An in-depth review of the evidence linking dietary salt intake and progression of chronic kidney disease

Spot urinary sodium in CKD patients: correlation with 24h-excretion and evaluation of commonly used prediction equations

BACKGROUND

Salt intake in CKD patients can affect cardiovascular risk and kidney disease progression. Twenty-four hour (24h) urine collections are often used to investigate salt metabolism but are cumbersome to perform. We assessed urinary sodium (U-Na) concentration in spot urine samples and investigated the correlation with 24h U-Na excretion and concentration in CKD patients under nephrological care. Further, we studied the role of CKD stage and diuretics and evaluated the performance of commonly used formulas for the prediction of 24h U-Na excretion from spot urine samples.

METHODS

One hundred eight patients of the German Chronic Kidney Disease (GCKD) study were included. Each participant collected a 24h urine and two spot urine samples within the same period. The first spot urine sample (AM) was part of the second morning urine. The second urine sample was collected before dinner (PM). Patients were advised to take their medication as usual without changing dietary habits. U-Na concentrations in the two spot urine samples and their average ((AM + PM)/2) were correlated with U-Na concentration and total Na excretion in the 24h urine collections. Correlations were subsequently studied after stratification by CKD stage and diuretic intake. The usefulness of three commonly applied equations to estimate 24h U-Na excretion from spot urine samples (Kawasaki, Tanaka and Intersalt) was determined using Bland-Altman plots, analyses of sensitivity, specificity, as well as positive (PPV) and negative predictive values (NPV).

RESULTS

Participants (42 women, 66 men) were on average (± SD) 62.2 (± 11.9) years old, with a mean serum creatinine of 1.6 (± 0.5) mg/dl. 95% had arterial hypertension, 37% diabetes mellitus and 55% were on diuretics. The best correlation with 24h U-Na total excretion was found for the PM spot U-Na sample. We also found strong correlations when comparing spot and 24h urine U-Na concentration. Correction of spot U-Na for U-creatinine did not improve strength of correlations. Neither CKD stage, nor intake of diuretics had significant impact on these correlations. All examined formulas revealed a significant mean bias. The lowest mean bias and the strongest correlation between estimated and measured U-Na excretion in 24h were obtained using the Tanaka-formula. Also, application of the Tanaka-formula with PM U-Na provided best sensitivity, specificity, PPV and NPV to estimate U-Na excretion > 4g/d corresponding to a salt consumption > 10g/d.

CONCLUSION

U-Na concentration of spot urine samples correlated with 24h U-Na excretion especially when PM spot U-Na was used. However, correlation coefficients were relatively low. Neither CKD stage nor intake of diuretics appeared to have an influence on these correlations. There was a significant bias for all tested formulas with the Tanaka-formula providing the strongest correlation with measured 24h U-Na excretion. In summary, using spot urine samples together with the Tanaka-formula in epidemiological studies appears feasible to determine associations between approximate salt intake and outcomes in CKD patients. However, the usefulness of spot-urine samples to guide and monitor salt consumption in individual patients remains limited.

Global nutritional challenges of reformulated food: A review

Food reformulation, the process of redesigning processed food products to make them healthier, is considered a crucial step in the fight against noncommunicable diseases. The reasons for reformulating food vary, with a common focus on reducing the levels of harmful substances, such as fats, sugars, and salts. Although this topic is broad, this review aims to shed light on the current challenges faced in the reformulation of food and to explore different approaches that can be taken to overcome these challenges. The review highlights the perception of consumer risk, the reasons for reformulating food, and the challenges involved. The review also emphasizes the importance of fortifying artisanal food processing and modifying microbial fermentation in order to meet the nutrient requirements of people in developing countries. The literature suggests that while the traditional reductionist approach remains relevant and yields quicker results, the food matrix approach, which involves engineering food microstructure, is a more complex process that may take longer to implement in developing economies. The findings of the review indicate that food reformulation policies are more likely to succeed if the private sector collaborates with or responds to the government regulatory process, and further research is conducted to establish newly developed reformulation concepts from different countries. In conclusion, food reformulation holds great promise in reducing the burden of noncommunicable diseases and improving the health of people around the world.

High Salt Induces a Delayed Activation of Human Neutrophils

High salt (NaCl) concentrations are found in a number of tissues under physiological and pathological conditions. Here, we analyzed the effects induced by high salt on the function of human neutrophils. The culture of neutrophils in medium supplemented with high salt (50 mM NaCl) for short periods (30-120 min) inhibited the ability of conventional agonists to induce the production of IL-8 and the activation of respiratory burst. By contrast, exposure to high salt for longer periods (6-18 h) resulted in the activation of neutrophils revealed by the production of high levels of IL-8, the activation of the respiratory burst, and a marked synergistic effect on the production of TNF-α induced by LPS. Increasing osmolarity of the culture medium by the addition of sorbitol or mannitol (100 mM) was shown to be completely unable to stimulate neutrophil responses, suggesting that high sodium but not an increased osmolarity mediates the activation on neutrophils responses. A similar biphasic effect was observed when the function of monocytes was analyzed. Short term exposure to high salt suppressed IL-8 and TNF-α production induced by LPS while culture for longer periods triggered the production of IL-8 but not TNF-α in the absence of LPS stimulation. Contradictory results have been published regarding how high salt modulates neutrophil function. Our results suggest that the modulation of neutrophil function by high salt is strongly dependent on the exposure time.

Associations of sodium and potassium intake with chronic kidney disease in a prospective cohort study: findings from the Hispanic Community Health Study/Study of Latinos, 2008-2017

BACKGROUND

According to dietary recommendations, reduction of sodium intake has potential to reduce Chronic Kidney Disease (CKD) risk; however the role of dietary potassium and the sodium -to- potassium ratio in the development of CKD is unclear.

METHODS

We studied 9778 participants of the Hispanic Community Health Study/Study of Latinos (HCHS/SOL) from four US urban communities. Participants were aged 18-74 yrs., free from CKD at baseline in 2008-2011 and re-examined between 2014 and - 2017. Dietary intake of sodium, potassium and the ratio of dietary sodium -to- potassium were measured from two baseline 24-h dietary recalls. Incident CKD was defined as: 1) estimated glomerular filtration rate (eGFR) decline of 1 unit per year and eGFR < 60 ml/min/1.73m2 or 2) albumin to creatinine ratio ≥ 30 mg/g at the follow-up visit. We used multivariable survey weighted Poisson regression to estimate adjusted incident rates of incident CKD.

RESULTS

At baseline, mean age was 41 years. Average follow up time was 6.2 years. From fully adjusted Poisson regression analyses, self-reported sodium intake was not associated with incident CKD. However, for each 500 mg decrement in potassium intake, there was an 11% increase risk of incident CKD (IRR = 1.11, 95% CI = 1.00, 1.24). Additionally, every 1 M ratio increment of sodium -to -potassium ratio was associated with a 21% increased risk of incident CKD (IRR = 1.21, 95% CI = 1.02, 1.45), p < 0.05).

CONCLUSIONS

We conclude that diets low in potassium and high in sodium are associated with increased risk of developing chronic kidney disease among healthy US Hispanic/Latino adults.

Ultraprocessed food consumption and kidney function decline in a population-based cohort in the Netherlands

BACKGROUND

Ultraprocessing makes food products more convenient, appealing, and profitable. Recent studies show that high ultraprocessed food (UPF) intake is associated with cardiometabolic diseases.

OBJECTIVES

The aim of this study is to investigate the association between UPF consumption and risks of kidney function decline in the general population.

METHODS

In a prospective, general population-based Lifelines cohort from Northern Netherlands, 78,346 participants free of chronic kidney disease (CKD) at baseline responded to a 110-item FFQ. We used a multivariable regression analysis to study the associations of the proportion (in grams/day) of UPFs in the total diet with a composite kidney outcome [incident CKD or a ≥30% estimated glomerular filtration rate (eGFR) decline relative to baseline] and annual change in eGFR.

RESULTS

On average, 37.7% of total food intake came from UPFs. After 3.6 ± 0.9 years of follow-up, 2470 participants (3.2%) reached the composite kidney outcome. Participants in the highest quartile of UPF consumption were associated with a higher risk of the composite kidney outcome (OR, 1.27; 95% CI, 1.09-1.47; P = 0.003) compared with those in the lowest quartile, regardless of their macro- or micronutrient intake or diet quality. Participants in the highest quartile had a more rapid eGFR decline (β, -0.17; 95% CI, -0.23 to -0.11; P < 0.001) compared with those in the lowest quartile. Associations were generally consistent across different subgroups.

CONCLUSIONS

Higher UPF consumption was associated with a higher risk of a composite kidney outcome (incident CKD or ≥30% eGFR decline) and a more rapid eGFR decline in the general population, independent of confounders and other dietary indices.

Current aspects of renal dysfunction after liver transplantation

The development of chronic kidney disease (CKD) after liver transplantation (LT) exerts a severe effect on the survival of patients. The widespread adoption of the model for end-stage liver disease score strongly impacted CKD incidence after the procedure, as several patients are transplanted with previously deteriorated renal function. Due to its multifactorial nature, encompassing pre-transplantation conditions, perioperative events, and nephrotoxic immunosuppressor therapies, the accurate identification of patients under risk of renal disease, and the implementation of preventive approaches, are extremely important. Methods for the evaluation of renal function in this setting range from formulas that estimate the glomerular filtration rate, to non-invasive markers, although no option has yet proved efficient in early detection of kidney injury. Considering the nephrotoxicity of calcineurin inhibitors (CNI) as a factor of utmost importance after LT, early nephroprotective strategies are highly recommended. They are based mainly on delaying the application of CNI during the immediate postoperative-period, reducing their dosage, and associating them with other less nephrotoxic drugs, such as mycophenolate mofetil and everolimus. This review provides a critical assessment of the causes of renal dysfunction after LT, the methods of its evaluation, and the interventions aimed at preserving renal function early and belatedly after LT.

Effect of a low-salt diet on chronic kidney disease outcomes: a systematic review and meta-analysis

OBJECTIVE

The benefits of a low-salt diet for patients with chronic kidney disease (CKD) are controversial. We conducted a systematic review and meta-analysis of the effect of a low-salt diet on major clinical outcomes.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

MEDLINE by Ovid, EMBASE and the Cochrane Library databases.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

We included randomised controlled trials (RCTs) and cohort studies that assessed the effect of a low-salt diet on the renal composite outcomes (more than 50% decline in estimated glomerular filtration rate (eGFR) during follow-up, doubling of serum creatinine or end-stage renal disease), rate of eGFR decline, change in proteinuria, all-cause mortality events, cardiovascular (CV) events, and changes in systolic blood pressure and diastolic blood pressure.

DATA EXTRACTION AND SYNTHESIS

Two independent researchers extracted data and evaluated their quality. Relative risks (RRs) with 95% CIs were used for dichotomous data. Differences in means (MDs) or standardised mean differences (SMDs) with 95% CIs were used to pool continuous data. We used the Cochrane Collaboration risk-of-bias tool to evaluate the quality of RCTs, and Newcastle-Ottawa Scale to evaluate the quality of cohort studies.

RESULTS

We found 9948 potential research records. After removing duplicates, we reviewed the titles and abstracts, and screened the full text of 230 publications. Thirty-three studies with 101 077 participants were included. A low-salt diet produced a 28% reduction in renal composite outcome events (RR: 0.72; 95% CI: 0.58 to 0.89). No significant effects were found in terms of changes in proteinuria (SMD: -0.71; 95% CI: -1.66 to 0.24), rate of eGFR (decline MD: 1.16; 95% CI: -2.02 to 4.33), risk of all-cause mortality (RR: 0.92; 95% CI: 0.58 to 1.46) and CV events (RR: 1.01; 95% CI: 0.46 to 2.22).

CONCLUSION

A low-salt diet seems to reduce the risk for renal composite outcome events in patients with CKD. However, no compelling evidence indicated that such a diet would reduce the eGFR decline rate, proteinuria, incidence of all-cause mortality and CV events. Further, more definitive studies are needed.

PROSPERO REGISTRATION NUMBER

CRD42017072395.

Association of Sodium, Potassium and Sodium-to-Potassium Ratio with Urine Albumin Excretion among the General Chinese Population

Mixed evidence was published regarding the association of sodium, potassium and sodium-to-potassium ratio (Na/K ratio) with renal function impairment. This study was conducted to further explore the relationship between sodium, potassium, NA/K ratio and kidney function in the general adult Chinese population. We performed a cross-sectional analysis using the baseline data from the Action on Salt China (ASC) study. 5185 eligible general adult participants from the baseline investigation of the ASC study were included in this analysis. Sodium, potassium and albumin excretion were examined from 24-h urine collection. Albuminuria was defined as albumin excretion rate (AER) greater than or equal to 30 mg/24-h. Mixed linear regression models, adjusted for confounders, were fitted to analyze the association between sodium, potassium and Na/K ratio, and natural log transformed AER. Mixed effects logistic regression models were performed to analyze the odds ratio of albuminuria at each quintile of sodium, potassium and Na/K ratio. The mean age of the participants was 49.5 ± 12.8 years, and 48.2% were male. The proportion of albuminuria was 7.5%.The adjusted mixed linear models indicated that sodium and Na/K ratio was positively associated with natural log transformed AER (Sodium: β = 0.069, 95%CI [0.050, 0.087], p < 0.001; Na/K ratio: β = 0.026, 95%CI [0.012, 0.040], p < 0.001). Mixed effects logistic regression models showed that the odds of albuminuria significantly increased with the quintiles of sodium (p < 0.001) and Na/K ratio (p = 0.001). No significant association was found between potassium and the outcome indicators. Higher sodium intake and higher Na/K ratio are associated with early renal function impairment, while potassium intake was not associated with kidney function measured by albumin excretion.

Altered dietary salt intake for people with chronic kidney disease

BACKGROUND

Evidence indicates that reducing dietary salt may reduce the incidence of heart disease and delay decline in kidney function in people with chronic kidney disease (CKD). This is an update of a review first published in 2015.

OBJECTIVES

To evaluate the benefits and harms of altering dietary salt for adults with CKD.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies up to 6 October 2020 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal and ClinicalTrials.gov.

SELECTION CRITERIA

Randomised controlled trials comparing two or more levels of salt intake in adults with any stage of CKD.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed studies for eligibility, conducted risk of bias evaluation and evaluated confidence in the evidence using GRADE. Results were summarised using random effects models as risk ratios (RR) for dichotomous outcomes or mean differences (MD) for continuous outcomes, with 95% confidence intervals (CI).

MAIN RESULTS

We included 21 studies (1197 randomised participants), 12 in the earlier stages of CKD (779 randomised participants), seven in dialysis (363 randomised participants) and two in post-transplant (55 randomised participants). Selection bias was low in seven studies, high in one and unclear in 13. Performance and detection biases were low in four studies, high in two, and unclear in 15. Attrition and reporting biases were low in 10 studies, high in three and unclear in eight. Because duration of the included studies was too short (1 to 36 weeks) to test the effect of salt restriction on endpoints such as death, cardiovascular events or CKD progression, changes in salt intake on blood pressure and other secondary risk factors were examined. Reducing salt by mean -73.51 mmol/day (95% CI -92.76 to -54.27), equivalent to 4.2 g or 1690 mg sodium/day, reduced systolic/diastolic blood pressure by -6.91/-3.91 mm Hg (95% CI -8.82 to -4.99/-4.80 to -3.02; 19 studies, 1405 participants; high certainty evidence). Albuminuria was reduced by 36% (95% CI 26 to 44) in six studies, five of which were carried out in people in the earlier stages of CKD (MD -0.44, 95% CI -0.58 to -0.30; 501 participants; high certainty evidence). The evidence is very uncertain about the effect of lower salt intake on weight, as the weight change observed (-1.32 kg, 95% CI -1.94 to -0.70; 12 studies, 759 participants) may have been due to fluid volume, lean tissue, or body fat. Lower salt intake may reduce extracellular fluid volume in the earlier stages of CKD (-0.87 L, 95% CI -1.17 to -0.58; 3 studies; 187 participants; low certainty evidence). The evidence is very uncertain about the effect of lower salt intake on reduction in antihypertensive dose (RR 2.45, 95% CI 0.98 to 6.08; 8 studies; 754 participants). Lower salt intake may lead to  symptomatic hypotension (RR 6.70, 95% CI 2.40 to 18.69; 6 studies; 678 participants; moderate certainty evidence). Data were sparse for other types of adverse events.

AUTHORS' CONCLUSIONS

We found high certainty evidence that salt reduction reduced blood pressure in people with CKD, and albuminuria in people with earlier stage CKD in the short-term. If such reductions could be maintained long-term, this effect may translate to clinically significant reductions in CKD progression and cardiovascular events. Research into the long-term effects of sodium-restricted diet for people with CKD is warranted.

Measured sodium excretion is associated with CKD progression: results from the KNOW-CKD study

BACKGROUND

Diet is a modifiable factor of chronic kidney disease (CKD) progression. However, the effect of dietary salt intake on CKD progression remains unclear. Therefore, we analyzed the effect of dietary salt intake on renal outcome in Korean patients with CKD.

METHODS

We measured 24-h urinary sodium (Na) excretion as a marker of dietary salt intake in the prospective, multi-center, longitudinal KoreaN cohort study for Outcome in patients With CKD (KNOW-CKD). Data were analyzed from CKD patients at Stages G3a to G5 (n = 1254). We investigated the association between dietary salt intake and CKD progression. Patients were divided into four quartiles of dietary salt intake, which was assessed using measured 24-h urinary Na excretion. The study endpoint was composite renal outcome, which was defined as either halving the estimated glomerular filtration rate or developing end-stage renal disease.

RESULTS

During a median (interquartile range) follow-up of 4.3 (2.8-5.8) years, 480 (38.7%) patients developed the composite renal event. Compared with the reference group (Q2, urinary Na excretion: 104.2 ≤ Na excretion < 145.1 mEq/day), the highest quartile of measured 24-h urinary Na excretion was associated with risk of composite renal outcome [Q4, urinary Na excretion ≥192.9 mEq/day, hazard ratio 1.8 (95% confidence interval 1.12-2.88); P = 0.015] in a multivariable hazards model. Subgroup analyses showed that high-salt intake was particularly associated with a higher risk of composite renal outcome in women, in patients <60 years of age, in those with uncontrolled hypertension and in those with obesity.

CONCLUSIONS

High salt intake was associated with increased risk of progression in CKD.

Clinical Management of Children with a Congenital Solitary Functioning Kidney: Overview and Recommendations

CONTEXT

A congenital solitary functioning kidney (cSFK) is a common developmental defect that predisposes to hypertension and chronic kidney disease (CKD) as a consequence of hyperfiltration. Every urologist takes care of patients with a cSFK, since some will need lifelong urological care or will come with clinical problems or questions to an adult urologist later in life.

OBJECTIVE

We aim to provide clear recommendations for the initial clinical management and follow-up of children with a cSFK.

EVIDENCE ACQUISITION

PubMed and EMBASE were searched to identify relevant publications, which were combined with guidelines on related topics and expert opinion.

EVIDENCE SYNTHESIS

Initially, cSFK diagnosis should be confirmed and risk factors for kidney injury should be identified using ultrasound. Although more research into early predictors of kidney injury is needed, additional congenital anomalies of the kidney or urinary tract and absence of compensatory kidney hypertrophy have repeatedly been associated with a worse prognosis. The role of voiding cystourethrography and antibiotic prophylaxis remains controversial, and is complicated by the exclusion of children with a cSFK from studies. A yearly follow-up for signs of kidney injury is recommended for children with a cSFK. As masked hypertension is prevalent, annual ambulatory blood pressure measurement should be considered. During puberty, an increasing incidence of kidney injury is seen, indicating that long-term follow-up is necessary. If signs of kidney injury are present, angiotensin converting enzyme inhibitors are the first-line drugs of choice.

CONCLUSIONS

This overview points to the urological and medical clinical aspects and long-term care guidance for children with a cSFK, who are at risk of hypertension and CKD. Monitoring for signs of kidney injury is therefore recommended throughout life. Large, prospective studies with long-term follow-up of clearly defined cohorts are still needed to facilitate more risk-based and individualized clinical management.

PATIENT SUMMARY

Many children are born with only one functioning kidney, which could lead to kidney injury later in life. Therefore, a kidney ultrasound is made soon after birth, and other investigations may be needed as well. Urologists taking care of patients with a solitary functioning kidney should realize the long-term clinical aspects, which might need medical management.

Treatment rationale for coronary heart disease in advanced CKD

Chronic kidney disease (CKD) is accompanied by coronary artery disease (CAD) in most patients. In this article we describe differences in the pathogenesis, diagnosis, and treatment of CAD compared with patients without kidney impairment. The histological phenotype as well as the clinical presentation of acute and chronic coronary syndromes differ from those of patients with normal kidney function. The risk of cardiovascular events including death is strikingly increased with higher stages of CKD. Traditional but even more nontraditional cardiovascular risk factors are contributing to this increase. Screening and diagnostic procedures show limited sensitivity and specificity. Lifestyle modification is important for reducing the progression of both CKD and CAD. A special emphasis should be placed on physical exercising. Equally important is a strict antihypertensive therapy due to the very high incidences of hypertension in CKD patients. Blockade of the renin-angiotensin-system is imperative providing that adverse effects can be managed. Target blood pressure should be at 130 mm Hg systolic. Antiglycemic treatment should be implemented with metformin and SGLT2-inhibitors as first-line therapy, and glomerular filtration rate thresholds must be respected for both drugs. The risk of hypoglycemia is increased with worsening kidney function. Statins are indicated for up to stage 5 CKD. When a revascularization procedure is indicated (percutaneous intervention or bypass grafting), higher rates or peri-interventional morbidity and mortality must be anticipated. Taken together, the available literature on patients with CKD and CAD is clearly restricted compared with that on CAD patients with preserved kidney function. Mechanisms of arteriosclerosis and atheromatosis in CKD deserve more attention in the future. One major innovation in the field is SGLT2-inhibitor treatment with its concordant advantages for kidney and cardiac protection.

Adherence to the Kidney Disease: Improving Global Outcomes CKD Guideline in Nephrology Practice Across Countries

Introduction

The uptake of the Kidney Disease: Improving Global Outcomes (KDIGO) 2012 chronic kidney disease (CKD) Guideline is not fully described in real-world nephrology practice across the world.

Methods

We used baseline data from the CKD Outcomes and Practice Patterns Study (2013-2017), a 4-country cohort of patients with estimated glomerular filtration rate <60 ml/min per 1.73 m² recruited from national samples of nephrology clinics, to describe adherence to measures for monitoring and delaying CKD progression. Data were collected as in clinical practice, except laboratory measures per protocol in France.

Results

The mean age ranged from 65 years in Brazil to 72 years in Germany. Albuminuria (mostly proteinuria) was measured routinely in 36% to 43% of patients in Brazil, Germany, and the United States. Blood pressure control (≤140/90 mm Hg) ranged from 49% in France to 76% in Brazil; <40% of patients had blood pressure ≤130/80 mm Hg everywhere but Brazil (52%). More than 40% of nephrologists in Brazil reported a systolic blood pressure target ≤130 mm Hg for nondiabetic patients without proteinuria, but only 19% to 24% elsewhere. Prescription of renin-angiotensin aldosterone system inhibitors ranged from 52% in the United States to 81% in Germany. Dietary advice was more frequent for salt than protein intake; dietitian visits were uncommon. In nondiabetic patients, achievement of all 3 targets including blood pressure ≤130/80 mm Hg, renin-angiotensin aldosterone system inhibition, and dietary advice, ranged from 10% in the United States to 32% in Brazil; in treated diabetic patients, this ranged from 6% to 11% after including hemoglobin A1c target.

Conclusion

Adherence to recommendations to slow CKD progression is low in typical practice settings, and substantial variation among countries for some indicates opportunities for improvement.

Past Sodium Intake, Contemporary Sodium Intake, and Cardiometabolic Health in Southwest Coastal Bangladesh

Background We compared the relationship of past and contemporary sodium (Na) intake with cardiometabolic biomarkers. Methods and Results A total of 1191 participants' data from a randomized controlled trial in coastal Bangladesh were analyzed. Participants provided 24-hour urine Na (24UNa) data for 5 monthly visits. Their fasting blood glucose, total cholesterol, triglycerides, high-density lipoprotein, blood pressure, and 24-hour urine protein were measured at the fifth visit. Participants' mean 24UNa over the first 4 visits was the past Na, and 24UNa of the fifth visit was the contemporary Na intake. We estimated the prevalence ratios of elevated cardiometabolic biomarkers and metabolic syndrome across 24UNa tertiles by multilevel logistic regression using participant-, household-, and community-level random intercepts. Models were adjusted for age, sex, body mass index, smoking, physical activity, alcohol consumption, sleep hours, religion, and household wealth. Compared with participants in tertile 1 of past urine Na, those in tertile 3 had 1.46 (95% CI, 1.08-1.99) times higher prevalence of prediabetes or diabetes mellitus, 5.49 (95% CI, 2.73-11.01) times higher prevalence of large waist circumference, and 1.60 (95% CI, 1.04-2.46) times higher prevalence of metabolic syndrome. Compared with participants in tertile 1 of contemporary urine Na, those in tertile 3 had 1.93 (95% CI, 1.24-3.00) times higher prevalence of prediabetes or diabetes mellitus, 3.14 (95% CI, 1.45-6.83) times higher prevalence of proteinuria, and 2.23 (95% CI, 1.34-3.71) times higher prevalence of large waist circumference. Conclusions Both past and contemporary Na intakes were associated with higher cardiometabolic disease risk.

Dietary sodium restriction decreases urinary NGAL in older adults with moderately elevated systolic blood pressure free from chronic kidney disease

Increased aortic stiffness may contribute to kidney damage by transferring excessive flow pulsatility to susceptible renal microvasculature, leading to constriction or vessel loss. We previously demonstrated that 5 weeks of dietary sodium restriction (DSR) reduces large-elastic artery stiffness as well as blood pressure in healthy middle-aged/older adults with moderately elevated systolic blood pressure (SBP) who are free from chronic kidney disease (CKD). We hypothesized that DSR in this cohort would also reduce urinary concentrations of renal tubular injury biomarkers, which predict incident CKD in the general population. We performed a post hoc analysis using stored 24 hours urine samples collected in 13 participants as part of a randomized, double-blind, crossover clinical trial of DSR (low sodium (LS) target: 50 mmol/day; normal sodium (NS) target: 150 mmol/day). Participants were 61±2 (mean±SEM) years (8 M/5 F) with a baseline blood pressure of 139±2/82±2 mm Hg and an estimated glomerular filtration rate of 79±3 mL/min/1.73 m² Twenty-four hour urinary sodium excretion was reduced from 149±7 to 66±8 mmol/day during week 5. Despite having preserved kidney function, participants had a 31% reduction in urinary neutrophil gelatinase-associated lipocalin concentrations with just 5 weeks of DSR (LS: 2.8±0.6 vs NS: 4.2±0.8 ng/mL, p<0.05). Results were similar when normalized to urinary creatinine (urinary creatinine did not change between conditions). Concentrations of another kidney tubular injury biomarker, kidney injury molecule-1, were below the detectable limit in all but one sample. In conclusion, DSR reduces an established clinical biomarker of kidney tubular damage in adults with moderately elevated SBP who are free from prevalent kidney disease.

Dietary Assessment of Korean Non-dialysis Chronic Kidney Disease Patients with or without Diabetes

BACKGROUND

Dietary intervention at the early stage of chronic kidney disease (CKD) is important for preventing progression to the end-stage renal disease (ESRD). However, few studies have investigated dietary intake of CKD patients in non-dialysis stage. Therefore, we investigated the dietary intake of Korean non-dialysis CKD patients and aimed to establish baseline data for the development of dietary education and intervention strategies for CKD patients.

METHODS

Three hundred fifty CKD patients who visited Seoul National University Hospital outpatient clinic from February 2016 to January 2017 were recruited for this cross-sectional study. Subjects on dialysis and those who had undergone kidney transplantation were excluded. Dietary intake, demographic information, and biochemical characteristics of 256 subjects who completed three-day dietary records were analyzed. Subjects were divided into four groups based on diabetes mellitus (DM) (DM-CKD and Non-DM-CKD groups) and kidney function (Early-CKD and Late-CKD groups).

RESULTS

Total energy intake was lower in the Late-CKD group compared with the Early-CKD group. In men, carbohydrate intake was higher and protein and fat intakes tended to be lower in the Late-CKD group compared with the Early-CKD group. In women, carbohydrate intake tended to be lower in the DM-CKD group than the Non-DM-CKD group. Protein intake tended to be higher in the DM-CKD groups. Phosphorus and sodium intakes were higher in the DM-CKD groups compared with the Non-DM-CKD groups in women, and tended to be higher in the DM-CKD groups in men.

CONCLUSION

DM and kidney function affected energy and nutrient intakes. Subjects in the Late-CKD group consumed less energy than those in the Early-CKD group. Non-DM subjects seemed to restrict protein intake starting from the Early-CKD stage than subjects with DM. Subjects in this study had low energy and high sodium intakes compared with recommended levels. Protein intake was lower in advanced CKD patients, but their intake level was still higher than the recommendation. Dietary intervention strategies for non-dialysis CKD patients need to be customized depending on the presence of DM and kidney function.

Development of objective indicators for quantitative analysis of sodium intake: the sodium to potassium ratio of second-void urine is correlated with 24-hour urinary sodium excretion

BACKGROUND/OBJECTIVES

To date, sodium intake has been evaluated based on spot urine instead of 24-hour (hr) urine collection. Nevertheless, the optimal method for assessing daily sodium intake remains unclear.

SUBJECTS/METHODS

Fifteen male (age 32.7 ± 6.5 years) participants were offered 3 meals with a total of 9-10 g salt over 24 hours, and 24-hr urine was collected from the second-void urine of the first day to the first-void urine of the second day. Twenty-four-hr urinary sodium (24UNa) was estimated using Tanaka's equation and the Korean formula, and spot urine Na, potassium (K), chloride (Cl), urea nitrogen (UN), creatinine (Cr), specific gravity (SG) and osmolality (Osm) were measured. The ratios of urinary Na to other parameters were calculated, and correlations with total measured 24UNa were identified.

RESULTS

Average 24-hr urine volume was 1,403 ± 475 mL, and measured 24UNa was 143.9 ± 42.1 mEq (range, 87.1-239.4 mEq). Measured 24UNa was significantly correlated with urinary Na/UN (r = 0.560, P < 0.01), urinary Na/Osm (r = 0.510, P < 0.01), urinary Na/Cr (r = 0.392, P < 0.01), urinary Na/K (r = 0.290, P < 0.01), 24UNa estimated using Tanaka's equation (r = 0.452, P < 0.01) and the Korean formula (r = 0.414, P < 0.01), age (r = 0.548, P < 0.01), weight (r = 0.497, P < 0.01), and height (r = 0.393, P < 0.01) in all spot urine samples. Estimated 24UNa based on the second-void spot urine of the first day tended to be more closely correlated with measured 24UNa than were estimates from the other spot urine samples. The significant parameters correlated with the second-void urine of the first day were urinary Na/K (r = 0.647, P < 0.01), urinary Na/Cr (r = 0.558, P < 0.05), and estimated 24UNa using Tanaka's equation (r = 0.616, P < 0.05) and the Korean formula (r = 0.588, P < 0.05).

CONCLUSIONS

Second-void urine is more reliable than first-void urine for estimating 24UNa. Urinary Na/K in the second-void urine on the first day is significantly correlated with 24UNa. Further studies are needed to establish the most reliable index and the optimal time of urine sampling for predicting 24UNa.

Economic Modelling of Chronic Kidney Disease: A Systematic Literature Review to Inform Conceptual Model Design

BACKGROUND

Chronic kidney disease (CKD) is a progressive condition that leads to irreversible damage to the kidneys and is associated with an increased incidence of cardiovascular events and mortality. As novel interventions become available, estimates of economic and clinical outcomes are needed to guide payer reimbursement decisions.

OBJECTIVE

The aim of the present study was to systematically review published economic models that simulated long-term outcomes of kidney disease to inform cost-effectiveness evaluations of CKD treatments.

METHODS

The review was conducted across four databases (MEDLINE, Embase, the Cochrane library and EconLit) and health technology assessment agency websites. Relevant information on each model was extracted. Transition and mortality rates were also extracted to assess the choice of model parameterisation on disease progression by simulating patient's time with end-stage renal disease (ESRD) and time to ESRD/death. The incorporation of cardiovascular disease in a population with CKD was qualitatively assessed across identified models.

RESULTS

The search identified 101 models that met the criteria for inclusion. Models were classified into CKD models (n = 13), diabetes models with nephropathy (n = 48), ESRD-only models (n = 33) and cardiovascular models with CKD components (n = 7). Typically, published models utilised frameworks based on either (estimated or measured) glomerular filtration rate (GFR) or albuminuria, in line with clinical guideline recommendations for the diagnosis and monitoring of CKD. Generally, two core structures were identified, either a microsimulation model involving albuminuria or a Markov model utilising CKD stages and a linear GFR decline (although further variations on these model structures were also identified). Analysis of parameter variability in CKD disease progression suggested that mean time to ESRD/death was relatively consistent across model types (CKD models 28.2 years; diabetes models with nephropathy 24.6 years). When evaluating time with ESRD, CKD models predicted extended ESRD survival over diabetes models with nephropathy (mean time with ESRD 8.0 vs. 3.8 years).

DISCUSSION

This review provides an overview of how CKD is typically modelled. While common frameworks were identified, model structure varied, and no single model type was used for the modelling of patients with CKD. In addition, many of the current methods did not explicitly consider patient heterogeneity or underlying disease aetiology, except for diabetes. However, the variability of individual patients' GFR and albuminuria trajectories perhaps provides rationale for a model structure designed around the prediction of individual patients' GFR trajectories. Frameworks of future CKD models should be informed and justified based on clinical rationale and availability of data to ensure validity of model results. In addition, further clinical and observational research is warranted to provide a better understanding of prognostic factors and data sources to improve economic modelling accuracy in CKD.

Membranous Lupus Nephritis: A Clinical Review

Membranous lupus nephritis (MLN) (Class V lupus nephritis [LN]) is a distinct form of LN defined by the presence of subepithelial immune complex deposits seen on kidney biopsy. MLN is often associated with the nephrotic syndrome. The histology of MLN closely resembles that of idiopathic (primary) membranous nephropathy (pMN). However, MLN typically has abundant mesangial deposits that are absent in primary membranous nephropathy. The clinical presentation, management, and prognosis of MLN differ from that of the proliferative forms of LN (Class III, IV, or Mixed III/IV + V). Although immunosuppressive therapy is often warranted in MLN, the optimal treatment regimen remains unclear. Here we describe the clinical presentation, histologic features, and natural history of MLN. We also review the role of supportive treatment and discuss when to deploy immunosuppressive management in MLN.

Deleting Death and Dialysis: Conservative Care of Cardio-Vascular Risk and Kidney Function Loss in Chronic Kidney Disease (CKD)

The uremic syndrome, which is the clinical expression of chronic kidney disease (CKD), is a complex amalgam of accelerated aging and organ dysfunctions, whereby cardio-vascular disease plays a capital role. In this narrative review, we offer a summary of the current conservative (medical) treatment options for cardio-vascular and overall morbidity and mortality risk in CKD. Since the progression of CKD is also associated with a higher cardio-vascular risk, we summarize the interventions that may prevent the progression of CKD as well. We pay attention to established therapies, as well as to novel promising options. Approaches that have been considered are not limited to pharmacological approaches but take into account lifestyle measures and diet as well. We took as many randomized controlled hard endpoint outcome trials as possible into account, although observational studies and post hoc analyses were included where appropriate. We also considered health economic aspects. Based on this information, we constructed comprehensive tables summarizing the available therapeutic options and the number and kind of studies (controlled or not, contradictory outcomes or not) with regard to each approach. Our review underscores the scarcity of well-designed large controlled trials in CKD. Nevertheless, based on the controlled and observational data, a therapeutic algorithm can be developed for this complex and multifactorial condition. It is likely that interventions should be aimed at targeting several modifiable factors simultaneously.

Assessment of a Salt Reduction Intervention on Adult Population Salt Intake in Fiji

Reducing population salt intake is a global public health priority due to the potential to save lives and reduce the burden on the healthcare system through decreased blood pressure. This implementation science research project set out to measure salt consumption patterns and to assess the impact of a complex, multi-faceted intervention to reduce population salt intake in Fiji between 2012 and 2016. The intervention combined initiatives to engage food businesses to reduce salt in foods and meals with targeted consumer behavior change programs. There were 169 participants at baseline (response rate 28.2%) and 272 at 20 months (response rate 22.4%). The mean salt intake from 24-h urine samples was estimated to be 11.7 grams per day (g/d) at baseline and 10.3 g/d after 20 months (difference: -1.4 g/day, 95% CI -3.1 to 0.3, p = 0.115). Sub-analysis showed a statistically significant reduction in female salt intake in the Central Division but no differential impact in relation to age or ethnicity. Whilst the low response rate means it is not possible to draw firm conclusions about these changes, the population salt intake in Fiji, at 10.3 g/day, is still twice the World Health Organization's (WHO) recommended maximum intake. This project also assessed iodine intake levels in women of child-bearing age and found that they were within recommended guidelines. Existing policies and programs to reduce salt intake and prevent iodine deficiency need to be maintained or strengthened. Monitoring to assess changes in salt intake and to ensure that iodine levels remain adequate should be built into future surveys.

Nutrition Label Use and Sodium Intake in the U.S

INTRODUCTION

High sodium intake is a major risk factor for hypertension, but evidence is limited on which interventions are effective in reducing sodium consumption. This study examined the associations between frequent use of nutrition labels and daily sodium intake and the consumption of high-sodium foods in the U.S.

METHODS

Using the 2007-2008 and 2009-2010 Flexible Consumer Behavior Survey, this study compared sodium intake measured from the 24-hour dietary recalls, availability of salty snacks at home, and frequencies of eating frozen meals/pizzas between frequent (i.e., always or most of the time) and infrequent nutrition label users. Also, the study examined the association between nutrition label use and sodium-related dietary behaviors across different demographic and socioeconomic groups. Data were analyzed in 2016.

RESULTS

Frequent users of nutrition labels consumed 92.79 mg less sodium per day (95% CI= -160.21, -25.37), were less likely to always or most of the time have salty snacks available at home (OR=0.86, 95% CI=0.76, 0.97), but were just as likely to eat frozen meals or pizzas (incidence rate ratio=0.96, 95% CI=0.84, 1.08) compared with infrequent label users. The associations between nutrition label use and sodium intake differed considerably across age, gender, and socioeconomic groups.

CONCLUSIONS

Frequent use of nutrition labels appears to be associated with lower consumption of sodium and high-sodium foods in the U.S. Given this small reduction, interventions such as enhancing nutrition label use could be less effective if implemented without other strategies.

Effect of Crystal Shape and Aggregation of Calcium Oxalate Monohydrate on Cellular Toxicity in Renal Epithelial Cells

Renal epithelial cell injury is a key step in inducing kidney stone formation. This injury induced by crystallites with different shapes and aggregation states has been receiving minimal research attention. To compare the shape and aggregation effects of calcium oxalate crystals on their toxicity, we prepared calcium oxalate monohydrate (COM) crystals with the morphology of a hexagonal lozenge, a thin hexagonal lozenge, and their corresponding aggregates. We then compared their toxicities toward human kidney proximal tubular epithelial (HK-2) cells. All four shapes of COM crystals caused cell-membrane rupture, upregulated intracellular reactive oxygen, and decreased mitochondrial membrane potential. This series of phenomena ultimately led to necrotic cell death. The overall damage in cells was determined in terms of both exterior and interior damage. Crystals with a large Ca2+ ion-rich (1̅01) active face showed the greatest toxicity in HK-2 cells and the largest extent of adhesion onto the cell surface. Crystals with sharp edges easily caused cell-membrane ruptures. The aggregation of sharp crystals aggravated cell injury, whereas the aggregation of blunt crystals weakened cell injury. Therefore, crystal shapes and aggregation states were important factors that affected crystal toxicity in renal epithelial cells. All of these findings elucidated the relationship between the physical properties of crystals and cytotoxicity and provided theoretical references for inhibiting stone formation.

Kidney dysfunction in patients with pulmonary arterial hypertension

Pulmonary arterial hypertension (PH) and chronic kidney disease (CKD) both profoundly impact patient outcomes, whether as primary disease states or as co-morbid conditions. PH is a common co-morbidity in CKD and vice versa. A growing body of literature describes the epidemiology of PH secondary to chronic kidney disease and end-stage renal disease (ESRD) (WHO group 5 PH). But, there are only limited data on the epidemiology of kidney disease in group 1 PH (pulmonary arterial hypertension [PAH]). The purpose of this review is to summarize the current data on epidemiology and discuss potential disease mechanisms and management implications of kidney dysfunction in PAH. Kidney dysfunction, determined by serum creatinine or estimated glomerular filtration rate, is a frequent co-morbidity in PAH and impaired kidney function is a strong and independent predictor of mortality. Potential mechanisms of PAH affecting the kidneys are increased venous congestion, decreased cardiac output, and neurohormonal activation. On a molecular level, increased TGF-β signaling and increased levels of circulating cytokines could have the potential to worsen kidney function. Nephrotoxicity does not seem to be a common side effect of PAH-targeted therapy. Treatment implications for kidney disease in PAH include glycemic control, lifestyle modification, and potentially Renin-Angiotensin-Aldosterone System (RAAS) blockade.

Stirring the Pot: Can Dietary Modification Alleviate the Burden of CKD?

Diet is one of the largest modifiable risk factors for chronic kidney disease (CKD)-related death and disability. CKD is largely a progressive disease; however, it is increasingly appreciated that hallmarks of chronic kidney disease such as albuminuria can regress over time. The factors driving albuminuria resolution remain elusive. Since albuminuria is a strong risk factor for GFR loss, modifiable lifestyle factors that lead to an improvement in albuminuria would likely reduce the burden of CKD in high-risk individuals, such as patients with diabetes. Dietary therapy such as protein and sodium restriction has historically been used in the management of CKD. Evidence is emerging to indicate that other nutrients may influence kidney health, either through metabolic or haemodynamic pathways or via the modification of gut homeostasis. This review focuses on the role of diet in the pathogenesis and progression of CKD and discusses the latest findings related to the mechanisms of diet-induced kidney disease. It is possible that optimizing diet quality or restricting dietary intake could be harnessed as an adjunct therapy for CKD prevention or progression in susceptible individuals, thereby reducing the burden of CKD.

Assessment of dietary intake of children with chronic kidney disease

OBJECTIVE

Our aim was to characterize the nutrient intake of children with chronic kidney disease (CKD) relative to recommended intake levels.

METHODS

We conducted a cross-sectional study of dietary intake assessed by Food Frequency Questionnaire (FFQ) in The North American Chronic Kidney Disease in Children (CKiD) prospective cohort study. Nutrient intake was analyzed to estimate the daily consumption levels of various nutrients and compared with national guidelines for intake.

RESULTS

There were 658 FFQs available for analysis; 69.9 % of respondents were boys, with a median age [Interquartile range (IQR)] of 11 years (8-15). Median daily sodium, potassium, and phosphorus intake was 3089 mg (2294-4243), 2384 mg (1804-3076), and 1206 mg (894-1612) respectively. Sodium and phosphorus consumptions were higher than recommended in all age groups. Caloric intake decreased with dropping glomerular filtration rate (GFR) (p = 0.003). The median daily caloric intakes were 1307 kcal in male children 2-3 years old, 1875 kcal in children 4-8 years old, 1923 kcal in those 9-13 years old, and 2427 kcal in those 14-18 years old. Respective levels for girls were 1467 kcal, 1736 kcal, 1803 kcal, and 2281 kcal. Median protein intake exceeded recommended levels in all age groups, particularly among younger participants. Younger children were more likely than older children to exceed the recommended intakes for phosphorus (p < 0.001) and the age-specific recommended caloric intake (p < 0.001). Macronutrient distribution (carbohydrate:fat:protein) was consistent with recommendation.

CONCLUSIONS

Children in the CKiD cohort consumed more sodium, phosphorus, protein, and calories than recommended. The gap between actual consumption and recommendations indicates a need for improved nutritional counseling and monitoring.

Beyond Sodium, Phosphate and Potassium: Potential Dietary Interventions in Kidney Disease

People with kidney disease are advised to restrict individual nutrients, such as sodium, potassium, and phosphate, in line with current best practice guidelines. However, there is limited evidence to support the efficacy of single nutrient strategies, and compliance remains a challenge for clinicians to overcome. Many factors contribute to poor compliance with dietary prescriptions, including conflicting priorities for single nutrient restriction, the arduous self-monitoring required, and the health-related knock-on effects resulting from targeting these nutrients in isolation. This paper reviews the evidence base for the overall pattern of eating as a potential tool to deliver a diet intervention in which all the nutrients and foods work cumulatively and synergistically to improve clinical outcomes. These interventions may assist in kidney disease management and overcome these innate challenges that single nutrient interventions possess. Healthy dietary patterns are typically plant-based and lower in sodium and animal proteins. These patterns may have numerous mechanistic benefits for cardiovascular health in kidney disease, most notably through the increase in fruit, vegetables, and plant-based protein, as well as improved gut health through the increase in dietary fiber. The evidence to date on optimal dietary patterns points toward use of a predominantly plant-based diet, and suggests its adoption may improve clinical outcomes in dialysis patients. However, clinical trials are needed to determine whether these diet interventions are feasible, safe, and effective in this patient population.

Protecting the Kidney in Liver Transplant Recipients: Practice-Based Recommendations From the American Society of Transplantation Liver and Intestine Community of Practice

Both acute and chronic kidney disease are common after liver transplantation and result in significant morbidity and mortality. The introduction of the Model for End-stage Liver Disease score has directly correlated with an increased prevalence of perioperative renal dysfunction and the number of simultaneous liver-kidney transplantations performed. Kidney dysfunction in this population is typically multifactorial and related to preexisting conditions, pretransplantation renal injury, perioperative events, and posttransplantation nephrotoxic immunosuppressive therapies. The management of kidney disease after liver transplantation is challenging, as by the time the serum creatinine level is significantly elevated, few interventions affect the course of progression. Also, immunological factors such as antibody-mediated kidney rejection have become of greater interest given the rising liver-kidney transplant population. Therefore, this review, assembled by experts in the field and endorsed by the American Society of Transplantation Liver and Intestine Community of Practice, provides a critical assessment of measures of renal function and interventions aimed at preserving renal function early and late after liver and simultaneous liver-kidney transplantation. Key points and practice-based recommendations for the prevention and management of kidney injury in this population are provided to offer guidance for clinicians and identify gaps in knowledge for future investigations.

Sodium in feline nutrition

High sodium levels in cat food have been controversial for a long time. Nonetheless, high sodium levels are used to enhance water intake and urine volume, with the main objective of reducing the risk of urolithiasis. This article is a review of current evidence of the putative risks and benefits of high dietary sodium levels. Its secondary aim is to report a possible safe upper limit (SUL) for sodium intake. The first part of the manuscript is dedicated to sodium physiology, with a focus on the mechanisms of sodium homeostasis. In this respect, there is only few information regarding possible interactions with other minerals. Next, the authors address how sodium intake affects sodium balance; knowledge of these effects is critical to establish recommendations for sodium feed content. The authors then review the consequences of changes in sodium intake on feline health, including urolithiasis, blood pressure changes, cardiovascular alterations and kidney disease. According to recent, long-term studies, there is no evidence of any deleterious effect of dietary sodium levels as high as 740 mg/MJ metabolizable energy, which can therefore be considered the SUL based on current knowledge.

Renal evaluation in patients with type 2 diabetes mellitus and its association with diastolic blood pressure

Background: HbA1c is correlated with the estimated glomerular filtration rate (eGFR) and diastolic blood pressure (DBP). Our main objective was to evaluate the trend of biochemical and clinical variables, in relation to the eGFR in patients with type 2 diabetes mellitus (T2DM). Methods: This was a retrospective, longitudinal, and descriptive study, including patients with T2DM, who were cared for from January 2014 until December 2014, at the Clínica de Diabetes, Hospital Regional “Gral. Ignacio Zaragoza", ISSSTE, Mexico City, Mexico. eGFR was calculated using three formulas: the chronic kidney disease – epidemiology collaboration (CKD-EPI), Cockcroft-Gault, and modification of diet in renal disease (MDRD), during two periods of observation, 3 and 6 months. The results were compared by Student t tests or Wilcoxon-Mann-Whitney test depending on the variable distribution. Pearson correlation was employed to determine the relation between the eGFR determined with each formula and the analyzed variables. Results: The mean age was 56.5±11.3 years in the group of 3 months’ follow-up (n=110) and 57.1±13.8 years in the group of 6 months’ follow-up (n=47). In both groups, the formula with the lowest percentages of cases of CKD was CKD-EPI and the difference of this formula had a basal and final significant positive correlation with the DBP. Conclusion: The CKD-EPI formula showed the lowest percentages of cases of CKD in a short follow-up period, and its difference is consistently associated with the DBP, confirming the importance of controlling the later to mitigate the evolution to CKD.

Early chronic kidney disease: diagnosis, management and models of care

Chronic kidney disease (CKD) is prevalent in many countries, and the costs associated with the care of patients with end-stage renal disease (ESRD) are estimated to exceed US$1 trillion globally. The clinical and economic rationale for the design of timely and appropriate health system responses to limit the progression of CKD to ESRD is clear. Clinical care might improve if early-stage CKD with risk of progression to ESRD is differentiated from early-stage CKD that is unlikely to advance. The diagnostic tests that are currently used for CKD exhibit key limitations; therefore, additional research is required to increase awareness of the risk factors for CKD progression. Systems modelling can be used to evaluate the impact of different care models on CKD outcomes and costs. The US Indian Health Service has demonstrated that an integrated, system-wide approach can produce notable benefits on cardiovascular and renal health outcomes. Economic and clinical improvements might, therefore, be possible if CKD is reconceptualized as a part of primary care. This Review discusses which early CKD interventions are appropriate, the optimum time to provide clinical care, and the most suitable model of care to adopt.

Altered dietary salt intake for people with chronic kidney disease

BACKGROUND

Salt intake shows great promise as a modifiable risk factor for reducing heart disease incidence and delaying kidney function decline in people with chronic kidney disease (CKD). However, a clear consensus of the benefits of reducing salt in people with CKD is lacking.

OBJECTIVES

This review evaluated the benefits and harms of altering dietary salt intake in people with CKD.

SEARCH METHODS

We searched the Cochrane Renal Group's Specialised Register to 13 January 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 compared two or more levels of salt intake in people with any stage of CKD.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed studies for eligibility and conducted risk of bias evaluation. 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. Mean effect sizes were calculated using the random-effects models.

MAIN RESULTS

We included eight studies (24 reports, 258 participants). Because duration of the included studies was too short (1 to 26 weeks) to test the effect of salt restriction on endpoints such as mortality, cardiovascular events or CKD progression, changes in salt intake on blood pressure and other secondary risk factors were applied. Three studies were parallel RCTs and five were cross-over studies. Selection bias was low in five studies and unclear in three. Performance and detection biases were low in two studies and unclear in six. Attrition and reporting biases were low in four studies and unclear in four. One study had the potential for high carryover effect; three had high risk of bias from baseline characteristics (change of medication or diet) and two studies were industry funded.There was a significant reduction in 24 hour sodium excretion associated with low salt interventions (range 52 to 141 mmol) (8 studies, 258 participants: MD -105.86 mmol/d, 95% CI -119.20 to -92.51; I(2) = 51%). Reducing salt intake significantly reduced systolic blood pressure (8 studies, 258 participants: MD -8.75 mm Hg, 95% CI -11.33 to -6.16; I(2) = 0%) and diastolic blood pressure (8 studies, 258 participants: MD -3.70 mm Hg, 95% CI -5.09 to -2.30; I(2) = 0%). One study reported restricting salt intake reduced the risk of oedema by 56%. Salt restriction significantly increased plasma renin activity (2 studies, 71 participants: MD 1.08 ng/mL/h, 95% CI 0.51 to 1.65; I(2) = 0%) and serum aldosterone (2 studies, 71 participants: 6.20 ng/dL (95% CI 3.82 to 8.58; I(2) = 0%). Antihypertensive medication dosage was significantly reduced with a low salt diet (2 studies, 52 participants): RR 5.48, 95% CI 1.27 to 23.66; I(2) = 0%). There was no significant difference in eGFR (2 studies, 68 participants: MD -1.14 mL/min/1.73 m(2), 95% CI -4.38 to 2.11; I(2) = 0%), creatinine clearance (3 studies, 85 participants): MD -4.60 mL/min, 95% CI -11.78 to 2.57; I(2) = 0%), serum creatinine (5 studies, 151 participants: MD 5.14 µmol/L, 95% CI -8.98 to 19.26; I(2) = 59%) or body weight (5 studies, 139 participants: MD -1.46 kg; 95% CI -4.55 to 1.64; I(2) = 0%). There was no significant change in total cholesterol in relation to salt restriction (3 studies, 105 participants: MD -0.23 mmol/L, 95% CI -0.57 to 0.10; I(2) = 0%) or symptomatic hypotension (2 studies, 72 participants: RR 6.60, 95% CI 0.77 to 56.55; I(2) = 0%). Salt restriction significantly reduced urinary protein excretion in all studies that reported proteinuria as an outcome, however data could not be meta-analysed.

AUTHORS' CONCLUSIONS

We found a critical evidence gap in long-term effects of salt restriction in people with CKD that meant we were unable to determine the direct effects of sodium restriction on primary endpoints such as mortality and progression to end-stage kidney disease (ESKD). We found that salt reduction in people with CKD reduced blood pressure considerably and consistently reduced proteinuria. If such reductions could be maintained long-term, this effect may translate to clinically significant reductions in ESKD incidence and cardiovascular events. Research into the long-term effects of sodium-restricted diet for people with CKD is warranted, as is investigation into adherence to a low salt diet.

Association of the estimated 24-h urinary sodium excretion with albuminuria in adult koreans: the 2011 Korea National Health and Nutrition Examination Survey

BACKGROUND

Sodium intake and albuminuria have important roles in blood pressure and renal progression. Although their relationship has been reported, the results have not been consistent and all studies have examined small populations.

OBJECTIVE

This study investigated the role of the estimated 24-h urinary sodium excretion as a marker of sodium intake and albuminuria.

DESIGN

This investigation included 5,187 individuals age 19 years and older from a cross-sectional, nationally representative, stratified survey: The Korea National Health and Nutrition Examination Survey (KNHANES V-2), in 2011. Albuminuria was defined as a urinary albumin/creatinine ratio ≥30 mg/g. The 24-h urinary sodium excretion was estimated from a spot urine.

RESULTS

On classifying our participants into quartiles based on the estimated 24-h urinary sodium excretion, the prevalence of albuminuria increased with the 24-h urinary sodium excretion (5.3, 5.7, 7.5, and 11.8% in the first through fourth quartiles, respectively, p for trend <0.001). Even after adjusting for age, sex, diabetes, obesity, and hypertension, the significance persisted. In a multiple logistic regression analysis, the second and third quartiles of the estimated 24-h urinary sodium excretion were not associated with the presence of albuminuria with the first quartile as a control. However, the fourth quartile was significantly associated with the presence of albuminuria (odds ratio 1.61 [95% confidence interval 1.71-2.21], p = 0.003) after adjusting for age, sex, diabetes, obesity, and hypertension.

CONCLUSIONS

These findings suggest that salt intake is associated with the presence of albuminuria in the general Korean adult population.

Sodium intake and renal outcomes: a systematic review

BACKGROUND

Sodium intake is an important determinant of blood pressure; therefore, reduction of intake may be an attractive population-based target for chronic kidney disease (CKD) prevention. Most guidelines recommend sodium intake of < 2.3 g/day, based on limited evidence. We reviewed the association between sodium intake and renal outcomes.

METHODS

We reviewed cohort studies and clinical trials, which were retrieved by searching electronic databases, that evaluated the association between sodium intake/excretion and measures of renal function, proteinuria, or new need for dialysis.

RESULTS

Of 4,337 reviewed citations, seven (n = 8,129) were eligible, including six cohort studies (n = 7,942) and one clinical trial (n = 187). Four studies (n = 1,787) included patients with CKD. All four cohort studies reported that high intake (> 4.6 g/day) was associated with adverse outcomes (vs. moderate/low), while none reported an increased risk with moderate intake (vs. low). Three studies (n = 6,342) included patients without CKD. Two cohort studies (n = 6,155) reported opposing directions of association between low (vs. moderate) sodium intake and renal outcomes, and one clinical trial (n = 187) reported a benefit from low intake (vs. moderate) on proteinuria but an adverse effect on serum creatinine.

CONCLUSIONS

Available, but limited, evidence supports an association between high sodium intake (> 4.6g/day) and adverse outcomes. However, the association with low intake (vs. moderate) is uncertain, with inconsistent findings from cohort studies. There is urgent need to clarify the long-term efficacy and safety of currently recommended low sodium intake in patients with CKD.

Analysis of correlation between 24-hour urinary sodium and the degree of blood pressure control in patients with chronic kidney disease and non-chronic kidney disease

We investigated the association between 24-hr urinary sodium (24UNA) and adequacy of blood pressure (BP) control in patients with chronic kidney disease (CKD) and nonCKD. All data were collected retrospectively by accessing the electrical medical records in patients with 24-hr urine collection and serum creatinine. Enrolled 400 subjects were subgrouped by the amount of 24UNA, or CKD stage. The appropriate BP was defined as BP < 130/80 mmHg for subjects with proteinuria, and BP < 140/90 mmHg for subjects without proteinuria. The mean level of 24UNA was 166±76 mEq/day. The 24UNA group was an independently related factor to diastolic BP as a continuous variable. The rate of appropriate BP control in patients with proteinuria was highest in 24UNA <100 mEq/L (P=0.012). The odds to fail achievement of BP target in subjects with 24UNA≥90 mEq/day was 2.441 (1.249-4.772, P=0.009) higher than that of 24UNA <90 mEq/day among participants with proteinuria. There was difference in the amount of 24UNA between CKD and non-CKD except each stage of CKD group. In conclusion, salt intake estimated by 24-hr urine sodium excretion is a risk factor to achieve appropriate BP control.

Kidney transplant access in the Southeast: view from the bottom

The Southeastern region of the United States has the highest burden of end-stage renal disease (ESRD) but the lowest rates of kidney transplantation in the nation. There are many patient-, dialysis facility-, ESRD Network- and health system-level barriers that contribute to this regional disparity. Compared to the rest of the nation, the Southeast has a larger population of African-Americans and higher poverty, as well as more prevalent ESRD risk factors including hypertension, obesity and diabetes. Dialysis facilities--where ESRD patients receive the majority of their healthcare--play an important role in transplant access. Identifying characteristics of individual dialysis units with low rates of kidney transplantation, such as understaffing or for-profit status, can help identify targets for quality improvement initiatives. Geographic differences across the country can identify opportunities to increase funding for healthcare resources in proportion to patient and disease burden. Focusing interventions among dialysis facilities with the lowest transplant rates within the Southeast, such as provider and patient education, has the potential to increase referrals for kidney transplantation, leading to higher rates of kidney transplants in this region. Referral for transplantation should be measured on a national level to monitor disparities in early access to transplantation. Transplant centers have an obligation to assist underserved populations in ensuring equity in access to services. Policies that improve access to care for patients, such as the Affordable Care Act and Medicaid expansion, are particularly important for Southern states and may alleviate geographic disparities.

Hyperosmolarity drives hypertension and CKD--water and salt revisited

An epidemic of chronic kidney disease (CKD) in Mesoamerica is providing new insights into the mechanisms by which salt and water might drive hypertension and CKD. Increasingly, evidence suggests that recurrent dehydration and salt loss might be a mechanism that causes CKD, and experimental studies suggest a key role for increased plasma osmolarity in activating both intrarenal (polyol-fructokinase) and extrarenal (vasopressin) pathways that drive renal injury. Thus, we propose that water and salt might influence blood pressure and kidney disease through the timing and combination of their intake, which affect plasma osmolarity as well as intrarenal and extrarenal mechanisms of renal injury. The type of fluid intake might also be important, as fluids containing fructose can trigger activation of these pathways. Future studies should investigate the effects of salt, sugar and fluid intake on plasma osmolarity as a potential pathogenetic mechanism in renal injury and high blood pressure.

Prevention, detection and management of early chronic kidney disease: a systematic review of clinical practice guidelines

AIM

In response to the increase in Chronic Kidney Disease (CKD) worldwide, several professional organizations have developed clinical practice guidelines to manage and prevent its progression. This study aims to compare the scope, content and consistency of published guidelines on CKD stages I-III.

METHODS

Electronic databases of the medical literature, guideline organizations, and the websites of nephrology societies were searched to November 2011. The Appraisal of Guidelines for Research and Evaluation (AGREE) II instrument and textual synthesis was used to appraise and compare recommendations.

RESULTS

One consensus statement and 15 guidelines were identified and included. Methodological rigour across guidelines was variable, with average domain scores ranging from 24% to 95%. For detection of CKD, all guidelines recommended estimated glomerular filtration rate measurement, some also recommended serum creatinine and dipstick urinalysis. The recommended protein and albumin creatinine ratios and proteinuria definition thresholds varied (>150-300 mg/day to >500 mg/day). Blood pressure targets ranged (<125/75 to <140/90 mmHg). Angiotensin converting enzyme inhibitor and angiotensin receptor blockers were recommended for hypertension, as combined or as monotherapy. Protein intake recommendations varied (no restriction or 0.75 g/kg per day-1.0 g/kg per day). Salt intake of 6 g/day was recommended by most. Psychosocial support and education were recommended by few but specific strategies were absent.

CONCLUSION

CKD guidelines were consistent in scope but were variable with respect to their recommendations, coverage and methodological quality. To promote effective primary and secondary prevention of CKD, regularly updated guidelines that are based on the best available evidence and augmented with healthcare context-specific strategies for implementation are warranted.

Salt Loading Promotes Kidney Injury via Fibrosis in Young Female Ren2 Rats

BACKGROUND/AIMS

It is increasingly recognized that there is sexual dimorphism in kidney disease progression; however, this disparity is lost in the presence of diabetes where women progress at a similar rate to men. The renin-angiotensin-aldosterone system (RAAS) is known to regulate diabetes-induced kidney injury, and recent literature would suggest that gender differences exist in RAAS-dependent responses in the kidney. In this regard, these gender differences may be overcome by excessive salt intake. Thereby, we hypothesized that salt would promote proteinuria in transgenic female rats under conditions of excess tissue angiotensin (Ang) II and circulating aldosterone.

MATERIALS AND METHODS

We utilized young female transgenic (mRen2)27 (Ren2) rats and Sprague-Dawley (SD) littermates and fed a high-salt diet (4%) over 3 weeks.

RESULTS

Compared to SD and Ren2 controls, female Ren2 rats fed a high-salt diet displayed increases in proteinuria, periarterial and interstitial fibrosis as well as ultrastructural evidence of basement membrane thickening, loss of mitochondrial elongation, mitochondrial fragmentation and attenuation of basilar canalicular infoldings. These findings occurred temporally with increases in transforming growth factor-β but not indices of oxidant stress.

CONCLUSIONS

Our current data suggest that a diet high in salt promotes progressive kidney injury as measured by proteinuria and fibrosis associated with transforming growth factor-β under conditions of excess tissue Ang II and circulating aldosterone.

Low dietary sodium in diabetes nephropathy

In a meta-analysis that investigated the effects of dietary sodium restriction in diabetes nephropathy, although blood pressure fell, there were significant increases in plasma renin and aldosterone levels. In this article, we hypothesise that in diabetic nephropathy, ACE-I or ARB treatment attenuates any rise in RAS hormones that might result from dietary salt restriction and that the beneficial effects of the salt restriction such as a lower blood pressure outweigh any potentially negative consequences of RAS activation such as a rise in intraglomerular pressure because of the synergistic effects of sodium restriction and RAS antagonist therapy.

Development and validation of a dietary screening tool for high sodium consumption in Australian renal patients

OBJECTIVE

The study objective was to develop and evaluate the feasibility and validity of a self-administered Scored Sodium Questionnaire (SSQ) for use in the routine clinical care of Australian chronic kidney disease (CKD) patients.

DESIGN AND METHODS

The study took place in community-based outreach clinics using a multidisciplinary model of care. Assessment of sources of dietary sodium intake in the target population used comprehensive diet history interviews (Phase 1) to inform development of a 10-item food frequency questionnaire that was scored and validated using 24-hour urinary sodium and 2 alternative dietary intake methods (Phase 2). Subjects were adults with CKD Stages 3 to 5 (Phase 1 n = 30; Phase 2 n = 47).

INTERVENTION

On a single day, participants (n = 47) completed the SSQ, feasibility survey, 24-hour urine collection, and 24-hour food record. A diet history interview was also conducted to confirm sodium intake on the day of data collection reflected habitual intake.

MAIN OUTCOME MEASURE

Validity of the SSQ score was confirmed by correlation with 24-hour urine sodium. Validity of a cutpoint on the SSQ score to correctly identify high- versus low-sodium consumers was confirmed by receiver operating characteristic curve analysis: area under the curve, sensitivity, and specificity.

RESULTS

Total SSQ score correlated significantly with 24-hour urine sodium (r = 0.371; P = .031). Correlation between 24-hour food record and diet history sodium confirmed consumption on the data collection day reflected habitual intake (r = 0.701; P ≤ .001). A cutpoint of 65 or greater on the SSQ score was confirmed as valid to identify high-sodium consumers: area under the curve 0.713, sensitivity 61%, and specificity 82%.

CONCLUSION

The SSQ is feasible and valid to assess habitual sodium intake in the Australian CKD population and to identify high-sodium consumers for referral to individualized counseling on a low-sodium diet.

The Oxford Renal (OxRen) cross-sectional study of chronic kidney disease in the UK

INTRODUCTION

Chronic kidney disease (CKD) diagnosed with objective measures of kidney damage and function has been recognised as a major public health burden. Independent of age, sex, ethnicity and comorbidity, strong associations exist between cardiovascular disease, mortality, morbidity and CKD, defined by reduced glomerular filtration rate and increased urinary albumin excretion. Detection of CKD within the population is therefore a priority for health systems.

METHODS AND ANALYSIS

15 000 patients aged 60 years or over meeting the inclusion criteria will be invited to the study. Recruitment will be stratified to represent the distribution of socioeconomic position in the UK general population. Patients will be excluded if terminally ill (expected survival <1 year), or if they have received a solid organ transplant. Patients will attend up to two screening visits, to determine if they have CKD, followed by an assessment visit where demographic and physiological parameters will be recorded alongside questionnaires on exercise, diet, cognitive assessment and quality of life. Blood and urine specimens will be taken for immediate routine assays as well as for freezing pending peptide and genetic studies. Patients will have office and home blood pressure measurements as well as pulse wave velocity assessment. Healthcare costs of screening and subsequent monitoring will be calculated.

ETHICS AND DISSEMINATION

The protocol and related documents have been approved by NRES Committee South Central-Oxford B-Reference 13/SC/0020.

Achieving salt restriction in chronic kidney disease

There is consistent evidence linking excessive dietary sodium intake to risk factors for cardiovascular disease and chronic kidney disease (CKD) progression in CKD patients; however, additional research is needed. In research trials and clinical practice, implementing and monitoring sodium intake present significant challenges. Epidemiological studies have shown that sodium intake remains high, and intervention studies have reported varied success with participant adherence to a sodium-restricted diet. Examining barriers to sodium restriction, as well as factors that predict adherence to a low sodium diet, can aid researchers and clinicians in implementing a sodium-restricted diet. In this paper, we critically review methods for measuring sodium intake with a specific focus on CKD patients, appraise dietary adherence, and factors that have optimized sodium restriction in key research trials and discuss barriers to sodium restriction and factors that must be considered when recommending a sodium-restricted diet.