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Ammonium is a major urinary buffer that is necessary for the normal excretion of the daily acid load. Its urinary rate of excretion (UNH

Kidney tubular secretion is an essential mechanism for clearing many common antihypertensive drugs and other metabolites and toxins. It is unknown whether novel measures of tubular secretion are associated with adverse events (AEs) during hypertension treatment.Among 2089 SPRINT (Systolic Blood Pressure Intervention Trial) participants with baseline eGFR60 ml/min per 1.73 mOverall, 30% of participants experienced at least one AE during a median follow-up of 3.0 years. In multivariable models adjusted for eGFR and albuminuria, lower (worse) secretion scores at baseline were associated with greater risk of the composite AE outcome (hazard ratio per 1-SD lower secretion score, 1.16; 95% confidence interval, 1.04 to 1.27). In analyses of the individual AEs, lower secretion score was associated with significantly greater risk of AKI, serious electrolyte abnormalities, and ambulatory hyperkalemia. Associations were similar across randomized treatment assignment groups.Among SPRINT participants with CKD, worse tubular secretion was associated with greater risk of AEs, independent of eGFR and albuminuria.

Metabolic acidosis affects about 15% of patients with chronic kidney disease. As kidney function declines, the kidneys progressively fail to eliminate acid, primarily reflected by a decrease in ammonium and titratable acid excretion. Several studies have shown that the net acid load remains unchanged in patients with reduced kidney function; the ensuing acid accumulation can precede overt metabolic acidosis, and thus, indicators of urinary acid or potential base excretion, such as ammonium and citrate, may serve as early signals of impending metabolic acidosis. Acid retention, with or without overt metabolic acidosis, initiates compensatory responses that can promote tubulointerstitial fibrosis via intrarenal complement activation and upregulation of endothelin-1, angiotensin II, and aldosterone pathways. The net effect is a cycle between acid accumulation and kidney injury. Results from small- to medium-sized interventional trials suggest that interrupting this cycle through base administration can prevent further kidney injury. While these findings inform current clinical practice guidelines, large-scale clinical trials are still necessary to prove that base therapy can limit chronic kidney disease progression or associated adverse events.

RATIONALE AND OBJECTIVE. While low estimated glomerular filtration rate (eGFR) is associated with cardiovascular disease (CVD) events and mortality, the clinical significance of variability in eGFR over time is uncertain. We aimed to evaluate the association between variability in eGFR and the risk of CVD events and all-cause mortality. STUDY DESIGN. Longitudinal analysis of clinical trial participants. SETTINGS AND PARTICIPANTS. 7,520 Systolic Blood Pressure Intervention Trial (SPRINT) participants aged ≥ 50 year with 1 or more CVD risk factors. PREDICTORS. eGFR variability, estimated by the coefficients of variation of eGFR measurements at the 6, 12, and 18-month study visits. OUTCOMES. SPRINT primary CVD composite outcome (myocardial infarction, acute coronary syndrome, stroke, heart failure, or CVD death) and all-cause mortality from month 18 to end of follow-up. ANALYTICAL APPROACH. Cox models evaluated associations between eGFR variability and CVD outcomes and all-cause mortality. Models were adjusted for demographics, randomization arm, CVD risk factors, albuminuria and month 18 eGFR. RESULTS. Mean age was 68±9 years, 65% were men, and 58% were white. The mean eGFR was 73±21 ml/min/1.73m(2) at 6 months. There were 370 CVD events and 154 deaths during a median follow-up of 2.4 years. Greater eGFR variability was associated with higher risk for all-cause mortality (hazard ratio (HR) per standard deviation (SD) greater variability, 1.29; 95% confidence interval (CI) 1.14 to 1.45) but not CVD events (HR 1.05; 95% CI 0.95 to 1.16) after adjusting for albuminuria at baseline, eGFR at month 18, and other CVD risk factors. Associations were similar when stratified by treatment arm and baseline CKD status, when accounting for concurrent systolic BP changes, use of angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs), and diuretic medications during follow-up. LIMITATIONS. Persons with diabetes and proteinuria > 1 g/day were excluded. CONCLUSIONS. In trial participants at high risk for CVD with hypertension, greater eGFR variability was independently associated with all-cause mortality but not CVD events.

Causes of secondary oxalate nephropathy include enteric dysfunction and excessive intake of oxalate or oxalate precursors. During the COVID-19 pandemic, there has been a dramatic rise in sales of supplements and vitamin C, during which time we observed an apparent increase in the proportion of ingestion-associated oxalate nephropathy.We retrospectively reviewed secondary oxalate nephropathy and compared pre-pandemic (2018-2019) and pandemic (2020-early 2022) time periods.We identified 35 patients with kidney biopsy proven (30 native, 5 allograft) oxalate nephropathy at a single academic institution. Supplement-associated oxalate nephropathy comprised a significantly higher proportion of cases during COVID-19 pandemic compared with the preceding 2 years (44% vsThere was a shift toward supplements rather than enteric hyperoxaluria as a leading cause of secondary oxalate nephropathy during the COVID-19 pandemic. Kidney outcomes are better than those observed for enteric hyperoxaluria, if the offending agent is identified and removed.

Background and objectives Kidney functional magnetic resonance imaging (MRI) requires further investigation to enhance the noninvasive identification of patients at high risk of CKD progression. Design, setting, participants, & measurements In this exploratory study, we obtained baseline diffusion-weighted and blood oxygen level–dependent MRI in 122 participants of the CKD Optimal Management with Binders and Nicotinamide trial, which was a multicenter, randomized, double-blinded, 12-month, four-group parallel trial of nicotinamide and lanthanum carbonate versus placebo conducted in individuals with eGFR 20–45 ml/min per 1.73 m2. Lower values of apparent diffusion coefficient (ADC) on diffusion-weighted MRI may indicate increased fibrosis, and higher values of relaxation rate (R2*) on blood oxygen level–dependent MRI may represent decreased oxygenation. Because there was no effect of active treatment on eGFR over 12 months, we tested whether baseline kidney functional MRI biomarkers were associated with eGFR decline in all 122 participants. In a subset of 87 participants with 12-month follow-up MRI data, we evaluated whether kidney functional MRI biomarkers change over time. Results Mean baseline eGFR was 32±9 ml/min per 1.73 m2, and mean annual eGFR slope was −2.3 (95% confidence interval [95% CI], −3.4 to −1.1) ml/min per 1.73 m2 per year. After adjustment for baseline covariates, baseline ADC was associated with change in eGFR over time (difference in annual eGFR slope per 1 SD increase in ADC: 1.3 [95% CI, 0.1 to 2.5] ml/min per 1.73 m2 per year, ADC×time interaction P=0.04). This association was no longer significant after further adjustment for albuminuria (difference in annual eGFR slope per 1 SD increase in ADC: 1.0 (95% CI, −0.1 to 2.2) ml/min per 1.73 m2 per year, ADC×time interaction P=0.08). There was no significant association between baseline R2* and change in eGFR over time. In 87 participants with follow-up functional MRI, ADC and R2* values remained stable over 12 months (intraclass correlation: 0.71 and 0.68, respectively). Conclusions Baseline cortical ADC was associated with change in eGFR over time, but this association was not independent of albuminuria. Kidney functional MRI biomarkers remained stable over 1 year. Clinical Trial registry name and registration number CKD Optimal Management with Binders and Nicotinamide (COMBINE), NCT02258074.

Background and objectives In early-phase studies of individuals with hypertensive CKD and normal serum total CO2, sodium bicarbonate reduced urinary TGF-β1 levels and preserved kidney function. The effect of sodium bicarbonate on kidney fibrosis and injury markers in individuals with diabetic kidney disease and normal serum total CO2 is unknown. Design, setting, participants, & measurements We conducted a randomized, double-blinded, placebo-controlled study in 74 United States veterans with type 1 or 2 diabetes mellitus, eGFR of 15–89 ml/min per 1.73 m2, urinary albumin-to-creatinine ratio (UACR) ≥30 mg/g, and serum total CO2 of 22–28 meq/L. Participants received oral sodium bicarbonate (0.5 meq/kg lean body wt per day; n=35) or placebo (n=39) for 6 months. The primary outcome was change in urinary TGF-β1-to-creatinine from baseline to months 3 and 6. Secondary outcomes included changes in urinary kidney injury molecule-1 (KIM-1)-to-creatinine, fibronectin-to-creatinine, neutrophil gelatinase-associated lipocalin (NGAL)-to-creatinine, and UACR from baseline to months 3 and 6. Results Key baseline characteristics were age 72±8 years, eGFR of 51±18 ml/min per 1.73 m2, and serum total CO2 of 24±2 meq/L. Sodium bicarbonate treatment increased mean total CO2 by 1.2 (95% confidence interval [95% CI], 0.3 to 2.1) meq/L, increased urinary pH by 0.6 (95% CI, 0.5 to 0.8), and decreased urinary ammonium excretion by 5 (95% CI, 0 to 11) meq/d and urinary titratable acid excretion by 11 (95% CI, 5 to 18) meq/d. Sodium bicarbonate did not significantly change urinary TGF-β1/creatinine (difference in change, 13%, 95% CI, −10% to 40%; change within the sodium bicarbonate group, 8%, 95% CI, −10% to 28%; change within the placebo group, −4%, 95% CI, −19% to 13%). Similarly, no significant effect on KIM-1-to-creatinine (difference in change, −10%, 95% CI, −38% to 31%), fibronectin-to-creatinine (8%, 95% CI, −15% to 37%), NGAL-to-creatinine (−33%, 95% CI, −56% to 4%), or UACR (1%, 95% CI, −25% to 36%) was observed. Conclusions In nonacidotic diabetic kidney disease, sodium bicarbonate did not significantly reduce urinary TGF-β1, KIM-1, fibronectin, NGAL, or UACR over 6 months.

Rational & objectiveMany drugs, metabolites, and toxins are cleared by the kidneys via tubular secretion. Whether novel endogenous measures of tubular secretion provide information about kidney, cardiovascular, and mortality risk is uncertain.Study designLongitudinal subgroup analysis of clinical trial participants.Setting & participants2,089 Systolic Blood Pressure Intervention Trial participants with estimated glomerular filtration rate (eGFR)1 g/d were excluded.ConclusionsAmong SPRINT participants with CKD, lower estimated tubular secretion was associated with faster eGFR decline, independent of baseline eGFR and albuminuria, but not with CKD progression, CVD, or mortality.

Serum concentrations of fibroblast growth factor 23 (FGF23) and parathyroid hormone (PTH) are elevated in patients with CKD, and higher concentrations are well established as risk factors for cardiovascular disease and death ([1][1]). In the Systolic Blood Pressure Intervention Trial (SPRINT)

BACKGROUND: Oral sodium bicarbonate (NaHCO(3)) may preserve kidney function in CKD, even if initiated when serum bicarbonate concentration is normal. Adequately powered trials testing this hypothesis have not been conducted, partly because the best dose for testing is unknown. METHODS: This multicenter pilot trial assessed the safety, tolerability, adherence, and pharmacodynamics of two doses of NaHCO(3) over 28 weeks in adults with eGFR 20–44 or 45–59 ml/min per 1.73 m(2) with urinary albumin/creatinine (ACR) ≥50 mg/g and serum bicarbonate 20–28 meq/L. We randomly assigned 194 participants from ten clinical sites to receive higher-dose (HD-NaHCO(3); 0.8 meq/kg of lean body wt per day; n=90) or lower-dose (LD-NaHCO(3); 0.5 meq/kg of lean body wt per day; n=52) NaHCO(3) or matching placebo (n=52). The dose was adjusted depending on side effects. The prescribed dose at week 28 was the primary outcome; a dose was considered acceptable for a full-scale trial if ≥67% of participants were on full-dose and ≥80% were on ≥25% of the per-protocol dose. RESULTS: Mean±SD baseline eGFR was 36±9 ml/min per 1.73 m(2), serum bicarbonate was 24±2 meq/L, and median (IQR) ACR was 181 (25–745) mg/g. Both doses were well tolerated without significant changes in BP, weight, or serum potassium. The proportions of adverse events and hospitalizations were similar across the groups. Consequently, 87% in HD-NaHCO(3), 96% in LD-NaHCO(3), and 87% in placebo were on full dose at week 28; and 91% in HD-NaHCO(3), 98% in LD-NaHCO(3), and 92% in placebo were on ≥25% of the per-protocol dose. Mean urinary ammonium excretion was 25% lower and serum bicarbonate concentration was 1.3 meq/L higher in HD-NaHCO(3) compared with LD-NaHCO(3) at week 28. However, mean ACR increased by 12% in the lower-dose group and 30% in the higher-dose group. CONCLUSIONS: Both NaHCO(3) doses were well tolerated over 28 weeks with no significant difference in adverse events or hospitalization compared with placebo. The higher dose lowered urinary ammonium excretion and increased serum bicarbonate more than the lower dose but was associated with a greater increase in ACR. The higher 0.8 meq/kg of lean body wt per day dose of NaHCO(3) may be a reasonable choice for future trials.

Background Low serum bicarbonate level is associated with increased mortality, but its role as a predictor of cardiovascular disease (CVD) is unclear. This study evaluates the association between serum bicarbonate concentration and CVD and whether the effect of intensive blood pressure (BP) lowering on CVD outcomes is modified by serum bicarbonate level. Methods The Systolic Blood Pressure Intervention Trial (SPRINT) randomized participants to a systolic BP target Results Over a median follow-up of 3.33 years (interquartile range 2.87–3.87 years), 618 (6.6%) participants experienced a primary CVD outcome. Participants with serum bicarbonate Conclusions In hypertensive individuals, serum bicarbonate level

Background: Kidney tubulointerstitial fibrosis on biopsy is a strong predictor of chronic kidney disease (CKD) progression, and CKD is associated with elevated risk of cardiovascular disease (CVD). Tubular health is poorly quantified by traditional kidney function measures, including estimated glomerular filtration rate (eGFR) and albuminuria. We hypothesized that urinary biomarkers of tubular injury, inflammation, and repair would be associated with higher risk of CVD and mortality in persons with CKD. Methods: We measured urinary concentrations of interleukin-18 (IL-18), kidney injury molecule-1, neutrophil gelatinase-associated lipocalin, monocyte chemoattractant protein-1, and chitinase-3-like protein-1 (YKL-40) at baseline among 2,377 participants of the Systolic Blood Pressure Intervention Trial who had an eGFR < 60 mL/min/1.73 m2. We used Cox proportional hazards models to evaluate biomarker associations with CVD events and all-cause mortality. Results: At baseline, the mean age of participants was 72 ± 9 years, and eGFR was 48 ± 11 mL/min/1.73 m2. Over a median follow-up of 3.8 years, 305 CVD events (3.6% per year) and 233 all-cause deaths (2.6% per year) occurred. After multivariable adjustment including eGFR, albuminuria, and urinary creatinine, none of the biomarkers showed statistically significant associations with CVD risk. Urinary IL-18 (hazard ratio [HR] per 2-fold higher value, 1.14; 95% CI 1.01–1.29) and YKL-40 (HR per 2-fold higher value, 1.08; 95% CI 1.02–1.14) concentrations were each incrementally associated with higher mortality risk. Associations were similar when stratified by randomized blood pressure arm. Conclusions: Among hypertensive trial participants with CKD, higher urinary IL-18 and YKL-40 were associated with higher risk of mortality, but not CVD.

Maintenance of normal blood pH is critical for cellular function. Yet, blood pH is uncommonly measured in the outpatient setting. Instead, serum [total CO2] ([TCO2]) is used to screen for acid-base disturbances, the argument being that both metabolic and respiratory disorders are generally

BACKGROUND AND OBJECTIVES: eGFR and albuminuria primarily reflect glomerular function and injury, whereas tubule cell atrophy and interstitial fibrosis on kidney biopsy are important risk markers for CKD progression. Kidney tubule injury markers have primarily been studied in hospitalized AKI. Here, we examined the association between urinary kidney tubule injury markers at baseline with subsequent loss of kidney function in persons with nondiabetic CKD who participated in the Systolic Blood Pressure Intervention Trial (SPRINT). DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: Among 2428 SPRINT participants with CKD (eGFR

Background: Accurate assessment of urine flow remains challenging in both inpatient and outpatient settings. We hypothesized we could derive an equation that would accurately estimate urine flow rate (eV) through derivation from other existing equations commonly used in nephrology clinical practice. Methods: The eV equation was derived using the Cockcroft-Gault and the measured creatinine clearance (CrCl = UCrV/PCr) equations. Within the African American Study of Kidney Disease and Hypertension (AASK; n = 570) and COMBINE (n = 133) clinical trials, we identified participants with concordant estimated and measured creatinine excretion rates to define a subset with highly accurate 24-h urine collections, to assure a reliable gold standard. We then compared eV to measured 24-h urine flow rates in these trials. Results: In AASK, we found a high correlation between eV and measured urine flow rate (V; r = 0.91, p < 0.001); however, Bland-Altman plots showed that eV was 9.5 mL/h lower than V, on average. Thus, we added a correction factor to the eV equation and externally validated the new equation in COMBINE. eV and V were again highly correlated (r = 0.91, p < 0.001), and bias was improved (mean difference 5.3 mL/h). Overall, 80% of individuals had eV that was within 20% of V. Conclusions: A simple equation using urine creatinine, demographics, and body weight can accurately predict urine flow rate and may have clinical utility in situations where it is difficult to accurately measure the urine flow rate.

The Dietary Approaches to Stop Hypertension (DASH) diet lowers blood pressure, an important risk factor for chronic kidney disease (CKD) and end-stage renal disease (ESRD). However, it is unclear whether adherence to a DASH diet confers protection against future ESRD, especially among those with pre-existing CKD and hypertension. We examined whether a DASH diet is associated with lower risk of ESRD among 1,110 adults aged ≥ 20 years with hypertension and CKD (estimated glomerular filtration rate, eGFR 30–59 ml/min/1.73 m(2)) enrolled in the National Health and Nutrition Examination Survey (1988–1994). Baseline DASH diet accordance score was assessed using a 24-hour dietary recall questionnaire. ESRD was ascertained by linkage to the U.S. Renal Data System registry. We used the Fine-Gray competing risks method to estimate the relative hazard (RH) for ESRD after adjusting for sociodemographics, clinical and nutritional factors, eGFR, and albuminuria. Over a median follow-up of 7.8 years, 18.4% of subjects developed ESRD. Compared to the highest quintile of DASH diet accordance, there was a greater risk of ESRD among subjects in quintiles 1 (RH[1.7; 95% CI 1.1–2.7) and 2 (RH 2.2; 95% CI 1.1–4.1). Significant interactions were observed with diabetes status and race/ethnicity, with the strongest association between DASH diet adherence and ESRD risk observed in individuals with diabetes and in non-Hispanic blacks. Low accordance to a DASH diet is associated with greater risk of ESRD in adults with moderate CKD and hypertension, particularly in non-Hispanic blacks and persons with diabetes.

Background and objectives Urinary ammonium excretion increases in response to nonvolatile acids to maintain normal systemic bicarbonate and pH. However, enhanced ammonia production promotes tubulointerstitial fibrosis in animal models. Therefore, a subset of individuals with CKD and normal bicarbonate may have acid-mediated kidney fibrosis that might be better linked with ammonium excretion than bicarbonate. We hypothesized that urine TGF-β1, as an indicator of kidney fibrosis, would be more tightly linked with urine ammonium excretion than serum bicarbonate and other acid-base indicators. Design, setting, participants, & measurements We measured serum bicarbonate and urinary ammonium, titratable acids, pH, and TGF-β1/creatinine in 144 persons with CKD. Multivariable-adjusted linear regression models determined the cross-sectional association between TGF-β1/creatinine and serum bicarbonate, urine ammonium excretion, urine titratable acids excretion, and urine pH. Results Mean eGFR was 42 ml/min per 1.73 m2, mean age was 65 years old, 78% were men, and 62% had diabetes. Mean urinary TGF-β1/creatinine was 102 (49) ng/g, mean ammonium excretion was 1.27 (0.72) mEq/h, mean titratable acids excretion was 1.14 (0.65) mEq/h, mean urine pH was 5.6 (0.5), and mean serum bicarbonate was 23 (3) mEq/L. After adjusting for eGFR, proteinuria, and other potential confounders, each SD increase of urine ammonium and urine pH was associated with a statistically significant 1.22-fold (95% confidence interval, 1.11 to 1.35) or 1.11-fold (95% confidence interval, 1.02 to 1.21) higher geometric mean urine TGF-β1/creatinine, respectively. Each SD increase of serum bicarbonate and urine titratable acids was associated with a nonsignificant 1.06-fold (95% confidence interval, 0.97 to 1.16) or 1.03-fold (95% confidence interval, 0.92 to 1.14) higher geometric mean urine TGF-β1/creatinine, respectively. Conclusions Urinary ammonium excretion but not serum bicarbonate is associated with higher urine TGF-β1/creatinine.

Background and objectives Low urine ammonium excretion is associated with ESRD in CKD. Few laboratories measure urine ammonium, limiting clinical application. We determined correlations between urine ammonium, the standard urine anion gap, and a modified urine anion gap that includes sulfate and phosphate and compared risks of ESRD or death between these ammonium estimates and directly measured ammonium. Design, setting, participants, & measurements We measured ammonium, sodium, potassium, chloride, phosphate, and sulfate from baseline 24-hour urine collections in 1044 African-American Study of Kidney Disease and Hypertension participants. We evaluated the cross-sectional correlations between urine ammonium, the standard urine anion gap (sodium + potassium − chloride), and a modified urine anion gap that includes urine phosphate and sulfate in the calculation. Multivariable-adjusted Cox models determined the associations of the standard urine anion gap and the modified urine anion gap with the composite end point of death or ESRD; these results were compared with results using urine ammonium as the predictor of interest. Results The standard urine anion gap had a weak and direct correlation with urine ammonium ( r =0.18), whereas the modified urine anion gap had a modest inverse relationship with urine ammonium ( r =−0.58). Compared with the highest tertile of urine ammonium, those in the lowest urine ammonium tertile had higher risk of ESRD or death (hazard ratio, 1.46; 95% confidence interval, 1.13 to 1.87) after adjusting for demographics, GFR, proteinuria, and other confounders. In comparison, participants in the corresponding standard urine anion gap tertile did not have higher risk of ESRD or death (hazard ratio, 0.82; 95% confidence interval, 0.64 to 1.07), whereas the risk for those in the corresponding modified urine anion gap tertile (hazard ratio, 1.32; 95% confidence interval, 1.03 to 1.68) approximated that of directly measured urine ammonium. Conclusions Urine anion gap is a poor surrogate of urine ammonium in CKD unless phosphate and sulfate are included in the calculation. Because the modified urine anion gap merely estimates urine ammonium and requires five measurements, direct measurements of urine ammonium are preferable in CKD.

Metabolic acidosis is not uncommon in CKD and is linked with bone demineralization, muscle catabolism, and higher risks of CKD progression and mortality. Clinical practice guidelines recommend maintaining serum total CO2 at ≥22 mEq/L to help prevent these complications. Although a definitive trial testing whether correcting metabolic acidosis improves clinical outcomes has not been conducted, results from small, single-center studies support this notion. Furthermore, biologic plausibility supports the notion that a subset of patients with CKD have acid-mediated organ injury despite having a normal serum total CO2 and might benefit from oral alkali before overt acidosis develops. Identifying these individuals with subclinical metabolic acidosis is challenging, but recent results suggest that urinary acid excretion measurements may be helpful. The dose of alkali to provide in this setting is unknown as well. The review discusses these topics and the prevalence and risk factors of metabolic acidosis, mechanisms of acid-mediated organ injury, results from interventional studies, and potential harms of alkali therapy in CKD.

Introduction It is unknown whether the criteria used to define protein−energy wasting (PEW) syndrome in dialysis patients reflect protein or energy wasting in the general and moderate CKD populations. Methods In 11,834 participants in the 1999 to 2004 National Health and Nutrition Examination Survey, individual PEW syndrome criteria and the number of PEW syndrome categories were related to lean body and fat masses (measured by dual-energy absorptiometry) using linear regression in the entire cohort and CKD subpopulation. Results Serum chemistry, body mass, and muscle mass PEW criteria tended to be associated with lower lean body and fat masses, but the low dietary protein and energy intake criteria were associated with significantly higher protein and energy stores. When the number of PEW syndrome categories was defined by nondietary categories alone, there was a monotonic inverse relationship with lean body and fat masses and a strong positive relationship with mortality. In contrast, when dietary category alone was present, mean body mass index was in the obesity range; the additional presence of 2 nondietary categories was associated with lower body mass index and lower lean body and fat masses. Thus, the association of a dietary category plus 2 additional nondietary categories with lower protein or energy stores was driven by the presence of the 2 nondietary categories. Results were similar in CKD subgroup. Discussion Hence, a definition of PEW syndrome without dietary variables has face validity and reflects protein or energy wasting.

Background Metabolic acidosis is associated with accelerated progression of chronic kidney disease (CKD). Whether treatment of metabolic acidosis with sodium bicarbonate improves kidney and patient survival in CKD is unclear. Methods We conducted a randomized (ratio 1:1). open-label, controlled trial (NCT number: NCT01640119. www.clinicaltrials.gov) to determine the effect in patients with CKD stage 3–5 of treatment of metabolic acidosis with sodium bicarbonate (SB) on creatinine doubling (primary endpoint), all-cause mortality and time to renal replacement therapy compared to standard care (SC) over 36-months. Parametric, non-parametric tests and survival analyses were used to assess the effect of SB on these outcomes. Results A total of 376 and 364 individuals with mean (SD) age 67.8 (14.9) years, creatinine clearance 30 (12) ml/min, and serum bicarbonate 21.5 (2.4) mmol/l were enrolled in SB and SC, respectively. Mean (SD) follow-up was 29.6 (9.8) vs 30.3 (10.7) months in SC and SB. respectively. The mean (SD) daily doses of SB was 1.13 (0.10). 1.12 (0.11). and 1.09 (0.12) mmol/kg*bw/day in the first, second and third year of follow-up, respectively. A total of 87 participants reached the primary endpoint [62 (17.0%) in SC vs 25 (6.6%) in SB, p

Low urinary ammonium (NH4+) excretion is a risk factor for kidney failure and death in CKD ([1][1]). Few clinical laboratories measure urine NH4+, limiting clinical application. The urinary anion gap (UAG) and urine osmolal gap (UOG) have been used to estimate urine NH4+. Unfortunately, the UAG had

Rationale & Objective Native Hawaiians and Pacific Islanders (NHPI) have been reported to have the highest rates of incident end-stage kidney disease (ESKD) compared with other races in the United States. However, these estimates were likely biased upward due to the exclusion of nearly half the NHPI population that reports multiple races in the US Census. We sought to estimate the incidence rate of ESKD, including individuals reporting multiple races, and describe the clinical characteristics of incident cases by race and location. Study Design Health care database study. Setting & Participants US residents of the 50 states and 3 Pacific Island territories of the United States whose ESKD was recorded in the US Renal Data System (USRDS) between 2007 and 2016, as well as US residents recorded in the 2010 Census. Predictors Age, sex, race, body mass index, primary cause of ESKD, comorbid conditions, estimated glomerular filtration rate, pre-ESKD nephrology care, and hemoglobin A1c level among ESKD cases. Outcome Initiation of maintenance dialysis or transplantation for kidney failure. Analytical Approach Crude ESKD incidence rates (cases/person-years) were estimated using both single- and multiple-race reporting. Results Even after inclusion of multirace reporting, NHPI had the highest ESKD incidence rate among all races in the 50 states (921 [95% CI, 904-938] per million population per year)—2.7 times greater than whites and 1.2 times greater than blacks. Also using multirace reporting, the NHPI ESKD incident rate in the US territories was 941 (95% CI, 895-987) per million population per year. Diabetes was listed as the primary cause of ESKD most frequently for NHPI and American Indians/Alaska Natives. Sensitivity analysis adjusting for age and sex demonstrated greater differences in rates between NHPI and other races. Diabetes was the primary cause of ESKD in 60% of incident NHPI cases. Patients with ESKD living in the territories had received less pre-ESKD nephrology care than had patients living in the 50 states. Limitations Different methods of race classification in the USRDS versus the US Census. Conclusions NHPI living in the 50 US states and Pacific territories had the highest rates of ESKD incidence compared with other races. Further research and efforts are required to understand the reasons for and define how best to address this racial disparity.

Thousands of years before Europeans reached the Pacific Ocean, Pacific peoples were settling islands scattered throughout Earth’s largest ocean. Using navigational techniques developed over generations of studying wind, wave, and ocean current patterns and the behavior of birds and memorizing

Background C3 glomerulopathy (C3G) includes both C3 glomerulonephritis (C3GN) and dense deposit disease (DDD) and is defined by C3-dominant deposits on immunofluorescence. Dysfunction of the alternative pathway (AP) of complement is central to the pathophysiology of C3G and young patients often harbor genetic alterations of AP mediators. Recently, a link between C3G and paraproteinemia has been established. We performed this study to better characterize older patients with C3G where this association is more frequently seen. Methods Fourteen biopsies from 12 patients meeting diagnostic criteria for C3G were identified in patients > 49 years of age from 2005 to 2015 after exclusion of cases containing masked monotypic immunoglobulin deposits. Pathologic and clinical features were reviewed. Results The median age was 63.5 years and 75% of patients were male. All had renal insufficiency at presentation. Kidney biopsy showed DDD in three patients and C3GN in the remainder. Serum protein electrophoresis revealed a paraprotein in 10 patients, 8 of which had a plasma cell dyscrasia on bone marrow biopsy. A membranoproliferative pattern of glomerular injury was seen in 64% of biopsies, while mesangial proliferative and endocapillary proliferative patterns were seen less frequently. Among patients with at least 1 year of follow-up (n = 9), five were on renal replacement therapy, three showed stable (but impaired) kidney function and one demonstrated improvement. Conclusions C3G is an uncommon but important cause of kidney injury in older adults and associates with a high prevalence of paraproteinemia. In adult patients with C3G, prognosis is guarded as most patients showed either progression to end-stage kidney disease or stable but impaired kidney function.

Chronic metabolic acidosis is not uncommon in patients with chronic kidney disease (CKD). Clinical practice guidelines suggest that clinicians administer alkali to maintain serum bicarbonate level at a minimum of 22 mEq/L to prevent the effects of acidosis on bone demineralization and protein catabolism. Small interventional studies support the notion that correcting acidosis slows CKD progression as well. Furthermore, alkaline therapy in persons with CKD and normal bicarbonate levels may also preserve kidney function. Observational studies suggest that targeting a serum bicarbonate level near 28 mEq/L may improve clinical outcomes above and beyond targeting a value ≥ 22 mEq/L, yet values > 26 mEq/L have been reported to be associated with incident heart failure and mortality in the CRIC (Chronic Renal Insufficiency Cohort) Study. Furthermore, correcting acidosis may provoke vascular calcification. This teaching case discusses several uncertainties regarding the management of acidosis in CKD, such as when to initiate alkali treatment, potential side effects of alkali, and the optimum serum bicarbonate level based on current evidence in CKD. Suggestions regarding the maximum sodium bicarbonate dose to administer to patients with CKD to achieve the target serum bicarbonate concentration are offered.

The typical complications of CKD, such as anemia and hyperparathyroidism, are common in patients with kidney transplants. However, the mechanisms and management of each are often more complicated in the transplant setting. Metabolic acidosis, for instance, can develop because of reduced nephron

Maintenance of normal acid-base homeostasis is one of the most important kidney functions. In chronic kidney disease, the capacity of the kidneys to excrete the daily acid load as ammonium and titratable acid is impaired, resulting in acid retention and metabolic acidosis. The prevalence of metabolic acidosis increases with declining glomerular filtration rate. Metabolic acidosis is associated with several clinically important complications, including chronic kidney disease progression, bone demineralization, skeletal muscle catabolism, and mortality. To mitigate these adverse consequences, clinical practice guidelines suggest treating metabolic acidosis with oral alkali in patients with chronic kidney disease. However, large clinical trials to determine the efficacy and safety of correcting metabolic acidosis with oral alkali in patients with chronic kidney disease have yet to be conducted. In this Core Curriculum article, established and emerging concepts regarding kidney acid-base regulation and the pathogenesis, risk factors, diagnosis, and management of metabolic acidosis in chronic kidney disease are discussed.

BACKGROUND AND OBJECTIVES: The Systolic Blood Pressure Intervention Trial (SPRINT) demonstrated that intensive BP lowering reduced the risk of cardiovascular disease, but increased eGFR decline. Serum parathyroid hormone (PTH) and fibroblast growth factor-23 (FGF23) concentrations are elevated in CKD and are associated with cardiovascular disease. We evaluated whether intact PTH or intact FGF23 concentrations modify the effects of intensive BP control on cardiovascular events, heart failure, and all-cause mortality in SPRINT participants with CKD. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: We measured PTH and FGF23 in 2486 SPRINT participants with eGFR

Aim Low serum bicarbonate is a strong mortality risk factor in people with low estimated glomerular filtration rate (eGFR). It may also raise mortality risk in people with normal eGFR. This study investigated whether higher net endogenous acid production (NEAP), an estimate of net dietary acid intake and a risk factor for chronic kidney disease (CKD) progression, associates with higher mortality in people with and without low eGFR. Methods NEAP was calculated among adult participants in the Third National Health and Nutrition Examination Survey as −10.2 + 54.5 x (protein intake in grams per day/potassium intake in milliequivalent per day). Cox models were performed in the (i) total population and (ii) low eGFR and (iii) normal eGFR subgroups using the lowest NEAP quartile as the reference. Results Sixteen thousand nine hundred six participants were included in the analysis. The mortality hazard ratios (95% confidence interval) for the highest NEAP quartile (72–145 mEq/day) were: (i) 0.75 (0.62–0.90) in the total population; (ii) 0.77 (0.51–1.17) in the low eGFR subgroup; and (iii) 0.75 (0.61–0.93) in the normal eGFR subgroup after adjusting for demographics, serum bicarbonate, eGFR, albuminuria and comorbidities. The mortality hazard ratios in the second and third NEAP quartiles were similar to the lowest (reference) NEAP quartile in the total population and low and normal eGFR subgroups. Conclusions Higher NEAP is not associated with higher mortality in people with low or normal eGFR. Future studies should consider the effect of modifying dietary acid and alkali intake on mortality and CKD progression in people with reduced eGFR.

BACKGROUND: Animal studies suggest that acidosis protects against arterial calcification, which contributes to arterial stiffness. The goal of this study was to investigate the associations of serum bicarbonate and pH with arterial stiffness in community-living older adults. METHODS: We performed cross-sectional analyses among 1698 well-functioning participants 70–79 years of age. Bicarbonate and pH were measured by arterialized venous blood gas at the point of care. Bicarbonate was categorized into low (7.40–7.42 and >7.42. Arterial stiffness was evaluated by pulse wave velocity (PWV) and high ankle-brachial index (ABI; >1.3/incompressible). We used linear and logistic regression to evaluate the association of bicarbonate and AVpH with PWV and high ABI, respectively. RESULTS: The mean age was 76 years and 15% had an estimated glomerular filtration rate (eGFR)

Background and objectives Cognitive function worsens as kidney function declines, but mechanisms contributing to this association are not completely understood. Metabolic acidosis, a common complication of CKD, leads to neural networks overexcitation and is involved in cerebral autoregulation. We aimed to evaluate the association between serum bicarbonate concentration as a measure of metabolic acidosis, and cognitive function in hypertensive adults with and without CKD. Design, setting, participants, & measurements Five cognitive summary scores were measured (global cognitive function, executive function, memory, attention/concentration, and language) in 2853 participants in the Systolic BP Intervention Trial (SPRINT). Multivariable linear regression models adjusted for demographics, comorbidities, systolic BP, medications, eGFR and albuminuria evaluated the cross-sectional association between bicarbonate and cognition at SPRINT baseline. In a subset ( n =681) who underwent brain magnetic resonance imaging, the models were adjusted for white matter hyperintensity volume, vascular reactivity, and cerebral blood flow. Results The mean age (SD) was 68 (8.5) years. Global cognitive and executive functions were positively associated with serum bicarbonate (estimate [SEM]: 0.014 [0.006]; P =0.01, and 0.018 [0.006]; P =0.003, respectively). Each 1 mEq/L lower bicarbonate level had a similar association with global cognitive and executive function as being 4.3 and 5.4 months older, respectively. The association with global cognition persisted after magnetic resonance imaging findings adjustment (estimate [SEM]: 0.03 [0.01]; P =0.01). There was no association between serum bicarbonate level and memory, attention/concentration, and language. Conclusions In a large cohort of hypertensive adults, higher serum bicarbonate levels were independently associated with better global cognitive and executive performance. (ClinicalTrials.gov: NCT01206062).

Abnormalities of serum potassium are common in patients with CKD. Although hyperkalemia is a well-recognized complication of CKD, the prevalence rates of hyperkalemia (14%-20%) and hypokalemia (12%-18%) are similar. CKD severity, use of medications such as renin-angiotensin-aldosterone system inhibitors and diuretics, and dietary potassium intake are major determinants of serum potassium concentration in CKD. Demographic factors, acid-base status, blood glucose, and other comorbidities contribute as well. Both hyperkalemia and hypokalemia are associated with similarly increased risks of death, cardiovascular disease, and hospitalization. On the other hand, limited evidence suggests a link between hypokalemia, but not hyperkalemia, and progression of CKD. This article reviews the prevalence rates and risk factors for hyperkalemia and hypokalemia, and their associations with adverse outcomes in CKD.

Aim The prevalence of metabolic acidosis increases as glomerular filtration rate falls. However, most patients with stage 4 chronic kidney disease have normal serum bicarbonate concentration while some with stage 3 chronic kidney disease have low serum bicarbonate, suggesting that other factors contribute to generation of acidosis. The purpose of this study is to identify risk factors, other than reduced glomerular filtration rate, for reduced serum bicarbonate in chronic kidney disease. Methods This is a cross-sectional analysis of baseline data from the Chronic Renal Insufficiency Cohort Study. Multivariable logistic and linear regression models were used to relate predictor variables to the odds of low serum bicarbonate (

Metabolic acidosis is associated with poor outcomes in CKD. Because impaired renal ammonium excretion is important in the pathogenesis of acidosis, urine ammonium excretion might be a better and perhaps earlier acid-base indicator of risk than serum bicarbonate, particularly in patients without acidosis. We evaluated the association between baseline ammonium excretion and clinical outcomes in African American Study of Kidney Disease and Hypertension participants (n=1044). Median daily ammonium excretion was 19.5 (95% confidence interval [95% CI], 6.5 to 43.2) mEq. In Cox regression models (adjusted for demographics, measured GFR, proteinuria, body mass index, net endogenous acid production, and serum potassium and bicarbonate), hazard ratios of the composite outcome of death or dialysis were 1.46 (95% CI, 1.13 to 1.87) in the low tertile and 1.14 (95% CI, 0.89 to 1.46) in the middle tertile of daily ammonium excretion compared with the high tertile. Among participants without acidosis at baseline, the adjusted hazard ratio for those with ammonium excretion

Chronic kidney disease is considered an inflammatory state and a high fiber intake is associated with decreased inflammation in the general population. Here, we determined whether fiber intake is associated with decreased inflammation and mortality in chronic kidney disease, and whether kidney disease modifies the associations of fiber intake with inflammation and mortality. To do this, we analyzed data from 14,543 participants in the National Health and Nutrition Examination Survey III. The prevalence of chronic kidney disease (estimated glomerular filtration rate less than 60 ml/min per 1.73 m(2)) was 5.8%. For each 10-g/day increase in total fiber intake, the odds of elevated serum C-reactive protein levels were decreased by 11% and 38% in those without and with kidney disease, respectively. Dietary total fiber intake was not significantly associated with mortality in those without but was inversely related to mortality in those with kidney disease. The relationship of total fiber with inflammation and mortality differed significantly in those with and without kidney disease. Thus, high dietary total fiber intake is associated with lower risk of inflammation and mortality in kidney disease and these associations are stronger in magnitude in those with kidney disease. Interventional trials are needed to establish the effects of fiber intake on inflammation and mortality in kidney disease.

Background and Aims: Cognitive impairment is a risk factor for death in dialysis patients and the general population. We sought to determine if cognitive impairment is associated with death in people with non-dialysis-dependent chronic kidney disease (CKD), and if so, whether this relationship is greater in the CKD population compared to the general population. Methods: National Health and Nutrition Examination Survey-III participants older than 60 years were asked to subtract 3 from 20 five times and to perform immediate and delayed recall of three items. A cognitive score of 0–11 was assigned based on the number of correct responses. Participants were categorized according to cognitive score (11, 9–10, 6–9, and 0–5) and CKD status. Survival analyses were conducted using Cox models. Results: Within the CKD subpopulation, those in the lowest cognitive score group had a twofold increased hazard of death compared to those with maximum score. Within the non-CKD subpopulation, those in the lowest cognitive score group had a 46% increased hazard of death compared to those with maximum score. However, the difference in the hazards of death in the CKD and non-CKD subpopulations with the lowest cognitive score was not significant (p = 0.99). Conclusions: Low cognitive score is associated with an increased risk of death in elderly individuals with and without CKD; however, there was no interaction of CKD and low cognitive score in this analysis.

Despite many years of experience with hemodialysis, the outcomes of maintenance dialysis patients remain poor. The Frequent Hemodialysis Network-Daily (FHN-Daily) Trial found that six times per week in-center short hemodialysis decreased left ventricular mass and improved self-reported physical functioning over a 1-year intervention period compared with conventional thrice-weekly dialysis. Despite the promising results, caution is needed in the projection of these intermediate outcomes to hard clinical endpoints, such as cardiovascular events and death.

Recent studies suggest that correcting low serum bicarbonate levels may reduce the progression of kidney disease; however, few patients with chronic kidney disease have low serum bicarbonate. Therefore, we examined whether higher levels of serum bicarbonate within the normal range (20-30 mmol/l) were associated with better kidney outcomes in the African American Study of Kidney Disease and Hypertension (AASK) trial. At baseline and during follow-up of 1094 patients, the glomerular filtration rates (GFR) were measured by iothalamate clearances and events were adjudicated by the outcomes committee. Mean baseline serum bicarbonate, measured GFR, and proteinuria were 25.1 mmol/l, 46 ml/min per 1.73 m(2), and 326 mg/g of creatinine, respectively. Each 1 mmol/l increase in serum bicarbonate within the normal range was associated with reduced risk of death, dialysis, or GFR event and with dialysis or GFR event (hazard ratios of 0.942 and 0.932, respectively) in separate multivariable Cox regression models that included errors-in-variables calibration. Cubic spline regression showed that the lowest risk of GFR event or dialysis was found at serum bicarbonate levels near 28-30 mmol/l. Thus, our study suggests that serum bicarbonate is an independent predictor of CKD progression. Whether increasing serum bicarbonate into the high-normal range will improve kidney outcomes during interventional studies will need to be considered.

Background/Aims: Cystic epithelia in polycystic kidney disease display features similar to malignant cells. Thiazolidinediones have been shown to have anti-neoplastic properties, therefore we tested the hypothesis that pioglitazone reduces cyst formation, improves renal function, and prolongs survival in a mouse model of polycystic kidney disease. Methods: PC-Pkd1-KO mice, which have homozygous mutations of the Pkd1 gene in principal cells, were used. On the day after giving birth, mothers were fed standard mouse chow with or without pioglitazone (30 mg/kg chow). After weaning, the assigned diet was continued. At 1 month of age, blood pressure was measured and animals were sacrificed to determine kidney weight, body weight, and serum urea. Kidneys were evaluated for proliferation using Ki-67, apoptosis using TUNEL analysis, and cyst number using MRI. Survival was observed. Results: Pioglitazone did not alter renal function, cell proliferation, apoptosis, or cyst formation in animals with polycystic kidney disease, however it did increase survival. Pioglitazone reduced blood pressure in PC-Pkd1-KO, but not in controls. Conclusion: These findings suggest that pioglitazone may have a unique antihypertensive effect in polycystic kidney disease, and that such an effect may promote improved survival.