A prospective cohort study of acute kidney injury and kidney outcomes, cardiovascular events, and death

Clinical value of soluble urokinase-type plasminogen activator receptor in predicting sepsis-associated acute kidney injury

BACKGROUND

Sepsis-associated acute kidney injury (S-AKI) is a critical illness and is often associated with high morbidity and mortality rates. The soluble urokinase-type plasminogen activator receptor (suPAR) is an important immune mediator and is involved in kidney injury. However, its diagnostic value in S-AKI patients remains unclear. Therefore, we assessed the early predictive value of suPAR for S-AKI patients.

METHODS

We prospectively enrolled adult patients, immediately after fulfilling the sepsis-3 criteria. Plasma suPAR levels at 0-, 12-, 24-, and 48-h post-sepsis diagnosis were measured. S-AKI development was the primary outcome. S-AKI risk factors were analyzed using logistic regression, and the value of plasma suPAR for early S-AKI diagnosis was assessed using receiver operating characteristic (ROC) curves.

RESULTS

Of 179 sepsis patients, 63 (35.2%) developed AKI during hospitalization. At 12-, 24-, and 48-h post-sepsis diagnosis, plasma suPAR levels were significantly higher in patients with S-AKI than in patients without S-AKI (p < 0.05). The plasma suPAR had the highest area under the ROC curve of 0.700 (95% confidence interval (CI), 0.621-0.779) at 24-h post-sepsis diagnosis, at which the best discrimination ability for S-AKI was achieved with suPAR of ≥6.31 ng/mL (sensitivity 61.9% and specificity 71.6%). Logistic regression analysis showed that suPAR at 24-h post-sepsis diagnosis remained an independent S-AKI risk factor after adjusting for mechanical ventilation, blood urea nitrogen, and pH.

CONCLUSIONS

The findings suggest that plasma suPAR may be a potential biomarker for early S-AKI diagnosis.

The Road to Precision Medicine for Acute Kidney Injury

OBJECTIVES

Acute kidney injury (AKI) is a common form of organ dysfunction in the ICU. AKI is associated with adverse short- and long-term outcomes, including high mortality rates, which have not measurably improved over the past decade. This review summarizes the available literature examining the evidence of the need for precision medicine in AKI in critical illness, highlights the current evidence for heterogeneity in the field of AKI, discusses the progress made in advancing precision in AKI, and provides a roadmap for studying precision-guided care in AKI.

DATA SOURCES

Medical literature regarding topics relevant to precision medicine in AKI, including AKI definitions, epidemiology, and outcomes, novel AKI biomarkers, studies of electronic health records (EHRs), clinical trial design, and observational studies of kidney biopsies in patients with AKI.

STUDY SELECTION

English language observational studies, randomized clinical trials, reviews, professional society recommendations, and guidelines on areas related to precision medicine in AKI.

DATA EXTRACTION

Relevant study results, statements, and guidelines were qualitatively assessed and narratively synthesized.

DATA SYNTHESIS

We synthesized relevant study results, professional society recommendations, and guidelines in this discussion.

CONCLUSIONS

AKI is a syndrome that encompasses a wide range of underlying pathologies, and this heterogeneity has hindered the development of novel therapeutics for AKI. Wide-ranging efforts to improve precision in AKI have included the validation of novel biomarkers of AKI, leveraging EHRs for disease classification, and phenotyping of tubular secretory clearance. Ongoing efforts such as the Kidney Precision Medicine Project, identifying subphenotypes in AKI, and optimizing clinical trials and endpoints all have great promise in advancing precision medicine in AKI.

A cohort study of sodium-glucose cotransporter-2 inhibitors after acute kidney injury among Veterans with diabetic kidney disease

Sodium-glucose cotransporter-2 inhibitors (SGLT2i) reduce the risk for several adverse outcomes among patients with diabetic kidney disease. Yet, optimal timing for SGLT2i after acute kidney injury (AKI) is uncertain, as are the providers responsible for post-AKI SGLT2i initiation. Using a retrospective cohort of United States Veterans with diabetes mellitus type 2 and proteinuria, we examined encounters by provider specialty before SGLT2i initiation and subsequent all-cause mortality after hospitalization with AKI, defined by a 50% or more rise in serum creatinine. Covariates included recovery, defined by return to a 110% or less of baseline creatinine, and time since AKI hospitalization. Among 21,330 eligible Veterans, 7,798 died (37%) and 6,562 received a SGLT2i (31%) over median follow-up of 2.1 years. Post-AKI SGLT2i use was associated with lower mortality risk [adjusted hazard ratio 0.63 (95% confidence interval 0.58-0.68)]. Compared with neither SGLT2i use nor recovery, mortality risk was similar with recovery without SGLT2i use [0.97 (0.91-1.02)] but was lower without recovery prior to SGLT2i use [0.62 (0.55-0.71)] and with SGLT2i use after recovery [0.60 (0.54-0.67)]. Finally, the effect of SGLT2i was stable over time (P for time-interaction 0.19). Thus, we observed reduced mortality with SGLT2i use after AKI among Veterans with diabetic kidney disease whether started earlier or later or before or after observed recovery. Hence, patients with diabetic kidney disease who receive a SGLT2i earlier after AKI experience no significant harm impacting mortality and experience a lower mortality risk than those who do not.

Acute Kidney Injury and Subsequent Cardiovascular Disease: Epidemiology, Pathophysiology, and Treatment

Cardiovascular disease poses a significant threat to individuals with kidney disease, including those affected by acute kidney injury (AKI). In the short term, AKI has several physiological consequences that can impact the cardiovascular system. These include fluid and sodium overload, activation of the renin-angiotensin-aldosterone system and sympathetic nervous system, and inflammation along with metabolic complications of AKI (acidosis, electrolyte imbalance, buildup of uremic toxins). Recent studies highlight the role of AKI in elevating long-term risks of hypertension, thromboembolism, stroke, and major adverse cardiovascular events, though some of this increased risk may be due to the impact of AKI on the course of chronic kidney disease. Current management strategies involve avoiding nephrotoxic agents, optimizing hemodynamics and fluid balance, and considering renin-angiotensin-aldosterone system inhibition or sodium-glucose cotransporter 2 inhibitors. However, future research is imperative to advance preventive and therapeutic strategies for cardiovascular complications in AKI. This review explores the existing knowledge on the cardiovascular consequences of AKI, delving into epidemiology, pathophysiology, and treatment of various cardiovascular complications following AKI.

Genome-wide association study of hospitalized patients and acute kidney injury

Acute kidney injury (AKI) is a common and devastating complication of hospitalization. Here, we identified genetic loci associated with AKI in patients hospitalized between 2002-2019 in the Million Veteran Program and data from Vanderbilt University Medical Center's BioVU. AKI was defined as meeting a modified KDIGO Stage1 or more for two or more consecutive days or kidney replacement therapy. Control individuals were required to have one or more qualifying hospitalizations without AKI and no evidence of AKI during any other observed hospitalizations. Genome-wide association studies (GWAS), stratified by race, adjusting for sex, age, baseline estimated glomerular filtration rate (eGFR), and the top ten principal components of ancestry were conducted. Results were meta-analyzed using fixed effects models. In total, there were 54,488 patients with AKI and 138,051 non-AKI individuals included in the study. Two novel loci reached genome-wide significance in the meta-analysis: rs11642015 near the FTO locus on chromosome 16 (obesity traits) (odds ratio 1.07 (95% confidence interval, 1.05-1.09)) and rs4859682 near the SHROOM3 locus on chromosome 4 (glomerular filtration barrier integrity) (odds ratio 0.95 (95% confidence interval, 0.93-0.96)). These loci colocalized with previous studies of kidney function, and genetic correlation indicated significant shared genetic architecture between AKI and eGFR. Notably, the association at the FTO locus was attenuated after adjustment for BMI and diabetes, suggesting that this association may be partially driven by obesity. Both FTO and the SHROOM3 loci showed nominal evidence of replication from diagnostic-code-based summary statistics from UK Biobank, FinnGen, and Biobank Japan. Thus, our large GWA meta-analysis found two loci significantly associated with AKI suggesting genetics may explain some risk for AKI.

Heart failure subtype after acute kidney injury

INTRODUCTION

Acute kidney injury (AKI) is associated with increased risk of heart failure (HF). Determining the type of HF experienced by AKI survivors (heart failure with preserved or reduced ejection fraction, HFpEF or HFrEF) could suggest potential mechanisms underlying the association and opportunities for improving post-AKI care.

METHODS

In this retrospective study of adults within the Vanderbilt University health system with a diagnosis of HF, we tested whether AKI events in the two years preceding incident HF associated more with HFpEF or HFrEF while controlling for known predictors. HF outcomes were defined by administrative codes and classified as HFpEF or HFrEF by echocardiogram data. We used multivariable logistic regression models to estimate the effects of AKI on the odds of incident HFpEF versus HFrEF.

RESULTS

AKI (all stages) trended towards a preferential association with HFpEF in adjusted analyses (adjusted OR 0.80, 95% CI 0.63 - 1.01). Stage 1 AKI was associated with higher odds of HFpEF that was statistically significant (adjusted OR 0.62, 95% CI 0.43 - 0.88), whereas stages 2-3 AKI showed a trend toward HFrEF that did not reach statistical significance (adjusted OR 1.11, 95% CI 0.76 - 1.63).

CONCLUSIONS

AKI as a binary outcome trended towards a preferential association with HFpEF. Stage 1 AKI was associated with higher odds of HFpEF, whereas stage 2-3 trended towards an association with HFrEF that did not meet statistical significance. Different mechanisms may predominate in incident HF following mild versus more severe AKI. Close follow-up with particular attention to volume status and cardiac function after discharge is warranted after even mild AKI.

Renal and major clinical outcomes and their determinants after nephrectomy in patients with pre-existing chronic kidney disease: A retrospective cohort study

The consequences of partial nephrectomy (PN) compared to radical nephrectomy (RN) are less documented in patients with pre-existing chronic kidney disease (CKD) or with solitary kidney (SK). We assessed renal outcomes, and their determinants, after PN or RN in a retrospective cohort of patients with moderate-to-severe CKD (RN-CKD and PN-CKD) or SK (PN-SK). All surgical procedures conducted between 2013 and 2018 in our institution in patients with pre-operative estimated glomerular filtration rate (eGFR)<60 mL/min/1.73m2 or with SK were included. The primary outcome was a composite criterion including CKD progression or major adverse cardio-vascular events (MACE) or death, assessed one year after surgery. Predictors of the primary outcome were determined using multivariate analyses. A total of 173 procedures were included (67 RN, and 106 PN including 27 SK patients). Patients undergoing RN were older, with larger tumors. Preoperative eGFR was not significantly different between the groups. One year after surgery, PN-CKD was associated with lower rate of the primary outcome compared to RN-CKD (43% vs 71% p = 0.007). In multivariate analysis, independent risk factors for the primary outcome were postoperative AKI (stage 1 to stage 3 ranging from OR = 8.68, 95% CI 3.23-23.33, to OR = 28.87, 95% CI 4.77-167.61), larger tumor size (OR = 1.21 per cm, 95% CI 1.02-1.45), while preoperative eGFR, age, sex, diabetes mellitus, and hypertension were not. Postoperative AKI after PN or RN was the major independent determinant of worse outcomes (CKD progression, MACE, or death) one year after surgery.

Acute Kidney Injury Duration and 20-Year Risks of CKD and Cardiovascular Disease

Introduction

Acute kidney injury (AKI) is associated with chronic kidney disease (CKD) and cardiovascular disease (CVD); however, it is unclear whether AKI duration affects the long-term risks of CKD and CVD. Therefore, we performed a population-based cohort study examining the associations between AKI duration and CKD and CVD.

Methods

We identified patients with laboratory-recorded AKI in Denmark from 1990 through 2018. AKIs were categorized as rapid reversal AKI (≤48 hours), persistent AKI (2-7 days), and acute kidney disease (AKD) (>7 days). We estimated 20-year risks and adjusted hazard ratios (aHRs) of incident CKD and CVD.

Results

The study comprised 169,582 patients with AKI, with 100,478 and 76,838 included in the analysis of CKD and CVD, respectively. The 20-year risks of CKD were 26.3%, 29.5%, and 28.7% for rapid reversal AKI, persistent AKI, and AKD, respectively. Compared with rapid reversal AKI, aHRs were 1.13 (95% confidence interval [CI], 1.08-1.19) for persistent AKI and 1.36 (95% CI, 1.30-1.41) for AKD. Risks and rates of overall CVD were similar for rapid reversal AKI, persistent AKI, and AKD. However, persistent AKI was associated with a slightly increased aHR of heart failure (1.09; 95% CI, 1.02-1.16), and aHRs of heart failure, ischemic heart disease, and peripheral artery disease were slightly increased for AKD (1.09 [95% CI, 1.03-1.15], 1.11 [95% CI, 1.03-1.19], and 1.10 [95% CI, 1.02-1.17], respectively).

Conclusion

AKI duration was associated with development of CKD, but not overall CVD; however, rates of heart failure, ischemic heart disease, and peripheral artery disease increased slightly with AKI duration.

Kidney and heart failure events are bidirectionally associated in patients with type 2 diabetes and cardiovascular disease

AIMS

This study aimed to evaluate the bidirectional relationship between kidney and cardiovascular (CV) events in trial participants with type 2 diabetes and CV disease.

METHODS AND RESULTS

Post hoc analyses of EMPA-REG OUTCOME using Cox regression models were performed to assess the association of baseline factors with risk of a kidney event and bidirectional associations of incident kidney events and CV events. Among placebo-treated participants, baseline factors significantly associated with greater kidney event risk included lower baseline estimated glomerular filtration rate, albuminuria, higher uric acid, low-density lipoprotein cholesterol levels, and prior heart failure (HF). Coronary artery disease was not associated with increased risk. In placebo-treated participants, occurrence of an incident non-fatal kidney event increased the subsequent risk of hospitalization for HF (HHF) but not 3-point major adverse CV events (non-fatal stroke, non-fatal myocardial infarction, and CV death). Vice versa, HHF (but not myocardial infarction/stroke) increased the risk of subsequent kidney events. These associations were generally also seen in empagliflozin-treated participants and in the overall population. Interestingly, the risk of kidney events following HHF was not significantly increased in the relatively small number of placebo-treated participants already diagnosed with HF at baseline.

CONCLUSIONS

These findings demonstrate a bidirectional inter-relationship between HHF and kidney events. Further exploration of this relationship and strategies to optimize the use of therapies to reduce both kidney and HF outcomes is warranted.

A Retrospective Cohort Study That Examined the Impact of Cannabis Consumption on Long-Term Kidney Outcomes

Background: Cannabis consumption for recreational and medical use is increasing worldwide. However, the long-term effects on kidney health and disease are largely unknown. Materials and Methods: Post hoc analysis of cannabis use as a risk factor for kidney disease was performed using data from the Assessment, Serial Evaluation, and Subsequent Sequelae of Acute Kidney Injury (ASSESS-AKI) study that enrolled hospitalized adults with and without acute kidney injury from four U.S. centers during 2009-2015. Associations between self-reported cannabis consumption and the categorical and continuous outcomes were determined using multivariable Cox regression and linear mixed models, respectively. Results: Over a mean follow-up of 4.5±1.8 years, 94 participants without chronic kidney disease (CKD) (estimated glomerular filtration rate [eGFR] >60 mL/min/1.73 m2) who consumed cannabis had similar rates of annual eGFR decline versus 889 nonconsumers (mean difference=-0.02 mL/min/1.73 m2/year, p=0.9) and incident CKD (≥25% reduction in eGFR compared with the 3-month post-hospitalization measured eGFR and achieving CKD stage 3 or higher) (adjusted hazard ratio [aHR]=1.2; 95% confidence interval [CI]=0.7-2.0). Nineteen participants with CKD (eGFR <60 mL/min/1.73 m2) who consumed cannabis had more rapid eGFR decline versus 597 nonconsumers (mean difference=-1.3 mL/min/1.73 m2/year; p=0.02) that was not independently associated with an increased risk of CKD progression (≥50% reduction in eGFR compared with the 3-month post-hospitalization eGFR, reaching CKD stage 5, or receiving kidney replacement therapy) (aHR=1.6; 95% CI=0.7-3.5). Cannabis consumption was not associated with the rate of change in urine albumin to creatinine ratio (UACR) over time among those with (p=0.7) or without CKD (p=0.4). Conclusions: Cannabis consumption did not adversely affect the kidney function of participants without CKD but was associated with a faster annual eGFR decline among participants with CKD. Cannabis consumption was not associated with changes in UACR over time, incident CKD, or progressive CKD regardless of baseline kidney function. Additional research is needed to investigate the kidney endocannabinoid system and the impact of cannabis use on kidney disease outcomes.

Assessment of Acute Kidney Injury using MRI

There has been growing interest in using quantitative magnetic resonance imaging (MRI) to describe and understand the pathophysiology of acute kidney injury (AKI). The ability to assess kidney blood flow, perfusion, oxygenation, and changes in tissue microstructure at repeated timepoints is hugely appealing, as this offers new possibilities to describe nature and severity of AKI, track the time-course to recovery or progression to chronic kidney disease (CKD), and may ultimately provide a method to noninvasively assess response to new therapies. This could have significant clinical implications considering that AKI is common (affecting more than 13 million people globally every year), harmful (associated with short and long-term morbidity and mortality), and currently lacks specific treatments. However, this is also a challenging area to study. After the kidney has been affected by an initial insult that leads to AKI, complex coexisting processes ensue, which may recover or can progress to CKD. There are various preclinical models of AKI (from which most of our current understanding derives), and these differ from each other but more importantly from clinical AKI. These aspects are fundamental to interpreting the results of the different AKI studies in which renal MRI has been used, which encompass different settings of AKI and a variety of MRI measures acquired at different timepoints. This review aims to provide a comprehensive description and interpretation of current studies (both preclinical and clinical) in which MRI has been used to assess AKI, and discuss future directions in the field. LEVEL OF EVIDENCE: 1 TECHNICAL EFFICACY: Stage 3.

Urinary Biomarkers and Kidney Injury in VA NEPHRON-D: Phenotyping Acute Kidney Injury in Clinical Trials

RATIONALE & OBJECTIVE

Urinary biomarkers of injury, inflammation, and repair may help phenotype acute kidney injury (AKI) observed in clinical trials. We evaluated the differences in biomarkers between participants randomized to monotherapy or to combination renin-angiotensin-aldosterone system (RAAS) blockade in VA NEPHRON-D, where an increased proportion of observed AKI was acknowledged in the combination arm.

STUDY DESIGN

Longitudinal analysis.

SETTING & PARTICIPANTS

A substudy of the VA NEPHRON-D trial.

PREDICTOR

Primary exposure was the treatment arm (combination [RAAS inhibitor] vs monotherapy). AKI is used as a stratifying variable.

OUTCOME

Urinary biomarkers, including albumin, EGF (epidermal growth factor), MCP-1 (monocyte chemoattractant protein-1), YKL-40 (chitinase 3-like protein 1), and KIM-1 (kidney injury molecule-1).

ANALYTICAL APPROACH

Biomarkers measured at baseline and at 12 months in trial participants were compared between treatment groups and by AKI. AKI events occurring during hospitalization were predefined safety end points in the original trial. The results were included in a meta-analysis with other large chronic kidney disease trials to assess global trends in biomarker changes.

RESULTS

In 707 participants followed for a median of 2.2 years, AKI incidence was higher in the combination (20.7%) versus the monotherapy group (12.7%; relative risk [RR], 1.64 [95% CI, 1.16-2.30]). Compared with the monotherapy arm, in the combination arm the urine biomarkers at 12 months were either unchanged (MCP-1: RR, -3% [95% CI, -13% to 9%], Padj=0.8; KIM-1: RR, -10% [95% CI, -20% to 1%], Padj=0.2; EGF, RR-7% [95% CI, -12% to-1%], Padj=0.08) or lower (albuminuria: RR, -24% [95% CI, -37% to-8%], Padj=0.02; YKL: RR, -40% to-44% [95% CI, -58% to-25%], Padj<0.001). Pooled meta-analysis demonstrated reduced albuminuria in the intervention arm across 3 trials and similar trajectories in other biomarkers.

LIMITATIONS

Biomarker measurement was limited to 2 time points independent of AKI events.

CONCLUSIONS

Despite the increased risk of serum creatinine-defined AKI, combination RAAS inhibitor therapy was associated with unchanged or decreased urinary biomarkers at 12 months. This suggests a possible role for kidney biomarkers to further characterize kidney injury in clinical trials.

PLAIN-LANGUAGE SUMMARY

The VA NEPHRON-D trial investigated inhibition of the renin-angiotensin-aldosterone system (RAAS) hormonal axis on kidney outcomes in a large population of diabetic chronic kidney disease patients. The trial was stopped early due to increased events of serum creatinine-defined acute kidney injury in the combination therapy arm. Urine biomarkers can serve as an adjunct to serum creatinine in identifying kidney injury. We found that urinary biomarkers in the combination therapy group were not associated with a pattern of harm and damage to the kidney, despite the increased number of kidney injury events in that group. This suggests that serum creatinine alone may be insufficient for defining kidney injury and supports further exploration of how other biomarkers might improve identification of kidney injury in clinical trials.

ER stress modulated Klotho restoration: A prophylactic therapeutic strategy against acute kidney injury-diabetes comorbidity

Klotho is a renoprotective factor that is at the forefront of research as a potential therapeutic agent and biomarker of acute kidney injury (AKI). Endoplasmic reticulum (ER) stress and Klotho downregulation are the critical hallmarks of AKI progression. Importantly, the crosstalk between ER and Klotho is still elusive in AKI under diabetic condition. Therefore, this study aimed to elucidate the affiliation between ER stress and Klotho regulation by using the ischemia-reperfusion renal injury (IRI) model based on male Wistar rats and the hypoxia-reperfusion injury (HRI) using NRK52E cells. Study outcomes demonstrated that the expression of AKI biomarkers: plasma creatinine, neutrophil gelatinase-associated lipocalin, kidney-injury molecule 1, and ER stress markers such as binding immunoglobulin binding protein (BiP), R/PKR-like ER kinase (PERK), and eukaryotic initiation factor-2 (eIF2α), were observed during AKI. Increased ER stress was associated with apoptosis induction as depicted by increased levels of Poly (ADP-ribose) polymerase (PARP) and caspase-7 and decreased tubular Klotho expression. Under diabetic settings, ER stress and apoptosis were exacerbated by additional Klotho downregulation. Treatment with Tauroursodeoxycholic acid (TUDCA) inhibited the ER stress, apoptosis, restored endogenous Klotho levels and ameliorated AKI under diabetic and non-diabetic conditions. ER stress and Klotho appear to be shared factors involved in the pathogenesis of AKI-diabetes comorbidity and targeting them could prove a novel therapeutic approach.

Impact of acute kidney injury on major adverse cardiovascular events in intensive care survivors

Background

Acute kidney injury commonly occurs in patients admitted to ICU. After acute kidney injury, kidney function may not completely recover leading to increased risk of future cardiovascular events. We sought to ascertain the rates of cardiovascular events in ICU survivors and if these rates were affected by the presence of acute kidney injury whilst in ICU.

Methods

This retrospective observational cohort study utilised routinely collected data to identify patients who had survived an admission to one of two ICUs between July 2015 and June 2018. Baseline serum creatinine and subsequent values were used to identify acute kidney injury. Major adverse cardiovascular events described were myocardial injury, coronary artery intervention, or radiological evidence of stroke.

Results

Of the 3994 ICU survivors, major adverse cardiovascular events were identified in 385 patients (9.6%; 95% confidence interval [CI] 8.8-10.6%). Presence of acute kidney injury whilst in ICU was significantly associated with future major adverse cardiovascular events (hazard ratio=1.38; 95% CI 1.12-1.70; P-value=0.003) and future biochemical myocardial injury (hazard ratio=1.48; 95% CI 1.16-1.89; P-value=0.001). Acute kidney injury did not have a statistically significant association with future coronary artery interventions or future cerebrovascular events.

Conclusions

One in 10 ICU survivors experiences a major adverse cardiovascular event after discharge. Acute kidney injury whilst in ICU was associated with an increased risk of major adverse cardiovascular events and specifically myocardial injury. Further research is warranted on whether ICU survivors with acute kidney injury merit enhanced strategies for cardiovascular protection.

A comprehensive description of kidney disease progression after acute kidney injury from a prospective, parallel-group cohort study

Acute kidney injury (AKI) is associated with adverse long-term outcomes, but many studies are retrospective, focused on specific patient groups or lack adequate comparators. The ARID (AKI Risk in Derby) Study was a five-year prospective parallel-group cohort study to examine this. Hospitalized cohorts with and without exposure to AKI were matched 1:1 for age, baseline kidney function, and diabetes. Estimated glomerular filtration rate (eGFR) and the urinary albumin:creatinine ratio (uACR) were measured at three-months, one-, three- and five-years. Outcomes included kidney disease progression, heart failure episodes and mortality. In 866 matched individuals, kidney disease progression at five years was found to be significantly increased in 30% of the exposed group versus 7% of those non-exposed (adjusted odds ratio 2.49 [95% confidence interval 1.43 to 4.36]). In the AKI group, this was largely characterized by incomplete recovery of kidney function by three months. Further episodes of AKI during follow-up were significantly more common in the exposed group (odds ratio 2.71 [1.94 to 3.77]) and had an additive effect on risk of kidney disease progression. Mortality and heart failure episodes were more frequent in the exposed group, but the association with AKI was no longer significant when models were adjusted for three-month eGFR and uACR. In a general hospitalized population, kidney disease progression after five years was common and strongly associated with AKI. Thus, the time course of changes and the attenuation of associations with adverse outcomes after adjustment for three-month eGFR and uACR suggest non-recovery of kidney function is an important assessment in post-AKI care and a potential future target for intervention. STUDY REGISTRATION: ISRCTN25405995.

The ASSESS-AKI Study found urinary epidermal growth factor is associated with reduced risk of major adverse kidney events

Biomarkers of tubular function such as epidermal growth factor (EGF) may improve prognostication of participants at highest risk for chronic kidney disease (CKD) after hospitalization. To examine this, we measured urinary EGF (uEGF) from samples collected in the Assessment, Serial Evaluation, and Subsequent Sequelae of Acute Kidney Injury (ASSESS-AKI) Study, a multi-center, prospective, observational cohort of hospitalized participants with and without AKI. Cox proportional hazards regression was used to investigate the association of uEGF/Cr at hospitalization, three months post-discharge, and the change between these time points with major adverse kidney events (MAKE): CKD incidence, progression, or development of kidney failure. Clinical findings were paired with mechanistic studies comparing relative Egf expression in mouse models of kidney atrophy or repair after ischemia-reperfusion injury. MAKE was observed in 20% of 1,509 participants over 4.3 years of follow-up. Each 2-fold higher level of uEGF/Cr at three months was associated with decreased risk of MAKE (adjusted hazards ratio 0.46, 95% confidence interval: 0.39-0.55). Participants with the highest increase in uEGF/Cr from hospitalization to three-month follow-up had a lower risk of MAKE (adjusted hazards ratio 0.52; 95% confidence interval: 0.36-0.74) compared to those with the least change in uEGF/Cr. A model using uEGF/Cr at three months combined with clinical variables yielded moderate discrimination for MAKE (area under the curve 0.73; 95% confidence interval: 0.69-0.77) and strong discrimination for kidney failure at four years (area under the curve 0.96; 95% confidence interval: 0.92-1.00). Accelerated restoration of Egf expression in mice was seen in the model of adaptive repair after injury, compared to a model of progressive atrophy. Thus, urinary EGF/Cr may be a biomarker of distal tubular health, with higher concentrations and increased uEGF/Cr post-discharge independently associated with reduced risk of MAKE in hospitalized patients.

The role of renin-angiotensin system in sepsis-associated acute kidney injury: mechanisms and therapeutic implications

PURPOSE OF REVIEW

This review aims to explore the relationship between the renin angiotensin system (RAS) and sepsis-associated acute kidney injury (SA-AKI), a common complication in critically ill patients associated with mortality, morbidity, and long-term cardiovascular complications. Additionally, this review aims to identify potential therapeutic approaches to intervene with the RAS and prevent the development of AKI.

RECENT FINDINGS

Recent studies have provided increasing evidence of RAS alteration during sepsis, with systemic and local RAS disturbance, which can contribute to SA-AKI. Angiotensin II was recently approved for catecholamine resistant vasodilatory shock and has been associated with improved outcomes in selected patients.

SUMMARY

SA-AKI is a common condition that can involve disturbances in the RAS, particularly the canonical angiotensin-converting enzyme (ACE) angiotensin-II (Ang II)/angiotensin II receptor 1 (AT-1R) axis. Increased renin levels, a key enzyme in the RAS, have been shown to be associated with AKI and may also guide vasopressor therapy in shock. In patients with high renin levels, angiotensin II administration may reduce renin concentration, improve intra-renal hemodynamics, and enhance signaling through the angiotensin II receptor 1. Further studies are needed to explore the role of the RAS in SA-AKI and the potential for targeted therapies.

Impact of Recovery from Acute Kidney Injury After Aortic Arch Repair

BACKGROUND

The impact of recovery from acute kidney injury (AKI) after open thoracic aortic surgery on follow-up outcomes is unclear.

METHODS

This retrospective study included 214 patients who underwent aortic arch surgery requiring hypothermic circulatory arrest between 2007 and 2019. Patients who required preoperative renal replacement therapy and patients who died within 7 postoperative days were excluded. The incidence of recovery from AKI was examined. Renal outcomes were compared among patients with no AKI (Group N), recovery from AKI (Group R), and persistent AKI (Group P).

RESULTS

Preoperative kidney function was similar among the 3 groups. Among the 115 patients who developed postoperative AKI, 80.9% recovered from AKI at discharge. The 5-year cumulative mortality rate was 18.0%, 24.5%, and 68.4% in Group N, R, and P, respectively (P < .001, Group R vs Group P). The 5-year cumulative incidence of renal replacement therapy dependency was 0.0%, 5.4%, and 22.7%, respectively (P = .04, Group N vs Group R; P = .01, Group R vs Group P). The medians (interquartile range) of estimated glomerular filtration rate (mL/min/1.73 m2) 2 years after surgery were 65.2 (50.4-80.2), 54.3 (41.4-65.9), and 56.9 (40.2-67.5), respectively (P = .03, Group N vs Group R).

CONCLUSIONS

The majority of patients recovered from AKI after thoracic aortic repair by discharge. However, the prolonged impact of AKI recovery on kidney function was observed during the follow-up period. Diligent follow-up after discharge is warranted for early identification of patients at high risk of kidney disease progression.

Epidemiology and outcomes of post-AKI proteinuria

Background

Acute kidney injury (AKI) has been associated with increased risks of new-onset and worsening proteinuria. However, epidemiologic data for post-AKI proteinuria was still lacking. This study aimed to determine the incidence, risk factors and clinical correlations of post-AKI proteinuria among hospitalized patients.

Methods

This study was conducted in a multicenter cohort including patients aged 18-100 years with hospital-acquired AKI (HA-AKI) hospitalized at 19 medical centers throughout China. The primary outcome was the incidence of post-AKI proteinuria. Secondary outcomes included AKI recovery and kidney disease progression. The results of both quantitative and qualitative urinary protein tests were used to define post-AKI proteinuria. Cox proportional hazard model with stepwise regression was used to determine the risk factors for post-AKI proteinuria.

Results

Of 6206 HA-AKI patients without proteinuria at baseline, 2102 (33.9%) had new-onset proteinuria, whereas of 5137 HA-AKI with baseline proteinuria, 894 (17.4%) had worsening proteinuria after AKI. Higher AKI stage and preexisting CKD diagnosis were risk factors for new-onset proteinuria and worsening proteinuria, whereas treatment with renin-angiotensin system inhibitors was associated with an 11% lower risk of incident proteinuria. About 60% and 75% of patients with post-AKI new-onset and worsening proteinuria, respectively, recovered within 3 months. Worsening proteinuria was associated with a lower incidence of AKI recovery and a higher risk of kidney disease progression.

Conclusions

Post-AKI proteinuria is common and usually transient among hospitalized patients. The risk profiles for new-onset and worsening post-AKI proteinuria differed markedly. Worsening proteinuria after AKI was associated with adverse kidney outcomes, which emphasized the need for close monitoring of proteinuria after AKI.

Renin-Angiotensin-Aldosterone System Blockade after AKI with or without Recovery among US Veterans with Diabetic Kidney Disease

SIGNIFICANCE STATEMENT

Among patients with CKD, optimal use of angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers after AKI is uncertain. Despite these medications' ability to reduce risk of mortality and other adverse outcomes, there is concern that ACEi/ARB use may delay recovery of kidney function or precipitate recurrent AKI. Prior studies have provided conflicting data regarding the optimal timing of these medications after AKI and have not addressed the role of kidney recovery in determining appropriate timing. This study in US Veterans with diabetes mellitus and proteinuria demonstrated an association between ACEi/ARB use and lower mortality. This association was more pronounced with earlier post-AKI ACEi/ARB use and was not meaningfully affected by initiating ACEis/ARBs before versus after recovery from AKI.

BACKGROUND

Optimal use of angiotensin-converting enzyme inhibitors (ACEis) or angiotensin II receptor blockers (ARBs) after AKI is uncertain.

METHODS

Using data derived from electronic medical records, we sought to estimate the association between ACEi/ARB use after AKI and mortality in US military Veterans with indications for such treatment (diabetes and proteinuria) while accounting for AKI recovery. We used ACEi/ARB treatment after hospitalization with AKI (defined as serum creatinine ≥50% above baseline concentration) as a time-varying exposure in Cox models. The outcome was all-cause mortality. Recovery was defined as return to ≤110% of baseline creatinine. A secondary analysis focused on ACEi/ARB use relative to AKI recovery (before versus after).

RESULTS

Among 54,735 Veterans with AKI, 31,146 deaths occurred over a median follow-up period of 2.3 years. Approximately 57% received an ACEi/ARB <3 months after hospitalization. In multivariate analysis with time-varying recovery, post-AKI ACEi/ARB use was associated with lower risk of mortality (adjusted hazard ratio [aHR], 0.74; 95% confidence interval [CI], 0.72 to 0.77). The association between ACEi/ARB use and mortality varied over time, with lower mortality risk associated with earlier initiation ( P for interaction with time <0.001). In secondary analysis, compared with those with neither recovery nor ACEi/ARB use, risk of mortality was lower in those with recovery without ACEi/ARB use (aHR, 0.90; 95% CI, 0.87 to 0.94), those without recovery with ACEi/ARB use (aHR, 0.69; 95% CI, 0.66 to 0.72), and those with ACEi/ARB use after recovery (aHR, 0.70; 95% CI, 0.67 to 0.73).

CONCLUSIONS

This study demonstrated lower mortality associated with ACEi/ARB use in Veterans with diabetes, proteinuria, and AKI, regardless of recovery. Results favored earlier ACEi/ARB initiation.

Tolerogenic dendritic cells protect against acute kidney injury

Ischemia reperfusion injury is a common precipitant of acute kidney injury that occurs following disrupted perfusion to the kidney. This includes blood loss and hemodynamic shock, as well as during retrieval for deceased donor kidney transplantation. Acute kidney injury is associated with adverse long-term clinical outcomes and requires effective interventions that can modify the disease process. Immunomodulatory cell therapies such as tolerogenic dendritic cells remain a promising tool, and here we tested the hypothesis that adoptively transferred tolerogenic dendritic cells can limit kidney injury. The phenotypic and genomic signatures of bone marrow-derived syngeneic or allogeneic, Vitamin-D3/IL-10-conditioned tolerogenic dendritic cells were assessed. These cells were characterized by high PD-L1:CD86, elevated IL-10, restricted IL-12p70 secretion and a suppressed transcriptomic inflammatory profile. When infused systemically, these cells successfully abrogated kidney injury without modifying infiltrating inflammatory cell populations. They also provided protection against ischemia reperfusion injury in mice pre-treated with liposomal clodronate, suggesting the process was regulated by live, rather than reprocessed cells. Co-culture experiments and spatial transcriptomic analysis confirmed reduced kidney tubular epithelial cell injury. Thus, our data provide strong evidence that peri-operatively administered tolerogenic dendritic cells have the ability to protect against acute kidney injury and warrants further exploration as a therapeutic option. This technology may provide a clinical advantage for bench-to-bedside translation to affect patient outcomes.

Integrated Analysis of Blood and Urine Biomarkers to Identify Acute Kidney Injury Subphenotypes and Associations With Long-term Outcomes

RATIONALE & OBJECTIVE

Acute kidney injury (AKI) is a heterogeneous clinical syndrome with varying causes, pathophysiology, and outcomes. We incorporated plasma and urine biomarker measurements to identify AKI subgroups (subphenotypes) more tightly linked to underlying pathophysiology and long-term clinical outcomes.

STUDY DESIGN

Multicenter cohort study.

SETTING & PARTICIPANTS

769 hospitalized adults with AKI matched with 769 without AKI, enrolled from December 2009 to February 2015 in the ASSESS-AKI Study.

PREDICTORS

29 clinical, plasma, and urinary biomarker parameters used to identify AKI subphenotypes.

OUTCOME

Composite of major adverse kidney events (MAKE) with a median follow-up period of 4.7 years.

ANALYTICAL APPROACH

Latent class analysis (LCA) and k-means clustering were applied to 29 clinical, plasma, and urinary biomarker parameters. Associations between AKI subphenotypes and MAKE were analyzed using Kaplan-Meier curves and Cox proportional hazard models.

RESULTS

Among 769 AKI patients both LCA and k-means identified 2 distinct AKI subphenotypes (classes 1 and 2). The long-term risk for MAKE was higher with class 2 (adjusted HR, 1.41 [95% CI, 1.08-1.84]; P=0.01) compared with class 1, adjusting for demographics, hospital level factors, and KDIGO stage of AKI. The higher risk of MAKE among class 2 was explained by a higher risk of long-term chronic kidney disease progression and dialysis. The top variables that were different between classes 1 and 2 included plasma and urinary biomarkers of inflammation and epithelial cell injury; serum creatinine ranked 20th out of the 29 variables for differentiating classes.

LIMITATIONS

A replication cohort with simultaneously collected blood and urine sampling in hospitalized adults with AKI and long-term outcomes was unavailable.

CONCLUSIONS

We identify 2 molecularly distinct AKI subphenotypes with differing risk of long-term outcomes, independent of the current criteria to risk stratify AKI. Future identification of AKI subphenotypes may facilitate linking therapies to underlying pathophysiology to prevent long-term sequalae after AKI.

PLAIN-LANGUAGE SUMMARY

Acute kidney injury (AKI) occurs commonly in hospitalized patients and is associated with high morbidity and mortality. The AKI definition lumps many different types of AKI together, but subgroups of AKI may be more tightly linked to the underlying biology and clinical outcomes. We used 29 different clinical, blood, and urinary biomarkers and applied 2 different statistical algorithms to identify AKI subtypes and their association with long-term outcomes. Both clustering algorithms identified 2 AKI subtypes with different risk of chronic kidney disease, independent of the serum creatinine concentrations (the current gold standard to determine severity of AKI). Identification of AKI subtypes may facilitate linking therapies to underlying biology to prevent long-term consequences after AKI.

Identification and validation of urinary CXCL9 as a biomarker for diagnosis of acute interstitial nephritis

BackgroundAcute tubulointerstitial nephritis (AIN) is one of the few causes of acute kidney injury with diagnosis-specific treatment options. However, due to the need to obtain a kidney biopsy for histological confirmation, AIN diagnosis can be delayed, missed, or incorrectly assumed. Here, we identify and validate urinary CXCL9, an IFN-γ-induced chemokine involved in lymphocyte chemotaxis, as a diagnostic biomarker for AIN.MethodsIn a prospectively enrolled cohort with pathologist-adjudicated histological diagnoses, termed the discovery cohort, we tested the association of 180 immune proteins measured by an aptamer-based assay with AIN and validated the top protein, CXCL9, using sandwich immunoassay. We externally validated these findings in 2 cohorts with biopsy-confirmed diagnoses, termed the validation cohorts, and examined mRNA expression differences in kidney tissue from patients with AIN and individuals in the control group.ResultsIn aptamer-based assay, urinary CXCL9 was 7.6-fold higher in patients with AIN than in individuals in the control group (P = 1.23 × 10-5). Urinary CXCL9 measured by sandwich immunoassay was associated with AIN in the discovery cohort (n = 204; 15% AIN) independently of currently available clinical tests for AIN (adjusted odds ratio for highest versus lowest quartile: 6.0 [1.8-20]). Similar findings were noted in external validation cohorts, where CXCL9 had an AUC of 0.94 (0.86-1.00) for AIN diagnosis. CXCL9 mRNA expression was 3.9-fold higher in kidney tissue from patients with AIN (n = 19) compared with individuals in the control group (n = 52; P = 5.8 × 10-6).ConclusionWe identified CXCL9 as a diagnostic biomarker for AIN using aptamer-based urine proteomics, confirmed this association using sandwich immunoassays in discovery and external validation cohorts, and observed higher expression of this protein in kidney biopsies from patients with AIN.FundingThis study was supported by National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) awards K23DK117065 (DGM), K08DK113281 (KM), R01DK128087 (DGM), R01DK126815 (DGM and LGC), R01DK126477 (KNC), UH3DK114866 (CRP, DGM, and FPW), R01DK130839 (MES), and P30DK079310 (the Yale O'Brien Center). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

Readmission and Mortality After Hospitalization With Acute Kidney Injury

RATIONALE & OBJECTIVE

Acute kidney injury (AKI) carries high rates of morbidity and mortality. This study quantified various short- and long-term outcomes after hospitalization with AKI.

STUDY DESIGN

Retrospective propensity score (PS)-matched cohort study.

SETTING & PARTICIPANTS

Optum Clinformatics, a national claims database, was used to identify patients hospitalized with and without an AKI discharge diagnosis between January 2007 and September 2020.

EXPOSURE

Among patients with prior continuous enrollment for at least 2years without AKI hospitalization, 471,176 patients hospitalized with AKI were identified and PS-matched to 471,176 patients hospitalized without AKI.

OUTCOME(S)

All-cause and selected-cause rehospitalizations and mortality 90 and 365 days after index hospitalization.

ANALYTICAL APPROACH

After PS matching, rehospitalization and death incidences were estimated using the cumulative incidence function method and compared using Gray's test. The association of AKI hospitalization with each outcome was tested using Cox models for all-cause mortality and, with mortality as competing risk, cause-specific hazard modeling for all-cause and selected-cause rehospitalization. Overall and stratified analyses were performed to evaluate for interaction between an AKI hospitalization and preexisting chronic kidney disease (CKD).

RESULTS

After PS matching, AKI was associated with higher rates of rehospitalization for any cause (hazard ratio [HR], 1.62; 95% CI, 1.60-1.65), end-stage renal disease (HR, 6.21; 95% CI, 1.04-36.92), heart failure (HR, 2.81; 95% CI, 2.66, 2.97), sepsis (HR, 2.62; 95% CI, 2.49-2.75), pneumonia (HR, 1.47; 95% CI, 1.37-1.57), myocardial infarction (HR, 1.48; 95% CI, 1.33-1.65), and volume depletion (HR, 1.64; 95% CI, 1.37-1.96) at 90 days after discharge compared with the group without AKI, with similar findings at 365 days. Mortality rate was higher in the group with AKI than in the group without AKI at 90 (HR, 2.66; 95% CI, 2.61-2.72) and 365 days (HR, 2.11; 95% CI, 2.08-2.14). The higher risk of outcomes persisted when participants were stratified by CKD status (P<0.01).

LIMITATIONS

Causal associations between AKI and the reported outcomes cannot be inferred.

CONCLUSIONS

AKI during hospitalization in patients with and without CKD is associated with increased risk of 90- and 365-day all-cause/selected-cause rehospitalization and death.

Genome-wide Association Study for AKI

Key Points

Two genetic variants in the DISP1-TLR5 gene locus were associated with risk of AKI. DISP1 and TLR5 were differentially regulated in kidney biopsy tissue from patients with AKI compared with no AKI.

Background

Although common genetic risks for CKD are well established, genetic factors influencing risk for AKI in hospitalized patients are poorly understood.

Methods

We conducted a genome-wide association study in 1369 participants in the Assessment, Serial Evaluation, and Subsequent Sequelae of AKI Study; a multiethnic population of hospitalized participants with and without AKI matched on demographics, comorbidities, and kidney function before hospitalization. We then completed functional annotation of top-performing variants for AKI using single-cell RNA sequencing data from kidney biopsies in 12 patients with AKI and 18 healthy living donors from the Kidney Precision Medicine Project.

Results

No genome-wide significant associations with AKI risk were found in Assessment, Serial Evaluation, and Subsequent Sequelae of AKI (P < 5×10 −8 ). The top two variants with the strongest association with AKI mapped to the dispatched resistance-nodulation-division (RND) transporter family member 1 (DISP1) gene and toll-like receptor 5 (TLR5) gene locus, rs17538288 (odds ratio, 1.55; 95% confidence interval, 1.32 to 182; P = 9.47×10 −8 ) and rs7546189 (odds ratio, 1.53; 95% confidence interval, 1.30 to 1.81; P = 4.60×10 −7 ). In comparison with kidney tissue from healthy living donors, kidney biopsies in patients with AKI showed differential DISP1 expression in proximal tubular epithelial cells (adjusted P = 3.9× 10−2) and thick ascending limb of the loop of Henle (adjusted P = 8.7× 10−3) and differential TLR5 gene expression in thick ascending limb of the loop of Henle (adjusted P = 4.9× 10−30).

Conclusions

AKI is a heterogeneous clinical syndrome with various underlying risk factors, etiologies, and pathophysiology that may limit the identification of genetic variants. Although no variants reached genome-wide significance, we report two variants in the intergenic region between DISP1 and TLR5 , suggesting this region as a novel risk for AKI susceptibility.

Risk for Chronic Kidney Disease Progression After Acute Kidney Injury: Findings From the Chronic Renal Insufficiency Cohort Study

BACKGROUND

Prior studies associating acute kidney injury (AKI) with more rapid subsequent loss of kidney function had methodological limitations, including inadequate control for differences between patients who had AKI and those who did not.

OBJECTIVE

To determine whether AKI is independently associated with subsequent kidney function trajectory among patients with chronic kidney disease (CKD).

DESIGN

Multicenter prospective cohort study.

SETTING

United States.

PARTICIPANTS

Patients with CKD (n = 3150).

MEASUREMENTS

Hospitalized AKI was defined by a 50% or greater increase in inpatient serum creatinine (SCr) level from nadir to peak. Kidney function trajectory was assessed using estimated glomerular filtration rate (eGFR) based on SCr level (eGFRcr) or cystatin C level (eGFRcys) measured at annual study visits.

RESULTS

During a median follow-up of 3.9 years, 433 participants had at least 1 AKI episode. Most episodes (92%) had stage 1 or 2 severity. There were decreases in eGFRcr (-2.30 [95% CI, -3.70 to -0.86] mL/min/1.73 m2) and eGFRcys (-3.61 [CI, -6.39 to -0.82] mL/min/1.73 m2) after AKI. However, in fully adjusted models, the decreases were attenuated to -0.38 (CI, -1.35 to 0.59) mL/min/1.73 m2 for eGFRcr and -0.15 (CI, -2.16 to 1.86) mL/min/1.73 m2 for eGFRcys, and the CI bounds included the possibility of no effect. Estimates of changes in eGFR slope after AKI determined by either SCr level (0.04 [CI, -0.30 to 0.38] mL/min/1.73 m2 per year) or cystatin C level (-0.56 [CI, -1.28 to 0.17] mL/min/1.73 m2 per year) also had CI bounds that included the possibility of no effect.

LIMITATIONS

Few cases of severe AKI, no adjudication of AKI cause, and lack of information about nephrotoxic exposures after hospital discharge.

CONCLUSION

After pre-AKI eGFR, proteinuria, and other covariables were accounted for, the association between mild to moderate AKI and worsening subsequent kidney function in patients with CKD was small.

PRIMARY FUNDING SOURCE

National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health.

Joint Modeling of Clinical and Biomarker Data in Acute Kidney Injury Defines Unique Subphenotypes with Differing Outcomes

BACKGROUND

AKI is a heterogeneous syndrome. Current subphenotyping approaches have only used limited laboratory data to understand a much more complex condition.

METHODS

We focused on patients with AKI from the Assessment, Serial Evaluation, and Subsequent Sequelae in AKI (ASSESS-AKI). We used hierarchical clustering with Ward linkage on biomarkers of inflammation, injury, and repair/health. We then evaluated clinical differences between subphenotypes and examined their associations with cardiorenal events and death using Cox proportional hazard models.

RESULTS

We included 748 patients with AKI: 543 (73%) of them had AKI stage 1, 112 (15%) had AKI stage 2, and 93 (12%) had AKI stage 3. The mean age (±SD) was 64 (13) years; 508 (68%) were men; and the median follow-up was 4.7 (Q1: 2.9, Q3: 5.7) years. Patients with AKI subphenotype 1 ( N =181) had the highest kidney injury molecule (KIM-1) and troponin T levels. Subphenotype 2 ( N =250) had the highest levels of uromodulin. AKI subphenotype 3 ( N =159) comprised patients with markedly high pro-brain natriuretic peptide and plasma tumor necrosis factor receptor-1 and -2 and low concentrations of KIM-1 and neutrophil gelatinase-associated lipocalin. Finally, patients with subphenotype 4 ( N =158) predominantly had sepsis-AKI and the highest levels of vascular/kidney inflammation (YKL-40, MCP-1) and injury (neutrophil gelatinase-associated lipocalin, KIM-1). AKI subphenotypes 3 and 4 were independently associated with a higher risk of death compared with subphenotype 2 and had adjusted hazard ratios of 2.9 (95% confidence interval, 1.8 to 4.6) and 1.6 (95% confidence interval, 1.01 to 2.6, P = 0.04), respectively. Subphenotype 3 was also independently associated with a three-fold risk of CKD and cardiovascular events.

CONCLUSIONS

We discovered four AKI subphenotypes with differing clinical features and biomarker profiles that are associated with longitudinal clinical outcomes.

Zinc finger protein 24-dependent transcription factor SOX9 up-regulation protects tubular epithelial cells during acute kidney injury

Transcriptional profiling studies have identified several protective genes upregulated in tubular epithelial cells during acute kidney injury (AKI). Identifying upstream transcriptional regulators could lead to the development of therapeutic strategies augmenting the repair processes. SOX9 is a transcription factor controlling cell-fate during embryonic development and adult tissue homeostasis in multiple organs including the kidneys. SOX9 expression is low in adult kidneys; however, stress conditions can trigger its transcriptional upregulation in tubular epithelial cells. SOX9 plays a protective role during the early phase of AKI and facilitates repair during the recovery phase. To identify the upstream transcriptional regulators that drive SOX9 upregulation in tubular epithelial cells, we used an unbiased transcription factor screening approach. Preliminary screening and validation studies show that zinc finger protein 24 (ZFP24) governs SOX9 upregulation in tubular epithelial cells. ZFP24, a Cys2-His2 (C2H2) zinc finger protein, is essential for oligodendrocyte maturation and myelination; however, its role in the kidneys or in SOX9 regulation remains unknown. Here, we found that tubular epithelial ZFP24 gene ablation exacerbated ischemia, rhabdomyolysis, and cisplatin-associated AKI. Importantly, ZFP24 gene deletion resulted in suppression of SOX9 upregulation in injured tubular epithelial cells. Chromatin immunoprecipitation and promoter luciferase assays confirmed that ZFP24 bound to a specific site in both murine and human SOX9 promoters. Importantly, CRISPR/Cas9-mediated mutation in the ZFP24 binding site in the SOX9 promoter in vivo led to suppression of SOX9 upregulation during AKI. Thus, our findings identify ZFP24 as a critical stress-responsive transcription factor protecting tubular epithelial cells through SOX9 upregulation.

Indian Hedgehog release from TNF-activated renal epithelia drives local and remote organ fibrosis

Progressive fibrosis is a feature of aging and chronic tissue injury in multiple organs, including the kidney and heart. Glioma-associated oncogene 1 expressing (Gli1+) cells are a major source of activated fibroblasts in multiple organs, but the links between injury, inflammation, and Gli1+ cell expansion and tissue fibrosis remain incompletely understood. We demonstrated that leukocyte-derived tumor necrosis factor (TNF) promoted Gli1+ cell proliferation and cardiorenal fibrosis through induction and release of Indian Hedgehog (IHH) from renal epithelial cells. Using single-cell-resolution transcriptomic analysis, we identified an "inflammatory" proximal tubular epithelial (iPT) population contributing to TNF- and nuclear factor κB (NF-κB)-induced IHH production in vivo. TNF-induced Ubiquitin D (Ubd) expression was observed in human proximal tubular cells in vitro and during murine and human renal disease and aging. Studies using pharmacological and conditional genetic ablation of TNF-induced IHH signaling revealed that IHH activated canonical Hedgehog signaling in Gli1+ cells, which led to their activation, proliferation, and fibrosis within the injured and aging kidney and heart. These changes were inhibited in mice by Ihh deletion in Pax8-expressing cells or by pharmacological blockade of TNF, NF-κB, or Gli1 signaling. Increased amounts of circulating IHH were associated with loss of renal function and higher rates of cardiovascular disease in patients with chronic kidney disease. Thus, IHH connects leukocyte activation to Gli1+ cell expansion and represents a potential target for therapies to inhibit inflammation-induced fibrosis.

Risk factors associated with acute kidney injury in a cohort of hospitalized patients with COVID-19

BACKGROUND

Patients with COVID-19 have a high incidence of acute kidney injury (AKI), which is associated with mortality. The objective of the study was to determine the factors associated with AKI in patients with COVID-19.

METHODOLOGY

A retrospective cohort was established in two university hospitals in Bogotá, Colombia. Adults hospitalized for more than 48 h from March 6, 2020, to March 31, 2021, with confirmed COVID-19 were included. The main outcome was to determine the factors associated with AKI in patients with COVID-19 and the secondary outcome was estimate the incidence of AKI during the 28 days following hospital admission.

RESULTS

A total of 1584 patients were included: 60.4% were men, 738 (46.5%) developed AKI, 23.6% were classified as KDIGO 3, and 11.1% had renal replacement therapy. The risk factors for developing AKI during hospitalization were male sex (OR 2.28, 95% CI 1.73-2.99), age (OR 1.02, 95% CI 1.01-1.03), history of chronic kidney disease (CKD) (OR 3.61, 95% CI 2.03-6.42), High Blood Pressure (HBP) (OR 6.51, 95% CI 2.10-20.2), higher qSOFA score to the admission (OR 1.4, 95% CI 1.14-1.71), the use of vancomycin (OR 1.57, 95% CI 1.05-2.37), piperacillin/tazobactam (OR 1.67, 95% CI 1.2-2.31), and vasopressor support (CI 2.39, 95% CI 1.53-3.74). The gross hospital mortality for AKI was 45.5% versus 11.7% without AKI.

CONCLUSIONS

This cohort showed that male sex, age, history of HBP and CKD, presentation with elevated qSOFA, in-hospital use of nephrotoxic drugs and the requirement for vasopressor support were the main risk factors for developing AKI in patients hospitalized for COVID-19.

Probing the Association between Acute Kidney Injury and Cardiovascular Outcomes

BACKGROUND

Patients hospitalized with AKI have higher subsequent risks of heart failure, atherosclerotic cardiovascular events, and mortality than their counterparts without AKI, but these higher risks may be due to differences in prehospitalization patient characteristics, including the baseline level of estimated glomerular filtration rate (eGFR), the rate of prior eGFR decline, and the proteinuria level, rather than AKI itself.

METHODS

Among 2177 adult participants in the Chronic Renal Insufficiency Cohort study who were hospitalized in 2013-2019, we compared subsequent risks of heart failure, atherosclerotic cardiovascular events, and mortality between those with serum creatinine-based AKI (495 patients) and those without AKI (1682 patients). We report both crude associations and associations sequentially adjusted for prehospitalization characteristics including eGFR, eGFR slope, and urine protein-creatinine ratio (UPCR).

RESULTS

Compared with patients hospitalized without AKI, those with hospitalized AKI had lower eGFR prehospitalization (42 versus 49 ml/min per 1.73 m 2 ), faster chronic loss of eGFR prehospitalization (-0.84 versus -0.51 ml/min per 1.73 m 2 per year), and more proteinuria prehospitalization (UPCR 0.28 versus 0.16 g/g); they also had higher prehospitalization systolic BP (130 versus 127 mm Hg; P < 0.01 for all comparisons). Adjustment for prehospitalization patient characteristics attenuated associations between AKI and all three outcomes, but AKI remained an independent risk factor. Attenuation of risk was similar after adjustment for absolute eGFR, eGFR slope, or proteinuria, individually or in combination.

CONCLUSIONS

Prehospitalization variables including eGFR, eGFR slope, and proteinuria confounded associations between AKI and adverse cardiovascular outcomes, but these associations remained significant after adjusting for prehospitalization variables.

SerpinA3K Deficiency Reduces Oxidative Stress in Acute Kidney Injury

We previously showed that SerpinA3K is present in urine from rats and humans with acute kidney injury (AKI) and chronic kidney disease (CKD). However, the specific role of SerpinA3K during renal pathophysiology is unknown. To begin to understand the role of SerpinA3K on AKI, SerpinA3K-deficient (KOSA3) mice were studied 24 h after inducing ischemia/reperfusion (I/R) and compared to wild type (WT) mice. Four groups were studied: WT+S, WT+IR, KOSA3+S, and KOSA3+IR. As expected, I/R increased serum creatinine and BUN, with a GFR reduction in both genotypes; however, renal dysfunction was ameliorated in the KOSA3+IR group. Interestingly, the increase in UH₂O₂ induced by I/R was not equally seen in the KOSA3+IR group, an effect that was associated with the preservation of antioxidant enzymes' mRNA levels. Additionally, FOXO3 expression was initially greater in the KOSA3 than in the WT group. Moreover, the increase in BAX protein level and the decrease in Hif1a and Vegfa induced by I/R were not observed in the KOSA3+IR group, suggesting that these animals have better cellular responses to hypoxic injury. Our findings suggest that SerpinA3K is involved in the renal oxidant response, HIF1α/VEGF pathway, and cell apoptosis.

Acute kidney injury and distant organ dysfunction-network system analysis

Acute kidney injury (AKI) occurs in about half of critically ill patients and associates with high in-hospital mortality, increased long-term mortality post-discharge and subsequent progression to chronic kidney disease. Numerous clinical studies have shown that AKI is often complicated by dysfunction of distant organs, which is a cause of the high mortality associated with AKI. Experimental studies have elucidated many mechanisms of AKI-induced distant organ injury, which include inflammatory cytokines, oxidative stress and immune responses. This review will provide an update on evidence of organ crosstalk and potential therapeutics for AKI-induced organ injuries, and present the new concept of a systemic organ network to balance homeostasis and inflammation that goes beyond kidney-crosstalk with a single distant organ.

Long-term outcomes after severe acute kidney injury in critically ill patients: the SALTO study

BACKGROUND

The extent of the consequences of an episode of severe acute kidney injury (AKI) on long-term outcome of critically ill patients remain debated. We conducted a prospective follow-up of patients included in a large multicenter clinical trial of renal replacement therapy (RRT) initiation strategy during severe AKI (the Artificial Kidney Initiation in Kidney Injury, AKIKI) to investigate long-term survival, renal outcome and health related quality of life (HRQOL). We also assessed the influence of RRT initiation strategy on these outcomes.

RESULTS

Follow-up of patients extended from 60 days to a median of 3.35 years [interquartile range (IQR), 1.89 to 4.09] after the end of initial study. Of the 619 patients included in the AKIKI trial, 316 survived after 60 days. The overall survival rate at 3 years from inclusion was 39.4% (95% CI 35.4 to 43.4). A total of 46 patients (on the 175 with available data on long-term kidney function) experienced worsening of renal function (WRF) at the time of follow-up [overall incidence of 26%, cumulative incidence at 4 years: 20.6% (CI 95% 13.0 to 28.3)]. Fifteen patients required chronic dialysis (5% of patients who survived after day 90). Among the 226 long-term survivors, 80 (35%) answered the EQ-5D questionnaire. The median index value reported was 0.67 (IQR 0.40 to 1.00) indicating a noticeable alteration of quality of life. Initiation strategy for RRT had no effect on any long-term outcome.

CONCLUSION

Severe AKI in critically ill patients was associated with a high proportion of death within the first 2 months but less so during long-term follow-up. A quarter of long-term survivors experienced a WRF and suffered from a noticeable impairment of quality of life. Renal replacement therapy initiation strategy was not associated with mortality outcome.

Incidence, predictors, clinical outcomes, and economic burden of recurrent acute kidney injury: a retrospective cohort study

OBJECTIVE

This study aimed to assess the incidence, predictors, mortality, and economic outcomes of recurrent Acute kidney injury (AKI) in Jordan.

METHODS

This was a retrospective cohort study that included adult patients who were admitted with AKI to university hospitals in the country from 2010-2019. Recurrent episodes of AKI, laboratory data, baseline medication list, and death dates were retrieved from patient's medical records. The incidence rate of recurrent AKI was estimated. Predictors of recurrent AKI and mortality during the five years post-discharge was evaluated. Total admission charges were described and evaluated in total and by service provided.

RESULTS

Among 1162 AKI patients, 57 patients (4.9%) died during the index admission (first admission during the study period), and among the survivors, 220 patients were re-hospitalized with a recurrent AKI during five years of follow-up. Patients with higher discharge serum creatinine level (SCr) at index admission had higher odds of AKI recurrence (OR = 1.001). Patients who were on respiratory, antineoplastic, or anticoagulant medications were also more susceptible to recurrence; ORs were 1.69, 2.77, and 4.16, respectively. Patients who were elderly, with recurrent AKI episodes, or with a more extended hospital stay at index admission were more likely to die during the five years post discharge. The median charge of recurrent admissions was higher than the median charge of the index admissions; 1519.17 JOD ($2142.7) versus 1362.85 JOD ($1922.2), respectively.

CONCLUSIONS

Recurrent AKI is associated with increased mortality and health expenditures. Higher discharge SCr levels at index admission, and chronic comorbidities are associated with a higher likelihood of AKI recurrence.

Diastolic dysfunction is an independent predictor for cardiovascular events after an acute kidney injury

BACKGROUND AND AIM

Acute kidney injury (AKI) conditions several short- and long-term complications. The aim of the present study was to analyse the impact of cardiac function and structure in the cardiovascular prognosis after an in-hospital AKI episode.

MATERIAL AND METHODS

This is an observational retrospective cohorts study including all in-hospital AKI episodes in 2013 and 2014 in our centre. At baseline, epidemiological values, comorbidities and echocardiography parameters were collected. During a follow-up of 49 ± 28 months, cardiovascular events (CVE) were collected, and associated factors were analysed.

RESULTS

1255 patients were included (55% male, age 75 ± 13 years). Of the 676 (54%) that had a previous echocardiogram, 46% had left ventricular hypertrophy, 38% pulmonary hypertension, 38% diastolic dysfunction and 22% systolic dysfunction. During the follow-up, 484 (39%) developed a CVE. Associated factors to VCE were male sex, age, diabetes mellitus, hypertension, dyslipidemia, coronary heart disease, heart failure, atrial fibrillation, neoplasia and chronic kidney disease (also, glomerular filtration rate at baseline and after the AKI episode). Survival curves demonstrated that all the echocardiographic parameters were associated to CVE. An adjusted Cox regression model showed that age (HR 1.017), diabetes (HR 1.576) and diastolic dysfunction (HR 1.358) were independent predictors for CVE.

CONCLUSION

Diastolic dysfunction is an independent predictor for long-term cardiovascular events after an in-hospital acute kidney injury episode.

Kidney function at 3 months after acute kidney injury is an unreliable indicator of subsequent kidney dysfunction: the NARA-AKI Cohort Study

BACKGROUND

The relationship between kidney function at 3 months after acute kidney injury (AKI) and kidney function prognosis has not been characterized.

METHODS

This retrospective cohort study included adults who underwent noncardiac surgery under general anesthesia. Exclusion criteria included obstetric or urological surgery, missing data and preoperative dialysis. Linear mixed-effects models were used to compare estimated glomerular filtration rate (eGFR) slopes in patients with and without AKI. Multivariable Cox proportional hazard models were used to examine the associations of AKI with incident chronic kidney disease (CKD) and decline in eGFR ≥30%.

RESULTS

Among 5272 patients, 316 (6.0%) developed AKI. Among 1194 patients with follow-up creatinine values, eGFR was stable or increased in patients with and without AKI at 3 months postoperatively and declined thereafter. eGFR decline after 3 months postoperatively was faster among patients with AKI than among patients without AKI (P = .09). Among 938 patients without CKD-both at baseline and at 3 months postoperatively-226 and 161 developed incident CKD and a decline in eGFR ≥30%, respectively. Despite adjustment for eGFR at 3 months, AKI was associated with incident CKD {hazard ratio [HR] 1.73 [95% confidence interval (CI) 1.06-2.84]} and a decline in eGFR ≥30% [HR 2.41 (95% CI 1.51-3.84)].

CONCLUSIONS

AKI was associated with worse kidney outcomes, regardless of eGFR at 3 months after surgery. Creatinine-based eGFR values at 3 months after AKI might be affected by acute illness-induced loss of muscle mass. Kidney function might be more accurately evaluated much later after surgery or using cystatin C values.

Acute kidney injury increases risk of kidney stones-a retrospective propensity score matched cohort study

BACKGROUND

Acute kidney injury (AKI) is common. An episode of AKI may modify the risk of developing kidney stones by potential long-term effects on urine composition. We aimed to investigate the association between AKI and the risk of kidney stone presentations.

METHODS

The retrospective cohort study used patient data (1 January 2008-31 December 2017), from an Australian Local Health District, which included AKI diagnosis, demographics, comorbidities and kidney stone admissions. Time-varying Cox proportional hazards and propensity-matched analysis were used to determine the impact of AKI on the risk of kidney stones. To address possible population inhomogeneity in comparisons between no AKI and hospitalized AKI, sub-group analysis was done comparing inpatient and outpatient AKI versus no AKI, to assess consistency of association with future stones. Sensitivity analysis was undertaken to capture the impact of a known AKI status and AKI severity.

RESULTS

Out of 137 635 patients, 23 001 (17%) had an AKI diagnosis and 2295 (2%) had kidney stone presentations. In the unadjusted analysis, AKI was associated with kidney stones, with AKI used as a time-varying exposure, [hazard ratio (HR) 1.32, 95% confidence interval (CI) 1.16-1.50)]. Both inpatient-AKI (HR 1.19, 95% CI 1.01-1.39) and outpatient-AKI (HR 1.59, 95% CI 1.30-1.94) were significantly associated with future stones compared to no AKI subjects. This association persisted in the adjusted analysis (HR 1.45, 95% CI 1.26-1.66), propensity-matched dataset (HR 1.67, 95% CI 1.40-1.99) and sensitivity analysis. There was a dose-response relationship with higher stages of AKI being associated with a greater risk of kidney stones.

CONCLUSIONS

In a large cohort of patients, AKI is associated with a greater risk of kidney stones, which increases with higher stages of AKI. This association should be examined in other cohorts and populations for verification.

Specificity of severe AKI aetiology and care in the elderly. The IRACIBLE prospective cohort study

INTRODUCTION

Acute Kidney Injury (AKI) is increasingly common in people over 65 years of age, but its causes and management are poorly described. The purpose of this study was to describe the causes, management and prognosis of patients over 65 hospitalised for severe acute kidney injury (AKI) in all departments of a tertiary centre.

METHOD

The prospective IRACIBLE (IRA: AKI in French; CIBLE: target in French) cohort included 480 patients hospitalised at a university hospital over 18 months for severe AKI or subgroup of AKIN3 (Acute Kidney Injury Network classification) defined by an acute creatinine increase > 354 μmol/L or managed with acute renal replacement therapy (RRT). The history, aetiology of AKI, management, and prognosis were compared in three age groups: < 65, 65-75, and > 75 years.

RESULTS

The study population included 480 subjects (73% men) with a median body mass index (BMI) of 26.6 kg/m² [23.3, 30.9], 176 (37%) diabetic patients, 124 (26%) patients < 65 years, 150 (31%) 65-75 years and 206 (43%) > 75 years. Increasing age class was associated with more comorbidities, a significantly lower median estimated glomerular filtration rate (eGFR) 6 months before inclusion (82; 62; 46 ml/min/1.73 m², p < 0.05) and aetiology of AKI, which was more often obstructive (12%; 15%; 23%, p = 0.03) or part of a cardio-renal syndrome (6%; 9%; /15%, p = 0.04). Older patients were less often managed in the intensive care unit  (54%; 47%; 24%, p < 0.0001), were less frequently treated by RRT (52%; 43%; 31%, p < 0.001) and received fewer invasive treatments  (6%; 9%; 22%, p < 0.0001). Older survivors returned home less often (80%; 73%; 62%, p = 0.05) in favour of transfers to rehabilitation services (10%; 13%; 22%) with higher mortality at 3 months (35%; 32%; 50%, p < 0.0001).

CONCLUSION

Older patients hospitalised for severe AKI have a specific profile with more comorbidities, lower baseline renal function, an aetiology of AKI of mainly extra-parenchymal causes and a complex pathway of care with an overall poor prognosis.

Prognosis of patients with heart disease with acute kidney injury undergoing dialysis treatment

OBJECTIVES

to verify the relationship of cardiovascular diseases with acute kidney injury and assess the prognosis of patients in renal replacement therapy.

METHODS

a cohort study, carried out in a public hospital specialized in cardiology. Treatment, comorbidities, duration of treatment, laboratory tests, discharge and deaths were analyzed.

RESULTS

of the 101 patients, 75 (74.3%) received non-dialysis treatment. The most frequent cardiological diagnoses were hypertension, cardiomyopathies and coronary syndrome. Hospitalization in patients undergoing dialysis was 18 days, hemoglobin <10.5g/dl and anuria in the first days of hospitalization contributed to the type of treatment. Each increase in hemoglobin units from the first day of hospitalization decreases the chance of dialysis by 19.2%. There was no difference in mortality.

CONCLUSIONS

the main cardiological diseases were not predictive of dialysis indication, and clinical treatment was the most frequent. Anuria and anemia were predictors for dialysis treatment.

Kidney Function Trajectory within Six Months after Acute Kidney Injury Inpatient Care and Subsequent Adverse Kidney Outcomes: A Retrospective Cohort Study

Timing and extent of kidney function recovery after an acute kidney injury (AKI) episode are associated with chronic kidney disease onset and progression. This study aimed to categorize AKI recovery patterns within 6 months after index hospital discharge and associate them with kidney outcomes. This was a retrospective cohort study of 234,867 patients, hospitalized between 2010 and 2017, and classified as AKI or no AKI. Kidney function recovery from pre-hospitalization baseline within 1.5× serum creatinine (SCr) were evaluated at 3 and 6 months after hospital discharge and categorized as persistent non-recovery (PNR: SCr not recovered at 3 and 6 months), non-recovery (NR: SCr not recovered at 6 months), and recovery (SCr recovered at 6 months). A composite of incident chronic kidney disease, kidney replacement therapy, and estimated glomerular filtration rate reduction >30% from baseline and <15 mL/min/1.73 m2 was evaluated. Of 14,673 AKI surviving patients, 10.18% had PNR and 14.33% showed NR. Compared with no AKI, PNR and NR of AKI were associated with an increased risk of composite adverse outcomes (adjusted subdistribution hazard ratio (SHR) 4.55; 95% CI, 4.05−5.11; SHR, 3.54; 95% CI, 3.18−3.94, respectively). Patients with NR showed a greater risk of adverse outcomes than those with non-rapid recovery at 3 months after hospital discharge. The AKI recovery pattern within 6 months following inpatient care revealed an increasing continuum of risk of long-term adverse kidney outcomes. Risk stratification and a kidney function monitoring plan at discharge are needed to improve post-AKI care.

Klotho restoration via ACE2 activation: A potential therapeutic strategy against acute kidney injury-diabetes comorbidity

Acute kidney injury (AKI) is a collection of clinical syndromes with persistent increases in morbidity and mortality rates. Hyperglycemia is a risk factor for AKI development. Renin-angiotensin-aldosterone system (RAS) disequilibrium and Klotho downregulation also play a pivotal role in the pathogenesis of AKI. Moreover, the relationship between Klotho and ACE2 (a component of non-conventional RAS) regulation in AKI remains an unexplored area of research. Hence, in this study, we investigated ACE2 and Klotho regulation in AKI using ischemic Wistar rats and NRK52E cells under normal and hyperglycemic conditions. Our findings suggested that hyperglycemia exacerbates renal ischemia-reperfusion injury (IRI)/hypoxia-reperfusion injury (HRI) induced AKI. Systemic and renal Klotho deficiency is a novel hallmark of AKI. Additionally, ACE2 is a protective component of the RAS, and its inhibition/deficiency leads to inflammation, apoptosis, Klotho downregulation, and thus AKI development. However, ACE2 activation resulted in the amelioration of AKI. Importantly, ACE2 plays an important role in Klotho upregulation, which might act as an intermediate for ACE2-mediated reno-protection. In conclusion, ACE2 activator i.e. DIZE restored endogenous ACE2-Ang-(1-7)-Klotho level, inhibited apoptosis and inflammation, and ameliorates IRI/HRI induced AKI under diabetic and non-diabetic conditions. Hence, in future, targeting ACE2-Ang-(1-7)-Klotho axis may prove a novel therapeutic strategy against AKI, where further preclinical and clinical investigations are required to verify the clinical potential of this finding.

Immune-mediated tubule atrophy promotes acute kidney injury to chronic kidney disease transition

Incomplete repair after acute kidney injury can lead to development of chronic kidney disease. To define the mechanism of this response, we compared mice subjected to identical unilateral ischemia-reperfusion kidney injury with either contralateral nephrectomy (where tubule repair predominates) or contralateral kidney intact (where tubule atrophy predominates). By day 14, the kidneys undergoing atrophy had more macrophages with higher expression of chemokines, correlating with a second wave of proinflammatory neutrophil and T cell recruitment accompanied by increased expression of tubular injury genes and a decreased proportion of differentiated tubules. Depletion of neutrophils and T cells after day 5 reduced tubular cell loss and associated kidney atrophy. In kidney biopsies from patients with acute kidney injury, T cell and neutrophil numbers negatively correlated with recovery of estimated glomerular filtration rate. Together, our findings demonstrate that macrophage persistence after injury promotes a T cell- and neutrophil-mediated proinflammatory milieu and progressive tubule damage.

Semiparametric marginal methods for clustered data adjusting for informative cluster size with nonignorable zeros

Clustered or longitudinal data are commonly encountered in clinical trials and observational studies. This type of data could be collected through a real-time monitoring scheme associated with some specific event, such as disease recurrence, hospitalization, or emergency room visit. In these contexts, the cluster size could be informative because of its potential correlation with disease status, since more frequency of observations may indicate a worsening health condition. However, for some clusters/subjects, there are no measures or relevant medical records. Under such circumstances, these clusters/subjects may have a considerably lower risk of an event occurrence or may not be susceptible to such events at all, indicating a nonignorable zero cluster size. There is a substantial body of literature using observations from those clusters with a nonzero informative cluster size only, but few works discuss informative nonignorable zero-sized clusters. To utilize the information from both event-free and event-occurring participants, we propose a weighted within-cluster-resampling (WWCR) method and its asymptotically equivalent method, dual-weighted generalized estimating equations (WWGEE) by adopting the inverse probability weighting technique. The asymptotic properties are rigorously presented theoretically. Extensive simulations and an illustrative example of the Assessment, Serial Evaluation, and Subsequent Sequelae of Acute Kidney Injury (ASSESS-AKI) study are performed to analyze the finite-sample behavior of our methods and to show their advantageous performance compared to the existing approaches.

The Role of Gut-Derived, Protein-Bound Uremic Toxins in the Cardiovascular Complications of Acute Kidney Injury

Acute kidney injury (AKI) is a frequent disease encountered in the hospital, with a higher incidence in intensive care units. Despite progress in renal replacement therapy, AKI is still associated with early and late complications, especially cardiovascular events and mortality. The role of gut-derived protein-bound uremic toxins (PBUTs) in vascular and cardiac dysfunction has been extensively studied during chronic kidney disease (CKD), in particular, that of indoxyl sulfate (IS), para-cresyl sulfate (PCS), and indole-3-acetic acid (IAA), resulting in both experimental and clinical evidence. PBUTs, which accumulate when the excretory function of the kidneys is impaired, have a deleterious effect on and cause damage to cardiovascular tissues. However, the link between PBUTs and the cardiovascular complications of AKI and the pathophysiological mechanisms potentially involved are unclear. This review aims to summarize available data concerning the participation of PBUTs in the early and late cardiovascular complications of AKI.

Overview of Diagnostic Criteria and Epidemiology of Acute Kidney Injury and Acute Kidney Disease in the Critically Ill Patient

Since the description ischuria renalis by William Heberden (1), AKI has remained a prominent complication of critical illness. Beyond KRT, treatment has been limited by the capacity to phenotype this condition. Here, we chronicle the evolution of attempts to classify AKI, including the adoption of consensus definitions, the expansion of diagnosis and prognosis with novel biomarkers, and emerging tools such as artificial intelligence (AI).

Angiopoietins as Prognostic Markers for Future Kidney Disease and Heart Failure Events after Acute Kidney Injury

BACKGROUND

The mechanisms underlying long-term sequelae after AKI remain unclear. Vessel instability, an early response to endothelial injury, may reflect a shared mechanism and early trigger for CKD and heart failure.

METHODS

To investigate whether plasma angiopoietins, markers of vessel homeostasis, are associated with CKD progression and heart failure admissions after hospitalization in patients with and without AKI, we conducted a prospective cohort study to analyze the balance between angiopoietin-1 (Angpt-1), which maintains vessel stability, and angiopoietin-2 (Angpt-2), which increases vessel destabilization. Three months after discharge, we evaluated the associations between angiopoietins and development of the primary outcomes of CKD progression and heart failure and the secondary outcome of all-cause mortality 3 months after discharge or later.

RESULTS

Median age for the 1503 participants was 65.8 years; 746 (50%) had AKI. Compared with the lowest quartile, the highest quartile of the Angpt-1:Angpt-2 ratio was associated with 72% lower risk of CKD progression (adjusted hazard ratio [aHR], 0.28; 95% confidence interval [CI], 0.15 to 0.51), 94% lower risk of heart failure (aHR, 0.06; 95% CI, 0.02 to 0.15), and 82% lower risk of mortality (aHR, 0.18; 95% CI, 0.09 to 0.35) for those with AKI. Among those without AKI, the highest quartile of Angpt-1:Angpt-2 ratio was associated with 71% lower risk of heart failure (aHR, 0.29; 95% CI, 0.12 to 0.69) and 68% less mortality (aHR, 0.32; 95% CI, 0.15 to 0.68). There were no associations with CKD progression.

CONCLUSIONS

A higher Angpt-1:Angpt-2 ratio was strongly associated with less CKD progression, heart failure, and mortality in the setting of AKI.

Oral anticoagulants and relative risk of acute kidney injury in patients with atrial fibrillation: A systematic review and network meta-analysis

Study objective

Oral anticoagulants (direct oral anticoagulants [DOACs] or warfarin) prevent stroke in patients with atrial fibrillation (AF), but their use may be associated with acute kidney injury (AKI). We aimed to compare AKI risk across individual oral anticoagulants in patients with AF.

Design

Systematic review and network meta-analysis.

Setting

Randomized trials and population-based studies.

Participants

Patients with AF.

Interventions

Oral anticoagulants.

Main outcome measures

AKI.

Results

A systematic literature search in Medline and Embase databases performed on December 17, 2021 identified ten randomized trials and eight population-based longitudinal studies based on prespecified inclusion criteria for systematic review. Clinical trials had short follow-ups and reported only low event rates of serious AKI. Retrospective longitudinal studies were assessed to be at higher risk for bias from confounding and outcome ascertainment, but follow-up was longer (1.5 to 8 years), with AKI incidence ranging from 2 to 29/100 person-years. Eight longitudinal studies that met transitivity assumption were included in a random-effects network meta-analysis within a Bayesian framework. All DOACs were associated with significantly lower risk of AKI compared to warfarin. Dabigatran was associated with lower risk of AKI compared to apixaban (hazard ratio [HR] = 0.82; 95% confidence interval [CI]: 0.68-0.99), rivaroxaban (HR = 0.84; 95%CI: 0.72-0.98), and warfarin (HR = 0.68; 95%CI: 0.59-0.77). Effect size estimates varied by chronic kidney disease status and study geographic locations.

Conclusion

Apixaban, rivaroxaban, and dabigatran were associated with lower long-term risk of AKI compared to warfarin among patients with AF, with dabigatran potentially associated with the lowest risk.