Silent Brain Infarction and Rapid Decline of Kidney Function in Patients With CKD: A Prospective Cohort Study

Kidney disease and stroke: epidemiology and potential mechanisms of susceptibility

Patients with chronic kidney disease (CKD) have an increased risk of both ischaemic and haemorrhagic stroke compared with the general population. Both acute and chronic kidney impairment are independently associated with poor outcome after the onset of a stroke, after adjustment for confounders. End-stage kidney disease (ESKD) is associated with a 7- and 9-fold increased incidence of both ischaemic and haemorrhagic strokes, respectively, poorer neurological outcome and a 3-fold higher mortality. Acute kidney injury (AKI) occurs in 12% of patients with stroke and is associated with a 4-fold increased mortality and unfavourable functional outcome. CKD patients seem to have less access to revascularisation techniques like thrombolysis and thrombectomy despite their poorer prognosis. Even if CKD patients could benefit from these specific treatments in acute ischaemic stroke, their prognosis remains poor. After thrombolysis, CKD is associated with a 40% increased risk of intracerebral haemorrhage (ICH), a 20% increase in mortality and poorer functional neurological outcomes. After thrombectomy, CKD is not associated with ICH but is still associated with increased mortality, and AKI with unfavourable outcome and mortality. The beneficial impact of gliflozins on the prevention of stroke is still uncertain. Non-traditional risk factors of stroke, like uraemic toxins, can lead to chronic cerebrovascular disease predisposing to stroke in CKD, notably through an increase in the blood-brain barrier permeability and impaired coagulation and thrombosis mechanisms. Preclinical and clinical studies are needed to specifically assess the impact of these non-traditional risk factors on stroke incidence and outcomes, aiming to optimize and identify potential therapeutic targets.

Association of kidney function and brain health: A systematic review and meta-analysis of cohort studies

OBJECTIVE

This study aimed to evaluate the bidirectional association between the kidney dysfunction and the brain health, including structural and functional abnormalities.

DESIGN

Systematic review and meta-analysis with network meta-analysis for outcomes with different estimated glomerular filtration rate (eGFR) ranges.

DATA SOURCES

PubMed, Embase database, Cochrane library and Web of Science (up to Dec. 2021).

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Longitudinal studies that provided evidence of the impact of kidney function estimated from eGFR and urine albumin-to-creatinine ratio (UACR) or chronic kidney disease (CKD) on structural and functional brain abnormalities, and those that provided evidence of the opposite relationship. Studies with study population mean age under 18 years old were excluded.

MAIN OUTCOME MEASURES

Two independent reviewers screened the included studies, extracted the data, and assessed the risk of bias. We performed a random-effects meta-analysis and a network meta-analysis for outcomes with compatible data. We assessed the risk of bias using the Newcastle-Ottawa Quality Assessment Scale criteria (NOS). Subgroup and sensitivity analyses were conducted to explore heterogeneity in the meta-analyses. Inconsistency analyses using the node-splitting method were performed to confirm the results of network meta-analysis.

RESULTS

A total of 53 studies with 3037,357 participants were included in the current systematic review. Among these, 16 provided evidence of structural brain abnormalities, and 38 provided evidence of cognitive impairment and dementia. Analysis of evidence of categorical kidney function showed a positive association between kidney dysfunction and cerebral small vessel disease (cSVD) (relative risk (RR) 1.77, 95% confidence interval (CI) 1.40-2.24, I² = 0.0%), but such results were not found in the analyses of evidence where the kidney function was measured as a continuous variable. Meanwhile, analysis of 28 prior longitudinal studies with 194 compatible sets of data showed that the worse kidney function as categorical variables was related to a greater risk of global brain cognitive disorder (RR 1.28, 95% CI 1.20-1.36, I² = 82.5%).

CONCLUSIONS

In this systematic review and meta-analysis, we found a positive association between CKD and functional brain disorders. However, the relationship between the kidney dysfunction and structural abnormalities in the brain remains controversial. As for the opposite relationship, structural brain abnormalities, especially cerebral microbleeds and silent infarction, but not functional brain abnormalities, are associated with worse renal function. In addition, a higher UACR, but not a lower eGFR, was associated with a higher risk of Alzheimer's disease and vascular dementia.

Does previous stroke modify the relationship between inflammatory biomarkers and clinical endpoints in CKD patients?

Background

Chronic kidney disease (CKD) is an independent risk factor for stroke. Stroke is also an independent risk factor for worse CKD outcomes and inflammation may contribute to this bidirectional relationship. This study aims to investigate inflammatory biomarkers in patients with non-dialysis CKD (ND-CKD) with and without stroke.

Methods

A propensity matched sample from > 3000 Salford Kidney Study (SKS) patients, differentiated by previous stroke at study recruitment, had stored plasma analyzed for interleukin- 6 (IL-6), Von Willebrand Factor (VWF) and C-reactive protein (CRP). Multivariable cox regression analysis investigated associations between inflammation and death, end-stage renal disease (ESRD) and future non-fatal cardiovascular events (NFCVE).

Results

A total of 157 previous stroke patients were compared against 162 non-stroke patients. There were no significant differences in inflammatory biomarkers between the two groups. Previous stroke was associated with greater mortality risk, hazard ratio (HR) (95% CI) was 1.45 (1.07–1.97). Higher inflammatory biomarker concentrations were independently associated with death but not ESRD or NFCVE in the total population. For each 1 standard deviation (SD) increase in log IL-6, VWF and CRP, the HR for all-cause mortality were 1.35 (1.10–1.70), 1.26 (1.05–1.51) and 1.34 (1.12–1.61), respectively. CRP retained its independent association (HR 1.47 (1.15–1.87)) with death in the stroke population.

Conclusion

Previous stroke is an important determinant of mortality. However, the adverse combination of stroke and ND-CKD does not seem to be driven by higher levels of inflammation detected after the stroke event. Biomarkers of inflammation were associated with worse outcome in both stroke and non-stroke ND-CKD patients.

Trial registration

15/NW/0818.

Chronic Kidney Disease and Cerebrovascular Disease: Consensus and Guidance From a KDIGO Controversies Conference

The global health burden of chronic kidney disease is rapidly rising, and chronic kidney disease is an important risk factor for cerebrovascular disease. Proposed underlying mechanisms for this relationship include shared traditional risk factors such as hypertension and diabetes, uremia-related nontraditional risk factors, such as oxidative stress and abnormal calcium-phosphorus metabolism, and dialysis-specific factors such as cerebral hypoperfusion and changes in cardiac structure. Chronic kidney disease frequently complicates routine stroke risk prediction, diagnosis, management, and prevention. It is also associated with worse stroke severity, outcomes and a high burden of silent cerebrovascular disease, and vascular cognitive impairment. Here, we present a summary of the epidemiology, pathophysiology, diagnosis, and treatment of cerebrovascular disease in chronic kidney disease from the Kidney Disease: Improving Global Outcomes Controversies Conference on central and peripheral arterial disease with a focus on knowledge gaps, areas of controversy, and priorities for research.

Impact of multimorbidity on risk and outcome of stroke: Lessons from chronic kidney disease

With both an aging population and greater post-stroke survival, multimorbidity is a growing healthcare challenge, affecting over 40% of stroke patients, and rising rapidly and predictably with increasing age. Commonly defined as the co-occurrence of two or more chronic conditions, multimorbidity burden is a strong adverse prognostic factor, associated with greater short- and long-term stroke mortality, worse rehabilitation outcomes, and reduced use of secondary prevention. Chronic kidney disease can be considered as the archetypal comorbidity, being age-dependent and also affecting about 40% of stroke patients. Chronic kidney disease and stroke share very similar traditional cardiovascular risk factor profiles such as hypertension and diabetes, though novel chronic kidney disease-specific risk factors such as inflammation and oxidative stress have also been proposed. Using chronic kidney disease as an exemplar condition, we explore the mechanisms of risk in multimorbidity, implications for management, impact on stroke severity, and downstream consequences such as post-stroke cognitive impairment and dementia.

Cerebrovascular Disease and Cognition in Chronic Kidney Disease Patients

Chronic kidney disease (CKD) affects both brain structure and function. Patients with CKD have a higher risk of both ischemic and hemorrhagic strokes. Age, prior disease history, hypertension, diabetes, atrial fibrillation, smoking, diet, obesity, and sedimentary lifestyle are most common risk factors. Renal-specific pathophysiologic derangements, such as oxidative stress, chronic inflammation, endothelial dysfunction, vascular calcification, anemia, gut dysbiosis, and uremic toxins are important mediators. Dialysis initiation constitutes the highest stroke risk period. CKD significantly worsens stroke outcomes. It is essential to understand the risks and benefits of established stroke therapeutics in patients with CKD, especially in those on dialysis. Subclinical cerebrovascular disease, such as of silent brain infarction, white matter lesions, cerebral microbleeds, and cerebral atrophy are more prevalent with declining renal function. This may lead to functional brain damage manifesting as cognitive impairment. Cognitive dysfunction has been linked to poor compliance with medications, and is associated with greater morbidity and mortality. Thus, understanding the interaction between renal impairment and brain is important in to minimize the risk of neurologic injury in patients with CKD. This article reviews the link between chronic kidney disease and brain abnormalities associated with CKD in detail.

Brain white matter microstructure in end-stage kidney disease, cognitive impairment, and circulatory stress

INTRODUCTION

Structural and functional brain white matter abnormalities are poorly characterized in patients with end-stage kidney disease.

METHODS

We examined the prevalence of the brain white matter microstructure disruption using diffusion tensor magnetic resonance imaging and its association with hemodynamic performance and cognitive defects in 49 incident hemodialysis (HD) patients and compared these to 25 age-matched normal controls. We analyzed fractional anisotropy (FA) and mean diffusivity (MD) maps of the images, a voxelwise statistical analysis was done using tract-based spatial statistics. Hemodynamic assessment was done using extrema points analysis model of continuous blood pressure monitoring.

FINDINGS

We found significant white matter damage in HD patients compared with normal controls (peak FA 0.471 ± 0.031 vs 0.486 ± 0.022 P = 0.023, peak MD 0.00194 ± 0.000363 10^-3 mm² .s^-1 vs 0.00167 ± 0.0003 10^-3 mm² .s^-1 P = 0.002). There was diffuse pattern of white matter damage in HD patients, which was independent of age, gender, and the presence of ischaemic heart disease and diabetes with significantly lower FA values in HD patients than normal controls (0.467 ± 0.037 vs 0.507 ± 0.026, P < 0.05 corrected for family wise error. HD patients had worse cognitive scores that correlated with white matter damage (for peak FA, Montreal cognitive assessment r = 0.478 P = 0.001, Trail A r = -0.486 P = 0.001, Trail B r = -0.464 P = 0.001; for peak MD, Montreal cognitive assessment r = -0.533 P < 0.001, Trail A r = 0.641 P < 0.001, Trail B r = 0.514 P < 0.001). In a multivariable linear regression analysis that included age, smoking, the presence of ischaemic heart disease, and diabetes mellitus, higher frequency of mean arterial blood pressure extrema points during HD was independently associated with white matter damage (β = -0.296, P = 0.036, Adjusted R² for the whole model = 0.400).

DISCUSSION

End-stage kidney disease patients on HD have more brain white matter damage and cognitive impairment than age-matched controls that are linked to hemodynamic functional measures.

Favourable renal outcomes after intravenous thrombolytic therapy for acute ischemic stroke: Clinical implication of kidney-brain axis

AIM

Recombinant tissue plasminogen activator (rt-PA) administration is the most prevalent treatment for acute ischemic within golden time. However, the effects of rt-PA on the kidney function in such patients remain unknown. This study determined long-term renal outcomes in patients with acute ischemic stroke receiving systemic rt-PA.

METHODS

We enroled patients who were hospitalized for acute ischemic stroke from January 2001 to January 2017. We applied 1:2 propensity score matching to eliminate various confounding variables. We defined surrogate renal outcomes as declining of estimated glomerular filtration rate (eGFR) greater than 30% and 50%, and chronic kidney disease (CKD) with eGFR less than 60 mL/min. We then compared the 1-year eGFR with paired t-test in patients treated with or without rt-PA.

RESULTS

Overall, 343 of 1739 patients received rt-PA within golden time. After 1:2 propensity score matching, their baseline characteristics were grouped as treated with rt-PA (n = 235) or not (n = 394). rt-PA-treated patients exhibited slower renal progression, including the risk of eGFR declining greater than 30% (hazard ratio (HR), 0.72; P = 0.03), risk of declining eGFR greater than 50% (HR, 0.63; P = 0.046) and risk of CKD (HR, 0.61; P = 0.005). After 1-year cohort, the rt-PA group exhibited an improved renal outcome by the paired t-test (propensity match: ΔGFR = 9.1 (95% confidence interval: 6.3, 11.8), P < 0.001 in rt-PA group; ΔGFR = -1.1 (95% confidence interval: -2.9, 0.7), P = 0.23 in non-rt-PA group). In patients with eGFR less than 45 mL/min (n = 34), intracerebral haemorrhage was not reported.

CONCLUSION

Patients receiving rt-PA for acute ischemic stroke exhibit favourable renal outcomes, and no increased incidence of intracerebral haemorrhage occurs in rt-PA patients with advanced CKD.

Brain Magnetic Resonance Imaging Findings in Children and Young Adults With CKD

BACKGROUND

The neuroanatomic basis for cognitive impairment in chronic kidney disease (CKD) is incompletely characterized. We performed advanced quantitative structural magnetic resonance imaging (MRI) to determine whether CKD affects brain structure and whether poorer neurocognitive performance in CKD is associated with structural brain differences.

STUDY DESIGN

Cross-sectional.

SETTING & PARTICIPANTS

85 individuals with CKD stages 2 to 5 and 63 healthy controls, aged 8 to 25 years PREDICTORS: CKD versus control, estimated glomerular filtration rate (eGFR), and kidney transplant status were analyzed as predictors of MRI findings. MRI volumes in 19 prespecified regions of gray matter (GM), white matter (WM), and cerebrospinal fluid were analyzed as predictors of neurocognitive performance (median z scores) in 7 prespecified domains.

OUTCOMES

19 prespecified brain regions of interest (ROIs) in 7 prespecified domains. Neurocognitive performance in 7 prespecified domains.

MEASUREMENTS

ROI volumes were compared in CKD versus controls using unadjusted t tests and analysis of covariance (ANCOVA). Associations of ROI volumes with eGFR and kidney transplant status in participants with CKD were analyzed using ANCOVA and linear regression. Associations of neurocognitive performance and ROI volumes were analyzed by linear regression.

RESULTS

Participants with CKD had lower whole-brain, cortical, and left parietal GM volumes than controls in unadjusted analyses, but no differences were found in adjusted analysis. In participants with CKD, lower eGFR was associated with higher WM volume in whole-brain (P=0.05) and frontal (P=0.04) ROIs, but differences were not significant after multiple comparisons correction. Kidney transplant recipients had lower GM volumes in whole-brain (P=0.01; Q=0.06), frontal (P=0.02; Q=0.08), and left and right parietal (P=0.01; Q=0.06; and P=0.03; Q=0.1) ROIs and higher whole-brain WM volume (P=0.04; Q=0.1). Neurocognitive performance in the CKD group was not associated with ROI volumes.

LIMITATIONS

Unable to assess changes in brain structure and kidney function over time; analysis limited to prespecified ROIs and neurocognitive domains.

CONCLUSIONS

CKD in children and young adults may be associated with lower GM and higher WM volumes in some ROIs. Differences were relatively subtle in the CKD group as a whole, but were more prominent in recipients of a kidney transplant. However, neurocognitive performance was not explained by differences in brain ROI volumes, suggesting a functional rather than structural basis for neurocognitive impairment in CKD.

Brain-kidney cross-talk: Definition and emerging evidence

Cross-talk is broadly defined as endogenous homeostatic signaling between vital organs such as the heart, kidneys and brain. Kidney-brain cross-talk remains an area with excitingly few publications despite its purported clinical relevance in the management of currently undertreated conditions such as resistant hypertension. Therefore, this review aims to establish an organ-specific definition for kidney-brain cross-talk and review the available and forthcoming literature on this topic.

Stroke and Risks of Development and Progression of Kidney Diseases and End-Stage Renal Disease: A Nationwide Population-Based Cohort Study

BACKGROUND

There is little information about the association between stroke and kidney diseases. We aimed to investigate the impact of stroke on long-term renal outcomes.

METHODS

In this large population-based retrospective cohort study, we identified 100,353 subjects registered in the National Health Insurance Research Database of Taiwan from January 1, 2000, through December 31, 2012, including 33,451 stroke patients and 66,902 age-, sex- and Charlson's comorbidity index score-matched controls.

RESULTS

The incidence rate of chronic kidney disease (CKD) was higher in the stroke than in the control cohort (17.5 vs. 9.06 per 1000 person-years). After multivariate adjustment, the risk of developing CKD was significantly higher in patients with stroke (adjusted hazard ratio [aHR] 1.43, 95% confidence interval [CI] 1.36-1.50, P<0.001). Subgroup analysis showed that stroke patients <50 years (aHR 1.61, P<0.001) and those with concomitant diabetes mellitus (aHR 2.12, P<0.001), hyperlipidemia (aHR 1.53, P<0.001) or gout (aHR 1.84, P<0.001) were at higher risk of incident CKD. Additionally, the risks of progression to advanced CKD and end-stage renal disease (ESRD) were significantly higher for stroke patients (aHRs, 1.22 and 1.30; P = 0.04 and P = 0.008, respectively), independent of age, sex, comorbidities and long-term medications.

CONCLUSIONS

Stroke is associated with higher risks for incident CKD, decline in renal function and ESRD. Younger stroke patients, as well as those with concomitant diabetes mellitus, hyperlipidemia or gout are at greater risk for kidney diseases.

Ischemic diabetic retinopathy as a possible prognostic factor for chronic kidney disease progression

PURPOSE

To assess the value of diabetic retinopathy (DR) severity as a possible predictive prognostic factor for the progression of chronic kidney disease (CKD).

PATIENTS AND METHODS

Retrospective cohort study. Patients (51) who were initially diagnosed with DR and CKD were enrolled and their medical records were evaluated. The following ophthalmic factors were assessed by fluorescein angiography at the initial visit: area of capillary nonperfusion, presence of neovascularization and vitreous hemorrhage, and DR grade. The effect of these factors on CKD progression over the 2-year period of the study, defined as doubling of serum creatinine or the development of end-stage renal disease requiring dialysis or renal transplant, was evaluated.

RESULTS

The study included 51 patients with DR and CKD; of these, 11 patients (21.6%) were found to have proliferative DR (PDR) and seven patients (13.7%) had high-risk PDR at baseline. Patients with ischemic DR, who showed extensive capillary nonperfusion (≥ 10 optic disc areas) in the retina, had a greater risk for CKD progression (hazard ratio = 6.64; P = 0.002).

CONCLUSION

We found that extensive capillary nonperfusion in the retina greatly increased the risk of progression of CKD in patients with DR. This suggests that the retina and the kidney may have shared risk factors for microvascular disease secondary to diabetes mellitus, and emphasizes the need for a team approach to diabetes care.

Calcium channel blocker enhances beneficial effects of an angiotensin II AT1 receptor blocker against cerebrovascular-renal injury in type 2 diabetic mice

Recent clinical trials have demonstrated that combination therapy with renin-angiotensin system inhibitors plus calcium channel blockers (CCBs) elicits beneficial effects on cardiovascular and renal events in hypertensive patients with high cardiovascular risks. In the present study, we hypothesized that CCB enhances the protective effects of an angiotensin II type 1 receptor blocker (ARB) against diabetic cerebrovascular-renal injury. Saline-drinking type 2 diabetic KK-A^y mice developed hypertension and exhibited impaired cognitive function, blood-brain barrier (BBB) disruption, albuminuria, glomerular sclerosis and podocyte injury. These brain and renal injuries were associated with increased gene expression of NADPH oxidase components, NADPH oxidase activity and oxidative stress in brain and kidney tissues as well as systemic oxidative stress. Treatment with the ARB, olmesartan (10 mg/kg/day) reduced blood pressure in saline-drinking KK-A^y mice and attenuated cognitive decline, BBB disruption, glomerular injury and albuminuria, which were associated with a reduction of NADPH oxidase activity and oxidative stress in brain and kidney tissues as well as systemic oxidative stress. Furthermore, a suppressive dose of azelnidipine (3 mg/kg/day) exaggerated these beneficial effects of olmesartan. These data support the hypothesis that a CCB enhances ARB-associated cerebrovascular-renal protective effects through suppression of NADPH oxidase-dependent oxidative stress in type 2 diabetes.

Incidence of stroke before and after dialysis initiation in older patients

The incidence of stroke is substantially higher among hemodialysis patients than among patients with earlier stages of CKD, but to what extent the initiation of dialysis accelerates the risk for stroke is not well understood. In this cohort study, we analyzed data from incident hemodialysis and peritoneal dialysis patients in 2009 who were at least 67 years old and had Medicare as primary payer. We noted whether each of the 20,979 hemodialysis patients initiated dialysis as an outpatient (47%) or inpatient (53%). One year before initiation, the baseline stroke rate was 0.15%-0.20% of patients per month (ppm) for both outpatient and inpatient initiators. Among outpatient initiators, stroke rates began rising approximately 90 days before initiation, reached 0.5% ppm during the 30 days before initiation, and peaked at 0.7% ppm (8.4% per patient-year) during the 30 days after initiation. The pattern was similar among inpatient initiators, but the stroke rate peaked at 1.5% ppm (18% per patient-year). For both hemodialysis groups, stroke rates rapidly declined by 1-2 months after initiation, fluctuated, and stabilized at approximately twice the baseline rate by 1 year. Among the 620 peritoneal dialysis patients, stroke rates were slightly lower and variable, but approximately doubled after initiation. In conclusion, these data suggest that the process of initiating dialysis may cause strokes. Further studies should evaluate methods to mitigate the risk for stroke during this high-risk period.

Cognitive disorders and dementia in CKD: the neglected kidney-brain axis

Epidemiologic data suggest that individuals at all stages of CKD have a higher risk of developing cognitive disorders and dementia. This risk is generally explained by the high prevalence of both symptomatic and subclinical ischemic cerebrovascular lesions. However, other potential mechanisms, including direct neuronal injury by uremic toxins, could also be involved, especially in the absence of obvious cerebrovascular disease. We discuss the prevalence and characteristics of cognitive disorders and dementia in patients with CKD, brain imaging findings, and traditional and nontraditional risk factors. Understanding the pathophysiologic interactions between renal impairment and brain function is important in order to minimize the risk for future cognitive impairment.

Anticoagulation in patients with dilated cardiomyopathy, low ejection fraction, and sinus rhythm: back to the drawing board

Heart failure patients present an important thrombo-embolic risk, including symptomatic or silent peripheral arterial embolism, pulmonary embolism, and stroke. Patients in sinus rhythm who have concomitant depressed (< 35%) left ventricular ejection fraction have a 4% rate of embolic events. Several prospective randomized trials of anticoagulation in this group of patients were either underpowered or had a short period of follow-up. Even though in two studies warfarin had a slight advantage over aspirin (in the WATCH and WARCEF trials), it was at the cost of an increased risk in major hemorrhage. To decrease bleeding rates and to improve anticoagulant effect, new treatment strategies have to be tested. Novel anticoagulants (dabigatran, rivaroxaban, and apixaban) seem to be a promising alternative.

Silent Brain Infarction – A Review of Recent Observations

Silent brain infarction is a cerebral ischaemic event evident on brain imaging without any clinical symptom. Silent brain infarction is often detected in apparently healthy, elderly people and in different selected patient groups as well. Lately, several studies were carried out in order to identify the clinical conditions leading to silent brain infarction. A large number of clinical and paraclinical parameters were found to increase silent brain infarction prevalence, and the continuously growing list of risk factors revealed that the majority of them are similar to those related to stroke. Accordingly, some consider silent brain infarction the preclinical stage of clinically overt stroke. This point of view emphasizes the early recognition and management of silent brain infarction-related risk factors, and a great need for comparative studies, which could elicit the most sensitive indicators of the increased silent brain infarction risk, especially the ones that could be cost-effectively screened in the large populations as well.

Is chronic kidney disease in older people a new geriatric giant?

The global population is aging, and the number of people above the age of 85 years is growing faster than any other age group. There is an age-related decline in kidney function; however, not all individuals will develop chronic kidney disease (CKD) with advancing age. Those who are genetically predisposed and exposed to lifetime cardiovascular risk factors are likely to develop systemic atherosclerosis and CKD as a part of its manifestation. CKD promotes poor health through its association with inflammation and oxidative stress. Malnutrition, weight loss and sarcopenia are common in CKD patients, leading to poor outcomes, such as physical and cognitive dysfunction, manifesting as major geriatric syndromes. Frailty is likely to be one of the underlying processes that leads to the clinical manifestations of geriatric syndromes in patients with CKD. Therefore, functional outcomes, such as cognition and physical functioning, might be more relevant outcomes to older patients with CKD. Interventions should be developed and assessed in terms of maintaining quality rather than quantity of life before disability develops.

Cardiorenal syndromes

Cardiorenal syndromes (CRS) have been subclassified as five defined entities which represent clinical circumstances in which both the heart and the kidney are involved in a bidirectional injury and dysfunction via a final common pathway of cell-to-cell death and accelerated apoptosis mediated by oxidative stress. Types 1 and 2 involve acute and chronic cardiovascular disease (CVD) scenarios leading to acute kidney injury or accelerated chronic kidney disease. Types 2 and 3 describe acute and chronic kidney disease leading primarily to heart failure, although it is possible that acute coronary syndromes, stroke, and arrhythmias could be CVD outcomes in these forms of CRS. Finally, CRS type 5 describes a simultaneous insult to both heart and kidneys, such as sepsis, where both organs are injured simultaneously. Both blood and urine biomarkers are reviewed in this paper and offer a considerable opportunity to enhance the understanding of the pathophysiology and known epidemiology of these recently defined syndromes.

Cardiorenal syndromes: pathophysiology to prevention

There is a strong association between both acute and chronic dysfunction of the heart and kidneys with respect to morbidity and mortality. The complex interrelationships of longitudinal changes in both organ systems have been difficult to describe and fully understand due to a lack of categorization of the common clinical scenarios where these phenomena are encountered. Thus, cardiorenal syndromes (CRSs) have been subdivided into five syndromes which represent clinical vignettes in which both the heart and the kidney are involved in bidirectional injury and dysfunction via a final common pathway of cell-to-cell death and accelerated apoptosis mediated by oxidative stress. Types 1 and 2 involve acute and chronic cardiovascular disease (CVD) scenarios leading to acute kidney injury (AKI) or accelerated chronic kidney disease (CKD). Types 3 and 4 describe AKI and CKD, respectively, leading primarily to heart failure, although it is possible that acute coronary syndromes, stroke, and arrhythmias could be CVD outcomes in these forms of CRS. Finally, CRSs type 5 describe a systemic insult to both heart and the kidneys, such as sepsis, where both organs are injured simultaneously in persons with previously normal heart and kidney function at baseline. Both blood and urine biomarkers, including the assessment of catalytic iron, a critical element to the generation of oxygen-free radicals and oxidative stress, are reviewed in this paper.