Metabolic Acidosis of CKD: An Update

Identification of L-shaped curve association between serum bicarbonate concentrations and short-term outcomes in patients with acute kidney injury: a retrospective cohort study

OBJECTIVE

This study aims to investigate the association between serum bicarbonate levels and short-term outcomes in patients with acute kidney injury (AKI), with a focus on 14-day mortality and AKI progression within a 14-day period.

METHODS

We conducted a secondary analysis using data from the Electronic Alerts for Acute Kidney Injury Amelioration (ELAIA) study. Serum bicarbonate levels and their associated outcomes were collected for all participants. Cox regression analysis and smooth curve fitting methods were employed to achieve the research objectives.

RESULTS

A total of 5,835 patients with AKI were included in the study. After adjustment for confounding factors, patients with serum bicarbonate concentrations below 22 mmol/L had a higher risk of both 14-day mortality and AKI progression compared to those with levels between 22 and 26 mmol/L (hazard ratio [HR] 1.90; 95% confidence interval [CI], 1.51-1.83 for mortality and HR 1.45; 95% CI, 1.23-1.71 for AKI progression, respectively). In contrast, patients with bicarbonate concentrations above 26 mmol/L had a lower risk of 14-day mortality (HR 0.70; 95% CI, 0.53-0.94) and AKI progression (HR 0.90; 95% CI, 0.74-1.10). Subsequent exploratory subgroup analyses revealed no statistically significant interactions (all p-values for interaction > 0.05) between 14-day mortality and serum bicarbonate levels.

CONCLUSIONS

In this cohort of AKI patients, serum bicarbonate concentrations below 22 mmol/L were associated with increased risks of 14-day mortality and AKI progression, while concentrations above 26 mmol/L were linked to a reduced risk of 14-day mortality.

Colorimetric Optode Sensor with Tripodal Ionophore for Rapid Urinary Ammonium Determination

The amount of ammonium excreted in urine is a crucial indicator for assessing renal metabolic acidosis. Therefore, there is a significant demand for chemical sensors capable of accurately determining urinary ammonium concentrations with high throughput. In this study, we developed an ammonia chemical sensor based on the ion-selective optode principle. This sensor employs strategically designed ionophores and a PTFE gas-permeable film to enhance selectivity for free NH3. The low basicity of the chromoionophore indicator and the weak affinity of the tripodal ammonium receptor (L, log β = 4.62 ± 0.18) contributed to a markedly reduced response time, achieving detection within seconds, a significant improvement over previous sensors. A limit of detection (LOD) of approximately 15 nM was obtained in colorimetric mode. Total inorganic ammonia content in undiluted human urine was successfully determined using the sensor. Additionally, the optode was adapted into a multiwell format, offering potential for high-throughput point-of-care testing of urinary ammonium concentrations and other samples.

Dissecting clinical features of COVID-19 in a cohort of 21,312 acute care patients

BACKGROUND

Although, COVID-19 has resulted in over 7 million deaths globally, many questions still remain about the risk factors for disease severity and the effects of variants and vaccinations over the course of the pandemic. To address this gap, we conducted a retrospective analysis of electronic health records from COVID-19 patients over 2.5 years of the COVID-19 pandemic to identify associated clinical features.

METHODS

We analyze a retrospective cohort of 21,312 acute-care patients over a 2.5 year period and define six clinical trajectory groups (TGs) associated with demographics, diagnoses, vitals, labs, imaging, consultations, and medications.

RESULTS

We show that the proportion of mild patients increased over time, particularly during Omicron waves. Additionally, while mild and fatal patients had differences in age, age did not distinguish patients with severe versus critical disease. Furthermore, we find that both male sex and Hispanic/Latino ethnicity are associated with more severe/critical TGs. More severe patients also have a higher rate of neuropsychiatric diagnoses and consultations, along with an immunological signature of high neutrophils and immature granulocytes, and low lymphocytes and monocytes. Interestingly, low albumin is one of the best lab predictors of COVID-19 severity in association with higher malnutrition in severe/critical patients, raising concern of nutritional insufficiency influencing COVID-19 outcomes. Despite this, only a small fraction of severe/critical patients had nutritional labs checked (e.g. Vitamin D, thiamine, B vitamins) or received vitamin supplementation.

CONCLUSIONS

Our findings expand on clinical risk factors in COVID-19, and highlight the interaction between severity, nutritional status, and neuropsychiatric complications in acute care patients to enable identification of patients at risk for severe disease.

Effects of dietary interventions for metabolic acidosis in chronic kidney disease: a systematic review and meta-analysis

BACKGROUND

Metabolic acidosis is a common complication of kidney disease and can result in further disease progression. Alkali therapy has been used to treat metabolic acidosis for decades. However, some concerns have been raised regarding its safety and long-term tolerability. Existing data suggest that dietary interventions can be beneficial in the management of chronic kidney disease (CKD). This systematic review and meta-analysis aims to summarize findings from studies comparing dietary interventions with placebo/usual care/no treatment in the management of metabolic acidosis in outpatient adults with CKD.

METHODS

Medline, Embase, Cochrane Central, CINAHL and Web of Science Core Collection were searched from inception to June 2022. Our primary outcome measure was change in serum bicarbonate. Any dietary intervention looking to manipulate dietary acid load was considered as an intervention. Data screening and extraction were performed by two independent reviewers. Random effects meta-analysis was performed to pool data.

RESULTS

Dietary interventions resulted in clinically significant improvement in serum bicarbonate [mean difference 2.98 (95% confidence interval 0.77, 5.19); I2: 91%] and higher estimated glomerular filtration rate (eGFR) levels [mean difference 3.16 (95% confidence interval 0.24, 6.08); I2: 67%] compared with controls. Serum potassium, albumin and body mass index remained unchanged. Dietary interventions were reported to be safe. Subgroup analyses indicated a superiority of plant-based over non-plant-based interventions in the improvement of acid-base balance and eGFR; however, these findings are from low-quality and heterogenous studies.

CONCLUSION

Our findings support the beneficial effects of dietary interventions aimed at reducing acid or adding base in the management of metabolic acidosis and kidney function in adults with CKD, with no adverse effects on serum potassium and nutritional status. Well-designed clinical trials looking at the treatment of metabolic acidosis with dietary interventions with a focus on adding base through fruit and vegetables are required.

Gender disparities in the association between atherogenic index of plasma and chronic kidney disease

OBJECTIVE

This study investigates the relationship between the atherogenic index of plasma (AIP) and chronic kidney disease (CKD) occurrence in the general population, with a focus on potential gender disparities.

METHODS

The study included 22,952 adults from the National Health and Nutrition Examination Survey (NHANES). Various statistical models were employed to evaluate the association between AIP and CKD occurrence and explore gender-specific differences.

RESULTS

Adjusted for confounding factors, higher AIP levels showed a mild association with increased CKD risk in the general population. Specifically, individuals in the highest AIP quartile had a slightly elevated odds ratio (OR) for CKD compared to the lowest quartile (OR: 1.24, 95% CI: 1.02-1.52, P for trend = 0.023). Gender-stratified analysis revealed significant differences. Among males, higher AIP levels were significantly associated with CKD risk (OR: 1.49, 95% CI: 1.15-1.94, P for trend < 0.001), whereas in females, the association was weaker and statistically non-significant (P for trend = 0.055). U-shaped relationships between AIP and CKD were observed. Mediation analysis provided insights into potential pathways underlying this association. Among males, changes in uric acid accounted for 44.50% of CKD prevalence related to AIP, while glomerular filtration rate (eGFR), BMI, and bicarbonate levels contributed 44.09%, 17.55%, and 15.36%, respectively. Among females, uric acid changes accounted for 45.53%, while eGFR, bicarbonate, C-reactive protein (CRP), sodium, and potassium levels contributed 37.96%, 12.43%, 6.37%, 5.58%, and 3.14%, respectively.

CONCLUSION

Our findings suggest that elevated AIP levels may increase CKD risk, particularly among males in the general U.S.

POPULATION

Potassium bicarbonate, not sodium bicarbonate, maintains acidosis-mediated bone dissolution

Treatments for metabolic acidosis are not well studied; however, one treatment that is commonly used is sodium bicarbonate administration. Sodium bicarbonate has been shown to help reduce symptoms of metabolic acidosis, but its benefits for bone health remain uncertain. Potassium bicarbonate has become a potential new treatment due to its reduction in bone resorption markers, unlike sodium bicarbonate. However, very few studies have looked at the connection between bone functionality and potassium bicarbonate supplementation, especially under the influence of an acidic challenge. To determine the impact of potassium bicarbonate and sodium bicarbonate on the mechanical, structural, compositional, and cellular properties of bone, acidotic mice were given either potassium bicarbonate or sodium bicarbonate for seven days. Blood gas analysis was conducted to evaluate their acidotic states throughout the study. After experimentation, the mice were euthanized, and their femurs excised for further analysis. Before bicarbonate supplementation, the acidotic mice given sodium bicarbonate were in acidosis while the acidotic mice given potassium bicarbonate were in acidemia. The bicarbonate treatment somewhat rescued the blood gas parameters in both acidosis groups, but acidemia and bone dissolution continued occurring in the acidotic mice given potassium bicarbonate, as made evident by the continuous elevation in blood sodium levels compared to the control. The acidosis group given potassium bicarbonate group also had worsened composition and structure, while the acidosis group given sodium bicarbonate had no changes in bone metrics. In this study, potassium bicarbonate was not effective at reducing bone dissolution under acidotic conditions.

Randomized Trial of Dietary Acid Reduction and Acid-Base Status of Patients With CKD and Normal Estimated GFR

Introduction

Modern acid-producing diets in patients with stage G3 to G5 chronic kidney disease (CKD) can cause severe acid accumulation with metabolic acidosis and less severe accumulation causing eubicarbonatemic acidosis in stages G2 to G3, each with kidney injury. The impact of these diets on acid accumulation in those with CKD but normal estimated glomerular filtration rate (eGFR) (CKD G1) is unclear.

Methods

We assessed whether acid accumulation occurs in patients with CKD and normal eGFR, and if added base-producing fruits and vegetables (F&Vs) or oral sodium bicarbonate (NaHCO3) (HCO3 -) reduces acid accumulation and/or lowers kidney injury. We randomized 153 participants with macroalbuminuric, nondiabetic, CKD stage G1 (mean eGFR = 101 ml/min per 1.73 m2) with hypertension-associated CKD to receive F&Vs in amounts to reduce dietary acid intake by 50% (F&V, n = 51), oral NaHCO3 to match alkali intake of F&V (HCO3 -, n = 51), or usual care (UC, n = 51) for 5 years. We assessed acid accumulation by comparing observed to expected increase in plasma total CO2 (PTCO2) in response to retained bicarbonate (dose - urine bicarbonate excretion) 2 hours after an oral NaHCO3 bolus.

Results

Baseline acid accumulation, eGFR, urine excretion of albumin, N-acetyl-β-D-glucosamine, and angiotensinogen were not different among groups. Five-year acid accumulation (mean [SD]) was lower in F&V (-1.2 [11.0] mmol] and in HCO3 - (-1.7 [10.8] mmol) than in UC (5.2 [10.3] mmol, P < 0.003), which is consistent with lower acid accumulation in F&V and HCO3 -. Five-year urine excretion of albumin, N-acetyl-β-D-glucosamine, and angiotensinogen were lower in F&V and HCO3 - than in UC, which is consistent with less kidney injury.

Conclusions

Dietary acid reduction reduces acid accumulation and kidney injury in patients with CKD and normal eGFR.

Health disparities in the risk of severe acidosis: real-world evidence from the All of Us cohort

OBJECTIVE

To assess the health disparities across social determinants of health (SDoH) domains for the risk of severe acidosis independent of demographical and clinical factors.

MATERIALS AND METHODS

A retrospective case-control study (n = 13 310, 1:4 matching) is performed using electronic health records (EHRs), SDoH surveys, and genomics data from the All of Us participants. The propensity score matching controls confounding effects due to EHR data availability. Conditional logistic regressions are used to estimate odds ratios describing associations between SDoHs and the risk of acidosis events, adjusted for demographic features, and clinical conditions.

RESULTS

Those with employer-provided insurance and those with Medicaid plans show dramatically different risks [adjusted odds ratio (AOR): 0.761 vs 1.41]. Low-income groups demonstrate higher risk (household income less than $25k, AOR: 1.3-1.57) than high-income groups ($100-$200k, AOR: 0.597-0.867). Other high-risk factors include impaired mobility (AOR: 1.32), unemployment (AOR: 1.32), renters (AOR: 1.41), other non-house-owners (AOR: 1.7), and house instability (AOR: 1.25). Education was negatively associated with acidosis risk.

DISCUSSION

Our work provides real-world evidence of the comprehensive health disparities due to socioeconomic and behavioral contributors in a cohort enriched in minority groups or underrepresented populations.

CONCLUSIONS

SDoHs are strongly associated with systematic health disparities in the risk of severe metabolic acidosis. Types of health insurance, household income levels, housing status and stability, employment status, educational level, and mobility disability play significant roles after being adjusted for demographic features and clinical conditions. Comprehensive solutions are needed to improve equity in healthcare and reduce the risk of severe acidosis.

Association between albumin-corrected anion gap and kidney function in individuals with hypertension - NHANES 2009-2016 cycle

OBJECTIVES

Long-term uncontrolled hypertension increases the risk of kidney decompensation. This study aimed to explore the connection between albumin-corrected anion gap (ACAG) and kidney function in hypertensive patients.

METHODS

This study utilized data from 1988 participants diagnosed with hypertension sourced from the NHANES database. Binary logistic regression analysis and subgroup analysis were utilized to investigate the relationship between ACAG and kidney function. The study employed restricted cubic spline (RCS) to assess the non-linear associations between ACAG and eGFR, as well as ACAG and ACR. Furthermore, mediation and moderation effect analyses were carried out, with blood pressure serving as the mediator and moderator, ACAG as the independent variable, and eGFR and ACR as the dependent variables. Finally, the study developed ACAG-based models for predicting kidney function decline.

RESULTS

Higher ACAG is identified as an independent risk factor for eGFR < 60 mL/minute/1.73 m2 and ACR ≥ 30 mg/g. Results from RCS indicate a non-linear relationship between ACAG and eGFR, as well as between ACAG and ACR. The mediation effect analysis revealed that DBP mediated the relationship between ACAG and eGFR. Analysis on moderation effect demonstrated that SBP played a significant role in moderating the interaction between ACAG and ACR. Moreover, the models based on ACAG showed strong performance.

CONCLUSIONS

The levels of ACAG are found to be independently associated with both eGFR and ACR. Additionally, ACAG shows promise as a new and dependable biomarker for predicting the decline in kidney function in hypertensive patients.

Longitudinal serum bicarbonate and mortality risk in older patients with advanced chronic kidney disease: analyses from the EQUAL cohort

Background

We aimed to explore the relationship between serum bicarbonate (SBC) and mortality in advanced chronic kidney disease (CKD) during three distinct treatment periods: during the pre-kidney replacement therapy (KRT) period, during the transition phase surrounding the start of KRT (transition-CKD) and during KRT.

Methods

Using the European QUALity Study on treatment in advanced CKD (EQUAL) cohort, which includes patients aged ≥65 years and estimated glomerular filtration rate (eGFR) ≤20 mL/min/1.73 m2 from six European countries, we explored the association between longitudinal SBC and all-cause mortality in three separate CKD populations: pre-KRT, transition-CKD and in the KRT populations, using multivariable time-dependent Cox regression models. We evaluated effect modification by pre-specified variables on the relationship between SBC and mortality.

Results

We included 1485 patients with a median follow-up of 2.9 (interquartile range 2.7) years, during which 529 (35.6%) patients died. A U-shaped relationship between SBC levels and all-cause mortality was observed in the pre-KRT population (P = .03). Low cumulative exposure, defined as the area under the SBC trajectory before KRT initiation, was associated with increased mortality risk after transitioning to KRT (P = .01). Similarly, in the KRT population, low SBC levels showed a trend towards increased mortality risk (P = .13). We observed effect modification by subjective global assessment category (P-value for interaction = .02) and KRT (P-value for interaction = .02).

Conclusions

A U-shaped relationship describes the association between SBC and mortality in the advanced CKD pre-KRT population, whereas in the KRT population a trend towards an increased mortality risk was observed for low SBC levels.

Association between Dietary Acid Load and Chronic Kidney Disease in the Chinese Population: A Comprehensive Analysis of the China Health and Nutrition Survey (2009)

BACKGROUND

Dietary acid load (DAL) is closely related to several chronic diseases. However, the link between DAL and chronic kidney disease (CKD) remains scarce and without data from the Chinese populations whose diet is quite different from people in Western countries.

METHODS

This study evaluated DAL by potential renal acid load (PRAL) and net endogenous acid production (NEAP). We clarified the relationship between DAL and CKD by logistic regression analysis based on data from the China Health and Nutrition Survey (CHNS).

RESULTS

The final analysis included 7699 individuals, of whom 811 (11.44%) were CKD patients. Although there was no notable link between PRAL and CKD, higher NEAP levels were independently correlated with CKD. As NEAP values rise, so does CKD prevalence. This trend remains highly significant even after adjustments. In subgroup analyses, the relationship between NEAP and CKD was more consistent in the elderly and subjects with a waistline of less than 82 cm and those without diabetes and heart disease. RCS analysis further confirmed the clear linear relationship between the OR of CKD and NEAP score.

CONCLUSIONS

This study highlighted that higher NEAP was positively correlated with the risk of CKD.

Dietary inflammatory index and lower glomerular filtration rate in Mexican adults

We hypothesized that higher scores on the dietary inflammatory index (DII) would be associated with a lower glomerular filtration rate (GFR). This cross-sectional study included 2098 participants from Mexican Teachers Cohort Study, the Health Workers Cohort Study, and the Comitán Study belonging to the RenMex consortium. Energy-adjusted DII scores were estimated using a semi-quantitative food frequency questionnaire (FFQ). eGFR was estimated by the CKD Epidemiology Collaboration equation. Quantile regression models and ordered regression models were estimated to assess the associations of interest. Median age of study participants was 47 years, median eGFR was 102.9 mL/min/1.73m2, and the median energy-adjusted DII was 0.89 (range, -2.25, +4.86). The median eGFR was lower in participants in the highest percentile of DII compared to those in the lowest percentile (103.8 vs 101.4). We found that continuous and categorical energy-adjusted DII scores were associated with lower eGFR, especially at the lower percentiles. In adjusted ordered logistic regression, we found that the highest DII category was associated with 1.80 times the odds of belonging to the mildly decreased eGFR category or moderately decreased eGFR category compared lowest DII category (OR: 1.80, 95%CI 1.35, 2.40). A high DII score was associated with a lower eGFR among the Mexican population. Additional studies are crucial to validate these findings and explore potential strategies to reduce the consumption of pro-inflammatory foods as a preventive approach for chronic kidney disease (CKD).

Sex-specific Stone-forming Phenotype in Mice During Hypercalciuria/Urine Alkalinization

Sex differences in kidney stone formation are well known. Females generally have slightly acidic blood and higher urine pH when compared with males, which makes them more vulnerable to calcium stone formation, yet the mechanism is still unclear. We aimed to examine the role of sex in stone formation during hypercalciuria and urine alkalinization through acetazolamide and calcium gluconate supplementation, respectively, for 4 weeks in wild-type (WT) and moderately hypercalciuric [TRPC3 knockout [KO](-/-)] male and female mice. Our goal was to develop calcium phosphate (CaP) and CaP+ calcium oxalate mixed stones in our animal model to understand the underlying sex-based mechanism of calcium nephrolithiasis. Our results from the analyses of mice urine, serum, and kidney tissues show that female mice (WT and KO) produce more urinary CaP crystals, higher [Ca2+], and pH in urine compared to their male counterparts. We identified a sex-based relationship of stone-forming phenotypes (types of stones) in our mice model following urine alkalization/calcium supplementation, and our findings suggest that female mice are more susceptible to CaP stones under those conditions. Calcification and fibrotic and inflammatory markers were elevated in treated female mice compared with their male counterparts, and more so in TRPC3 KO mice compared with their WT counterparts. Together these findings contribute to a mechanistic understanding of sex-influenced CaP and mixed stone formation that can be used as a basis for determining the factors in sex-related clinical studies.

Prevalence, Risk Factors, and Management of Metabolic Acidosis in Chronic Kidney Disease Patients: A Multicenter Retrospective Study in Malaysia

Background Metabolic acidosis in chronic kidney disease (CKD) patients has lately gained attention due to the growing evidence of its treatment benefits. This study aims to provide baseline data on the prevalence, risk factors, and current management of metabolic acidosis among the pre-dialysis adult Malaysian CKD population. Methodology This multicenter cross-sectional retrospective study involved pre-dialysis CKD patients above 18 years old on regular nephrology clinic follow-up at three Malaysian government hospitals with nephrology subspecialty. Demographic data, clinical information, laboratory data, and a list of concomitant medications were collected. Factors associated with the occurrence of metabolic acidosis were identified via multiple logistic regression. Results Six hundred and fifty-seven CKD patients were screened for this study, in which only 39.4% (n=259) had available bicarbonate levels. From this, a total of 86.1% (n=223) had metabolic acidosis. Higher estimated glomerular filtration rate (odds ratio (OR) 0.96, 95% confidence interval (CI) 0.93-1.00, p=0.043) and those with cardiovascular disease (OR 0.33, 95% CI 0.15-0.73; p=0.007) were significantly associated with lower odds of metabolic acidosis. There were 43.0% (n=96) on alkali therapy with sodium bicarbonate solution being the most common (n=91, 94.8%). Among those receiving alkali therapy, only 19.8% (n=19) achieved bicarbonate levels of ≥ 22 mEq/L. Conclusion Our study showed that metabolic acidosis was highly prevalent, although few achieved target levels despite supplementation, supporting the need for focused management of metabolic acidosis in the CKD population.

VALOR-CKD: A Multicenter, Randomized, Double-Blind Placebo-Controlled Trial Evaluating Veverimer in Slowing Progression of CKD in Patients with Metabolic Acidosis

SIGNIFICANCE STATEMENT

Metabolic acidosis is a common complication of CKD and is associated with more rapid decline of kidney function, but well-powered controlled randomized trials testing the effect of treating metabolic acidosis on slowing CKD progression have not been conducted. The VALOR-CKD study randomized 1480 individuals with CKD and metabolic acidosis, across 320 sites to placebo or veverimer (a novel hydrochloric acid binder). The findings did not demonstrate the efficacy of veverimer in slowing CKD progression, but the difference in serum bicarbonate between placebo and drug arms was only approximately 1 mEq/L. Veverimer was safe and well tolerated.

BACKGROUND

Metabolic acidosis is common in CKD, but whether its treatment slows CKD progression is unknown. Veverimer, a novel hydrochloric acid binder that removes acid from the gastrointestinal tract, leads to an increase in serum bicarbonate.

METHODS

In a phase 3, double-blind, placebo-controlled trial, patients with CKD (eGFR of 20-40 ml/min per 1.73 m 2 ) and metabolic acidosis (serum bicarbonate of 12-20 mEq/L) from 35 countries were randomized to veverimer or placebo. The primary outcome was the composite end point of CKD progression, defined as the development of ESKD (kidney transplantation or maintenance dialysis), a sustained decline in eGFR of ≥40% from baseline, or death due to kidney failure.

RESULTS

The mean (±SD) baseline eGFR was 29.2±6.3 ml/min per 1.73 m 2 , and serum bicarbonate was 17.5±1.4 mEq/L; this increased to 23.4±2.0 mEq/L after the active treatment run-in. After randomized withdrawal, the mean serum bicarbonate was 22.0±3.0 mEq/L and 20.9±3.3 mEq/L in the veverimer and placebo groups at month 3, and this approximately 1 mEq/L difference remained stable for the first 24 months. A primary end point event occurred in 149/741 and 148/739 patients in the veverimer and placebo groups, respectively (hazard ratio, 0.99; 95% confidence interval, 0.8 to 1.2; P = 0.90). Serious and overall adverse event incidence did not differ between the groups.

CONCLUSIONS

Among patients with CKD and metabolic acidosis, treatment with veverimer did not slow CKD progression. The lower than expected bicarbonate separation may have hindered the ability to test the hypothesis.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

VALOR-CKD, NCT03710291 .

Pathophysiology of Diet-Induced Acid Stress

Diets can influence the body's acid-base status because specific food components yield acids, bases, or neither when metabolized. Animal-sourced foods yield acids and plant-sourced food, particularly fruits and vegetables, generally yield bases when metabolized. Modern diets proportionately contain more animal-sourced than plant-sourced foods, are, thereby, generally net acid-producing, and so constitute an ongoing acid challenge. Acid accumulation severe enough to reduce serum bicarbonate concentration, i.e., manifesting as chronic metabolic acidosis, the most extreme end of the continuum of "acid stress", harms bones and muscles and appears to enhance the progression of chronic kidney disease (CKD). Progressive acid accumulation that does not achieve the threshold amount necessary to cause chronic metabolic acidosis also appears to have deleterious effects. Specifically, identifiable acid retention without reduced serum bicarbonate concentration, which, in this review, we will call "covert acidosis", appears to cause kidney injury and exacerbate CKD progression. Furthermore, the chronic engagement of mechanisms to mitigate the ongoing acid challenge of modern diets also appears to threaten health, including kidney health. This review describes the full continuum of "acid stress" to which modern diets contribute and the mechanisms by which acid stress challenges health. Ongoing research will develop clinically useful tools to identify stages of acid stress earlier than metabolic acidosis and determine if dietary acid reduction lowers or eliminates the threats to health that these diets appear to cause.

Association of body mass index with the development of metabolic acidosis in patients with chronic kidney disease

Aims

Higher body mass index (BMI) is associated with higher bone mass and bone serves as a buffer during the development of metabolic acidosis. The authors sought to examine the relationship between BMI and metabolic acidosis in patients with chronic kidney disease (CKD).

Materials and Methods

The study utilized a large US longitudinal data repository including over 103 million patients from healthcare provider organizations to evaluate the relationship between the exposure variable (BMI) and the prevalence and incidence of metabolic acidosis among patients with estimated glomerular filtration rate <60 ml/min/1.73 m2. Incident metabolic acidosis was identified at the first of two consecutive post-index serum bicarbonate values, 10-365 days apart, between 12 and <22 mEq/L in patients with normal index serum bicarbonate. Cox proportional hazard models were adjusted for multiple variables including demographics, comorbidities, income, education, and kidney function.

Results

103,766 patients qualified for this study; 6472 (6.2%) had metabolic acidosis at index. An inverse association between BMI category and metabolic acidosis was observed for both baseline (prevalence) and new-onset (incidence) metabolic acidosis. Compared to BMI category of 18.5 to <25 kg/m2, each category of incrementally higher BMI was associated with a decreasing risk of incident metabolic acidosis; the adjusted hazard ratios (95% confidence interval) were 0.866 (0.824-0.911), 0.770 (0.729-0.813), 0.664 (0.622-0.709), and 0.612 (0.571-0.655) for BMI 25 to <30, 30 to <35, 35 to <40, and 40+ kg/m2, respectively.

Conclusions

Among patients with CKD, an incremental increase in BMI was inversely associated with both the prevalence and incidence of metabolic acidosis. These associations suggest that increased body weight may protect against the development of metabolic acidosis, a risk factor for progressive loss of kidney function.

Association of Plant-Based Protein Intake with Cognitive Function in Adults with CKD

Key Points

Higher plant protein intake was associated with higher cognitive scores in people with kidney disease. Future trials are needed to determine whether increasing plant protein intake improves measures of cognition in patients with kidney disease.

Background

Patients with CKD have accelerated cardiovascular and cognitive aging when compared with the non-CKD population. This cognitive decline contributes to excessive rates of physical and functional decline, reduced quality of life, and mortality in the CKD population. Mediterranean diets, a plant-forward diet, have been associated with positive cognitive performance in the general non-CKD population and with some beneficial outcomes in CKD. However, it is still unclear whether plant-based diets are associated with cognitive decline in patients with CKD.

Methods

Using the National Health and Nutrition Examination Survey 2011–2012 and 2013–14 data, we conducted a secondary analysis evaluating the relationship of plant-based and unprocessed plant protein with cognitive outcome measures in eligible participants aged 60 years and older. All data were extracted from the available National Health and Nutrition Examination Survey demographic, questionnaire, examination, and laboratory data. CKD was calculated and defined in participants as urine albumin to creatinine ratio ≥30 mg/g and/or eGFR <60 ml/min. In incremental models, we adjusted for total energy intake, age, sex, race/ethnicity, body mass index, total energy intake, diabetes, hypertension, education, smoking, and alcohol.

Results

Higher plant-based protein above median dietary intakes was significantly associated with higher executive function scores in participants with CKD (P < 0.05). For all patients and in those with CKD, plant-based protein was significantly associated (P < 0.05) with higher composite cognitive scores in nearly all statistical models. Higher unprocessed plant protein was significantly associated (P < 0.05) with higher composite cognitive scores in all categorical models.

Conclusions

Higher plant protein intake was a significant predictor of certain individual and composite cognitive score measures within the general and in the CKD population. Future interventional trials are needed to determine whether increasing plant-based protein intake improves measures of cognition in patients with CKD.

Administration of alendronate exacerbates ammonium chloride-induced acidosis in mice

Bone disease is highly prevalent in patients with chronic kidney disease (CKD), leading to an increased risk of bone fractures. This is due in part to metabolic acid-induced bone dissolution. Bisphosphonates (BPPs) are a potential treatment for inhibiting bone dissolution; however, there are limited studies observing the use of BPPs on acidotic patients. We aimed to determine efficacy of BPPs on maintaining bone health and pH regulation in acid-exposed mice. Using a diet-induced murine model of metabolic acidosis, we examined bone structure, composition, and mechanics as well as blood gases for three groups: control, acidosis, and acidosis + bisphosphonates (acidosis+BPP). Acidosis was induced for 14 days and alendronate was administered every 3 days for the acidosis+BPP group. The administration of BPP had little to no effect on bone structure, mechanics, and composition of the acidosis bones. However, administration of BPP did cause the mice to develop more severe acidosis than the acidosis only group. Overall, we discovered that BPPs may exacerbate acidosis symptoms by inhibiting the release of buffering ions from bone. Therefore, we propose that BPP administration should be carefully considered for those with CKD and that alkali supplementation could help minimize acidifying effects.

Effects of Oral Sodium Bicarbonate Supplementation on Protein Metabolism and Inflammation in Iraqi Hemodialysis Patients: An Open-Label Randomized Controlled Trial

BACKGROUND

The effect of correcting metabolic acidosis on protein metabolism in hemodialysis patients is controversial.

OBJECTIVES

To study the effects of oral sodium bicarbonate on protein metabolism and markers of inflammation in acidotic hemodialysis patients. Patients and Methods. An open-label randomized controlled trial was conducted at a single center. Sixty-six clinically stable adult hemodialysis patients were recruited with an average predialysis serum bicarbonate level of <22 mmol/l and a dialysate bicarbonate concentration of 35 mmol/l. Forty-nine participants have completed the study. Oral sodium bicarbonate tablets of 500 mg were given daily in the intervention group (n = 25) for 12 weeks versus the standard of care in the control group (n = 24). Outcomes compared intervention versus nonintervention in both groups at equivalent time points (0 and 3 months). The clinical data, anthropometry, dialysis adequacy, albumin, normalized protein catabolism rate, blood gas analysis, and bicarbonate were recorded at 0 and 3 months. In addition, muscle mass and handgrip strength were measured. Finally, IL-6 as a marker of inflammation was measured at randomization and three months.

RESULTS

Serum bicarbonate and pH increased significantly from 17.57 ± 3.34 mmol/L to 20.69 ± 2.54 mmol/L and from 7.26 ± 0.06 to 7.34 ± 0.04, respectively (p < 0.0001). Serum albumin was significantly higher in the intervention group at three months than in the control group, 4.11 ± 0.45 vs. 3.79 ± 0.47 (p value 0.011). Serum potassium significantly decreased in the intervention group at three months compared to the control group, 5.00 ± 0.43 mEq/l vs. 5.33 ± 0.63 mEq/l (p value 0.03). Muscle strength expressed as handgrip has improved significantly in the intervention group at three months compared to the control group, 45.01 ± 19.19 vs. 33.93 ± 15.06 (p value 0.03). The IL-6 values were less in the intervention group at 3 months with a p value of 0.01. The interdialytic weight of the intervention group at three months was 2.42 ± 0.64 compared to the 2.20 ± 1.14 control group, but this did not reach statistical significance (p value of 0.4). The composite of (albumin + nPCR) at three months was achieved in 59.18% of the intervention group compared to 14.28% with a p value of 0.01.

CONCLUSIONS

Correcting metabolic acidosis in hemodialysis patients improved serum albumin and nPCR without hypokalemia or significant interdialytic weight gain. This was particularly evident in patients with minimal inflammation with low IL-6 values.

Hidden Acid Retention with Normal Serum Bicarbonate Level in Chronic Kidney Disease

Management of metabolic acidosis is crucial for preserving bone, muscle, and renal health, as evidenced by the results of several interventional studies conducted on patients with chronic kidney disease (CKD). Considering the continuity of CKD progression over time, it is reasonable to deduce that a subclinical form of metabolic acidosis may exist prior to the manifestation of overt metabolic acidosis. Covert H⁺ retention with normal serum bicarbonate level in patients with CKD may result in maladaptive responses that contribute to kidney function deterioration, even in the early stages of the disease. The loss of adaptive compensatory mechanisms of urinary acid excretion may be a key factor in this process. Early modulation of these responses could be an important therapeutic strategy in preventing CKD progression. However, to date, the optimal approach for alkali therapy in subclinical metabolic acidosis in CKD remains uncertain. There is a lack of established guidelines on when to initiate alkali therapy, potential side effects of alkali agents, and the optimal blood bicarbonate levels based on evidence-based practices. Therefore, further research is necessary to address these concerns and establish more robust guidelines for the use of alkali therapy in patients with CKD. Herein, we provide an overview of recent developments on this subject and examine the potential therapeutic approaches that interventional treatments may present for patients with hidden H⁺ retention, exhibiting normal serum bicarbonate levels - commonly described as subclinical or eubicarbonatemic metabolic acidosis in patients with CKD.

Diet and Metabolism in CKD-Related Metabolic Acidosis

Metabolic acidosis is a common complication in patients with chronic kidney disease that occurs when the daily nonvolatile acid load produced in metabolism cannot be excreted fully by the kidney. A reduction in urine net acid excretion coupled with a high nonvolatile acid load may play a role in its pathogenesis. Diet is important in generation of the nonvolatile acid load. Acids are produced from metabolism of dietary protein and from the endogenous production of organic anions from neutral precursors. Acids can be balanced by alkali precursors ingested in the diet in the form of combustible organic anions. These typically are reflected indirectly by the excess of mineral cations to mineral anions in a food or diet. These principles underscore widely used methods to estimate the nonvolatile acid load from dietary intake using formulas such as the net endogenous acid production equation and the potential renal acid load equation. Empiric data largely validate these paradigms with high net endogenous acid production and potential renal acid load contributed by foods such as protein, grains, and dairy, and low net endogenous acid production and potential renal acid load contributed by fruits and vegetables along with corresponding dietary patterns. Although further studies are needed to understand the health benefits of altering nonvolatile acid load via diet, this review provides a detailed assessment on our current understanding of the role of diet in chronic kidney disease-related acidosis, providing an updated resource for researchers and clinicians.

Patient Perception of Plant Based Diets for Kidney Disease

OBJECTIVE

Plant-based diets can delay the progression of chronic kidney disease (CKD) and help manage complications and comorbid conditions such as hypertension, acidosis, diabetes, and cardiovascular disease. The objective of this study was to understand nephrology patients' familiarity, perception, and use of plant-based diets.

DESIGN & METHODS

A survey was shared via the National Kidney Foundation's social media channels. Analysis included 844 responses. Survey items were evaluated with descriptive statistics. Differences across items were determined using chi-square tests.

RESULTS

Most respondents were 61-70 years of age (26.7%, n = 225), female (56.5%, n = 477) and achieved a Bachelor's or advanced degree (49.9%, n = 421). The majority of respondents suffered from nondialysis-dependent CKD (34%) or received a kidney transplant (34%). About half (45%) of respondents were familiar with plant-based diets and most (58%) were aware that plant-based diets can improve CKD. Twenty-two percent reported following some version of a vegetarian diet, and 29% reported "eating less meat". Respondents were not confident (Mdn = 2, IQR = 2, on a scale of 1-5) in their ability to plan a balanced plant-based meal, and were moderately confident that a plant-based diet could help blood pressure (Mdn = 3, IQR = 2) and slow progression of CKD (Mdn = 3, IGR = 2). Family eating preference, meal planning skills, preference for meat, figuring out what is healthy to eat, food cost, time constraints, and ease of cooking were rated as equal barriers to following a plant-based diet (Mdn = 3). A sample meal plan, individual counseling session with a Registered Dietitian Nutritionist (RDN), handouts, and cooking classes were resources rated most helpful to transition to a plant-based diet (Mdn = 4).

CONCLUSION

Approximately half of respondents were aware that plant-based diets can be beneficial for CKD. Many patients are following a vegetarian or plant-based eating pattern. More research should be done to see how effective RDNs are in educating and moving patients toward a plant-based eating pattern, as they are an underutilized resource in the CKD population.

The mechanisms of alkali therapy in targeting renal diseases

Chronic kidney disease (CKD) is characterized by progressive reduction in kidney function and treatments aiming at stabilizing or slowing its progression may avoid or delay the necessity of kidney replacement therapy and the increased mortality associated with reduced kidney function. Metabolic acidosis, and less severe stages of the acid stress continuum, are common consequences of CKD and some interventional studies support that its correction slows the progression to end-stage kidney disease. This correction can be achieved with mineral alkali in the form of bicarbonate or citrate salts, ingestion of diets with fewer acid-producing food components or more base-producing food components, or a pharmacological approach. In this mini-review article, we summarize the potential mechanisms involved in the beneficial effects of alkali therapy. We also discuss the perspectives in the field and challenges that must be overcome to advance our understanding of such mechanisms.

Mathematical modelling of bicarbonate supplementation and acid-base chemistry in kidney failure patients on hemodialysis

Acid-base regulation by the kidneys is largely missing in end-stage renal disease patients undergoing hemodialysis (HD). Bicarbonate is added to the dialysis fluid during HD to replenish the buffers in the body and neutralize interdialytic acid accumulation. Predicting HD outcomes with mathematical models can help select the optimal patient-specific dialysate composition, but the kinetics of bicarbonate are difficult to quantify, because of the many factors involved in the regulation of the bicarbonate buffer in bodily fluids. We implemented a mathematical model of dissolved CO2 and bicarbonate transport that describes the changes in acid-base equilibrium induced by HD to assess the kinetics of bicarbonate, dissolved CO2, and other buffers not only in plasma but also in erythrocytes, interstitial fluid, and tissue cells; the model also includes respiratory control over the partial pressures of CO2 and oxygen. Clinical data were used to fit the model and identify missing parameters used in theoretical simulations. Our results demonstrate the feasibility of the model in describing the changes to acid-base homeostasis typical of HD, and highlight the importance of respiratory regulation during HD.

Sodium bicarbonate for kidney transplant recipients with metabolic acidosis in Switzerland: a multicentre, randomised, single-blind, placebo-controlled, phase 3 trial

BACKGROUND

Metabolic acidosis is common in kidney transplant recipients and is associated with declining graft function. Sodium bicarbonate treatment effectively corrects metabolic acidosis, but no prospective studies have examined its effect on graft function. Therefore, we aimed to test whether sodium bicarbonate treatment would preserve graft function and slow the progression of estimated glomerular filtration rate (GFR) decline in kidney transplant recipients.

METHODS

The Preserve-Transplant Study was a multicentre, randomised, single-blind, placebo-controlled, phase 3 trial at three University Hospitals in Switzerland (Zurich, Bern, and Geneva), which recruited adult (aged ≥18 years) male and female long-term kidney transplant recipients if they had undergone transplantation more than 1 year ago. Key inclusion criteria were an estimated GFR between 15 mL/min per 1·73 m2 and 89 mL/min per 1·73 m2, stable allograft function in the last 6 months before study inclusion (<15% change in serum creatinine), and a serum bicarbonate of 22 mmol/L or less. We randomly assigned patients (1:1) to either oral sodium bicarbonate 1·5-4·5 g per day or matching placebo using web-based data management software. Randomisation was stratified by study centre and gender using a permuted block design to guarantee balanced allocation. We did multi-block randomisation with variable block sizes of two and four. Treatment duration was 2 years. Acid-resistant soft gelatine capsules of 500 mg sodium bicarbonate or matching 500 mg placebo capsules were given at an initial dose of 500 mg (if bodyweight was <70 kg) or 1000 mg (if bodyweight was ≥70 kg) three times daily. The primary endpoint was the estimated GFR slope over the 24-month treatment phase. The primary efficacy analyses were applied to a modified intention-to-treat population that comprised all randomly assigned participants who had a baseline visit. The safety population comprised all participants who received at least one dose of study drug. The trial is registered with ClinicalTrials.gov, NCT03102996.

FINDINGS

Between June 12, 2017, and July 10, 2019, 1114 kidney transplant recipients with metabolic acidosis were assessed for trial eligibility. 872 patients were excluded and 242 were randomly assigned to the study groups (122 [50%] to the placebo group and 120 [50%] to the sodium bicarbonate group). After secondary exclusion of two patients, 240 patients were included in the intention-to-treat analysis. The calculated yearly estimated GFR slopes over the 2-year treatment period were a median -0·722 mL/min per 1·73 m2 (IQR -4·081 to 1·440) and mean -1·862 mL/min per 1·73 m2 (SD 6·344) per year in the placebo group versus median -1·413 mL/min per 1·73 m2 (IQR -4·503 to 1·139) and mean -1·830 mL/min per 1·73 m2 (SD 6·233) per year in the sodium bicarbonate group (Wilcoxon rank sum test p=0·51; Welch t-test p=0·97). The mean difference was 0·032 mL/min per 1·73 m2 per year (95% CI -1·644 to 1·707). There were no significant differences in estimated GFR slopes in a subgroup analysis and a sensitivity analysis confirmed the primary analysis. Although the estimated GFR slope did not show a significant difference between the treatment groups, treatment with sodium bicarbonate effectively corrected metabolic acidosis by increasing serum bicarbonate from 21·3 mmol/L (SD 2·6) to 23·0 mmol/L (2·7) and blood pH from 7·37 (SD 0·06) to 7·39 (0·04) over the 2-year treatment period. Adverse events and serious adverse events were similar in both groups. Three study participants died. In the placebo group, one (1%) patient died from acute respiratory distress syndrome due to SARS-CoV-2 and one (1%) from cardiac arrest after severe dehydration following diarrhoea with hypotension, acute kidney injury, and metabolic acidosis. In the sodium bicarbonate group, one (1%) patient had sudden cardiac death.

INTERPRETATION

In adult kidney transplant recipients, correction of metabolic acidosis by treatment with sodium bicarbonate over 2 years did not affect the decline in estimated GFR. Thus, treatment with sodium bicarbonate should not be generally recommended to preserve estimated GFR (a surrogate marker for graft function) in kidney transplant recipients with chronic kidney disease who have metabolic acidosis.

FUNDING

Swiss National Science Foundation.

Sodium zirconium cyclosilicate and metabolic acidosis: Potential mechanisms and clinical consequences

Metabolic acidosis is frequent in chronic kidney disease (CKD) and is associated with accelerated progression of CKD, hypercatabolism, bone disease, hyperkalemia, and mortality. Clinical guidelines recommend a target serum bicarbonate ≥ 22 mmol/L, but metabolic acidosis frequently remains undiagnosed and untreated. Sodium zirconium cyclosilicate (SZC) binds potassium in the gut and is approved to treat hyperkalemia. In clinical trials with a primary endpoint of serum potassium, SZC increased serum bicarbonate, thus treating CKD-associated metabolic acidosis. The increase in serum bicarbonate was larger in patients with more severe pre-existent metabolic acidosis, was associated to decreased serum urea and was maintained for over a year of SZC therapy. SZC also decreased serum urea and increased serum bicarbonate after switching from a potassium-binding resin in normokalemic individuals. Mechanistically, these findings are consistent with SZC binding the ammonium ion (NH₄⁺) generated from urea by gut microbial urease, preventing its absorption and, thus, preventing the liver regeneration of urea and promoting the fecal excretion of H⁺. This mechanism of action may potentially result in benefits dependent on corrected metabolic acidosis (e.g., improved well-being, decreased catabolism, improved CKD mineral bone disorder, better control of serum phosphate, slower progression of CKD) and dependent on lower urea levels, such as decreased protein carbamylation. A roadmap is provided to guide research into the mechanisms and clinical consequences of the impact of SZC on serum bicarbonate and urate.

One-Year Mortality after Hemodialysis Initiation: The Prognostic Role of the CHA2DS2-VASc Score

BACKGROUND

CKD is a significant cause of morbidity, cardiovascular and all-cause mortality. CHA2DS2-VASc is a score used in patients with atrial fibrillation to predict thromboembolic risk; it also appears to be useful to predict mortality risk. The aim of the study was to evaluate CHA2DS2-VASc scores as a tool for predicting one-year mortality after hemodialysis is started and for identifying factors associated with higher mortality.

METHODS

Retrospective analysis of patients who started hemodialysis between January 2014 and December 2019 in Centro Hospitalar Universitário Lisboa Norte. We evaluated mortality within one year of hemodialysis initiation. The CHA2DS2-VASc score was calculated at the start of hemodialysis.

RESULTS

Of 856 patients analyzed, their mean age was 68.3 ± 15.5 years and the majority were male (61.1%) and Caucasian (84.5%). Mortality within one-year after starting hemodialysis was 17.8% (n = 152). The CHA2DS2-VASc score was significantly higher (4.4 ± 1.7 vs. 3.5 ± 1.8, p < 0.001) in patients who died and satisfactorily predicted the one-year risk of mortality (AUC 0.646, 95% CI 0.6-0.7, p < 0.001), with a sensitivity of 71.7%, a specificity of 49.1%, a positive predictive value of 23.9% and a negative predictive value of 89.2%. In the multivariate analysis, CHA2DS2-VASc ≥3.5 (adjusted HR 2.24 95% CI (1.48-3.37), p < 0.001) and central venous catheter at dialysis initiation (adjusted HR 3.06 95% CI (1.93-4.85)) were significant predictors of one-year mortality.

CONCLUSION

A CHA2DS2-VASc score ≥3.5 and central venous catheter at hemodialysis initiation were predictors of one-year mortality, allowing for risk stratification in hemodialysis patients.

Muscle plasticity is influenced by renal function and caloric intake through the FGF23-vitamin D axis

Skeletal muscle, the main metabolic engine in the body of vertebrates, is endowed with great plasticity. The association between skeletal muscle plasticity and two highly prevalent health problems: renal dysfunction and obesity, which share etiologic links as well as many comorbidities, is a subject of great relevance. It is important to know how these alterations impact on the structure and function of skeletal muscle because the changes in muscle phenotype have a major influence on the quality of life of the patients. This literature review aims to discuss the influence of a nontraditional axis involving kidney, bone, and muscle on skeletal muscle plasticity. In this axis, the kidneys play a role as the main site for vitamin D activation. Renal disease leads to a direct decrease in 1,25(OH)₂-vitamin D, secondary to reduction in renal functional mass, and has an indirect effect, through phosphate retention, that contributes to stimulate fibroblast growth factor 23 (FGF23) secretion by bone cells. FGF23 downregulates the renal synthesis of 1,25(OH)₂-vitamin D and upregulates its metabolism. Skeletal production of FGF23 is also regulated by caloric intake: it is increased in obesity and decreased by caloric restriction, and these changes impact on 1,25(OH)₂-vitamin D concentrations, which are decreased in obesity and increased after caloric restriction. Thus, both phosphate retention, that develops secondary to renal failure, and caloric intake influence 1,25(OH)₂-vitamin D that in turn plays a key role in muscle anabolism.

Effects of oral alkali drug therapy on clinical outcomes in pre-dialysis chronic kidney disease patients: a systematic review and meta-analysis

BACKGROUND

Metabolic acidosis accelerates the progression of chronic kidney disease (CKD) and increases the mortality rate. Whether oral alkali drug therapy benefits pre-dialysis CKD patients is controversial. We performed a meta-analysis of the effects of oral alkali drug therapy on major clinical outcomes in pre-dialysis CKD patients.

METHODS

We systematically searched MEDLINE using the Ovid, EMBASE, and Cochrane Library databases without language restriction. We included all eligible clinical studies that involved pre-dialysis CKD adults and compared those who received oral alkali drug therapy with controls.

RESULTS

A total of 18 eligible studies, including 14 randomized controlled trials and 4 cohort studies reported in 19 publications with 3695 participants, were included. Oral alkali drug therapy led to a 55% reduction in renal failure events (relative risk [RR]: 0.45; 95% confidence interval [CI]: 0.25-0.82), a rate of decline in the estimated glomerular filtration rate (eGFR) of 2.59 mL/min/1.73 m2 per year (95% CI, 0.88-4.31). There was no significant effect on decline in eGFR events (RR: 0.34; 95% CI: 0.09-1.23), proteinuria (standardized mean difference: -0.32; 95% CI: -1.08 to 0.43), all-cause mortality events (RR: 0.90; 95% CI: 0.40-2.02) and cardiovascular (CV) events (RR: 1.03; 95% CI: 0.32-3.37) compared with the control groups.

CONCLUSION

Based on the available and low-to-moderate certainty evidence, oral alkali drug therapy might potentially reduce the risk of kidney failure events, but no benefit in reducing all-cause mortality events, CV events, decline in eGFR and porteninuria.

Associations of Metabolic Syndrome and Abdominal Obesity with Anion Gap Metabolic Acidosis among US Adults

BACKGROUND

Obesity is a recently identified risk factor for metabolic acidosis and anion gap elevations in the absence of CKD. Metabolic acidosis is a treatable condition with substantial adverse effects on human health. Additional investigations are needed to characterize at-risk populations and explore potential mechanisms. We hypothesized metabolic syndrome (MetS) and waist circumference (WC) would be closely associated with this pathology.

METHODS

Adult participants from NHANES 1999-2018 meeting study criteria were compiled as main (n=31,163) and fasting (n=12,860) cohorts. Regression models adjusted for dietary acid, eGFR, and other factors examined associations of WC and MetS features with anion gap metabolic acidosis and its components (serum bicarbonate ≤23 mEq/L and anion gap >95th percentile).

RESULTS

Greater WC and MetS features were associated with progressively lower bicarbonate, higher anion gap, and greater odds ratios (OR) of metabolic acidosis (MA) and anion gap metabolic acidosis (AGMA). Compared with the reference, participants with the highest WC had ORs for MA and AGMA of 2.26; 95% CI, 1.96 to 2.62 and 2.89; 95% CI, 1.97 to 4.21; those with three and four versus zero MetS features had ORs for AGMA of 2.52; 95% CI, 1.95 to 2.94 and 3.05; 95% CI, 2.16 to 3.82. Associations of body mass index with outcomes were attenuated or absent after adjustment for WC or MetS. Findings were preserved after excluding eGFR <90 ml/min per 1.73 m² and albuminuria. A lower MA cutoff (<22 mEq/L) raised the estimate of association between MetS and MA (OR for three and four vs zero features: 3.56; 95% CI, 2.53 to 5.02 and 5.44; 95% CI, 3.66 to 8.08).

CONCLUSIONS

Metabolic diseases are characterized by metabolic acidosis and anion gap elevations. Metabolic dysfunction may predispose patients without CKD to systemic acidosis from endogenous sources. Comprehensive acid-base analyses may be informative in patients with metabolic diseases.

Beyond the Urine Anion Gap: In Support of the Direct Measurement of Urinary Ammonium

Ammonium is a major urinary buffer that is necessary for the normal excretion of the daily acid load. Its urinary rate of excretion (UNH₄) may be increased several fold in the presence of extrarenal metabolic acidosis. Therefore, measurement of UNH₄ can provide important clues about causes of metabolic acidosis. Because UNH₄ is not commonly measured in clinical laboratories, the urinary anion gap (UAG) was proposed as its surrogate about 4 decades ago, and it is still frequently used for that purpose. Several published studies strongly suggest that UAG is not a good index of UNH₄ and support the concept that direct measurement of UNH₄ is an important parameter to define in clinical nephrology. Low UNH₄ levels have recently been found to be associated with a higher risk of metabolic acidosis, loss of kidney function, and death in persons with chronic kidney disease, while surrogates like the UAG do not recapitulate this risk. In order to advance the field it is necessary for the medical community to become more familiar with UNH₄ levels in a variety of clinical settings. Herein, we review the literature, searching for available data on UNH₄ under normal and various pathological conditions, in an attempt to establish reference values to interpret UNH₄ results if and when UNH₄ measurements become available as a routine clinical test. In addition, we present original data in 2 large populations that provide further evidence that the UAG is not a good predictor of UNH₄. Measurement of urine NH₄ holds promise to aid clinicians in the care of patients, and we encourage further research to determine its best diagnostic usage.

New mechanisms for the kidney-protective effect of alkali in chronic kidney disease

Worldwide, more than one in ten adults are estimated to have chronic kidney disease (CKD). As CKD progresses, both the cost of treatment and associated risk of morbidity and mortality increase exponentially. As such, there is a great need for therapies that effectively slow CKD progression. Evidence from several small clinical trials indicates that alkali therapy may slow the rate of CKD progression. The biological mechanisms underlying this protective effect, however, remain unknown. In their recently published manuscript, Pastor Arroyo et al. (Clin Sci (Lond) (2022) 136(8): https://doi.org/10.1042/CS20220095) demonstrate that the alkali sodium bicarbonate protects against loss of renal function in a crystal nephropathy model in mice. Using unbiased approaches in both mice and human tissue, the authors go on to identify two novel mechanisms that may underly this protection. The first pathway is through promoting pathways of cell metabolism, which they speculate helps the remaining functional nephrons adapt to the greater metabolic needs required to maintain kidney filtration. The second pathway is by restoration of α-Klotho levels, which may limit the expression of adhesion molecules in the injured kidney. This, the authors speculate, may prevent inflammation from driving the functional decline of the kidney. Identifying these novel pathways represents an important step forward harnessing the potential benefits of alkali therapy in CKD.

Metabolic acidosis post kidney transplantation

Metabolic acidosis, a common complication in patients with chronic kidney disease (CKD), results in a multitude of deleterious effects. Though the restoration of kidney function following transplantation is generally accompanied by a correction of metabolic acidosis, a subset of transplant recipients remains afflicted by this ailment and its subsequent morbidities. The vulnerability of kidney allografts to metabolic acidosis can be attributed to reasons similar to pathogenesis of acidosis in non-transplant CKD, and to transplant specific causes, including donor related, recipient related, immune mediated factors, and immunosuppressive medications. Correction of metabolic acidosis in kidney transplantation either with alkali therapy or through dietary manipulations may have potential benefits and the results of such clinical trials are eagerly awaited. This review summarizes the published evidence on the pathogenesis and clinical consequences of chronic metabolic acidosis in kidney transplant recipients.

[Record-Breaking Acidosis]

Record-Breaking Acidosis Abstract. To maintain a stable cellular metabolism, tight regulation of blood pH within a normal range (pH 7,35-7,45) is essential. Even small aberrations can have detrimental effects, and pH values <6,8 or pH >7,8 are considered - based on current medical and physiological knowledge - incompatible with life [9-19].

Distinct phenotypes of hospitalized patients with hyperkalemia by machine learning consensus clustering and associated mortality risks

BACKGROUND

Hospitalized patients with hyperkalemia are heterogeneous, and cluster approaches may identify specific homogenous groups. This study aimed to cluster patients with hyperkalemia on admission using unsupervised machine learning (ML) consensus clustering approach, and to compare characteristics and outcomes among these distinct clusters.

METHODS

Consensus cluster analysis was performed in 5133 hospitalized adult patients with admission hyperkalemia, based on available clinical and laboratory data. The standardized mean difference was used to identify each cluster's key clinical features. The association of hyperkalemia clusters with hospital and 1-year mortality was assessed using logistic and Cox proportional hazard regression.

RESULTS

Three distinct clusters of hyperkalemia patients were identified using consensus cluster analysis: 1661 (32%) in cluster 1, 2455 (48%) in cluster 2 and 1017 (20%) in cluster 3. Cluster 1 was mainly characterized by older age, higher serum chloride and acute kidney injury (AKI), but lower estimated glomerular filtration rate (eGFR), serum bicarbonate and hemoglobin. Cluster 2 was mainly characterized by higher eGFR, serum bicarbonate and hemoglobin, but lower comorbidity burden, serum potassium and AKI. Cluster 3 was mainly characterized by higher comorbidity burden, particularly diabetes and end-stage kidney disease, AKI, serum potassium, anion gap, but lower eGFR, serum sodium, chloride and bicarbonate. Hospital and 1-year mortality risk was significantly different among the three identified clusters, with highest mortality in cluster 3, followed by cluster 1 and then cluster 2.

CONCLUSION

In a heterogeneous cohort of hyperkalemia patients, three distinct clusters were identified using unsupervised ML. These three clusters had different clinical characteristics and outcomes.

Regulation of Acid-Base Balance in Patients With Chronic Kidney Disease

Normallly the kidneys handle the daily acid load arising from net endogenous acid production from the metabolism of ingested animal protein (acid) and vegetables (base). With chronic kidney disease, reduced acid excretion by the kidneys is primarily due to reduced ammonium excretion such that when acid excertion falls below acid porduction, acid accumulation occurs. With even mild reductions in glomerular filtration rate (60 to 90 ml/min), net acid excretion may fall below net acid production resulting in acid retention which may be initially sequestered in interstitial compartments in the kidneys, bones, and muscles resulting in no fall in measured systemic bicarbonate levels (eubicarbonatemic metabolic acidosis). With greater reductions in kidney function, the greater quantities of acid retained spillover systemically resulting in low pH (overt metabolic acidosis). The evaluation of acid-base balance in patients with CKD is complicated by the heterogeneity of clinical acid-base disorders and by the eubicarbonatemic nature of the early phase of acid retention. If supported by more extensive studies, blood gas analyses to confirm the acid-base disorder and newer ways for assessing the presence of acidosis such as urinary citrate measurements may become routine tools to evaluate and treat acid-base disorders in individuals with CKD.

Exercise and Interorgan Communication: Short-Term Exercise Training Blunts Differences in Consecutive Daily Urine 1H-NMR Metabolomic Signatures between Physically Active and Inactive Individuals

Physical inactivity is a worldwide health problem, an important risk for global mortality and is associated with chronic noncommunicable diseases. The aim of this study was to explore the differences in systemic urine ¹H-NMR metabolomes between physically active and inactive healthy young males enrolled in the X-Adapt project in response to controlled exercise (before and after the 3-day exercise testing and 10-day training protocol) in normoxic (21% O₂), normobaric (~1000 hPa) and normal-temperature (23 °C) conditions at 1 h of 50% maximal pedaling power output (W_peak) per day. Interrogation of the exercise database established from past X-Adapt results showed that significant multivariate differences existed in physiological traits between trained and untrained groups before and after training sessions and were mirrored in significant differences in urine pH, salinity, total dissolved solids and conductivity. Cholate, tartrate, cadaverine, lysine and N6-acetyllisine were the most important metabolites distinguishing trained and untrained groups. The relatively little effort of 1 h 50% W_peak per day invested by the untrained effectively modified their resting urine metabolome into one indistinguishable from the trained group, which hence provides a good basis for the planning of future recommendations for health maintenance in adults, irrespective of the starting fitness value. Finally, the 3-day sessions of morning urine samples represent a good candidate biological matrix for future delineations of active and inactive lifestyles detecting differences unobservable by single-day sampling due to day-to-day variability.

The Impact of Chronic Kidney Disease on Nutritional Status and Its Possible Relation with Oral Diseases

Several studies have demonstrated a strong relation between periodontal diseases and chronic kidney disease (CKD). The main mechanisms at the base of this link are malnutrition, vitamin dysregulation, especially of B-group vitamins and of C and D vitamins, oxidative stress, metabolic acidosis and low-grade inflammation. In particular, in hemodialysis (HD) adult patients, an impairment of nutritional status has been observed, induced not only by the HD procedures themselves, but also due to numerous CKD-related comorbidities. The alteration of nutritional assessment induces systemic manifestations that have repercussions on oral health, like oral microbiota dysbiosis, slow healing of wounds related to hypovitaminosis C, and an alteration of the supporting bone structures of the oral cavity related to metabolic acidosis and vitamin D deficiency. Low-grade inflammation has been observed to characterize periodontal diseases locally and, in a systemic manner, CKD contributes to the amplification of the pathological process, bidirectionally. Therefore, CKD and oral disease patients should be managed by a multidisciplinary professional team that can evaluate the possible co-presence of these two pathological conditions, that negatively influence each other, and set up therapeutic strategies to treat them. Once these patients have been identified, they should be included in a follow-up program, characterized by periodic checks in order to manage these pathological conditions.

Lower bicarbonate level is associated with CKD progression and all-cause mortality: a propensity score matching analysis

Background

Although metabolic acidosis is known as a potential complication of chronic kidney disease (CKD), there is limited information concerning the association between metabolic acidosis and clinical outcomes.

Methods

Five hundred fifty-two patients referred to renal division of Iwata City Hospital from 2015 to 2017 were included as a retrospective CKD cohort, and finally 178 patients with CKD stage III or IV and 20 to 80 years of age were analyzed. We examined the association between serum bicarbonate (HCO₃⁻) levels and clinical outcomes using Kaplan-Meier methods after the matching of baseline characteristics by propensity scores.

Results

Of 178 patients with CKD, patients with lower HCO₃⁻ levels (N = 94), as compared with patients with higher HCO₃⁻ levels (N = 84), were more likely to be male (P < 0.05), had more severe CKD stages (P < 0.05), more frequent use of renin-angiotensin system inhibitor (P < 0.05) or uric acid lowering agent (P < 0.001), heavier body weight (P < 0.001) and lower estimated glomerular filtration rate (P < 0.05). In Kaplan-Meier analysis after propensity score matching, the incidence of composite outcome as the doubling of serum creatinine level from baseline, end-stage kidney disease requiring the initiation of dialysis, or death from any causes was significantly fewer in the higher HCO₃⁻ group than the lower HCO₃⁻ group (N = 57 each group, P = 0.016).

Conclusions

Lower HCO₃⁻ level is significantly associated with the doubling of serum creatinine level, end-stage kidney disease or all-cause mortality in patients with CKD.

Trial registration

This study was registered with the Clinical Trial Registry of the University Hospital Medical Information Network (http://www.umin.ac.jp/, study number: UMIN000044861).

Trajectories of Nutritional Parameters Before and After Prescribed Oral Nutritional Supplements: A Longitudinal Cohort Study of Patients With Chronic Kidney Disease Not Requiring Dialysis

Background:

The association between oral nutritional supplement use and nutritional parameters among patients with nondialysis chronic kidney disease (CKD-ND) with or at high risk of undernutrition/protein-energy wasting has not been previously studied. The definition of patient subgroups most likely to benefit from oral nutritional supplementation (ONS) is also an area where more research is needed.

Objective:

To assess nutritional parameter trajectories among patients with CKD-ND prescribed oral nutritional supplements in British Columbia, and to compare trajectories by nutritional phenotype.

Design:

Longitudinal cohort study, pre-post design.

Setting:

Multidisciplinary CKD clinics across British Columbia.

Patients:

A total of 3957 adult patients with CKD-ND, who entered multidisciplinary CKD clinics during 2010 to 2019, met criteria for oral nutritional supplement prescription based on dietitian assessment, and received ≥1 oral nutritional supplement prescription.

Measurements:

Longitudinal nutritional parameters, including body mass index (BMI), serum albumin, serum bicarbonate, serum phosphate, and neutrophil-to-lymphocyte ratio (NLR).

Methods:

Using linear mixed models, slopes for nutritional and inflammation parameters were assessed in the 2-year periods before and after the first oral nutritional supplement prescription. Hierarchical cluster analysis was applied to identify nutritional phenotypes using baseline data, and slope analysis was repeated by cluster.

Results:

In the pre-oral-nutritional-supplement period, declines in BMI (−0.87 kg/m2/year, 95% confidence interval [CI]: −0.99 to −0.75), albumin (−1.11 g/L/year, 95% CI: −1.27 to −0.95), and bicarbonate (−0.49 mmol/L/year; 95% CI: −0.59 to −0.39), and increases in NLR (+0.79/year; 95% CI: 0.60 to 0.98) and phosphate (+0.05 mmol/L/year; 95% CI: 0.04 to 0.06) were observed. Following oral nutritional supplement prescription, there were statistically significant increases in BMI slope (+0.91 kg/m2/year, P < .0001), albumin slope (+0.82 g/L/year, P < .0001), and phosphate slope (+0.02 mmol/L/year, P = .005), as well as a decline in NLR slope of −0.55/year ( P < .0001). There was no significant change in bicarbonate slope. Cluster analysis identified 5 distinct phenotypes. The cluster with the highest mean baseline NLR and lowest mean BMI demonstrated the greatest number of improvements in nutritional parameter slopes in the post-oral-nutritional-supplement period.

Limitations:

Possibility of residual confounding. Data on dietary intake, muscle mass, and nutritional scoring systems were not available in the registry.

Conclusions:

Among patients with CKD-ND prescribed oral nutritional supplements, there were improvements in nutrition/inflammation parameters over time following the first ONS prescription. The heterogeneity in response to ONS by cluster subgroup suggests an individualized approach to nutritional management may be beneficial.

Effect of Sodium Zirconium Cyclosilicate on Serum Potassium and Bicarbonate in Patients with Hyperkalemia and Metabolic Acidosis Associated with Chronic Kidney Disease: Rationale and Design of the NEUTRALIZE Study

INTRODUCTION

Sodium zirconium cyclosilicate (SZC) is a selective potassium (K+) binder for hyperkalemia management that provides rapid and sustained correction of hyperkalemia. The NEUTRALIZE study is investigating whether SZC, in addition to correcting hyperkalemia and maintaining normal serum K+, can provide sustained increases in serum bicarbonate (HCO3-) in patients with hyperkalemia and metabolic acidosis associated with chronic kidney disease (CKD).

METHODS

This is a prospective, randomized, double-blind, placebo-controlled phase 3b study of US adults with stage 3-5 CKD not on dialysis with hyperkalemia (K+ >5.0-≤5.9 mmol/L) and low-serum HCO3- (16-20 mmol/L). In the open-label correction phase, all eligible patients receive SZC 10 g three times daily for up to 48 h. Patients who achieve normokalemia (K+ ≥3.5-≤5.0 mmol/L) are then randomized 1:1 to once-daily SZC 10 g or placebo for a 4-week, double-blind, placebo-controlled maintenance phase. The primary endpoint is the proportion of patients with normokalemia at the end of treatment (EOT) without rescue therapy for hyperkalemia. Key secondary endpoints include mean change in serum HCO3-, the proportion of patients with an increase in serum HCO3- of ≥2 or ≥3 mmol/L without rescue therapy for metabolic acidosis, and the proportion of patients with serum HCO3- ≥22 mmol/L at EOT.

CONCLUSIONS

NEUTRALIZE will establish whether SZC can provide sustained increases in serum HCO3- while lowering serum K+ in patients with hyperkalemia and CKD-associated metabolic acidosis and may provide insights on the mechanism(s) underlying the increased serum HCO3- with SZC treatment.

Nutritional Status, Nutritional Phenotypes, and Oral Nutritional Supplement Prescription Patterns Among Patients With Non-Dialysis Chronic Kidney Disease in British Columbia

OBJECTIVES

Management of protein-energy wasting and undernutrition with oral nutritional supplements (ONS) has not been systematically studied in the non-dialysis chronic kidney disease (CKD-ND) population. We aimed to describe nutritional status, identify phenotypes of patients prescribed ONS, and evaluate ONS prescription patterns among CKD-ND patients in British Columbia.

DESIGN AND METHODS

This observational study assessed adult CKD-ND patients who entered multidisciplinary CKD clinics during 2013-2018 in British Columbia. Descriptive statistics were used to describe baseline nutrition and inflammation parameters among patients prescribed ONS versus patients not prescribed ONS within 1 year of clinic entry. Hierarchical clustering method with consensus clustering was applied to identify phenotypes of patients prescribed ONS. Multivariable logistic regression was used to assess the associations between ONS prescription and health region/dietitian full-time equivalents per 1,000 CKD patients.

RESULTS

Of 15,859 CKD-ND patients, 9% of patients entering CKD clinics were prescribed ONS within 1 year of clinic entry, and these patients demonstrated lower baseline estimated glomerular filtration rate, body mass index (BMI), serum albumin, bicarbonate, as well as greater age, serum phosphate, and neutrophil-to-lymphocyte ratio compared with those not receiving ONS. Cluster analysis revealed 5 phenotypes of ONS users: cluster 1 had the highest mean neutrophil-to-lymphocyte ratio; cluster 2 had the lowest mean albumin; cluster 3 had the lowest mean BMI; cluster 4 had the highest mean BMI; and cluster 5 had the lowest mean bicarbonate. There was regional variability in ONS prescription, and an odds ratio for ONS prescription of 1.32 (95% confidence interval 1.16-1.50) for every 1-unit increase in dietitian full-time equivalents per 1,000 patients. Over 3 years of follow-up, overall ONS use among CKD-ND patients remained stable.

CONCLUSIONS

This study demonstrates appropriate prescribing of ONS to patients with suboptimal nutritional status, although regional variation exists. Patients receiving ONS represent a heterogenous group with phenotypes reflecting several clinical and biochemical features of the protein-energy wasting syndrome. These findings will assist with updating ONS policy, planning quality improvement initiatives, and informing dietitian resource allocation.

Time-updated anion gap and cardiovascular events in advanced CKD: a cohort study

Background

Studies examining associations between metabolic acidosis and cardiovascular events in chronic kidney disease (CKD) have shown conflicting results and have not differentiated between normal anion gap (hyperchloremic) acidosis and high anion gap acidosis. We aimed to examine the impact of normal and high anion gap acidosis, separately, on the risk of cardiovascular events among patients with CKD.

Methods

This retrospective cohort study included 1168 patients with an estimated glomerular filtration rate (eGFR) of 10–60 mL/min/1.73 m² and available data on anion gap. We analyzed the association of time-updated high anion gap (anion gap ≥9.2) with the rate of cardiovascular events using marginal structural models (MSMs) to account for time-dependent confounding. We also analyzed the association between time-updated normal anion gap acidosis (anion-gap-adjusted bicarbonate level ≤22.8 mEq/L) and cardiovascular events.

Results

The mean baseline eGFR of the cohort was 28 mL/min/1.73 m². The prevalence rates of high anion gap in CKD stages G3a, G3b, G4 and G5 were 20%, 16%, 27% and 46%, respectively. During a median follow-up period of 2.9 years, 132 patients developed cardiovascular events (3.3/100 patient-years). In MSMs, high anion gap was associated with a higher rate of cardiovascular events [hazard ratio (HR) 1.87; 95% confidence interval (95% CI) 1.13‒3.09; P = 0.02] and the composite of cardiovascular events or all-cause death (HR 3.28; 95% CI 2.19‒4.91; P < 0.001). Normal anion gap acidosis was not associated with cardiovascular events (HR 0.74; 95% CI, 0.47‒1.17; P = 0.2).

Conclusions

Among patients with advanced CKD, high anion gap was associated with an increased risk of cardiovascular events.

The Effects of Oral Sodium Bicarbonate on Renal Function and Cardiovascular Risk in Patients with Chronic Kidney Disease: A Systematic Review and Meta-Analysis

OBJECTIVE

Oral sodium bicarbonate is often used to correct acid-base disturbance in patients with chronic kidney disease (CKD). However, there is little evidence on patient-level benign outcomes to support the practice.

METHODS

We conducted a systematic review and meta-analysis to examine the efficacy and safety of oral sodium bicarbonate in CKD patients. A total of 1853 patients with chronic metabolic acidosis or those with low-normal serum bicarbonate (22-24 mEq/L) were performed to compare the efficacy and safety of oral sodium bicarbonate in patients with CKD.

RESULTS

There was a significant increase in serum bicarbonate level (MD 2.37 mEq/L; 95% CI, 1.03 to 3.72) and slowed the decline in estimated glomerular filtration rate (eGFR) (MD -4.44 mL/min per 1.73 m2, 95% CI, -4.92 to -3.96) compared with the control groups. The sodium bicarbonate lowered T50-time, an indicator of vascular calcification (MD -20.74 min; 95% CI, -49.55 to 8.08); however, there was no significant difference between the two groups. In addition, oral sodium bicarbonate dramatically reduced systolic blood pressure (MD -2.97 mmHg; 95% CI, -5.04 to -0.90) and diastolic blood pressure (MD -1.26 mmHg; 95% CI, -2.33 to -0.19). There were no statistically significant body weight, urine pH and mean mid-arm muscle circumference.

CONCLUSION

Treatment of metabolic acidosis with sodium bicarbonate may slow the decline rate of kidney function and potentially significantly improve vascular endothelial function in patients with CKD.

PROSPERO REGISTRATION NUMBER

CRD42020207185.

Establishment of an RI for the urine ammonia-to-creatinine ratio in dogs

Background

Ammonia is produced and excreted by the kidney, contributing to systemic acid‐base homeostasis through the production of bicarbonate. Disorders of acid‐base balance can lead to many clinical problems and measuring ammonia excretion helps in determining if the kidneys are responding to acid‐base challenges appropriately. Reference intervals are integral to clinical decision‐making, and there is no current RI for the urine ammonia‐to‐creatinine ratio (UACR) in dogs.

Objective

This study aimed to generate an RI for the UACR in healthy adult dogs.

Methods

The study used adult, client‐owned dogs that were presented to the University of Florida Primary Care and Dentistry service (n = 60). Physical examinations were performed and serum chemistry and urinalysis samples were obtained. Urine ammonia and creatinine concentrations were determined. Dogs were excluded if there were significant abnormalities in either their urinalysis or serum chemistry results. The RI for the UACR was calculated according to the recommendation of the American Society for Veterinary Clinical Pathology. Data were evaluated for correlation with serum bicarbonate, weight, age, and sex.

Results

The RIs for the UACR were 0.16‐23.69 with 90% confidence intervals for the lower and upper limits of (0.13‐1.17) and (20.50‐23.75), respectively. No significant impact of age, sex, or weight was found. There was no discernable relationship between serum bicarbonate and UACR.

Conclusions

Establishing an RI for UACR in healthy adult dogs will allow for further studies to determine if alterations are observed during specific disease states.