junction stone on imaging, and uric acid stone composition. Ten-year recurrence rates varied from 12% to 56% between the first and fifth quintiles of nomogram score. The Recurrence of Kidney Stone nomogram identifies kidney stone formers at greatest risk for a second symptomatic episode. Such individuals may benefit from medical intervention and be good candidates for prevention trials.

Environmental and stressful factors affecting the occurrence of kidney stones and the kidney colic

The first renal disease described from Hippocrates is nephrolithiasis with renal colic, which is the pain of stone passage and is also a common renal problem with easily recognizable characteristics. There has been much written about dietary factors, which have unequivocally been proved to play an important role in the formation of kidney stones. In this regard, it is of interest that the contribution of factors such as stressful events, life style, or occupation in the formation of kidney stones has not been well studied. This review examines the clinical evidence of the stressful events and other environmental factors affecting the occurrence of kidney stones.

Kidney stones: pathophysiology and medical management

The formation of stones in the urinary tract stems from a wide range of underlying disorders. That clinicians look for the underlying causes for nephrolithiasis is imperative to direct management. There are many advances in genetics, pathophysiology, diagnostic imaging, medical treatment, medical prevention, and surgical intervention of nephrolithiasis. Here, I provide a brief general background and focus mainly on pathophysiology and medical treatment of kidney stones. Although important advances have been made in understanding nephrolithiasis from single gene defects, the understanding of polygenetic causes of kidney stones is still largely elusive. A substantial proportion of data that resulted in new methods of treatment and prevention, which can be empirical or definitive, has focused on urinary luminal chemical composition of the precipitating solutes. Manipulation of inhibitors and epithelial factors is important and needs further investigation. Advances in the management of nephrolithiasis depend on combined efforts of clinicians and scientists to understand the pathophysiology.

Fluid intake and epidemiology of urolithiasis

A low urine volume is an important risk factor in urinary stone formation. The present article summarizes available data from epidemiological and clinical studies to elucidate the impact of fluid intake and urine volume on the risk of urinary stone formation and the prevention of stone recurrence. A review of the literature shows that an increased urine volume achieved by a high fluid intake exerts an efficacious preventive effect on the onset and recurrence of urinary stones. A high water intake and urine dilution results in a marked reduction in saturation of lithogenous salts. The type of fluids should be carefully selected to achieve the appropriate change of urine composition depending on stone composition. A sufficient intake of fluid is one of the most important preventive measures for stone recurrence.

Experimental Evaluation of Transport Force in the Rabbit Ureter

Background

Cleaning the urinary tract by so-called “wash-out effect” and promoting high diuresis has long been advocated but has had very little scientific backing and few prospective studies in international journals.

Aim

To verify whether the physical laws describing the transport force of water in rivers and pipes are also valid for urinary outflow.

Methods

A laboratory model for measuring transport force, given liquid and solid capacity, was adapted to create an in vivo model based on the rabbit urinary tract.

Results

Fluid flow in the rabbit renal pelvis and ureters was found similar to flow in pipes, obeying the physical laws of water transport to some extent. When the quantity of liquid flowing in the urinary tract in unit time was doubled, the transport force increased by various orders of magnitude. When the liquid increased by a larger factor, the transport force became enormous.

Conclusions

The results confirm the utility of maintaining high diuresis in patients with renal calculus, but stress the utility of drinking 1–2 liters of hypotonic water in a short time to obtain an enormous increase in transport force which increases the probability of a cleansing effect.

Stone recurrence predictive score (SRPS) for patients with calcium oxalate stones

PURPOSE

We developed a convenient, self-administered 8-item stone recurrence predictive score (SRPS) to predict the recurrence of calcium oxalate stones.

MATERIALS AND METHODS

An 8-item SRPS to predict stone recurrence was developed based on general patient data, including age, sex, urine volume, smoking, wine drinking, family history, stone number and history of gouty arthritis. Mean age of the 204 studied patients with calcium oxalate stones +/- SD was 59.4 +/- 14.5 years (range 24 to 83). The male-to-female ratio was 3:1. Of the patients 115 were recurrent stone formers and 89 were single stone formers. We compared all available general data in the recurrence and control groups.

RESULTS

Family history, stone number, gouty arthritis and SRPS were independent risk factors for stone recurrence. Mean SRPS in recurrent and single stone formers was 7.6 +/- 3.1 and 5.1 +/- 2.0, respectively (p = 0). An increase in SRPS had a significant positive correlation with stone recurrence (r2 = 0.859, p <0.0001). At an SRPS cutoff of 7 or greater we achieved 61.7% sensitivity and 75.3% specificity to predict stone recurrence. At an SRPS of 11 or greater we found that 100% of patients had recurrent stones.

CONCLUSIONS

With the introduction of the 8-item SRPS we provide a simple, convenient and reliable tool to predict calcium oxalate stone recurrence. Due to the characteristics of the high incidence of stone recurrence thorough metabolic evaluation may be justified in patients with an SRPS of 7 or greater and preventive measures are highly recommended in those with an SRPS of 11 or greater.

Urinary stone disease in diabetes mellitus

OBJECTIVE

Diabetes mellitus (DM) and urinary stone disease (USD) are common diseases in the community. The prevalence of USD has not previously been studied in DM patients.

MATERIAL AND METHODS

We evaluated 286 diabetics and 111 age-matched controls by means of direct urinary system X-ray, ultrasonography and/or intravenous pyelography. We also examined the history, risk factors and clinical aspects of USD in DM patients.

RESULTS

The prevalence of USD (21% vs 8%; p < 0.05) and the rate of recurrence (2.1 +/- 2.2 vs 1.3 +/- 0.5 stones/case; p < 0.05) were higher in the diabetics compared to the controls. Family history and male gender were significant risk factors for the development of USD in the DM patients. Increased daily total fluid consumption was not preventive for USD in the DM patients, and the type of fluid consumed did not have an impact on the risk of USD. Alcohol consumption was a significant risk factor for the development USD in the DM patients (odds ratio 3.68; 95% confidence interval 1.29-10.45; p < 0.05). Crystaluria (10% vs 1%; p < 0.05) and positive urine culture (8% vs 1%; p < 0.05) were also more prominent in the diabetics compared to the controls.

CONCLUSIONS

The results of this study suggest that DM is a risk factor for the development USD.

Medical treatment of nephrolithiasis

The medical treatment of nephrolithiasis is aimed in particular at the prevention of relapses, even though in some cases, such as cystine or uric acid lithiasis, the calculi also can be dissolved on site. When the diagnosis and metabolic profile have been performed correctly, medical treatment is effective in a large number of patients. The greatest difficulty is the patient's compliance with the most suitable prevention measures and the frequency of follow-up controls. This compliance can be influenced significantly by the amount of time that the doctor spends to explain the origin of the disease. This article reviews the main methods available for the medical treatment of various nephrolithiasis types, namely water intake, diet, and drugs, supplying the relevant information about the mechanism of action, metabolic consequences, indications, evidence provided from studies, dosage, efficacy, and side-effects. Finally, brief simplified guidelines are given for the medical treatment of stone disease caused by calcium oxalate or calcium phosphate, uric acid, cystine, and struvite.

Comparison of two diets for the prevention of recurrent stones in idiopathic hypercalciuria

BACKGROUND

A low-calcium diet is recommended to prevent recurrent stones in patients with idiopathic hypercalciuria, yet long-term data on the efficacy of a low-calcium diet are lacking. Recently, the efficacy of a low-calcium diet has been questioned, and greater emphasis has been placed on reducing the intake of animal protein and salt, but again, long-term data are unavailable.

METHODS

We conducted a five-year randomized trial comparing the effect of two diets in 120 men with recurrent calcium oxalate stones and hypercalciuria. Sixty men were assigned to a diet containing a normal amount of calcium (30 mmol per day) but reduced amounts of animal protein (52 g per day) and salt (50 mmol of sodium chloride per day); the other 60 men were assigned to the traditional low-calcium diet, which contained 10 mmol of calcium per day.

RESULTS

At five years, 12 of the 60 men on the normal-calcium, low-animal-protein, low-salt diet and 23 of the 60 men on the low-calcium diet had had relapses. The unadjusted relative risk of a recurrence for the group on the first diet, as compared with the group on the second diet, was 0.49 (95 percent confidence interval, 0.24 to 0.98; P=0.04). During follow-up, urinary calcium levels dropped significantly in both groups by approximately 170 mg per day (4.2 mmol per day). However, urinary oxalate excretion increased in the men on the low-calcium diet (by an average of 5.4 mg per day [60 micromol per day]) but decreased in those on the normal-calcium, low-animal-protein, low-salt diet (by an average of 7.2 mg per day [80 micromol per day]).

CONCLUSIONS

In men with recurrent calcium oxalate stones and hypercalciuria, restricted intake of animal protein and salt, combined with a normal calcium intake, provides greater protection than the traditional low-calcium diet.

Pharmacology for renal calculi

Stone disease is as old as recorded history but despite advances in diagnosis and treatment, it continues to cause significant morbidity. This review summarises the current pharmacologic management of urinary calculi based upon the stone type. All patients with stone disease are advised to increase fluid intake, limit dietary protein and limit sodium. Calcium oxalate stones can be managed on a selective or non-selective basis depending on the cause of the hypercalciuria or hyperoxaluria. Agents currently in use include sodium cellulose phosphate, thiazides, orthophosphates, oral calcium supplements, pyridoxine, cholestyramine, citrate, magnesium and allopurinol. Classically, struvite stones occur in the presence of urea splitting organisms and are composed of magnesium, ammonium phosphate and carbonate apatite. The goal of treatment is to make patients stone free as bacteria retained in stone fragments lead to stone growth. Urease inhibitors, aluminium hydroxide gel, hemiacidrin, and Suby G and M solutions are infrequently used in treatment. Cystine stones are the result of an autosomal recessive disorder. D-Penicillamine, captopril and alpha-mercaptopropionylglycine (MPG) are all oral agents that have proven to be efficacious. As more randomised trials are conducted and the understanding of endogenous stone inhibitors progresses, the medical management of stone disease will continue to improve.

Metabolic risk factors in patients with first-time and recurrent stone formations as determined by comprehensive metabolic evaluation

OBJECTIVES

To determine whether patients with recurrent calcium stone formation have more significant metabolic abnormalities compared with patients with first-time stone formation as determined by a comprehensive metabolic evaluation.

METHODS

We investigated metabolic abnormalities in 37 patients (14 men, 23 women) with first-time and 136 patients (83 men, 53 women) with recurrent calcium stones, stratified according to sex. Calcium oxalate supersaturation indexes of Tiselius (1991) and Ogawa (1996) were also compared between the groups. In addition to the specific metabolic abnormalities, we analyzed the total number of such defects for each group.

RESULTS

In men, the average number of metabolic abnormalities in each patient was greater in patients with recurrent stones (2.20+/-0.86) than in those with first-time stones (1.46+/-1.27). Such a difference could only be demonstrated for women if low urine volume was excluded as a specific abnormality. Although the frequency of each abnormality was higher in patients with recurrent stones, a statistically significant difference was only noted in the frequency of hypocitraturia between women with first-time and recurrent stone formation (11.1% versus 37.8%, P < 0.05). There were no significant differences in the calcium oxalate supersaturation indexes between first-time and recurrent stone formation in either men or women.

CONCLUSIONS

Women with recurrent stones have a higher prevalence of hypocitraturia than women with first-time stones. Potassium citrate therapy for prevention of urolithiasis may be especially useful for this patient population.

Apical extracellular calcium/polyvalent cation-sensing receptor regulates vasopressin-elicited water permeability in rat kidney inner medullary collecting duct

During antidiuresis, increases in vasopressin (AVP)-elicited osmotic water permeability in the terminal inner medullary collecting duct (tIMCD) raise luminal calcium concentrations to levels (> or = 5 mM) above those associated with the formation of calcium-containing precipitates in the urine. Calcium/polycation receptor proteins (CaRs) enable cells in the parathyroid gland and kidney thick ascending limb of Henle to sense and respond to alterations in serum calcium. We now report the presence of an apical CaR in rat kidney tIMCD that specifically reduces AVP-elicited osmotic water permeability when luminal calcium rises. Purified tIMCD apical membrane endosomes contain both the AVP-elicited water channel, aquaporin 2, and a CaR. In addition, aquaporin 2-containing endosomes also possess stimulatory (G(alpha q)/G(alpha 11) and inhibitory (G(alpha i1, 2, and 3)) GTP binding proteins reported previously to interact with CaRs as well as two specific isoforms (delta and zeta) of protein kinase C. Immunocytochemistry using anti-CaR antiserum reveals the presence of CaR protein in both rat and human collecting ducts. Together, these data provide support for a unique tIMCD apical membrane signaling mechanism linking calcium and water metabolism. Abnormalities in this mechanism could potentially play a role in the pathogenesis of renal stone formation.

Medical therapy, calcium oxalate urolithiasis

The development of diagnostic protocols that identify specific risk factors for calcium oxalate nephrolithiasis has led to the formulation of directed medical regimens that are aimed at correcting the underlying metabolic disturbances. Initiation of these treatment programs has reduced markedly the rate of stone formation in the majority of patients who form stones. This article discusses the rationale that underlies the choice of medical therapy for the various pathophysiologic causes of calcium oxalate nephrolithiasis and the appropriate use of available medications.

The financial effects of kidney stone prevention

Prevention of nephrolithiasis (NL) is now medically feasible and widely recommended. However, diagnosis and treatment of remediable causes of stones requires testing and drugs that impose a cost; this cost is balanced by the presumed reductions in stone related events and medical encounters. In order to assess the balance between these, we have analyzed results from 1092 patients with NL unselected except for having clinical follow-up during treatment. From this population, we have derived the changes in rates of new stones, hospitalizations, cystoscopies, and surgical procedures. From these changes, and assignment of a range of possible dollar costs, we estimate that medical stone prevention will result in an average saving of $2,158 +/- $500 (SEM)/patient/year, which is the difference between an expenditure of $1,068/patient on yearly drugs and testing, and a reduction of $3,226 per patient in medical costs. Medical prevention of NL seems justified on a cost saving basis quite apart from its benefits to patients in terms of reduced morbidity and risk from procedures, obstruction, and infection.