Uric acid is not associated with decline in renal function or time to renal replacement therapy initiation in a referred cohort of patients with Stage III, IV and V chronic kidney disease

Management of de novo nephrolithiasis after kidney transplantation: a comprehensive review from the European Renal Association CKD-MBD working group

The lifetime incidence of kidney stones is 6%-12% in the general population. Nephrolithiasis is a known cause of acute and chronic kidney injury, mediated via obstructive uropathy or crystal-induced nephropathy, and several modifiable and non-modifiable genetic and lifestyle causes have been described. Evidence for epidemiology and management of nephrolithiasis after kidney transplantation is limited by a low number of publications, small study sizes and short observational periods. Denervation of the kidney and ureter graft greatly reduces symptomatology of kidney stones in transplant recipients, which may contribute to a considerable underdiagnosis. Thus, reported prevalence rates of 1%-2% after kidney transplantation and the lack of adverse effects on allograft function and survival should be interpreted with caution. In this narrative review we summarize current state-of-the-art knowledge regarding epidemiology, clinical presentation, diagnosis, prevention and therapy of nephrolithiasis after kidney transplantation, including management of asymptomatic stone disease in kidney donors. Our aim is to strengthen clinical nephrologists who treat kidney transplant recipients in informed decision-making regarding management of kidney stones. Available evidence, supporting both surgical and medical treatment and prevention of kidney stones, is presented and critically discussed. The specific anatomy of the transplanted kidney and urinary tract requires deviation from established interventional approaches for nephrolithiasis in native kidneys. Also, pharmacological and lifestyle changes may need adaptation to the specific situation of kidney transplant recipients. Finally, we point out current knowledge gaps and the need for additional evidence from future studies.

Sex differences in the association between urate metabolism and kidney outcomes in patients with chronic kidney disease

BACKGROUND

The association between serum uric acid (SUA) concentration and kidney outcomes in patients with chronic kidney disease (CKD) is controversial. Furthermore, there are no reports regarding the association of clearance of uric acid (CUA) with kidney outcomes. We aimed to determine whether SUA or CUA was associated with kidney outcomes in patients with CKD stratified by sex.

METHODS

The present prospective study was conducted in 815 patients (523 men and 292 women) with CKD. The participants were divided into quartiles (Q1-Q4) of SUA or CUA for each sex. Endpoints were defined as a composite of doubling of serum creatinine (SCr), end-stage kidney disease (ESKD), or death (outcome 1) and a composite of doubling of SCr or ESKD (outcome 2).

RESULTS

During a median follow-up of 2.5 years, outcomes 1 and 2 occurred in 363 and 321 patients, respectively. Multivariable-adjusted Cox analyses showed that in men, the hazard ratios (95% confidence intervals) for outcome 1 of Q1, Q2, and Q3 of CUA were 2.08 (1.18-3.70), 2.03 (1.22-3.39), and 1.85 (1.17-2.95), respectively, compared with Q4. Additionally, there were similar associations between lower CUA quartiles and outcome 2 in men. However, no associations between SUA and either outcome were observed in men. Conversely, in women, neither SUA nor CUA was associated with an outcome.

CONCLUSION

In CKD, lower CUA was independently associated with poor kidney outcomes only in men, and in both sexes, there was no association of SUA with kidney outcomes.

Longitudinal uric acid has nonlinear association with kidney failure and mortality in chronic kidney disease

We investigated the shape of the relationship between longitudinal uric acid (UA) and the hazard of kidney failure and death in chronic kidney disease (CKD) patients, and attempted to identify thresholds associated with increased hazards. We included CKD stage 3-5 patients from the CKD-REIN cohort with one serum UA measurement at cohort entry. We used cause-specific multivariate Cox models including a spline function of current values of UA (cUA), estimated from a separate linear mixed model. We followed 2781 patients (66% men, median age, 69 years) for a median of 3.2 years with a median of five longitudinal UA measures per patient. The hazard of kidney failure increased with increasing cUA, with a plateau between 6 and 10 mg/dl and a sharp increase above 11 mg/dl. The hazard of death had a U-shape relationship with cUA, with a hazard twice higher for 3 or 11 mg/dl, compared to 5 mg/dl. In CKD patients, our results indicate that UA above 10 mg/dl is a strong risk marker for kidney failure and death and that low UA levels below 5 mg/dl are associated with death before kidney failure.

The Association of Excess Body Weight with Risk of ESKD Is Mediated Through Insulin Resistance, Hypertension, and Hyperuricemia

Background

Insulin resistance, hypertension, hyperuricemia, and hypercholesterolemia are hypothesized to be important intermediates in the relationship between excess body weight and CKD risk. However, the magnitude of the total effect of excess body weight on ESKD mediated through these four pathways remains to be quantified.

Methods

We applied a model for analysis of correlated mediators to population-based data from 100,269 Austrian individuals (mean age 46.4 years). Association of body mass index (BMI) was coalesced with ESKD risk into direct association. Indirect associations were mediated through the triglyceride-glucose (TyG) index (as an indicator of insulin resistance), mean arterial pressure (MAP), uric acid (UA), and total cholesterol (TC).

Results

Mean follow-up was 23.1 years with 463 (0.5%) incident ESKD cases. An unhealthy metabolic profile (prevalence 32.4%) was associated with a markedly increased ESKD risk (multivariably adjusted hazard ratio (aHR), 3.57; 95% CI, 2.89 to 4.40), independent of BMI. A 5-kg/m2 higher BMI was associated with a 57% increased ESKD risk (aHRtotal association, 1.57; 1.38 to 1.77). Of this association, 99% (76% to 140%) arose from all mediators jointly; 33% (22% to 49%) through TyG index; 34% (24% to 50%) through MAP; 30% (21% to 45%) through UA; and 2% (−1% to 4%) through TC. The remaining direct association was nonsignificant (aHRdirect association, 1.01; 0.88 to 1.14).

Conclusions

TyG index, MAP, and UA, but not TC, mediate the association of BMI with ESKD in middle-aged adults. Our findings highlight that in addition to weight reduction, the control of metabolic risk factors might be essential in mitigating the adverse effects of BMI on kidney function.

A systematic review and meta-analysis of the association between uric acid levels and chronic kidney disease

The function of uric acid (UA) in the genesis and evolution of chronic kidney disease (CKD) has motivated numerous studies, but the results remain inconclusive. We sought to conduct a systematic review and meta-analysis of cohort studies aiming to analyze the association of UA levels with the incidence and progression of CKD. Pubmed/Medline, Lilacs/Bireme and Web of Science were searched to identify eligible studies, following the PRISMA protocol. Data were presented for CKD incidence and progression separately. For the meta-analysis, studies with data stratified by subgroups according to serum UA levels were selected. The inverse variance-weighted random effects model was used to generate a combined effect estimate. Meta-regressions were performed to identify the causes of heterogeneity. The Newcastle-Ottawa Scale was used to assess the risk of bias. The publication bias was tested by funnel plot and Egger's test. Eighteen CKD incidence studies (n = 398,663) and six CKD progression studies (n = 13,575) were included. An inverse relationship was observed between UA levels and protection from CKD incidence and progression. Lower UA levels were protective for the risk of CKD incidence (RR 0.65 [95% CI 0.56-0.75]) and progression (RR 0.55 [95% CI 0.44-0.68]). UA seems to be implicated both in the genesis of CKD and its evolution.

The Association between Baseline, Changes in Uric Acid, and Renal Failure in the Elderly Chinese Individuals: A Prospective Study with a 3-Year Follow-Up

OBJECTIVE

The objective is to find whether serum uric acid (SUA) levels are associated with the progression of chronic kidney disease (CKD) remains uncertain, and follow-up data among the elderly population are relatively lacking, especially in China. The aim of the present study was to reveal the association between baseline SUA levels, changes in SUA levels, and renal failure in Chinese elderly adults.

METHODS

In this retrospective cohort study, 425 subjects (age range 71-100 years) were analyzed and divided into quartiles based on baseline SUA levels (Q1: <4.8; Q2: <5.7; Q3: <6.5; and Q4: ≥6.5 mg/dl). CKD was defined as estimated glomerular filtration rate (eGFR) < 60 ml/min/1.73 m². We used multiple linear and logistic regressions to compare the risk of renal dysfunction among the different SUA level groups.

RESULTS

The prevalence of hyperuricemia was 24.24% in the elderly subjects. In the multivariable analysis, the odds ratio (OR) for the development of CKD increased with the increase in SUA quartiles at baseline (1.00 vs. 1.79 (95% CI, 1.00-3.22), 3.4 (95% CI, 1.79-6.47), and 6.79 (95% CI, 3.45-13.75), respectively; P for linear trend <0.001), and a per unit increase in baseline SUA levels gave an OR of 1.76 (95% CI, 1.45-2.14) for renal failure. At the same time, a change in SUA levels had a stronger inverse correlation with a change in eGFR in females (r = -0.318, P < 0.001) than in males (r = -0.187, P < 0.01). In a linear regression analysis, a 1 mg/dl increase in SUA levels was associated with an additional 1.25 (95% CI, -1.83 to -0.67) ml/min/1.73 m² decrease in eGFR over a 3-year period.

CONCLUSION

Elevated baseline SUA levels and changes in SUA levels were associated with a decline in eGFR and an increased risk of CKD in an elderly Chinese population.

Different clinical impact of hyperuricemia according to etiologies of chronic kidney disease: Gonryo Study

BACKGROUND

Hyperuricemia is highly prevalent in chronic kidney disease (CKD) patients, but the evidence for a relationship between uric acid (UA) and clinical outcomes in CKD patients is limited and inconsistent. We hypothesized that UA has a different impact on clinical outcomes according to the underlying disease causing CKD.

METHODS

This study prospectively investigated the associations between UA and renal and non-renal outcomes according to the underlying disease causing CKD in 2,797 Japanese patients under the care of nephrologists. The patients were categorized into four groups: primary renal disease (n = 1306), hypertensive nephropathy (n = 467), diabetic nephropathy (n = 275), and other nephropathy (n = 749). The renal outcome was defined as end-stage renal disease (ESRD), and the non-renal outcome was defined as a composite endpoint of cardiovascular events (CVEs) and all-cause mortality.

RESULTS

During a median 4.8-year follow-up, 359 (12.8%) patients reached the renal outcome, and 260 (9.3%) reached the non-renal outcome. In the all-patient analysis, hyperuricemia was not associated with the risks for renal and non-renal outcomes, but in primary renal disease (PRD) and hypertensive renal disease (HTN) patients, hyperuricemia was significantly associated with non-renal outcomes. Per 1 mg/dl higher UA level, multivariable adjusted hazard ratio was 1.248 (95% CI: 1.003 to 1.553) for PRD, and 1.250 (1.035 to 1.510) for HTN. Allopurinol did not reduce the risks for renal and non-renal outcomes, both in all patients and in the subgroup analysis.

CONCLUSIONS

The effect of hyperuricemia on clinical outcomes in CKD patients varies according to the underlying disease causing CKD. Hyperuricemia is an independent risk factor for non-renal outcomes in primary renal disease and hypertensive renal disease patients. Allopurinol did not decrease the risks for renal and non-renal outcomes.

[Asymptomatic Hyperuricemia and Risk Of Cardiovascular and Renal Diseases]

Asymptomatic hyperuricemia (HU) is common in the population and significantly contributes to the general cardiovascular risk. Despite extensive study of this condition there is still no conclusive answers to questions about detection of asymptomatic HU and its effect on the risk for development and progression of cardiovascular and kidney diseases. This review summarizes key information about these issues, which has been accumulated by the present time.

The Value of a Cystatin C-based Estimated Glomerular Filtration Rate for Cardiovascular Assessment in a General Japanese Population: Results From the Iwate Tohoku Medical Megabank Project

BACKGROUND

Epidemiological studies have shown that high circulating cystatin C is associated with a risk of cardiovascular disease (CVD) independent of creatinine-based renal function measurements. The present study investigated the comparison between the cystatin C-based estimated glomerular filtration rate (GFRcys) and creatinine-based GFR (GFRcr) to determine whether these measurements are associated with CV biomarkers and elevated CVD risk in a general Japanese population.

METHODS

The Iwate Tohoku Medical Megabank Organization pooled individual participant data from a general population-based cohort study in Iwate prefecture (n = 29,375). Chronic kidney disease (CKD) was estimated using the GFRcys, GFRcr and the urine albumin-to-creatinine ratio (UACR).

RESULTS

The prevalence of CKD in the participants was found to be higher based on the GFRcr than the GFRcys. Multiple variable analyses after adjusting for baseline characteristics showed that high-sensitivity cardiac troponin T (hs-cTnT) and N-terminal pro-brain natriuretic peptide (NT-proBNP) were associated with the GFRcys. The area under the receiver operating characteristic (AUROC) curve for identifying individuals with a high Suita score was higher for the GFRcys (AUROC = 0.68) than it was for the GFRcr (AUROC = 0.64, P < 0.001). The GFRcys provided reclassification improvement for the CVD risk prediction model by the GFRcr (net reclassification improvement = 0.341; integrated discrimination improvement = 0.018, respectively, P < 0.001).

CONCLUSIONS

The GFRcys is more closely associated with CV biomarkers, including hs-cTnT and NT-proBNP levels, and a high Suita score than the GFRcr, and it provides additional value in the assessment of CVD risk using GFRcr.

Effects of uric acid on kidney function decline differ depending on baseline kidney function in type 2 diabetic patients

BACKGROUND

Most existing data regarding effects of uric acid (UA) on diabetic kidney disease have considered patients with preserved kidney function. We examined a hypothesis that there are differences in the effects of serum UA levels on the decline in kidney function depending on baseline kidney function in diabetic patients.

METHODS

In this historical cohort study, 7033 type 2 diabetic patients were analyzed and classified into two groups as follows: nonchronic kidney disease (non-CKD), with an estimated glomerular filtration rate (eGFR) ≥60 mL/min/1.73 m2 (n = 4994), and CKD, with an eGFR <60 mL/min/1.73 m2 (n = 2039). The composite endpoint was a ≥30% decrease in eGFR from baseline or the initiation of renal replacement therapy. The hazard ratio (HR) of serum UA levels at baseline was estimated using multivariate Cox proportional hazards models.

RESULTS

There was a significant interaction between UA levels and baseline eGFR with respect to the endpoint (P < 0.001). The HRs of 1 mg/dL increase in UA levels were 1.13 [95% confidence interval (CI) 1.05-1.22, P = 0.002] and 0.93 (95% CI 0.88-0.99, P = 0.02) in the non-CKD and CKD groups, respectively. When patients were classified by quintile of UA levels, the HRs of those in the 5th quintile (versus 1st quintile) were 1.64 (95% CI 1.23-2.18, P < 0.001) and 0.76 (95% CI 0.58-0.99, P = 0.05) in the non-CKD and CKD groups, respectively.

CONCLUSIONS

The effects of UA on kidney function decline might differ depending on baseline kidney function in type 2 diabetic patients. High UA levels are the prognostic factor only in patients with preserved kidney function.

Uric acid in CKD: has the jury come to the verdict?

Epidemiological studies show that hyperuricemia independently predicts the development of chronic kidney disease (CKD) in individuals with normal kidney function both in the general population and in subjects with diabetes. As a matter of fact, an unfavorable role of uric acid may somewhat be harder to identify in the context of multiple risk factors and pathogenetic mechanisms typical of overt CKD such as proteinuria and high blood pressure. Although the discrepancy in clinical results could mean that urate lowering treatment does not provide a constant benefit in all patients with hyperuricemia and CKD, we believe that the inconsistency in the results from available meta-analysis is mainly due to inadequate sample size, short follow-up times and heterogeneity in study design characterizing the randomized controlled trials included in the analyses. Therefore, available data support the view that hyperuricemia has a damaging impact on kidney function, while preliminary evidence suggests that treatment of so-called asymptomatic hyperuricemia may be helpful to slow or delay the progression of chronic kidney.

Uric acid and left ventricular hypertrophy: another relationship in hemodialysis patients

Background

The impact of serum uric acid (UA) on morbidity and mortality in hemodialysis (HD) patients is quite controversial in relation to the general population. The aim of this study was to evaluate the association of serum UA with both mortality and left ventricular hypertrophy (LVH) in HD patients.

Methods

This longitudinal study enrolled 225 prevalent HD patients who were classified into three groups according to their follow-up-averaged UA (FA-UA) levels: low FA-UA (FA-UA <400 µmol/L), intermediate/reference FA-UA (FA-UA between 400 and 450 µmol/L) and high FA-UA (FA-UA >450 µmol/L). Echocardiography was performed on a nondialysis day and the presence of LVH was defined based on a left ventricular mass index (LVMI) >131 and >100 g/m² for men and women, respectively. The patients were followed during a 60-month period.

Results

The mean FA-UA level was 425 ± 59 µmol/L (range 294–620). There was a consistent association of higher FA-UA with better nutritional status (higher body mass index, normalized protein catabolic rate, creatinine, albumin and phosphorus), higher hemoglobin, but lower C-reactive protein and LVMI. During the 5-year follow-up, 81 patients died (36%) and the main causes of death were cardiovascular (CV) related (70%). When compared with the reference group, the hazard ratio for all-cause mortality was 1.75 [95% confidence interval (CI) 1.02–2.98; P = 0.041] in the low FA-UA group, but there was no significant association with the high FA-UA group. In contrast, FA-UA did not show an association with CV mortality neither with the lower nor with the high FA-UA group. The unadjusted odds ratio (OR) of LVH risk in the low FA-UA compared with the reference FA-UA group was 3.11 (95% CI 1.38–7.05; P = 0.006), and after adjustment for age, gender, diabetes and CV disease, ORs for LVH persisted significantly only in the low FA-UA group [OR 2.82 (95% CI 1.16–6.88,); P = 0.002].

Conclusions

Low serum UA is a mortality risk factor and is associated with LVH in HD patients. These results are in contrast with the association of UA in the general population and should be the subject of further research.

Effects of hyperuricemia on incident renal replacement therapy and all-cause mortality among patients with chronic kidney disease stages 3-5: a retrospective cohort study

BACKGROUND

Findings regarding the effects of hyperuricemia on renal function and mortality have been inconsistent.

OBJECTIVES

To investigate the effects of hyperuricemia on incident renal replacement therapy and all-cause mortality among patients with chronic kidney disease (CKD).

DESIGN AND SETTING

Retrospective cohort study conducted in a medical center in Taiwan.

METHODS

Patients with CKD in stages 3-5, without histories of renal replacement therapy, were consecutively recruited from 2007 to 2013. Their medical history, laboratory and medication data were collected from hospital records. The mean uric acid level in the first year of follow-up was used for analyses. Hyperuricemia was defined as mean uric acid level ≥ 7.0 mg/dl in men or ≥ 6.0 mg/dl in women. The primary outcomes were incident renal replacement therapy and all-cause mortality, and these data were retrospectively collected from hospital records until the end of 2015.

RESULTS

A total of 4,381 patients were analyzed (mean age 71.0 ± 14.8 years; males 62.7%), and the median follow-up period was 2.5 years. Patients with hyperuricemia were at increased risk of incident renal replacement therapy and all-cause mortality, especially those with CKD in stages 4 or 5. Compared with patients with CKD in stage 3 and normouricemia, patients with CKD in stages 4 or 5 presented significantly higher risk of all-cause mortality only if they had hyperuricemia.

CONCLUSIONS

In patients with CKD in stages 3-5, hyperuricemia was associated with higher risk of incident renal replacement therapy and all-cause mortality. Whether treatment with uric acid-lowering drugs in these patients would improve their outcomes merits further investigation.

Decline in serum uric acid predicts higher risk for mortality in peritoneal dialysis patients-a propensity score analysis

BACKGROUND

The level of serum uric acid (SUA) in treatment follow-up is associated with mortality in peritoneal dialysis (PD) patients, but it remains unknown if the longitudinal change in SUA affects mortality.

METHODS

309 PD patients who were not using UA-lowering agents were enrolled. The longitudinal change in SUA was estimated by comparing the values between the run-in and follow-up periods. Based the calculated values, the patients were divided into SUA decliner and SUA non-decliner. A propensity score (PS) was calculated using the parameters measured in run-in period. After PS matching, the time-to-event analysis was performed for all-cause death.

RESULTS

After PS matching, 86 patients of each group were left. A higher mortality of 19/86 existed in SUA decliner compared with SUA non-decliner which is 3/86 (p < 0.001). Kaplan-Meier analysis in sub-cohort showed worse survival in the SUA decliner. Standard and stratified Cox regression analysis both showed SUA decline to be an independent risk factor for all-cause death in PD patients.

CONCLUSIONS

The decline in SUA in the follow-up may predict the all-cause mortality of PD patients, the reason of which may result from reducing scavenging effects of SUA or may reflect general condition. More studies need to be done.

Serum uric acid to creatinine ratio is a useful predictor of renal dysfunction among diabetic persons

BACKGROUND

Serum uric acid (SUA) has been shown to be a predictor of renal disease progression in most but not all studies. This study aims to test whether renal function-normalized SUA {i.e, SUA/creatinine (Cr) ratio} is a predictor of decreased renal function among diabetic patients.

METHODS

The subjects comprised 185 men aged 72 ± 11 (mean ± standard deviation) years and 175 women aged 77 ± 10 years from a rural hospital. We examined the relationship between SUA/creatinine (Cr) ratio and renal function evaluated by estimated glomerular filtration rate (eGFR) using the Modification of Diet in Renal Disease Study Group equation.

RESULTS

Annual eGFR decline rate was significantly increased with increased tertile of baseline SUA/Cr ratio (p = 0.011), and prevalence of the rapid progression types (≥3.0 ml/min/1.73 m²/year) was significantly higher in the second and third tertile (≥7,21) of baseline SUA/Cr ratio than the first tertile (<5.86) (p = 0.032). Pearson's correlation coefficient showed that baseline SUA/Cr ratio (r = 0.136, p = 0.012) as well as systolic blood pressure (SBP) and SUA were significantly correlated with annual eGFR decline rate. Multiple regression analysis using annual eGFR decline rate as an objective variable, adjusted for confounding factors as explanatory variables, showed that baseline SUA/Cr ratio (β = 0.334, p < 0.001) as well as gender and SBP were significantly and independently associated with annual eGFR decline rate. The multivariate-adjusted odds ratios (ORs) (95% confidence interval) of the baseline tertile of the SUA/Cr ratio for rapid progression of annual eGFR decline rate were 1.0, 3.15 (1.66-5.95) and 3.19 (1.57-6.51), respectively.

CONCLUSION

Our data demonstrated that baseline SUA/Cr ratio was independently and significantly associated with future renal function decline among diabetic patients.

Hyperuricemia Predicts an Early Decline in Renal Function among Older People: A Community-Based Cohort Study

Whether elevated serum uric acid levels (SUA) predict renal dysfunction remains controversial in the elderly. Therefore, we investigated the association between SUA and early renal function decline defined as an estimated glomerular filtration rate (eGFR) reduction ≥30% over 2 years. From 2001 to 2010, we conducted a longitudinal cohort study comprising 44,078 participants aged ≥65 years in the Taipei City Elderly Health Examination Database. Participants were classified by 1-mg/dL increment of SUA. We used multivariable logistic and Cox regression analyses to compare the risk of early renal function decline in different SUA groups. Compared to the reference SUA group of 5.0–5.9 mg/dL, hyperuricemic participants had increased risks of eGFR decline, starting at SUA ≥6.0 mg/dL (adjusted odds ratio [aOR] = 1.21, 95% confidence interval [CI] = 1.00–1.45). The risk progressively elevated as SUA increased, with the highest in the SUA ≥10.0 mg/dL group (aOR = 3.20, CI = 2.39–4.28). Multivariable Cox regression further confirmed that hyperuricemia was 1.12-fold (CI = 1.03–1.22, SUA ≥6.0 mg/dL) to 1.6-fold (CI = 1.37–1.86, SUA ≥10.0 mg/dL) more likely to develop early eGFR decline. Hyperuricemia-associated increased risks for early eGFR decline were consistent across subgroup and sensitivity analyses. Collectively, SUA ≥6.0 mg/dL independently predicted early renal dysfunction with eGFR decline ≥30% over 2 years in older people.

Decline of kidney function during the pre-dialysis period in chronic kidney disease patients: a systematic review and meta-analysis

Purpose

Substantial heterogeneity exists in reported kidney function decline in pre-dialysis chronic kidney disease (CKD). By design, kidney function decline can be studied in CKD 3–5 cohorts or dialysis-based studies. In the latter, patients are selected based on the fact that they initiated dialysis, possibly leading to an overestimation of the true underlying kidney function decline in the pre-dialysis period. We performed a systematic review and meta-analysis to compare the kidney function decline during pre-dialysis in CKD stage 3–5 patients, in these two different study types.

Patients and methods

We searched PubMed, EMBASE, Web of Science and Cochrane to identify eligible studies reporting an estimated glomerular filtration rate (eGFR) decline (mL/min/1.73 m²) in adult pre-dialysis CKD patients. Random-effects meta-analysis was performed to obtain weighted mean annual eGFR decline.

Results

We included 60 studies (43 CKD 3–5 cohorts and 17 dialysis-based studies). The meta-analysis yielded a weighted annual mean (95% CI) eGFR decline during pre-dialysis of 2.4 (95% CI: 2.2, 2.6) mL/min/1.73 m² in CKD 3–5 cohorts compared to 8.5 (95% CI: 6.8, 10.1) in dialysis-based studies (difference 6.0 [95% CI: 4.8, 7.2]).

Conclusion

To conclude, dialysis-based studies report faster mean annual eGFR decline during pre-dialysis than CKD 3–5 cohorts. Thus, eGFR decline data from CKD 3–5 cohorts should be used to guide clinical decision making in CKD patients and for power calculations in randomized controlled trials with CKD progression during pre-dialysis as the outcome.

Effect of immediate and prolonged GLP-1 receptor agonist administration on uric acid and kidney clearance: Post-hoc analyses of four clinical trials

AIMS

To determine the effects of glucagon-like peptide (GLP)-1 receptor agonists (RA) on uric acid (UA) levels and kidney UA clearance.

MATERIAL AND METHODS

This study involved post-hoc analyses of 4 controlled clinical trials, which assessed actions of GLP-1RA administration on kidney physiology. The immediate effects of GLP-1RA exenatide infusion vs placebo were determined in 9 healthy overweight men (Study-A) and in 52 overweight T2DM patients (Study-B). The effects of 12 weeks of long-acting GLP-1RA liraglutide vs placebo in 36 overweight T2DM patients (Study-C) and of 8 weeks of short-acting GLP-1RA lixisenatide vs once-daily titrated insulin glulisine in 35 overweight T2DM patients (Study-D) were also examined. Plasma UA, fractional (inulin-corrected) and absolute urinary excretion of UA (UE_UA ) and sodium (UE_Na ), and urine pH were determined.

RESULTS

Median baseline plasma UA level was 5.39 to 6.33 mg/dL across all studies (17%-22% of subjects were hyperuricaemic). In Study-A, exenatide infusion slightly increased plasma UA (+0.07 ± 0.02 mg/dL, P = .04), and raised absolute-UE_UA (+1.58 ± 0.65 mg/min/1.73 m² , P = .02), but did not affect fractional UE_UA compared to placebo. Fractional UE_UA and absolute UE_UA correlated with increases in urine pH (r:0.86, P = .003 and r:0.92, P < .001, respectively). Fractional UE_UA correlated with increased fractional UE_Na (r:0.76, P = .02). In Study-B, exenatide infusion did not affect plasma UA, but increased fractional UE_UA (+0.76 ± 0.38%, P = .049) and absolute UE_UA (+0.75 ± 0.27 mg/min/1.73 m² , P = .007), compared to placebo. In regression analyses, both parameters were explained by changes in urine pH and, in part, by changes in UE_Na . In Study-C, liraglutide treatment did not affect plasma UA, UE_UA, UE_Na or urine pH, compared to placebo. In Study-D, lixisenatide treatment increased UE_Na and urine pH from baseline, but did not affect plasma UA or UE_UA .

CONCLUSION

Immediate exenatide infusion increases UE_UA in overweight healthy men and in T2DM patients, probably by inhibiting Na⁺ /H⁺ -exchanger type-3 in the renal proximal tubule. Prolonged treatment with a long-acting or short-acting GLP-1RA does not affect plasma UA or UE_UA in T2DM patients with normal plasma UA levels and at relatively low cardiovascular risk. Our results suggest that the cardio-renal benefits of GLP-1RA are not mediated through changes in UA.

Risk model for deaths and renal replacement therapy dependence in patients with acute kidney injury after cardiac surgery

OBJECTIVES

Acute kidney injury (AKI) is a serious complication after cardiac surgery and is associated with increased in-hospital deaths. Renal replacement therapy (RRT) is becoming a routine strategy for severe AKI. Our goal was to evaluate the risk factors for death and RRT dependence in patients with AKI after cardiac surgery.

METHODS

We included 190 eligible adult patients who had AKI following cardiac surgery and who required RRT at our centre from November 2010 to March 2015. We collected preoperative, intraoperative, postoperative and RRT data for all patients.

RESULTS

In this cohort, 87 patients had successful RRT in the hospital, whereas 103 patients had RRT that failed (70 deaths and 33 cases of RRT dependence). The multivariable logistic analysis identified old age [odds ratio (OR): 1.042, 95% confidence interval (CI): 1.012-1.074; P = 0.011], serum uric acid (OR: 1.015, 95% CI: 1.003-1.031; P = 0.024), intraoperative concentrated red blood cell transfusions (OR: 1.144, 95% CI: 1.006-1.312; P = 0.041), postoperative low cardiac output syndrome (OR: 3.107, 95% CI: 1.179-8.190; P = 0.022) and multiple organ failure (OR: 5.786, 95% CI: 2.115-15.832; P = 0.001) as factors associated with a higher risk for RRT failure. The prediction model (-4.3 + 0.002 × preuric acid + 0.10 × concentrated red blood cells + 0.04 × age + 1.12 × [low cardiac output syndrome = 1] + 1.67 × [multiple organ failure = 1]) based on the multivariate analysis had statistically significant different incriminatory power with an area under the curve of 0.786.

CONCLUSIONS

The prediction model may serve as a simple, accurate tool for predicting in-hospital RRT failure for patients with AKI following cardiac surgery.

Mendelian randomization analysis indicates serum urate has a causal effect on renal function in Chinese women

PURPOSE

High levels of serum uric acid can predict the progression of stage I and II chronic kidney disease (CKD), but whether serum urate is an independent risk factor or has causal impact on serum creatinine (SCr) and renal function remains unclear.

METHODS

Mendelian randomization was used to determine whether serum uric acid had a causal effect on renal function, represented by estimated glomerular filtration rate (eGFR), with potential confounding factors, in 3734 subjects from the Taizhou Longitudinal Study. In the two-stage least squares method of Mendelian randomization, serum uric acid level was selected as the exposure, genetic risk score of uric acid transporters was selected as the instrumental variable, and SCr and eGFR were selected as the outcomes.

RESULTS

The result of the analysis showed that increased serum uric acid was not a causal effect on renal function, but it was a causal effect on reducing estimated glomerular filtration rate in both the female population and the subjects who were under 65 years old. We also found that increased serum uric acid levels led to impaired renal function only in the subjects with normal eGFR values. In addition, the serum uric acid was a risk factor for renal function in the subjects with relatively high levels of fasting glucose or who were currently smokers.

CONCLUSIONS

Although serum urate is not an independent risk factor for renal dysfunction, it has a causal effect on renal dysfunction in either female or individuals of under 65, or normal eGFR, or high level of fasting glucose, or current smokers.

Relationship between uric acid levels and risk of chronic kidney disease in a retrospective cohort of Brazilian workers

Uric acid (UA) levels are increased in patients with kidney dysfunction. We analyzed the association between asymptomatic hyperuricemia and new-onset chronic kidney disease (CKD). A retrospective cohort study was designed to collect data from employees of an energy generation and distribution company in the city of Rio de Janeiro, Brazil, who had undergone the company's annual medical checkup from 2008 to 2014. People with ≤2 years of follow-up, with baseline estimated glomerular filtration rate (eGFR) <60 mL·min-1·(1.73 m2)-1 or with incomplete data were excluded. The endpoint was defined as eGFR <60 mL·min-1·(1.73 m2)-1 estimated through the chronic kidney disease epidemiology collaboration equation (CKD-EPI). The study included 1094 participants. The mean follow-up period was 5.05±1.05 years and 44 participants exhibited new-onset CKD. The prevalence of hyperuricemia was 4.2%. There was a significant inverse correlation between baseline serum levels of UA and baseline eGFR (R=-0.21, P<0.001). Female gender (OR=4.00; 95%CI=1.92-8.29, P<0.001) and age (OR=1.06; 95%CI=1.02-1.11, P=0.004) but not UA levels (OR=1.12; 95%CI=0.83-1.50; P=0.465) were associated with new-onset CKD. Diabetes mellitus and body mass index were independent factors for fast progression (OR=2.17; 95%CI=1.24-3.80, P=0.007 and OR=1.04; 95%CI=1.01-1.07; P=0.020). These results did not support UA as an independent predictor for CKD progression in the studied population.

Hyperuricemia after orthotopic liver transplantation: divergent associations with progression of renal disease, incident end-stage renal disease, and mortality

Background

Although hyperuricemia is common after orthotopic liver transplantation (OLT), its relationship to mortality, progressive kidney disease, or the development of end stage renal disease (ESRD) is not well-described.

Methods

Data from 304 patients undergoing OLT between 1996 and 2010 were used to assess the association of mean serum uric acid (UA) level in the 3-months post-OLT with mortality, doubling of creatinine, and ESRD incidence. Post-OLT survival to event outcomes according to UA level and eGFR was assessed using the Kaplan Meier method and multivariate Cox proportional hazards models.

Results

Mean UA level among the 204 patients with an eGFR level ≥60 ml/min/1.73 m² was 6.4 mg/dl compared to 7.9 mg/dl among the 100 patients with eGFR <60 (p < 0.0001). During a median of 4.6 years of follow-up, mortality rate, doubling of creatinine, and ESRD incidence were 48.9, 278.2, and 20.7 per 1000 person-years, respectively. In the first 5 years of follow-up, elevated UA was associated with mortality (Hazard Ratio, HR = 1.7; p = 0.045). However, among those with eGFR ≥ 60, UA level did not predict mortality (HR = 1.0; p = 0.95), and among those with eGFR < 60, elevated UA was a strong predictor of mortality (HR = 3.7[1.1, 12.0]; p = 0.03). UA was not associated with ESRD, but was associated with doubling of creatinine among diabetics (HR = 2.2[1.1, 4.3]; p = 0.025).

Conclusion

In this post-OLT cohort, hyperuricemia independently predicted mortality, particularly among patients with eGFR < 60, and predicted doubling of creatinine among diabetics.

Electronic supplementary material

The online version of this article (doi:10.1186/s12882-017-0518-5) contains supplementary material, which is available to authorized users.

Serum Uric Acid and Progression of Kidney Disease: A Longitudinal Analysis and Mini-Review

Background

Increasing evidence supports the association between hyperuricemia and incident chronic kidney disease (CKD); however, there are conflicting data regarding the role of hyperuricemia in the progression of CKD. This study retrospectively assessed the longitudinal association between uric acid (UA) level and CKD progression in a Chinese population lived in Taiwan.

Methods

Patients with physician diagnosis of hyperuricemia or receiving urate-lowering therapy between 2003 and 2005 were identified in the electronic medical records (EMR) of a tertiary medical center and were followed up until December 31, 2011. Patients were divided into four UA categories at the cut-off 6, 8, and 10 mg/dL. CKD progression was estimated by the change of estimated glomerular filtration rate (eGFR) in the linear mixed models. Kidney failure was defined as an eGFR less than 15 mL/min/1.73 m² or requiring renal replacement therapy.

Results

A total of 739 patients were analyzed. In the full-adjusted model, patients with a baseline UA level ≥6 mg/dL had greater decline in eGFR ((β = -9.6, 95% CI -16.1, -3.1), comparing to those with a UA level less than 6 mg/dL. When stratifying patients into four UA categories, all three hyperuricemia categories (UA6-8, 8–10, ≥10 mg/dL) associated with a greater decline in eGFR over the follow-up period with an increasing dose-response, comparing to the lowest UA category. The risk of progression to renal failure increased 7% (hazard ratio 1.07, 95% CI 1.00, 1.14) for each 1mg/dL increase in baseline UA level. The influences of hyperuricemia on eGFR decline and the risk of kidney failure were more prominent in patients without proteinuria than those with proteinuria.

Conclusion

Our study showed a higher uric acid level is associated with a significant rapid decline in eGFR and a higher risk of kidney failure, particularly in patients without proteinuria. Our findings suggest hyperuricemia is a potential modifiable factor of CKD progression.

Stop chronic kidney disease progression: Time is approaching

Progression of chronic kidney disease (CKD) is inevitable. However, the last decade has witnessed tremendous achievements in this field. Today we are optimistic; the dream of withholding this progression is about to be realistic. The recent discoveries in the field of CKD management involved most of the individual diseases leading the patients to end-stage renal disease. Most of these advances involved patients suffering diabetic kidney disease, chronic glomerulonephritis, polycystic kidney disease, renal amyloidosis and chronic tubulointerstitial disease. The chronic systemic inflammatory status and increased oxidative stress were also investigated. This inflammatory status influences the anti-senescence Klotho gene expression. The role of Klotho in CKD progression together with its therapeutic value are explored. The role of gut as a major source of inflammation, the pathogenesis of intestinal mucosal barrier damage, the role of intestinal alkaline phosphatase and the dietary and therapeutic implications add a novel therapeutic tool to delay CKD progression.

Targeting Uric Acid and the Inhibition of Progression to End-Stage Renal Disease--A Propensity Score Analysis

Background

The role of uric acid (UA) in the progression of chronic kidney disease (CKD) remains controversial due to the unavoidable cause and result relationship. This study was aimed to clarify the independent impact of UA on the subsequent risk of end-stage renal disease (ESRD) by a propensity score analysis.

Methods

A retrospective CKD cohort was used (n = 803). Baseline 23 covariates were subjected to a multivariate binary logistic regression with the targeted time-averaged UA of 6.0, 6.5 or 7.0 mg/dL. The participants trimmed 2.5 percentile from the extreme ends of the cohort underwent propensity score analyses consisting of matching, stratification on quintile and covariate adjustment. Covariate balances after 1:1 matching without replacement were tested for by paired analysis and standardized differences. A stratified Cox regression and a Cox regression adjusted for logit of propensity scores were examined.

Results

After propensity score matching, the higher UA showed elevated hazard ratios (HRs) by Kaplan-Meier analysis (≥6.0 mg/dL, HR 4.53, 95%CI 1.79–11.43; ≥6.5 mg/dL, HR 3.39, 95%CI 1.55–7.42; ≥7.0 mg/dL, HR 2.19, 95%CI 1.28–3.75). The number needed to treat was 8 to 9 over 5 years. A stratified Cox regression likewise showed significant crude HRs (≥6.0 mg/dL, HR 3.63, 95%CI 1.25–10.58; ≥6.5 mg/dL, HR 3.46, 95%CI 1.56–7.68; ≥7.0 mg/dL, HR 2.05, 95%CI 1.21–3.48). Adjusted HR lost its significance at 6.0 mg/dL. The adjustment for the logit of the propensity scores showed the similar results but with worse model fittings than the stratification method. Upon further adjustment for other covariates the significance was attained at 6.5 mg/dL.

Conclusions

Three different methods of the propensity score analysis showed consistent results that the higher UA accelerates the progression to the subsequent ESRD. A stratified Cox regression outperforms other methods in generalizability and adjusting for residual bias. Serum UA should be targeted less than 6.5 mg/dL.