A systematic review of glomerular hyperfiltration assessment and definition in the medical literature

Kidney Measurement and Glomerular Filtration Rate Evolution in Children with Polycystic Kidney Disease

Autosomal dominant polycystic kidney disease (ADPKD) is an inherited disorder characterized by renal tubular cystic dilatations. The cysts can develop anywhere along the nephron, and over time the cystic dilatation leads to kidney enlargement. On the other hand, the cysts begin to reduce the number of functional nephrons as a consequence of cystic expansion that further contributes to the decline in renal function over the years. The pressure exerted by the dilated cysts leads to compensatory mechanisms that further contribute to the decline in renal function. These structural changes are responsible of glomerular hyperfiltration states, albuminuria, proteinuria, and hematuria. However, the presentation of ADPKD varies in children, from a completely asymptomatic child with incidental ultrasound detection of cysts to a rapidly progressive disease. There have been reports of early onset ADPKD in children younger than 2 years that showed a more rapid decline in renal function. ADPKD is caused by a mutation in PKD1 and PKD2 genes. Today, the PKD1 gene mutation seems to account for up to 85% of the cases worldwide, and it is associated with worse renal outcomes. Individuals with PKD2 gene mutation seem to present a milder form of the disease, with a more delayed onset of end-stage kidney disease. The cardinal sign of ADPKD is the presence of renal cysts during renal ultrasound. The current guidelines provide clinicians the recommendations for genetic testing in children with a positive family history. Given that the vast majority of children with ADPKD present with normal or supra-normal kidney function, we explored the glomerular filtration rates dynamics and the renal ultrasound-adjusted percentiles. In total, 14 out of 16 patients had kidney percentiles over 90%. The gene mutations were equally distributed among our cohort. In addition, we compared the modified Schwartz formula to the quadratic equation after adjusting the serum creatinine measurements. It seems that even though children with ADPKD have enlarged kidneys, the renal function is more likely normal or near normal when the quadratic estimation of glomerular filtration rate is used (qGFR tended to be lower, 111.95 ± 12.43 mL/min/1.73 m2 when compared to Schwartz eGFR 126.28 ± 33.07 mL/min/1.73 m2, p = 0.14). Also, when the quadratic equation was employed, not even a single patient reached the glomerular hyperfiltration threshold. The quadratic formula showed that glomerular filtration rates are linear or slightly decreasing after 1 year of follow-up (quadratic ΔeGFR = -0.32 ± 5.78 mL/min/1.73 m2), as opposed to the Schwartz formula that can falsely classify children in a hyperfiltration state (ΔeGFR = 7.51 ± 19.46 mL/min/1.73 m2), p = 0.019.

The 10-Year Effects of Intensive Lifestyle Intervention on Kidney Outcomes

Rationale & Objective

Limited data exist on longitudinal kidney outcomes after nonsurgical obesity treatments. We investigated the effects of intensive lifestyle intervention on kidney function over 10 years.

Study Design

Post hoc analysis of Action for Health in Diabetes (Look AHEAD) randomized controlled trial.

Setting & Participants

We studied 4,901 individuals with type 2 diabetes and body mass index of ≥25 kg/m2 enrolled in Look AHEAD (2001-2015). The original Look AHEAD trial excluded individuals with 4+ urine dipstick protein, serum creatinine level of >1.4 mg/dL (women), 1.5 mg/dL (men), or dialysis dependence.

Exposures

Intensive lifestyle intervention versus diabetes support and education (ie, usual care).

Outcome

Primary outcome was estimated glomerular filtration rate (eGFR, mL/min/1.73 m2) slope. Secondary outcomes were mean eGFR, slope, and mean urine albumin to creatinine ratio (UACR, mg/mg).

Analytical Approach

Linear mixed-effects models with random slopes and intercepts to evaluate the association between randomization arms and within-individual repeated measures of eGFR and UACR. We tested for effect modification by baseline eGFR.

Results

At baseline, mean eGFR was 89, and 83% had a normal UACR. Over 10 years, there was no difference in eGFR slope (+0.064 per year; 95% CI: -0.036 to 0.16; P = 0.21) between arms. Slope or mean UACR did not differ between arms. Baseline eGFR, categorized as eGFR of <80, 80-100, or >100, did not modify the intervention's effect on eGFR slope or mean.

Limitations

Loss of muscle may confound creatinine-based eGFR.

Conclusions

In patients with type 2 diabetes and preserved kidney function, intensive lifestyle intervention did not change eGFR slope over 10 years. Among participants with baseline eGFR <80, lifestyle intervention had a slightly higher longitudinal mean eGFR than usual care. Further studies evaluating the effects of intensive lifestyle intervention in people with kidney disease are needed.

Age- and gender-adjusted estimated glomerular filtration rate definition reveals hyperfiltration as a risk factor for renal function deterioration in type 2 diabetes

AIM

To assess the role of hyperfiltration for diabetic kidney disease (DKD) progression.

MATERIALS AND METHODS

A retrospective observational cohort study enrolled type 2 diabetes (T2D) patients with an initial estimated glomerular filtration rate (eGFR) of 60 mL/min/1.73m2 or higher. Patients were categorized into two groups: hyperfiltration (eGFR exceeding the age- and gender-specific 95th percentile values from a prior national cohort study) and normofiltration. Rapid DKD progression was defined as an eGFR decline of more than 5 mL/min/1.73m2/year. We used a linear mixed effect model and Cox regression with time-varying covariate model to compare eGFR changes and identify factors associated with rapid DKD progression.

RESULTS

Of the enrolled 7563 T2D patients, 7.2% had hyperfiltration. The hyperfiltration group exhibited a higher rate of eGFR decline compared with the normofiltration group (-2.0 ± 0.9 vs. -1.1 ± 0.9 mL/min/1.73m2/year; P < .001). During an average follow-up period of 4.65 ± 3.86 years, 24.7% of patients with hyperfiltration experienced rapid DKD progression, compared with 15.7% of patients with normofiltration (P < .001). Cox regression analyses identified that initial hyperfiltration was a significant determinant of rapid DKD progression, with a hazard ratio of 1.66 (95% confidence interval: 1.41-1.95; P < .001). When combined with albuminuria, the risk of progression was further compounded (hazard ratio 1.76-3.11, all P < .001).

CONCLUSIONS

In addition to using the current Kidney Disease: Improving Global Outcomes CGA classification system, considering glomerular hyperfiltration status can improve the accuracy of predicting DKD progression.

Fractional Excretion of Urate is Positively Associated with Type 2 Diabetes in HUA Patients: A Cross-Sectional Study

Purpose

People with hyperuricemia (HUA) are often related to metabolic disorders such as diabetes, metabolic syndrome (MetS), and obesity. However, the correlation between excretion of uric acid and these diseases is unclear. Our study aimed to explore the relationship between uric acid excretion and type 2 diabetes (T2D).

Methods

A total of 228 HUA patients from Tianjin Medical University General Hospital from 2022 to 2023 were included in this study. We collected demographic, biochemical, and anthropometric data on each subject. Urine uric acid excretion (UUAE) was calculated enzymatically from a single urine collection that lasted 24 hours. And fractional excretion of uric acid (FEUA) was calculated from serum uric acid and creatinine and uric acid and creatinine. Binary logistic regression modeling assessed the association between uric acid excretion and T2D.

Results

Of the 228 subjects, 13.4% had T2D and 48.7% had obesity. The obesity group had a lower FEUA (p<0.05) and a higher UUAE compared to the control group (p<0.05). And FEUA had a stronger correlation with the risk of T2D (p<0.001). Also, there was a negative association between BMI and FEUA and a positive link between BMI and UUAE in the outpatients.

Conclusion

Increased FEUA levels were significantly associated with T2D in HUA patients. Therefore, routine calculating of FEUA is essential for proper diagnosis and appropriate treatment T2D of in HUA patients.

Assessment of Risk Factors for Acute Kidney Injury with Machine Learning Tools in Children Undergoing Hematopoietic Stem Cell Transplantation

Background: Although acute kidney injury (AKI) is a common complication in patients undergoing hematopoietic stem cell transplantation (HSCT), its prophylaxis remains a clinical challenge. Attempts at prevention or early diagnosis focus on various methods for the identification of factors influencing the incidence of AKI. Our aim was to test the artificial intelligence (AI) potential in the construction of a model defining parameters predicting AKI development. Methods: The analysis covered the clinical data of children followed up for 6 months after HSCT. Kidney function was assessed before conditioning therapy, 24 h after HSCT, 1, 2, 3, 4, and 8 weeks after transplantation, and, finally, 3 and 6 months post-transplant. The type of donor, conditioning protocol, and complications were incorporated into the model. Results: A random forest classifier (RFC) labeled the 93 patients according to presence or absence of AKI. The RFC model revealed that the values of the estimated glomerular filtration rate (eGFR) before and just after HSCT, as well as methotrexate use, acute graft versus host disease (GvHD), and viral infection occurrence, were the major determinants of AKI incidence within the 6-month post-transplant observation period. Conclusions: Artificial intelligence seems a promising tool in predicting the potential risk of developing AKI, even before HSCT or just after the procedure.

Pre-transplant glomerular hyperfiltration is not a risk factor for increased renal morbidity and mortality in pediatric stem cell transplant patients

Low glomerular filtration rate (GFR) prior to stem cell transplant (SCT) is associated with increased morbidity and mortality. The implications of abnormally high GFRs, or glomerular hyperfiltration, prior to SCT are unknown. Twenty-two of 74 consecutive pediatric SCT patients over 2 years old at a single center were hyperfiltrating prior to SCT, median nuclear medicine GFR 154 mL/min/1.73 m2 [interquartile range: 146-170]. There was no association between hyperfiltration and any transplant demographics, nor between hyperfiltration and acute kidney injury (p = .8), renal replacement therapy (p = .63), 1-year event-free survival (p = 1), or abnormal creatinine-based estimated GFR at a median follow-up of 4.7 years (p = .73).

Prevalence and risk factors of glomerular hyperfiltration in adults with type 2 diabetes: A population-based study

AIMS

Glomerular hyperfiltration characterises the earliest stage of diabetic nephropathy and predicts adverse kidney and cardiovascular outcomes. We aimed to assess the prevalence and risk factors of glomerular hyperfiltration in a population-based contemporary cohort of individuals with type 2 diabetes (T2D).

MATERIALS AND METHODS

The prevalence of unequivocal glomerular hyperfiltration (defined by an estimated glomerular filtration rate >120 mL/min/1.73 m2 ) and its associated risk factors were identified in a cohort of 202,068 adult patients with T2D receiving specialist care in 2021-2022, whose center-aggregated data were automatically extracted from electronic medical records of 75 diabetes clinics in Italy.

RESULTS

Glomerular hyperfiltration was identified in 1262 (0.6%) participants. The prevalence of glomerular hyperfiltration varied widely across centers (0%-3.4%) and correlated with mean center age, HbA1c , body mass index (BMI), and low-density lipoprotein cholesterol. Patients in centers with high glomerular hyperfiltration prevalence (>0.8%) were more often men and had lower age and BMI, but more frequent albuminuria and worse glucose, lipid, and blood pressure control, compared with low-normal prevalence centers.

CONCLUSIONS

Unequivocal glomerular hyperfiltration can be identified in up to 3.4% of patients receiving up-to-date specialist diabetes care. Glomerular hyperfiltration prevalence varies across centers and substantially increases with suboptimal control of metabolic risk factors, which would require improved management to mitigate the negative health consequences of this pathological condition.

KIM-1, IL-18, and NGAL, in the Machine Learning Prediction of Kidney Injury among Children Undergoing Hematopoietic Stem Cell Transplantation-A Pilot Study

Children undergoing allogeneic hematopoietic stem cell transplantation (HSCT) are prone to developing acute kidney injury (AKI). Markers of kidney damage: kidney injury molecule (KIM)-1, interleukin (IL)-18, and neutrophil gelatinase-associated lipocalin (NGAL) may ease early diagnosis of AKI. The aim of this study was to assess serum concentrations of KIM-1, IL-18, and NGAL in children undergoing HSCT in relation to classical markers of kidney function (creatinine, cystatin C, estimated glomerular filtration rate (eGFR)) and to analyze their usefulness as predictors of kidney damage with the use of artificial intelligence tools. Serum concentrations of KIM-1, IL-18, NGAL, and cystatin C were assessed by ELISA in 27 children undergoing HSCT before transplantation and up to 4 weeks after the procedure. The data was used to build a Random Forest Classifier (RFC) model of renal injury prediction. The RFC model established on the basis of 3 input variables, KIM-1, IL-18, and NGAL concentrations in the serum of children before HSCT, was able to effectively assess the rate of patients with hyperfiltration, a surrogate marker of kidney injury 4 weeks after the procedure. With the use of the RFC model, serum KIM-1, IL-18, and NGAL may serve as markers of incipient renal dysfunction in children after HSCT.

Glomerular hyperfiltration is an independent predictor of postoperative outcomes: A NSQIP multi-specialty surgical cohort analysis

AIM

While high estimated glomerular filtration rate (eGFR) has been associated with increased overall mortality, its effect on postoperative outcomes is relatively understudied. We sought to investigate the association between high eGFR and 30-day postoperative outcomes using a multi-specialty surgical cohort.

METHODS

Using the National Surgical Quality Improvement Program database, we selected adult for whom eGFR could be calculated using the 2021 Chronic Kidney Disease Epidemiology Collaboration equation. Based on sex-specific distributions of eGFR stratified by age quintiles, we classified patients into low (<5th percentile), normal (5-95th percentile) and high eGFR (>95th percentile). The primary outcome was a composite of any 30-day major adverse outcomes, including: death, reoperation, cardiac arrest, myocardial infarction and stroke. Secondary outcomes included 30-day infectious complications, venous thromboembolism (VTE), bleeding requiring transfusion, prolonged length of stay and unplanned readmission. After matching for demographic differences, comorbidity burden and operative characteristics, logistic regression models were used to evaluate the association between extremes of eGFR and the outcomes of interest.

RESULTS

Of 1 668 447 patients, 84 115 (5.07%) had a high eGFR. High eGFR was not associated with major adverse outcomes (odds ratio [OR] 1.00 [95% confidence interval (CI): 0.97, 1.03]); however, it was associated with reoperation (OR 1.04 [95% CI: 1.00,1.08]), infectious complications (OR 1.14 [95% CI: 1.11, 1.16]), VTE (OR 1.15 [95% CI: 1.09, 1.22]) and prolonged length of stay (OR 1.19 [95% CI: 1.16, 1.21]).

CONCLUSION

Our findings support an association between high eGFR and adverse 30-day postoperative outcomes.

Pharmacokinetic relevance of glomerular hyperfiltration for drug dosing

In chronic kidney disease (CKD) patients, hypofiltration may lead to the accumulation of drugs that are cleared mainly by the kidney and, vice versa, hyperfiltration may cause augmented renal excretion of the same drugs. In this review we mainly focus on the issue of whether hyperfiltration significantly impacts the renal clearance of drugs and whether the same alteration may demand an up-titration of the doses applied in clinical practice. About half of severely ill, septic patients and patients with burns show glomerular hyperfiltration and this may lead to enhanced removal of drugs such as hydrophilic antibiotics and a higher risk of antibiotic treatment failure. In general, hyperfiltering obese individuals show higher absolute drug clearances than non-obese control subjects, but this depends on the body size descriptor adopted to adjust for fat excess. Several mechanisms influence pharmacokinetics in type 2 diabetes, including renal hyperfiltration, reduced tubular reabsorption and augmented tubular excretion. However, no consistent pharmacokinetic alteration has been identified in hyperfiltering obese subjects and type 2 diabetics. Non-vitamin K antagonist oral anticoagulants (NOACs) have exhibited lower plasma concentrations in hyperfiltering patients in some studies in patients with atrial fibrillation, but a recent systematic review failed to document any excess risk for stroke and systemic embolism in these patients. Hyperfiltration is common among severely ill patients in intensive care units and drug levels should be measured whenever possible in these high-risk patients to prevent underdosing and treatment failure. Hyperfiltration is also common in patients with obesity or type 2 diabetes, but no consistent pharmacokinetic alteration has been described in these patients. No NOAC dose adjustment is indicated in patients with atrial fibrillation being treated with these drugs.

Association of eGFR and mortality with use of a joint model: results of a nationwide study in Iceland

OBJECTIVES

Prior studies on the association of estimated glomerular filtration rate (eGFR) and mortality have failed to include methods to account for repeated eGFR determinations. The aim of this study was to estimate the association between eGFR and mortality in the general population in Iceland employing a joint model.

METHODS

We obtained all serum creatinine and urine protein measurements from all clinical laboratories in Iceland in the years 2008-16. Clinical data were obtained from nationwide electronic medical records. eGFR was calculated using the Chronic Kidney Disease Epidemiology Collaboration equation and categorized as follows: 0-29, 30-44, 45-59, 60-74, 75-89, 90-104 and >104 mL/min/1.73 m2. A multiple imputation method was used to account for missing urine protein data. A joint model was used to assess risk of all-cause mortality.

RESULTS

We obtained 2 120 147 creatinine values for 218 437 individuals, of whom 84 364 (39%) had proteinuria measurements available. Median age was 46 (range 18-106) years and 47% were men. Proteinuria associated with increased risk of death for all eGFR categories in persons of all ages. In persons ≤65 years, the lowest risk was observed for eGFR of 75-89 mL/min/1.73 m2 without proteinuria. For persons aged >65 years, the lowest risk was observed for eGFR of 60-74 mL/min/1.73 m2 without proteinuria. eGFR of 45-59 mL/min/1.73 m2 without proteinuria did not associate with increased mortality risk in this age group. eGFR >104 mL/min/1.73 m2 associated with increased mortality.

CONCLUSIONS

These results lend further support to the use of age-adapted eGFR thresholds for defining chronic kidney disease. Very high eGFR needs to be studied in more detail with regard to mortality.

Population pharmacokinetics of Amisulpride in Chinese patients with schizophrenia with external validation: the impact of renal function

Introduction: Amisulpride is primarily eliminated via the kidneys. Given the clear influence of renal clearance on plasma concentration, we aimed to explicitly examine the impact of renal function on amisulpride pharmacokinetics (PK) via population PK modelling and Monte Carlo simulations. Method: Plasma concentrations from 921 patients (776 in development and 145 in validation) were utilized. Results: Amisulpride PK could be described by a one-compartment model with linear elimination where estimated glomerular filtration rate, eGFR, had a significant influence on clearance. All PK parameters (estimate, RSE%) were precisely estimated: apparent volume of distribution (645 L, 18%), apparent clearance (60.5 L/h, 2%), absorption rate constant (0.106 h-1, 12%) and coefficient of renal function on clearance (0.817, 10%). No other significant covariate was found. The predictive performance of the model was externally validated. Covariate analysis showed an inverse relationship between eGFR and exposure, where subjects with eGFR= 30 mL/min/1.73 m2 had more than 2-fold increase in AUC, trough and peak concentration. Simulation results further illustrated that, given a dose of 800 mg, plasma concentrations of all patients with renal impairment would exceed 640 ng/mL. Discussion: Our work demonstrated the importance of renal function in amisulpride dose adjustment and provided a quantitative framework to guide individualized dosing for Chinese patients with schizophrenia.

The Association Between Metabolic Syndrome, Hyperfiltration, and Long-Term GFR Decline in the General Population

Introduction

One-quarter of adults worldwide meet the criteria of metabolic syndrome (MetS). MetS increases the risk of diabetes, chronic kidney disease (CKD), and cardiovascular disease. However, the association between MetS, hyperfiltration, and long-term glomerular filtration rate (GFR) decline in the general population is unknown.

Methods

In the Renal Iohexol Clearance Survey (RENIS), we investigated 1551 people aged 50 to 63 years; representative of the general population without diabetes, cardiovascular disease, or kidney disease. The GFR was measured using iohexol clearance at baseline and twice during 11 years of follow-up. Hyperfiltration at baseline was defined as an absolute GFR (ml/min) above the 90th percentile adjusted for sex, age, and height, because these variables correlate with nephron number. MetS was defined as increased waist circumference and 2 risk factors among hypertension, hyperglycemia, elevated triglycerides, and low high density lipoprotein (HDL)-cholesterol levels. The GFR decline rate was calculated using linear mixed models.

Results

MetS was associated with hyperfiltration at baseline (odds ratio [OR] 2.4; 95% CI: 1.7-3.5, P < 0.001) and a steeper GFR decline rate during follow-up (-0.30 [-0.43 to -0.16] ml/min per 1.73 m2/yr). Compared to those without MetS, GFR decline was -0.83 (95% CI: -1.13 to -0.53) ml/min per 1.73 m2/yr in those with MetS and baseline hyperfiltration and -0.15 (-0.30 to 0.00) in those MetS without hyperfiltration, P = 0.2 for interaction.

Conclusions

In the nondiabetic general population, those with MetS had an increased OR of hyperfiltration and steeper long-term GFR decline. Randomized controlled trials are needed to explore whether treatment of hyperfiltration can prevent loss of GFR in persons with MetS.

Low agreement between various eGFR formulae in pediatric and young adult ADPKD patients

BACKGROUND

Young autosomal dominant polycystic kidney disease (ADPKD) patients are becoming the new target population for the development of new treatment options. Determination of a reliable equation for estimated glomerular filtration rate (eGFR) from early stages is needed with the promising potential interventional therapies.

METHODS

Prospective and longitudinal study on a cohort of 68 genotyped ADPKD patients (age range 0-23 years) with long-term follow-up. Commonly used equations for eGFR were compared for their relative performance.

RESULTS

The revised Schwartz formula (CKiD) showed a highly significant decline in eGFR with aging (- 3.31 mL/min/1.73 m2/year, P < 0.0001). The recently updated equation by the Schwartz group (CKiDU25) showed a smaller (- 0.90 mL/min/1.73 m2/year) but significant (P = 0.001) decline in eGFR with aging and also showed a significant sex difference (P < 0.0001), not observed by the other equations. In contrast, the full age spectrum (FAS) equations (FAS-SCr, FAS-CysC, and the combined) showed no age and sex dependency. The prevalence of hyperfiltration is highly dependent on the formula used, and the highest prevalence was observed with the CKiD Equation (35%).

CONCLUSIONS

The most widely used methods to calculate eGFR in ADPKD children (CKiD and CKiDU25 equations) were associated with unexpected age or sex differences. The FAS equations were age- and sex-independent in our cohort. Hence, the switch from the CKiD to CKD-EPI equation at the transition from pediatric to adult care causes implausible jumps in eGFR, which could be misinterpreted. Having reliable methods to calculate eGFR is indispensable for clinical follow-up and clinical trials. A higher resolution version of the Graphical abstract is available as Supplementary information.

AACC/NKF Guidance Document on Improving Equity in Chronic Kidney Disease Care

BACKGROUND

Kidney disease (KD) is an important health equity issue with Black, Hispanic, and socioeconomically disadvantaged individuals experiencing a disproportionate disease burden. Prior to 2021, the commonly used estimated glomerular filtration rate (eGFR) equations incorporated coefficients for Black race that conferred higher GFR estimates for Black individuals compared to non-Black individuals of the same sex, age, and blood creatinine concentration. With a recognition that race does not delineate distinct biological categories, a joint task force of the National Kidney Foundation and the American Society of Nephrology recommended the adoption of the CKD-EPI 2021 race-agnostic equations.

CONTENT

This document provides guidance on implementation of the CKD-EPI 2021 equations. It describes recommendations for KD biomarker testing, and opportunities for collaboration between clinical laboratories and providers to improve KD detection in high-risk populations. Further, the document provides guidance on the use of cystatin C, and eGFR reporting and interpretation in gender-diverse populations.

SUMMARY

Implementation of the CKD-EPI 2021 eGFR equations represents progress toward health equity in the management of KD. Ongoing efforts by multidisciplinary teams, including clinical laboratorians, should focus on improved disease detection in clinically and socially high-risk populations. Routine use of cystatin C is recommended to improve the accuracy of eGFR, particularly in patients whose blood creatinine concentrations are confounded by processes other than glomerular filtration. When managing gender-diverse individuals, eGFR should be calculated and reported with both male and female coefficients. Gender-diverse individuals can benefit from a more holistic management approach, particularly at important clinical decision points.

Renal Dysfunction Phenotypes in Patients Undergoing Obesity Surgery

Obesity surgery candidates are at an increased risk of kidney injury, but pre-operative evaluation usually neglects kidney function assessment. This study aimed to identify renal dysfunction in candidates for bariatric surgery. To reduce the sources of bias, subjects with diabetes, prediabetes under metformin treatment, neoplastic or inflammatory diseases were excluded. Patients' (n = 192) average body mass index was 41.7 ± 5.4 kg/m². Among these, 51% (n = 94) had creatinine clearance over 140 mL/min, 22.4% (n = 43) had proteinuria over 150 mg/day and 14.6% (n = 28) albuminuria over 30 mg/day. A creatinine clearance higher than 140 mL/min was associated with higher levels of proteinuria and albuminuria. Univariate analysis identified sex, glycated hemoglobin, uric acid, HDL and VLDL cholesterol as being associated with albuminuria, but not with proteinuria. On multivariate analysis, glycated hemoglobin and creatinine clearance as continuous variables were significantly associated with albuminuria. In summary, in our patient population prediabetes, lipid abnormalities and hyperuricemia were associated with albuminuria, but not with proteinuria, suggesting different disease mechanisms might be implicated. Data suggest that in obesity-associated kidney disease, tubulointerstitial injury precedes glomerulopathy. A significant proportion of obesity surgery candidates present clinically relevant albuminuria and proteinuria along with renal hyperfiltration, suggesting that routine pre-operative assessment of these parameters should be considered.

Predictive performance of glomerular filtration rate equations based on cystatin C, creatinine and their combination in critically ill patients

OBJECTIVE

24-hour urine creatinine clearance (ClCr 24 hours) remains the gold standard for estimating glomerular filtration rate (GFR) in critically ill patients; however, simpler methods are commonly used in clinical practice. Serum creatinine (SCr) is the most frequently used biomarker to estimate GFR; and cystatin C, another biomarker, has been shown to reflect GFR changes earlier than SCr. We assess the performance of equations based on SCr, cystatin C and their combination (SCr-Cyst C) for estimating GFR in critically ill patients.

METHODS

Observational unicentric study in a tertiary care hospital. Patients with cystatin C, SCr and ClCr 24 hours measurements in ±2 days admitted to an intensive care unit were included. ClCr 24 hours was considered the reference method. GFR was estimated using SCr-based equations: Chronic Kidney Disease Epidemiology Collaboration based on creatinine (CKD-EPI-Cr) and Cockcroft-Gault (CG); cystatin C-based equations: CKD-EPI-CystC and CAPA; and Cr-CystC-based equations: CKD-EPI-Cr-CystC. Performance of each equation was assessed by calculating bias and precision, and Bland-Altman plots were built. Further analysis was performed with stratified data into CrCl 24 hours <60, 60-130 and ≥130 mL/min/1.73 m².

RESULTS

We included 275 measurements, corresponding to 186 patients. In the overall population, the CKD-EPI-Cr equation showed the lowest bias (2.6) and best precision (33.1). In patients with CrCl 24 hours <60 mL/min/1.73 m², cystatin-C-based equations showed the lowest bias (<3.0) and CKD-EPI-Cr-CystC was the most accurate (13.6). In the subgroup of 60≤ CrCl 24 hours <130mL/min/1.73 m², CKD-EPI-Cr-CystC was the most precise (20.9). However, in patients with CrCl 24 hours ≥130mL/min/1.73 m², cystatin C-based equations underestimated GFR, while CG overestimated it (22.7).

CONCLUSIONS

Our study showed no evidence of superiority of any equation over the others for all evaluated parameters: bias, precision and Lin's concordance correlation coefficient. Cystatin C-based equations were less biased in individuals with impaired renal function (GFR <60 mL/min/1.73 m²). CKD-EPI-Cr-CystC performed properly in patients with GFR from 60-130 mL/min/1.73 m² and none of them were accurate enough in patients ≥130 mL/min/1.73 m².

Sex-specific association of body mass index and fatty liver index with prevalence of renal hyperfiltration: a cross sectional study using Japanese health check-up data

BACKGROUND

The relationship between obesity and nonalcoholic fatty liver disease and renal hyperfiltration is controversial. This study aimed to assess the correlations of body mass index and fatty liver index, respectively, with renal hyperfiltration in non-diabetic subjects, considering age, sex, and body surface area.

METHODS

This cross-sectional study assessed the Japanese health check-up data (FY2018) of 62,379 non-diabetic individuals from a health insurance database. Renal hyperfiltration is the ≥ 95th percentile of estimated glomerular filtration rate (derived by Chronic Kidney Disease Epidemiology Collaboration formula) by gender and age in healthy subjects. After adjusting for potential confounders, multiple logistic regression models were applied to evaluate the correlation of renal hyperfiltration with body mass index categories and fatty liver index (10 equal parts).

RESULTS

A negative and positive correlation, respectively, were noted when the body mass index was < 21 and ≥ 30 in women; however, a positive correlation was noted for BMI < 18.5 and ≥ 30 in men. Renal hyperfiltration prevalence increased when fatty liver index increased for both sexes; the cutoff value for fatty liver index was 14.7 for women and 30.4 for men.

CONCLUSIONS

Body mass index and renal hyperfiltration correlated linearly in women; however, in men, the correlation was U-shaped; therefore, differing by sex. However, fatty liver index correlated linearly with renal hyperfiltration in both sexes. Non-alcoholic fatty liver disease might be associated with renal hyperfiltration; Fatty liver index is a simple marker that can be obtained from health check-ups. Since a high fatty liver index correlated with renal hyperfiltration, it may be beneficial to monitor the renal function in such a population.

Metabolically healthy obesity is associated with higher risk of both hyperfiltration and mildly reduced estimated glomerular filtration rate: the role of serum uric acid in a cross-sectional study

BACKGROUND

The impact of metabolically healthy obesity (MHO) on kidney dysfunction remains debatable. Moreover, few studies have focused on the early stages of kidney dysfunction indicated by hyperfiltration and mildly reduced eGFR. Thus, we aimed to investigate the association between the MHO and early kidney dysfunction, which is represented by hyperfiltration and mildly reduced estimated glomerular filtration rate (eGFR), and to further explore whether serum uric acid affects this association.

METHODS

This cross-sectional study enrolled 1188 residents aged ≥ 40 years old from Yonghong Communities. Metabolically healthy phenotypes were categorized based on Adult Treatment Panel III criteria. Obesity was defined as body mass index (BMI) ≥ 25 kg/m². Mildly reduced eGFR was defined as being in the range 60 < eGFR ≤ 90 ml/min/1.73m². Hyperfiltration was defined as eGFR > 95th percentile after adjusting for sex, age, weight, and height.

RESULTS

Overall, MHO accounted for 12.8% of total participants and 24.6% of obese participants. Compared to metabolically healthy non-obesity (MHNO), MHO was significantly associated with an increased risk of mildly reduced eGFR (odds ratio [OR] = 1.85, 95% confidence interval [CI]  1.13-3.01) and hyperfiltration (OR = 2.28, 95% CI 1.03-5.09). However, upon further adjusting for uric acid, the association between the MHO phenotype and mildly reduced eGFR was reduced to null. Compared with MHNO/non-hyperuricemia, MHO/non-hyperuricemia was associated with an increased risk of mildly reduced eGFR (OR = 2.04, 95% CI  1.17-3.58), whereas MHO/hyperuricemia was associated with an observably increased risk (OR = 3.07, 95% CI  1.34-7.01).

CONCLUSIONS

MHO was associated with an increased risk of early kidney dysfunction, and the serum uric acid partially mediated this association. Further prospective studies are warranted to clarify the causality.

Onset timing and duration of augmented renal clearance in a mixed intensive care unit

BACKGROUND

Augmented renal clearance (ARC) is associated with lower blood plasma concentrations of renally excreted drugs; however, its time course is unknown. The current study aimed to determine the onset timing/duration of ARC, its risk factors, and its association with clinical outcomes by continuous monitoring of urinary creatinine clearance (CrCl) in critically ill patients.

METHODS

Data were retrospectively obtained from the medical records of 2592 critically ill patients admitted to the intensive care unit (ICU) from January 2019 to June 2022 at a tertiary emergency hospital. Among these, patients with continuously measured urinary CrCl were selected and observed over time. We evaluated the onset timing and duration of ARC by plotting Kaplan-Meier curves. Furthermore, by multivariate analyses, factors associated with the onset and persistence of ARC were analyzed, and the association between the ARC time course and clinical outcomes was evaluated.

RESULTS

The prevalence of ARC was 33.4% (245/734). ARC onset was within 3 days of admission in approximately half of the cases, and within 1 week in most of the other cases. In contrast, the persistence duration of ARC varied widely (median, 5 days), and lasted for more than a month in some cases. Multivariate analysis identified younger age, male sex, lower serum creatinine at admission, admission with central nervous system disease, no medical history, use of mechanically assisted ventilation, and vasopressor use as onset factors for ARC. Furthermore, factors associated with ARC persistence such as younger age and higher urinary CrCl on ARC day 1 were detected. The onset of ARC was significantly associated with reduced mortality, but persistent of ARC was significantly associated with fewer ICU-free days.

CONCLUSIONS

Despite the early onset of ARC, its duration varied widely and ARC persisted longer in younger patients with higher urinary CrCl. Since the duration of ARC was associated with fewer ICU-free days, it may be necessary to consider a long-term increased-dose regimen of renally excreted drugs beginning early in patients who are predicted to have a persistent ARC.

Association of glomerular hyperfiltration with carotid artery plaque in the general population

BACKGROUND AND AIMS

Glomerular hyperfiltration (GHF) is a hemodynamic change of the kidney as an adaptive response to nephron loss. Although GHF is associated with metabolic risk factors and cardiovascular disease (CVD), the mechanisms that explain these relationships remain largely unknown. This is partially caused by a non-unified definition of GHF based on pathophysiologic vascular changes. Thus, the objective of this study was to evaluate the association between various definitions of GHF and carotid plaque in a health checkup cohort.

METHODS

A total of 4493 individuals without history of CVD who had carotid ultrasonography (USG) results available between January 2016 and June 2018 were enrolled. GHF was defined as >90th percentile of eGFR residuals after adjusting for confounding factors. Carotid plaque score was calculated based on carotid USG results.

RESULTS

Of 4493 individuals (mean age, 52.3 ± 10.1 years; 3224 [71.8%] males), 449 subjects were included in the GHF group (mean eGFR, 107.0 ± 7.1 ml/min/1.73 m²) and 4044 subjects were included in the non-GHF group (mean eGFR, 92.5 ± 12.3 ml/min/1.73 m²). When the GHF group was compared to the non-GHF group, GHF was associated with the presence of significant carotid plaque (carotid plaque score ≥2) (adjusted OR: 1.46; 95% CI: 1.16 to 1.83; p = 0.001). GHF defined in this study showed higher sensitivity to the presence of carotid plaque than other definitions of GHF.

CONCLUSIONS

GHF status was associated with risk of carotid plaque in individuals without history of CVD. Presence of subclinical carotid plaque was associated with risk of future CVD. Therefore, GHF based on creatinine could be a useful surrogate marker for surveillance of CVD in asymptomatic individuals.

Targeting Glomerular Hemodynamics for Kidney Protection

The kidney microcirculation is a unique structure as it is composed to 2 capillary beds in series: the glomerular and peritubular capillaries. The glomerular capillary bed is a high-pressure capillary bed, having a 60 mm Hg to 40 mm Hg pressure gradient, capable of producing an ultrafiltrate of plasma quantified as the glomerular filtration rate (GFR), thereby allowing for waste products to be removed and establishing sodium/volume homeostasis. Entering the glomerulus is the afferent arteriole, and the exiting one is the efferent arteriole. The concerted resistance of each of these arterioles is what is known as glomerular hemodynamics and is responsible for increasing or decreasing GFR and renal blood flow. Glomerular hemodynamics play an important role in how homeostasis is achieved. Minute-to-minute fluctuations in the GFR are achieved by constant sensing of distal delivery of sodium and chloride in the specialized cells called macula densa leading to upstream alternation in afferent arteriole resistance altering the pressure gradient for filtration. Specifically, 2 classes of medications (sodium glucose cotransporter-2 inhibitors and renin-angiotensin system blockers) have shown to be effective in long-term kidney health by altering glomerular hemodynamics. This review will discuss how tubuloglomerular feedback is achieved, and how different disease states and pharmacologic agents alter glomerular hemodynamics.

Clinical outcomes among young patients with Fabry disease who initiated agalsidase beta treatment before 30 years of age: An analysis from the Fabry Registry

BACKGROUND

Clinical manifestations of classic Fabry disease (α-galactosidase A deficiency) usually occur in childhood, while complications involving major organs typically develop in adulthood. Outcomes of Fabry-specific treatment among young patients have not been extensively reported. Our aim was to analyze clinical outcomes among patients aged 5-30 years at initiation of treatment with agalsidase beta using data from the Fabry Registry (NCT00196742, sponsor: Sanofi).

METHODS

Reported GLA variants were predicted to be associated with the classic phenotype or not classified in fabry-database.org. Linear mixed models were conducted to assess changes over ≥2-year follow-up in the estimated glomerular filtration rate (eGFR) stratified by low (LRI) and high (HRI) renal involvement (defined by proteinuria/albuminuria levels), and changes in interventricular septal thickness (IVST) and left ventricular posterior wall thickness (LVPWT) Z-scores stratified by median age at first treatment. Self-reports ('yes'/'no') of abdominal pain, diarrhea, chronic peripheral pain (denoting neuropathic pain), and acute pain crises at baseline were compared with reports after ≥0.5-year and ≥2.5-year follow-up using McNemar's test.

RESULTS

Male (n = 117) and female patients (n = 59) with LRI initiated treatment at a median age of 19.9 and 23.6 years, respectively, and were followed for a median of 6.3 and 5.0 years, respectively. The eGFR slopes were -1.18 (P_{from 0} <0.001) and -0.92 mL/min/1.73 m²/year (P_{from 0} = 0.040), respectively. Males with HRI (n = 23, median UPCR 1.0 g/g), who started treatment at a median age of 26.7 years, had an eGFR slope of -2.39 mL/min/1.73 m²/year (P_{from 0} <0.001; P_difference = 0.055, as compared with the slope of -1.18 mL/min/1.73 m²/year for LRI males) during a median follow-up of 5.6 years. Echocardiographic variables were stable among males, regardless of age, and among young females (median follow-up >5.5 years and ≥4.5 years, respectively). Older females (treatment initiation at median age 27.5 years) had a slope of LVPWT Z-scores of 0.18/year (n = 12, P_{from 0} = 0.028), whereas IVST Z-scores remained stable (n = 13, 0.10/year, P_{from 0} = 0.304) during a median follow-up of ≥3.7 years. These slopes did not significantly differ from slopes of younger females. Reports of chronic peripheral pain and acute pain crises by males, and of diarrhea and acute pain crises by females, significantly reduced after a median follow-up of ≥4.0 years. After a median follow-up of ≥5.4 years, reports of all four symptoms significantly decreased among males, whereas among females only reports of abdominal pain significantly decreased.

CONCLUSIONS

During sustained treatment with agalsidase beta in young Fabry patients with a predicted classic phenotype or with unclassified GLA variants with similar characteristics, the decline in eGFR was modest among male and female patients with LRI. The greater decline in eGFR among older, proteinuric (i.e., HRI) males may suggest a benefit of earlier treatment. Overall, echocardiographic variables remained stable, particularly among males and younger females. Significant reductions in symptom reports occurred primarily among males after longer follow-up and were less noticeable among females. These observed trends are suggestive of an overall improvement after treatment in young patients, but warrant larger longitudinal studies.

Glomerular hyperfiltration is a predictor of adverse outcomes following major urologic oncology surgery

PURPOSE

Glomerular hyperfiltration (GHF) has been associated with cardiovascular disease and all-cause mortality. We aimed to evaluate whether preoperative GHF is associated with 30-day complications following major urologic oncology procedures.

METHODS

We conducted a retrospective cohort study using subjects from the 2006 to 2019 American College of Surgeons National Surgical Quality Improvement Program database who underwent prostatectomy, cystectomy, or nephrectomy. Estimated glomerular filtration rate (eGFR) was calculated using the CKD-EPI equation. Patients were classified as having either low, normal, or high eGFR based on the 5th and 95th percentiles of age- and sex-specific quintiles for eGFR. Using multivariable logistic regression, we evaluated GHF as an independent predictor of postoperative complications.

RESULTS

A total of 120,013 patients were eligible for analysis, of which 1706 (1.4%) were identified as having GHF, with a median eGFR of 105.37 ml/min per 1.73 m² (IQR 94.84-116.77). Compared to patients with normal eGFR, patients with GHF were older (68 years, [IQR 60-71], p < 0.001), had a lower BMI (27.52 kg/m² [IQR 23.71-31.95], p < 0.001), and greater 5-item modified frailty index scores (≥ 1, 70.6%, p < 0.001). Multivariable logistic regression demonstrated that GHF was associated with greater odds of any complication (OR 1.23, 95% CI 1.08-1.40, p = 0.002), non-home discharge (OR 1.86, 95% CI 1.50-2.30, p < 0.001), and prolonged LOS (OR 1.33, 95% CI 1.18-1.51, p < 0.001).

CONCLUSION

GHF is associated with greater odds of 30-day complications following major urologic oncology surgery.

Association of Estimated Glomerular Filtration Rate With Progression of Albuminuria in Individuals With Type 2 Diabetes

OBJECTIVE

To elucidate the association of glomerular filtration rate (GFR) at baseline with subsequent progression of albuminuria in individuals with type 2 diabetes.

RESEARCH DESIGN AND METHODS

This was a single-center retrospective cohort study of 6,618 Japanese adults with type 2 diabetes and urinary albumin-to-creatinine ratio of <300 mg/g, comprising 2,459 women and 4,159 men with a mean (± SD) age of 60 ± 12 years. The exposure was baseline estimated GFR (eGFR) (mL/min/1.73 m2), treated as a categorical variable and classified into five categories: ≥90, 75-90, 60-75, 45-60, and <45, as well as a continuous variable. The outcome was progression of albuminuria category (i.e., from normoalbuminuria to micro- or macroalbuminuria or from micro- to macroalbuminuria). Hazard ratios (HRs) for the outcome were estimated using the multivariable Cox proportional hazards model. In the analysis treating baseline eGFR as a continuous variable, the multivariable-adjusted restricted cubic spline model was used.

RESULTS

During the median follow-up period of 6.3 years, 1,190 individuals reached the outcome. When those with a baseline eGFR of 75-90 mL/min/1.73 m2 were considered the reference group, HRs (95% CIs) for the outcome in those with a baseline eGFR of ≥90, 60-75, 45-60, or <45 mL/min/1.73 m2 were 1.38 (1.14-1.66), 1.34 (1.14-1.58), 1.81 (1.50-2.20), or 2.37 (1.84-3.05), respectively. Furthermore, the inverse J-shaped curve was more clearly shown by the spline model.

CONCLUSIONS

This study of Japanese adults with type 2 diabetes suggests that both high and low GFRs are implicated in the pathogenesis of albuminuria progression.

Novel insights in classic versus relative glomerular hyperfiltration and implications on pharmacotherapy

PURPOSE OF REVIEW

Glomerular filtration rate (GFR) assessment and its estimation (eGFR) is a long-lasting challenge in medicine and public health. Current eGFR formulae are indexed for standardized body surface area (BSA) of 1.73 m2, ignoring persons and populations wherein the ratio of BSA or metabolic rate to nephron number might be different, due to increased BSA, increased metabolic rate or reduced nephron number. These equations are based on creatinine, cystatin C or a combination of the two, which adds another confounder to eGFR assessment. Unusually high GFR values, also known as renal hyperfiltration, have not been well defined under these equations.

RECENT FINDINGS

Special conditions such as solitary kidney in kidney donors, high dietary protein intake, obesity and diabetes are often associated with renal hyperfiltration and amenable to errors in GFR estimation. In all hyperfiltration types, there is an increased intraglomerular pressure that can be physiologic, but its persistence over time is detrimental to glomerulus leading to progressive glomerular damage and renal fibrosis. Hyperfiltration might be underdiagnosed due to BSA standardization embedded in the formula. Hence, timely intervention is delayed. Reducing intraglomerular pressure in diabetes can be achieved by SGLT2 inhibitors or low protein diet to reverse the glomerulopathy process.

SUMMARY

Accurate identification of glomerular hyperfiltration as a pre-CKD condition needs accurate estimation of GFR in the above normal range should establish a threshold for timely intervention.

[Liver transplantation in aged patients]

Due to the demographic changes and the increasing incidence of chronic, especially nutritively toxic liver diseases, the number of patients over 65 years of age with indications for liver transplantation is rising considerably. Patient age alone is not a contraindication for organ transplantation; however, in order to ensure the postoperative outcome, a structured interdisciplinary assessment is necessary, especially in older potential organ recipients. With knowledge of comorbidities, individualized prehabilitation enables the perioperative risk to be minimized. The postoperative morbidity in aged patients appears to be comparable to that of younger patients, especially after careful evaluation. Overall, there is a clear survival advantage compared with the best conservative treatment for liver disease. In addition to the perioperative procedure, differences in follow-up care and long-term outcome should also be considered. In this context, predominantly the pharmacological peculiarities, such as polypharmacy and the mutual influence of immunosuppression and comorbidities, have to be taken into account. In addition to old organ recipients, livers from old donors (so-called marginal organs) increasingly play a crucial role in transplantation medicine due to the organ shortage. These are more susceptible to ischemia reperfusion injury and thus put the recipient at a higher risk for delayed or lack of organ function recovery. New ethical issues are raised by the increasing age of donors and recipients, complicating decision making about organ acceptance or rejection for the transplantation physician.

Glomerular hyperfiltration: part 2-clinical significance in children

Glomerular hyperfiltration (GHF) is a phenomenon that can occur in various clinical conditions affecting the kidneys such as sickle cell disease, diabetes mellitus, autosomal dominant polycystic kidney disease, and solitary functioning kidney. Yet, the pathophysiological mechanisms vary from one disease to another and are not well understood. More so, it has been demonstrated that GHF may occur at the single-nephron in some clinical conditions while in others at the whole-kidney level. In this review, we explore the pathophysiological mechanisms of GHF in relation to various clinical conditions in the pediatric population. In addition, we discuss the role and mechanism of action of important factors such as gender, low birth weight, and race in the pathogenesis of GHF. Finally, in this current review, we further highlight the consequences of GHF in the progression of kidney disease.

Glomerular hyperfiltration: part 1 - defining the threshold - is the sky the limit?

Glomerular hyperfiltration (GHF) is an increase in single-nephron glomerular filtration rate (GFR) that occurs in both physiological states and pathological states. Whole-kidney GHF is often used as a surrogate for single-nephron hyperfiltration since determining single-nephron GFR is impossible in routine clinical care. A clear definition (read threshold) of GHF is lacking. The aim of the first part of this review was to find evidence for defining the threshold for GHF, based on literature review, including systematic reviews and meta-analysis data, with both measured and estimated GFR. The consensus pediatric threshold for GHF as obtained from reviews, measured and estimated GFR studies, can reliably be set to 135 mL/min/1.73 m² for children aged > 2 years. Diagnosing GHF from SCr-based estimated GFR is not reliable in subjects with reduced muscle mass. In these cases, it could be of interest to confirm the state of GHF using cystatin C-based eGFR, or preferably, by measured GFR, using methods that are accurate in the high GFR-range.

The non-vitamin K antagonist oral anticoagulants in atrial fibrillation patients with high-normal renal function - A systematic review

Non-vitamin K antagonist oral anticoagulants (NOACs) have revolutionized treatment of atrial fibrillation. Although benefits of anticoagulation therapy are clear, a minority of patients still experience treatment inefficacy or harm. All NOACs have varying degree of renal clearance, which may significantly affect plasma concentrations. Pivotal clinical trials have explored the effects of dose reduction in patients with chronic renal disease. None of these have, however, specifically addressed the need for a dose up-titration in patients with renal hyperfiltration, in whom lower drug plasma levels are to be expected. A signal for lower efficacy in this patient subset has recently emerged. We systematically assessed the peer-reviewed scientific literature on this topic, including a recently reported randomized pharmacokinetic study in renal hyperfiltrators also reporting on ischemic and bleeding events. We conclude that the reduction in NOAC plasma levels in AF patients with renal hyperfiltration is limited in extent and, does not translate into a clinically meaningful reduction in efficacy for NOACs as compared to vitamin K antagonists (VKAs) in such patients. At the current state of knowledge, NOAC current dosing should not be altered in patients with high-normal renal function.

Change of renal function after short-term use of cardioprotective agents in patients with type 2 diabetes is not accurately assessed by the change of estimated glomerular filtration rate: an observational study

BACKGROUND

After initiating cardioprotective agents, a fall of estimated glomerular filtration rate (eGFR) has been reported in several studies. Our goal was to evaluate the accuracy of change of Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) eGFR in patients with type 2 diabetes (T2D) after short-term pharmacological intervention with angiotensin-converting enzyme inhibitor, angiotensin-receptor blocker, gliptin or sodium-glucose cotransporter-2 inhibitor.

METHODS

We analyzed 190 patients with T2D in the early stage of the disease, having no overt renal impairment by CKD-EPI equation. In each patient, we measured GFR (mGFR) by applying the constant infusion input clearance technique with sinistrin (Inutest; Fresenius, Linz, Austria) at baseline and after short-term (4-12 weeks) pharmacological intervention with cardioprotective agents (ramipril, telmisartan, linagliptin, metformin, empagliflozin) that potentially lead to an alteration of renal function. Simultaneously, a standardized analysis of serum creatinine was performed and eGFR was estimated by the CKD-EPI equation.

RESULTS

Average mGFR was 111 ± 20 ml/min/1.73m², whereas eGFR was lower with 93 ± 13 ml/min/1.73m². The ratio eGFR/mGFR in relation to mGFR was almost curvilinear, showing an underestimation of renal function by eGFR in the upper normal range. At baseline only 80 patients (42%) lay within ± 10% of mGFR and the concordance correlation coefficient (CCC) was extremely low (- 0.07). After short-term pharmacological intervention changes in eGFR and mGFR correlated with each other (r = 0.286, p < 0.001). For example, for a given mGFR of 111 ml/min/1.73m², a change of mGFR by ± 10% corresponded to ± 11 ml/min/1.73m², but the confidence interval of eGFR was 25 ml/min/1.73m². The CCC was low (0.22).

CONCLUSION

The agreement between eGFR by CKD-EPI and mGFR is modest and the change of renal function after short-term pharmacological intervention is not accurately and precisely reflected by the change of eGFR in patients with T2D in the early stage of their disease.

Repeatedly Measured Serum Creatinine and Cognitive Performance in Midlife: The Cardiovascular Risk in Young Finns Study

BACKGROUND AND OBJECTIVES

Serum creatinine is typically used to assess kidney function. Impaired kidney function and thereby high serum creatinine increases risk of poor cognitive performance. However, serum creatinine might have a non-linear association as low serum creatinine has been linked with cardiovascular risk and impaired cognitive performance. We studied the longitudinal association between serum creatinine and cognitive performance in midlife.

METHODS

Since 2001, participants from the Cardiovascular Risk in Young Finns Study were followed up for 10 years. Serum creatinine was measured repeatedly in 2001, 2007, and 2011. Sex-specific longitudinal trajectories for serum creatinine among participants without kidney disease were identified using latent class growth mixture modeling. Overall cognitive function and four specific domains such as 1) working memory, 2) episodic memory and associative learning, 3) reaction time, and 4) information processing were assessed using a computerized cognitive test.

RESULTS

Four serum creatinine trajectory groups all with clinically normal serum creatinine were identified for both men (N=973) and women (N=1,204). After 10 years of follow-up, cognitive testing was performed for 2,026 participants aged 34 to 49 years (mean age 41.8 years). In men and women, consistently low serum creatinine was associated with poor childhood school performance, low adulthood education, low adulthood annual income, low physical activity, and smoking. Compared to the men in the low serum creatinine trajectory group, those in the high serum creatinine group had better overall cognitive performance (β=0.353 SD, 95%CI 0.022-0.684) and working memory (β=0.351 SD, 95%CI 0.034-0.668), while those in the moderate (β=0.247 SD, 95%CI 0.026-0.468) or the normal (β=0.244 SD, 95%CI 0.008-0.481) serum creatinine groups had better episodic memory and associative learning. No associations were found for women.

DISCUSSION

Our results indicate that, in men, compared to low serum creatinine levels consistently high levels may associate with better memory and learning function in midlife.

Glomerular hyperfiltration

Circulating blood is filtered across the glomerular barrier to form an ultrafiltrate of plasma in the Bowman's space. The volume of glomerular filtration adjusted by time is defined as the glomerular filtration rate (GFR), and the total GFR is the sum of all single-nephron GFRs. Thus, when the single-nephron GFR is increased in the context of a normal number of functioning nephrons, single glomerular hyperfiltration results in 'absolute' hyperfiltration in the kidney. 'Absolute' hyperfiltration can occur in healthy people after high protein intake, during pregnancy and in patients with diabetes, obesity or autosomal-dominant polycystic kidney disease. When the number of functioning nephrons is reduced, single-nephron glomerular hyperfiltration can result in a GFR that is within or below the normal range. This 'relative' hyperfiltration can occur in patients with a congenitally reduced nephron number or with an acquired reduction in nephron mass consequent to surgery or kidney disease. Improved understanding of the mechanisms that underlie 'absolute' and 'relative' glomerular hyperfiltration in different clinical settings, and of whether and how the single-nephron haemodynamic and related biomechanical forces that underlie glomerular hyperfiltration promote glomerular injury, will pave the way toward the development of novel therapeutic interventions that attenuate glomerular hyperfiltration and potentially prevent or limit consequent progressive kidney injury and loss of function.

The association between skinfold thicknesses and estimated glomerular filtration rate in adolescents: a cross-sectional study

Background

Obesity is one of the causes of glomerular hyperfiltration. Studies on the relationship between body fat content and glomerular hyperfiltration have been limited to special children. Therefore, we aimed to evaluate the correlation between skinfold thickness, which represents body fat content, and estimated glomerular filtration rate (eGFR).

Methods

The cross-sectional study included 6655 participants (3532 boys and 3123 girls; age: 12 − 17.99 years); data was obtained from the National Health and Nutrition Examination Survey (NHANES; 2001–2010). The independent variables were subscapular skinfold thickness and triceps skinfold thickness. The dependent variable was eGFR. We used multivariate linear regression models to evaluate their associations and also performed subgroup analyses.

Results

After adjusting for age, standing height, race, family income, blood urea nitrogen and uric acid variables, multivariate regression analysis identified that triceps skinfold thickness and subscapular skinfold thickness were positively correlated with eGFR and glomerular hyperfiltration in boys. In subgroup analyses stratified by age and body mass index, triceps skinfold thickness was also associated with glomerular hyperfiltration in boys. There was a linear relationship between triceps skinfold thickness and eGFR in boys (β = 0.389, P < 0.001) and girls (β = 0.159, P = 0.0003).

Conclusions

Triceps skinfold thickness and subscapular skinfold thickness are positively correlated with eGFR and glomerular hyperfiltration in US male adolescents. In all adolescents, there is a linear relationship between triceps skinfold thickness and eGFR.

Glomerular Biomechanical Stress and Lipid Mediators during Cellular Changes Leading to Chronic Kidney Disease

Hyperfiltration is an important underlying cause of glomerular dysfunction associated with several systemic and intrinsic glomerular conditions leading to chronic kidney disease (CKD). These include obesity, diabetes, hypertension, focal segmental glomerulosclerosis (FSGS), congenital abnormalities and reduced renal mass (low nephron number). Hyperfiltration-associated biomechanical forces directly impact the cell membrane, generating tensile and fluid flow shear stresses in multiple segments of the nephron. Ongoing research suggests these biomechanical forces as the initial mediators of hyperfiltration-induced deterioration of podocyte structure and function leading to their detachment and irreplaceable loss from the glomerular filtration barrier. Membrane lipid-derived polyunsaturated fatty acids (PUFA) and their metabolites are potent transducers of biomechanical stress from the cell surface to intracellular compartments. Omega-6 and ω-3 long-chain PUFA from membrane phospholipids generate many versatile and autacoid oxylipins that modulate pro-inflammatory as well as anti-inflammatory autocrine and paracrine signaling. We advance the idea that lipid signaling molecules, related enzymes, metabolites and receptors are not just mediators of cellular stress but also potential targets for developing novel interventions. With the growing emphasis on lifestyle changes for wellness, dietary fatty acids are potential adjunct-therapeutics to minimize/treat hyperfiltration-induced progressive glomerular damage and CKD.

Cardiorenal Function and Survival in In-Hospital Cardiac Arrest: A Nationwide Study of 22,819 Cases

BACKGROUND

We studied the association between cardiorenal function and survival, neurological outcome and trends in survival after in-hospital cardiac arrest (IHCA).

METHODS

We included cases aged ≥18 years in the Swedish Cardiopulmonary Resuscitation Registry during 2008 to 2020. The CKD-EPI equation was used to calculate estimated glomerular filtration rate (eGFR). A history of heart failure was defined according to contemporary guideline criteria. Logistic regression was used to study survival. Neurological outcome was assessed using cerebral performance category (CPC).

RESULTS

We studied 22,819 patients with IHCA. The 30-day survival was 19.3%, 16.6%, 22.5%, 28.8%, 39.3%, 44.8% and 38.4% in cases with eGFR <15, 15-29, 30-44, 45-59, 60-89, 90-130 and 130-150 ml/min/1.73 m², respectively. All eGFR levels below and above 90 ml/min/1.73 m² were associated with increased mortality. Probability of survival at 30 days was 62% lower in cases with eGFR <15 ml/min/1.73 m², compared with normal kidney function. At every level of eGFR, presence of heart failure increased mortality markedly; patients without heart failure displayed higher mortality only at eGFR below 30 ml/min/1.73 m². Among survivors with eGFR <15 ml/min/1.73 m², good neurological outcome was noted in 87.2%. Survival increased in most groups over time, but most for those with eGFR <15 ml/min/1.73 m², and least for those with normal eGFR.

CONCLUSIONS

All eGFR levels below and above normal range are associated with increased mortality and this association is modified by the presence of heart failure. Neurological outcome is good in the majority of cases, across kidney function levels and survival is increasing.

Update on Pathogenesis of Glomerular Hyperfiltration in Early Diabetic Kidney Disease

In the existing stages of diabetic kidney disease (DKD), the first stage of DKD is called the preclinical stage, characterized by glomerular hyperfiltration, an abnormally elevated glomerular filtration rate. Glomerular hyperfiltration is an independent risk factor for accelerated deterioration of renal function and progression of nephropathy, which is associated with a high risk for metabolic and cardiovascular disease. It is imperative to understand hyperfiltration and identify potential treatments to delay DKD progress. This paper summarizes the current mechanisms of hyperfiltration in early DKD. We pay close attention to the effect of glucose reabsorption mediated by sodium-glucose cotransporters and renal growth on hyperfiltration in DKD patients, as well as the mechanisms of nitric oxide and adenosine actions on renal afferent arterioles via tubuloglomerular feedback. Furthermore, we also focus on the contribution of the atrial natriuretic peptide, cyclooxygenase, renin-angiotensin-aldosterone system, and endothelin on hyperfiltration. Proposing potential treatments based on these mechanisms may offer new therapeutic opportunities to reduce the renal burden in this population.

Effect of Normalizing eGFR to Standard Body Surface Area on Rates of Obesity-Related Hyperfiltration among Diverse Female Adolescents

INTRODUCTION

Obesity is more prevalent among African American individuals, increasing the risk for cardiorenal morbidity. We explored interactions between race, BMI, and the risk of hyperfiltration associated with obesity-related glomerulopathy (ORG).

METHODS

We created a cohort of female adolescents from electronic health records. Glomerular filtration rate (GFR) was estimated in two ways: (A) using standard age recommended formulae and (B) absolute eGFR - adjusted to individual body surface area (BSA). Multivariate logistic regression was used to analyze the contribution of risk factors for ORG-associated hyperfiltration defined as 135 mL/min/1.73 m2 or 135 mL/min, according to BMI group. Pearson's coefficient was used to assess correlation with creatinine clearance (CrCl).

RESULTS

The final cohort included 7,315 African American and 15,102 non-African American adolescent females, with CrCl available for internal validation in 207 non-African American and 107 African American individuals. Compared with non-African American ethnicity, African American ethnicity was independently associated with a lower risk of hyperfiltration with standard eGFR calculations (odds ratio [OR] = 0.57, 95% confidence intervals [CIs] 0.45-0.71), associations were enhanced for absolute eGFR (OR = 0.81, 95% CI 0.69-0.95). Absolute eGFR values agreed better with CrCl (r = 0.63), compared to standard indexed eGFR formulae. Proportions classified as hyperfiltration changed with standard versus absolute eGFR; they were similar across BMI groups with the first and reflected obesity with the later.

CONCLUSION

Adjusting to individual BSA improves estimation of GFR and identification of obesity-related hyperfiltration. More accurate and earlier ascertainment of obesity-related hyperfiltration may have important consequences for preservation of kidney function.

Role of Heart Rate Variability in Association Between Glomerular Hyperfiltration and All-Cause Mortality

Background

Glomerular hyperfiltration (GHF) is paradoxically associated with increased cardiovascular events in healthy individuals, but the pathogenesis remains unclear. We aim to investigate whether GHF is associated with mortality and whether decreased heart rate variability (HRV) is associated with GHF.

Methods and Results

We retrospectively analyzed 1615 participants (aged 66.1±17.3 years, 61.9% men) without prior cardiovascular events. The glomerular filtration rate was estimated using the Chronic Kidney Disease Epidemiology Collaboration equation. GHF was defined as glomerular filtration rate >the 95th percentile after stratification for age and sex, whereas normal filtration was defined as the 25th to 75th percentiles. HRV indexes, including time domain, frequency domain, and sample entropy, were measured using 24‐hour ambulatory electrocardiography. Clinical outcomes were defined as all‐cause mortality at 2 years. During a mean follow‐up of 16.5±8.2 months, there were 117 deaths (7.2%). GHF was associated with a higher risk of death (hazard ratio and 95% CIs, 1.97 [1.15–3.37]). Reduced HRV indexes, including time domain, frequency domain, and sample entropy (odds ratio and 95% CIs, 0.79 [0.70–0.89]) were all independently associated with the presence of GHF after accounting for age, sex, mean heart rate, morbidities, and medications. In subgroup analysis, reduced HRV was more predictive of GHF in the young than the elderly. Mediation analysis revealed a significant mediation effect between HRV and GHF in addition to their respective detrimental effects on survival.

Conclusions

Reduced HRV was independently associated with the presence of GHF. Autonomic dysfunction may be involved in the pathogenesis of adverse outcomes of GHF in individuals without prior cardiovascular events.

Smoking tobacco is associated with renal hyperfiltration

Tobacco consumption is a renal risk factor, but the effects on the estimated glomerular filtration rate (eGFR) remain unclear. We aimed to evaluate the possible impact of using tobacco products (smoking and snus) on eGFR based on creatinine or cystatin C. We used a first cohort with 949 participants and a second cohort with 995 participants; none had pre-existing renal disease. All subjects donated a blood sample and completed a questionnaire, including questions about tobacco use. To assess the effect on eGFR, hierarchical multiple linear regression models were used. Active smoking associated independently with a higher eGFRcreatinine in all subjects (p < 0.001; β = 0.11). Further analyses stratified for sex, showed similar findings for men (p < 0.001; β = 0.14) and for women (p = 0.026; β = 0.10). eGFRcystatin C was significantly associated with active smoking in all subjects (p = 0.040; β = -0.05), but no association was seen after stratification for sex. Snus did not associate with eGFR. In conclusion, smoking associated significantly with a higher eGFRcreatinine. The mechanism may be renal hyperfiltration of smaller molecules such as creatinine. This is probably caused by substances from smoked tobacco other than nicotine, as no effect was seen for snus.

Obesity Related Glomerulopathy in Adolescent Women: The Effect of Body Surface Area

Background

Adolescent obesity, a risk factor for cardiorenal morbidity in adulthood, has reached epidemic proportions. Obesity-related glomerulopathy (ORG) has an early reversible stage of hyperfiltration. Age-appropriate formulae for eGFR, which are standardized to ideal body surface area (BSA) and provide assessment of kidney function in ml/min/1.73 m², may underestimate prevalence of early ORG. We investigated whether adjusting eGFR to actual BSA more readily identifies early ORG.

Methods

We studied a cohort of 22,417 young individuals, aged 12-21 years, from a New York metropolitan multi-institutional electronic health records clinical database. eGFR was calculated in two ways: BSA-standardized eGFR, and absolute eGFR. Hyperfiltration was defined above a threshold of 135 ml/min per 1.73 m² or 135 ml/min, respectively. The prevalence of hyperfiltration according to each formula was assessed in parallel to creatinine clearance.

Results

Serum creatinine values and hyperfiltration prevalence according to BSA-standardized eGFR were similar, 13%-15%, across body mass index (BMI) groups. The prevalence of hyperfiltration determined by absolute eGFR differed across BMI groups: underweight, 2%; normal weight, 6%; overweight, 17%; and obese, 31%. This trend paralleled the rise in creatinine clearance across BMI groups.

Conclusions

Absolute eGFR more readily identifies early ORG than the currently used formulae, which are adjusted to a standardized BSA and are not representative of current population BMI measures. Using absolute eGFR in clinical practice and research may improve the ability to identify, intervene, and reverse early ORG, which has great importance with increasing obesity rates.

Glomerular Hyperfiltration Interacts With Abnormal Metabolism to Enhance Arterial Stiffness in Middle-Aged and Elderly People

Introduction: Glomerular hyperfiltration (GHF) is an early kidney injury. We investigated whether GHF is associated with arterial stiffness expressed by increase of brachial-ankle pulse wave velocity (baPWV) and pulse pressure (PP), and whether the coexistence of GHF and abnormal metabolism increases the risk of arterial stiffness. Methods: In this prospective cohort study, 2,133 non-chronic kidney disease (CKD) participants aged ≥40 years were followed for a mean period of 3.3 years. The extent of arterial stiffness was expressed by measures of baPWV and PP. GHF was defined as eGFR exceeding the age- and sex-specific 90th percentile. Multivariate logistic regression models were used to assess the association between GHF/abnormal metabolism and increased baPWV/PP. The interaction indexes of GHF and abnormal metabolism on arterial stiffness were calculated based on the OR in a multivariate logistic regression model. Results: GHF alone was not associated with increased baPWV or PP in all participants in this study. However, when GHF coexisted with abnormal metabolism, the risk of increased PP increased 3.23-fold [OR = 3.23(1.47-7.13)] compared with participants with normal filtration and normal metabolism, in which the interaction accounted for 55.1% of the total effect and 79.8% of the effect from GHF and abnormal metabolism. After subtracting the independent effects of GHF and abnormal metabolism, their combined effect still resulted in a 1.78-fold increase in PP. Conclusion: GHF could interact with abnormal metabolism to significantly enhance arterial stiffness. Since abnormal metabolism commonly exists in the general population, even slight changes in renal function should be distinguished to prevent arterial stiffness risk.

Mortality-based definition of renal hyperfiltration in middle-aged men: a 35-year cohort from Finland

Background

While the impact of low glomerular filtration rate (eGFR) on various outcomes has been extensively studied, the other adverse occurrence, renal hyperfiltration (RHF), remains understudied, poorly defined, and, therefore, its impact on mortality unestablished.

Methods

Using a population-based subcohort from the Kuopio Ischaemic Disease Risk Factor Study restricted to non-diabetic Finnish men aged 54 or 55 years, we followed up n = 1179 study participants for up to 35 years. We evaluated the hazard of all-cause mortality associated to RHF at different cutoff points defining eGFR. Based on models’ accuracy we suggested an optimal eGFR cutoff point for the definition of RHF. We divided the RHF category to three subgroups and evaluated them in terms of baseline characteristics and mortality hazard.

Results

The eGFR value of 97 mL/min/1.73 m² corresponded to the models with the highest accuracy. Overall RHF associated with an increased risk of mortality (hazard ratio [HR] 1.42; 95% confidence interval [CI] 1.21 to 1.67). Moderate RHF associated with a decreased HR of mortality when compared to mild (0.64; 95% CI 0.46 to 0.9) or to extreme RHF (0.61; 95% CI 0.43 to 0.85), suggesting a rather U-shaped relationship between RHF’s eGFR values and mortality hazard.

Conclusion

The burden of increased eGFR within what is still considered normal eGFR category was highly underestimated. RHF’s eGFR values had a U-shaped association with the risk of overall mortality. A more uniform consensual definition of RHF is needed, as higher to normal eGFR values that are not without consequences.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11255-021-03048-6.

Risk factors for impaired renal function in HIV-infected and HIV-uninfected adults: cross-sectional study in North-Western Tanzania

BACKGROUND

Although the burden of impaired renal function is rising in sub-Saharan Africa (SSA), little is known about correlates of impaired renal function in the region. We determined factors associated with estimated glomerular filtration rate (eGFR) and impaired renal function in HIV-infected and HIV-uninfected adults.

METHODS

We undertook cross-sectional analysis of data from 1947 adults at enrolment for a cohort study on diabetes and associated complications in HIV patients in Mwanza, north-western Tanzania. A structured questionnaire was used to collect data on sociodemography, smoking, alcohol, physical activity, antiretroviral therapy (ART) and anthropometry. We measured blood pressure, tested blood samples for creatinine, glucose and HIV, and performed Kato Katz for Schistosoma mansoni. Correlates of eGFR (mL/min/1.73 m2) and impaired renal function (eGFR< 60 mL/min/1.73 m2) were determined using linear regression and logistic regression, respectively.

RESULTS

655 (34%) participants were HIV-uninfected, 956 (49%) were ART-naive HIV-infected and 336 (17%) were HIV-infected adults on ART. The mean age was 41 years (SD12) and majority (59%) were females. Overall, the mean eGFR was 113.6 mL/min/1.73 m2 but 111.2 mL/min/1.73 m2 in HIV-uninfected, 109.7 mL/min/1.73 m2 in ART-naive HIV-infected and 129.5 mL/min/1.73 m2 in HIV-infected ART-experienced adults, and respective prevalence of impaired renal function was 7.0, 5.7, 8.1 and 6.3%. Correlates of lower eGFR were increasing age, higher socioeconomic status, unhealthy alcohol drinking, higher body mass index and diabetes mellitus. Anaemia was associated with 1.9 (95% Confidence Interval (CI):1.2, 2.7, p = 0.001) higher odds of impaired renal function compared to no anaemia and this effect was modified by HIV status (p value 0.02 for interaction).

CONCLUSION

Impaired renal function is prevalent in this middle-aged study population. Interventions for prevention of impaired renal function are needed in the study population with special focus in HIV-infected adults and those with high socioeconomic status. Interventions targeting modifiable risk factors such as alcohol and weight reduction are warranted.

Evaluating prediction methods for glomerular filtration to optimise drug doses in obese and nonobese patients

AIMS

The most suitable method for predicting the glomerular filtration rate (GFR) in obesity is currently debated. Therefore, multiple GFR/creatinine clearance prediction methods were applied to (morbidly) obese and nonobese patients ranging from moderate renal impairment to glomerular hyperfiltration and their predictions were rated based on observed fosfomycin pharmacokinetics, as this model drug is exclusively eliminated via glomerular filtration.

METHODS

The GFR/creatinine clearance predictions via the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI), Modification of Diet in Renal Disease (MDRD; indexed and de-indexed by body surface area) and creatinine clearance via the Cockcroft-Gault formula (CLCR_CG ) using different body size descriptors were compared to the fosfomycin clearance (CL_FOF ) from 30 surgical patients (body mass index = 20.1-52.0 kg m^-2 ), receiving 8000 mg as intravenous infusion.

RESULTS

The concordance between CL_FOF and creatinine clearance predictions was highest for CLCR_CG employing either ideal body weight or adjusted body weight (if body mass >1.3 ideal body weight; CLCR_{CG_ABW-Schwartz} , concordance-correlation coefficient [95% confidence interval] = 0.474 [0.156; 0.703], CCC) and GFR predictions via the de-indexed MDRD equation (concordance-correlation coefficient = 0.452 [0.137; 0.685]). The proportion of predicted GFR values within ±30% of the observed CL_FOF (P₃₀  = 72.3-76.7%) was only marginally lower than the reported P₃₀ in the original CKD-EPI and MDRD publications (P₃₀  = 84.1-90.0%).

CONCLUSION

This analysis represents a successful proof-of-concept for evaluating GFR/creatinine clearance prediction methods: Across all body mass index classes CLCR_{CG_ABW-Schwartz} or the de-indexed MDRD were most suitable for predicting creatinine clearance/GFR also in (morbidly) obese, CKD stage <3B individuals in therapeutic use. Their application is proposed in optimising doses for vital therapies in obese patients requiring monitoring of renal function (e.g. methotrexate dosing).

Clinical and genetic factors are associated with kidney complications in African children with sickle cell anaemia

Clinical and genetic factors have been reported as influencing the development of sickle cell nephropathy (SCN). However, such data remain limited in the paediatric population. In this cross-sectional study, we enrolled 361 sickle cell disease children from the Democratic Republic of Congo. Participants were genotyped for the beta (β)-globin gene, apolipoprotein L1 (APOL1) risk variants, and haem oxygenase-1 (HMOX1) GT-dinucleotide repeats. As markers of kidney damage, albuminuria, hyperfiltration and decreased estimated glomerular filtration with creatinine (eGFRcr) were measured. An association of independent clinical and genetic factors with these markers of kidney damage were assessed via regression analysis. Genetic sequencing confirmed sickle cell anaemia in 326 participants. Albuminuria, hyperfiltration and decreased eGFRcr were present in 65 (20%), 52 (16%) and 18 (5·5%) patients, respectively. Regression analysis revealed frequent blood transfusions, indirect bilirubin and male gender as clinical predictors of SCN. APOL1 high-risk genotype (G1/G1, G2/G2 and G1/G2) was significantly associated with albuminuria (P = 0·04) and hyperfiltration (P = 0·001). HMOX1 GT-dinucleotide long repeats were significantly associated with lower eGFRcr. The study revealed a high burden of kidney damage among Congolese children and provided evidence of the possible role of APOL1 and HMOX1 in making children more susceptible to kidney complications.

Similar Piperacillin/Tazobactam Target Attainment in Obese versus Nonobese Patients despite Differences in Interstitial Tissue Fluid Pharmacokinetics

Precision dosing of piperacillin/tazobactam in obese patients is compromised by sparse information on target-site exposure. We aimed to evaluate the appropriateness of current and alternative piperacillin/tazobactam dosages in obese and nonobese patients. Based on a prospective, controlled clinical trial in 30 surgery patients (15 obese/15 nonobese; 0.5-h infusion of 4 g/0.5 g piperacillin/tazobactam), piperacillin pharmacokinetics were characterized in plasma and at target-site (interstitial fluid of subcutaneous adipose tissue) via population analysis. Thereafter, multiple 3-4-times daily piperacillin/tazobactam short-term/prolonged (recommended by EUCAST) and continuous infusions were evaluated by simulation. Adequacy of therapy was assessed by probability of pharmacokinetic/pharmacodynamic target-attainment (PTA ≥ 90%) based on time unbound piperacillin concentrations exceed the minimum inhibitory concentration (MIC) during 24 h (%fT>MIC). Lower piperacillin target-site maximum concentrations in obese versus nonobese patients were explained by the impact of lean (approximately two thirds) and fat body mass (approximately one third) on volume of distribution. Simulated steady-state concentrations were 1.43-times, 95%CI = (1.27; 1.61), higher in plasma versus target-site, supporting targets of %fT>2×MIC instead of %fT>4×MIC during continuous infusion to avoid target-site concentrations constantly below MIC. In all obesity and renally impairment/hyperfiltration stages, at MIC = 16 mg/L, adequate PTA required prolonged (thrice-daily 4 g/0.5 g over 3.0 h at %fT>MIC = 50) or continuous infusions (24 g/3 g over 24 h following loading dose at %fT>MIC = 98) of piperacillin/tazobactam.

Longitudinal study of glomerular hyperfiltration and normalization of estimated glomerular filtration in adults with sickle cell disease

Glomerular hyperfiltration is common in sickle cell disease (SCD) and precedes proteinuria and declining kidney function. We evaluated hyperfiltration in SCD patients and its "normalization." Routine visit data were collected retrospectively from adult SCD patients in a single centre from 2004 to 2013. Baseline was defined as first available serum creatinine and hyperfiltration as estimated glomerular filtration rates (eGFR) >130 ml/min/1·73 m² for women and >140 ml/min/1·73 m² for men. Normalization of hyperfiltration was eGFR reduction to 90-130 ml/min/1·73 m² for women or 90-140 ml/min/1·73 m² for men. Among 292 patients, median age was 27 years [interquartile range (IQR):20·0-38·0], and 56·8% had baseline hyperfiltration. Baseline hyperfiltration was inversely associated with age [odds ratio (OR):0·86, 95% confidence interval (CI): 0·82-0·90; P < 0·0001], male sex (OR:0·16, 95% CI: 0·07-0·41; P = 0·0001), haemoglobin (OR:0·76, 95% CI 0·61-0·94; P = 0·01), weight (OR:0·96, 95% CI: 0·93-0·99; P = 0·004), and angiotensin-converting enzyme inhibitor/angiotensin receptor blocker (ACE-I/ARB) use (OR:0·08, 95% CI: 0·01-0·75; P = 0·03), and positively with hydroxycarbamide use (OR:2·99, 95% CI: 1·18-7·56; P = 0·02). Of 89 hyperfiltration patients without baseline proteinuria, 10 (11·2%) developed new-onset proteinuria [median 1·05 years (IQR:0·63-2·09)]. Normalization of hyperfiltration was less likely with higher baseline eGFR [hazard ratio (HR):0·90, 95% CI: 0·86-0·95; P < 0·0001] and more likely in males (HR:6·35, 95% CI:2·71-14·86, <0·0001). Hyperfiltration is common in adult SCD patients, particularly when younger. Decline to normal values is more likely in males, possibly representing kidney function loss rather than improvement in hyperfiltration.

Male renal functions are associated with serum short- and medium-chain chlorinated paraffins in residents from Jinan, China

BACKGROUND

Chlorinated paraffins (CPs) are contaminants ubiquitously detected in environmental samples, and reports addressing CPs in human samples are expanding. While CP exposure was suggested to impair kidney function by in vivo/in vitro experiments, epidemiological evidence is lacking.

OBJECTIVE

To examine the associations between serum total short-chain CP and medium-chain CP concentrations (∑SCCPs and ∑MCCPs) with human kidney function.

METHODS

The study samples were obtained from 387 participants living in Jinan, North China. We quantified ∑SCCPs and ∑MCCPs in serum samples and evaluated the kidney function of included subjects by estimated glomerular filtration rate (eGFR). The associations between serum ∑SCCPs, ∑MCCPs and eGFR were estimated using multivariable linear regression and logistic regression. The possible gender-dependent effects were studied by stratified analysis.

RESULTS

After adjusting for age, education, smoking status, drinking status, body mass index (BMI), family history of chronic kidney disease (CKD), fasting serum glucose, systolic blood pressure and diastolic blood pressure, higher concentrations of serum ∑SCCPs and ∑MCCPs were associated with higher male eGFR (β = 3.13 mL/min/1.73 m² per one ln-unit increase of serum ∑SCCPs, 95%CI: 1.72, 4.54, p = 0.016; β = 3.52 mL/min/1.73 m² per one ln-unit increase of serum ∑MCCPs, 95%CI: 1.89, 5.17, p = 0.011). Associations between serum ∑SCCPs, ∑MCCPs and female eGFR were null. Comparing higher (above the median serum CP levels) vs. lower exposure groups, serum ∑SCCPs and ∑MCCPs were associated with an elevated risk of glomerular hyperfiltration (GH, eGFR ≥ 135 mL/min/1.73 m²), which was associated with glomerular damage and represented as an early stage of chronic kidney disease (OR = 2.98; 95% CI: 1.24, 4.71 for SCCPs; OR = 3.25; 95% CI: 1.20, 5.29 for MCCPs).

CONCLUSIONS

Our study suggests that male serum ∑SCCPs and ∑MCCPs are associated with an increased risk of GH, indicating early-stage kidney impairment.

Endocytic adaptation to functional demand by the kidney proximal tubule

The kidney proximal tubule (PT) efficiently recovers the low level of albumin and other proteins that normally escape the glomerular filtration barrier. Two large receptors, megalin and cubilin/amnionless (CUBAM), bind to and efficiently retrieve these predominantly low molecular-weight proteins via clathrin-mediated endocytosis. Studies in cell culture models suggest that PT cells may sense changes in shear stress to modulate recovery of filtered proteins in response to normal variations in filtration rate. Impairments in PT endocytic function lead to the excretion of filtered proteins into the urine (tubular proteinuria). Remarkably, when the glomerular filtration barrier is breached, the PT is able to recover excess albumin with a capacity that is orders of magnitude higher than normal. What mediates this excess capacity for albumin uptake under nephrotic conditions, and why doesn't it compensate to prevent tubular proteinuria? Here we propose an integrated new working model to describe the PT recovery of filtered proteins under normal and nephrotic states. We hypothesize that uptake via the fluid phase provides excess capacity to recover high concentrations of filtered proteins under nephrotic conditions. Further, concentration of tubular fluid along the tubule axis will enhance the efficiency of uptake in more distal regions of the PT. By contrast to cells where fluid phase and receptor-mediated uptake are independent pathways, expression of megalin is required to maintain apical endocytic pathway integrity and is essential for both uptake mechanisms. This model accounts for both the high-affinity and the high-capacity responses to filtration load in physiological and pathological states.