Neurological complications in renal failure: a review

Altered functional connectivity density in the brains of hemodialysis end-stage renal disease patients: An in vivo resting-state functional MRI study

Background

End-stage renal disease (ESRD) patients usually suffer from a high prevalence of central nervous system abnormalities, including cognitive impairment and emotional disorders, which severely influence their quality of life. There have been many neuroimaging research developments in ESRD patients with brain function abnormalities; however, the dysfunction of the salience network (SN) of them has received little attention. The purpose of this study was to investigate the changes of global functional connectivity density (gFCD) in brains of ESRD patients undergoing hemodialysis using resting-state functional magnetic resonance imaging (re-fMRI).

Methods

re-fMRI data were collected from 30 ESRD patients undergoing hemodialysis (14 men, 38.33±7.44 years old) and 30 matched healthy controls (13 men, 39.17±5.7 years old). Neuropsychological tests including the Montreal Cognitive Assessment (MoCA) and Beck Depression Inventory (BDI) were used to evaluate the neurocognitive and psychiatric conditions of the subjects. Blood biochemistry tests, including hemoglobin level, serum albumin level, blood urea level, serum phosphate, serum calcium, and parathyroid hormone level, and dialysis-related indicators, including blood pressure fluctuations in dialysis, single-pool Kt/V(spKt/V), and ultrafiltration volume of dialysis were obtained from the ESRD patients. A two-sample t-test was used to examine the group differences in gFCD between ESRD patients and healthy controls after controlling for age, gender and education.

Results

Compared with healthy controls, ESRD patients exhibited a significantly increased gFCD in the salience network, including the bilateral insula, and dorsal anterior cingulated cortex (dACC), and there was no significant correlation between gFCD and the structural mean grey matter volume in patients for every cluster in the brain regions showing significant different gFCD between the two groups. Furthermore, there were significant negative correlations between the degree of connectivity in the right insula and spKt/V.

Conclusion

Our findings revealed abnormal intrinsic dysconnectivity pattern of salience network-related regions in ESRD patients from the whole brain network perspective. The negative correlation between the right insula and spKt/V suggested that increased fractional removal of urea may reduce the pathological activity in the insula.

Nocturnal dialysis improves sleep apnea more than daytime dialysis: a meta-analysis of crossover studies

PURPOSE

To systematically review the literature for articles evaluating differences in polysomnography (PSG) data when patients are on primarily daytime hemodialysis (conventional hemodialysis or continuous ambulatory peritoneal dialysis) versus nocturnal hemodialysis (nocturnal hemodialysis or nocturnal peritoneal dialysis). Then to perform a meta-analysis on the available PSG data, specifically evaluating differences in apnea hypopnea index (AHI) and mean saturation of oxygen (SpO₂) between these two groups.

METHODS

Two authors systematically searched MEDLINE/Pubmed, Scopus, EMBASE, CINAHL, and Cochrane. Searches were performed through December 6, 2018.

RESULTS

A total of four adult crossover studies (91 patients, age 50.4 ± 12.4, BMI 25.1 ± 5.3) reported PSG data. The daytime hemodialysis (DHD) and nocturnal hemodialysis (NHD) AHI decreased from 24.6 ± 18.2 to 12.6 ± 11.8 (events/hour) with a mean difference of -11.9 [95% CI -13.47, -10.37], Z score of 15.07 (P < 0.00001). The standardized mean difference was -1.35 [95% CI -2.70, 0.01]. Two studies reported mean SpO₂ changes during PSG. The DHD and NHD SpO₂ increased from 92.7 ± 2.4 to 94.7 ± 2.2 with a mean difference of 2.26 [95% CI -0.18, 4.71], Z score 1.82 (P = 0.07).

CONCLUSION

In the current literature, nocturnal hemodialysis improves AHI more than daytime hemodialysis. A trend towards improvement in mean SpO₂ with nocturnal dialysis was noted, but did not reach statistical significance. Consideration can be given for transitioning patients who have end stage renal disease and sleep apnea from daytime to nocturnal hemodialysis as an adjunct to other treatment modalities.

A Clinical and Electrophysiological Study of Peripheral Neuropathies in Predialysis Chronic Kidney Disease Patients and Relation of Severity of Peripheral Neuropathy with Degree of Renal Failure

Objective:

To study the prevalence, clinical features, electrophysiological features, and severity of peripheral neuropathy in predialysis chronic kidney disease (CKD) patients with respect to severity of renal failure and presence of diabetes mellitus.

Materials and Methods:

Between May 2015 and December 2016, 200 predialysis CKD patients were assessed prospectively.

Results:

The prevalence of peripheral neuropathy in predialysis CKD patients in the present study was 45% based on clinical symptoms and 90% electrophysiologically. Mean age of 200 predialysis CKD patients who participated in the study was 53.2 ± 13.2 years. One hundred and thirty-six (68%) patients were male and 64 (32%) patients were female. Mean duration of disease was 2.2 ± 1.6 years. Nearly 45% patients of patients had asymptomatic peripheral neuropathy in the present study, which was more common in mild-to-moderate renal failure group. One hundred twenty-six patients (63%) had definite damage and 54 patients (27%) had early damage. In mild-to-moderate renal failure (n = 100) and severe renal failure patients (n = 100), 88% and 92% had significant peripheral neuropathy, respectively. Most common nerves involved were sural nerve, median sensory nerve, and ulnar sensory nerve. Diabetic patients (97%) showed more severe and high prevalence of peripheral neuropathy when compared to nondiabetic patients (83%). Most common patterns were pure axonal sensorimotor neuropathy and mixed sensorimotor neuropathy.

Conclusion:

Peripheral neuropathy is common in predialysis patients, prevalence and severity of which increases as renal failure worsens. Predialysis patients with diabetes show higher prevalence and severity of peripheral neuropathy when compared with nondiabetics.

Chronic kidney disease and the olfactory system

Alterations in the sense of smell (dysosmia, anosmia, hyposmia) are frequently experienced by patients with chronic kidney disease. However, currently, the aetiology and consequences are poorly understood, with no effective treatments available to address such impairment. In general, the capacity of olfactory perception is affected in patients with chronic kidney disease (even in those who have not undergone dialysis therapy), and whether these alterations improve after dialysis is disputed. Patients in peritoneal dialysis and haemodialysis have the same olfactory perception defects. Kidney transplantation improves olfactory perception, and one important consequence of such impairment is the potential impact on the patient's nutritional status.

Accumulation of uremic solutes in the cerebrospinal fluid in experimental acute renal failure

The accumulation of uremic solutes in kidney failure may impair mental function. The present study profiled the accumulation of uremic solutes in the cerebrospinal fluid (CSF) in acute renal failure. CSF and plasma ultrafiltrate were obtained from rats at 48 h after sham operation (control; n = 10) or bilateral nephrectomy (n = 10) and analyzed using an established metabolomic platform. Two hundred forty-eight solutes were identified as uremic based on their accumulation in the plasma ultrafiltrate of nephrectomized compared with control rats. CSF levels of 124 of these solutes were sufficient to allow calculation of CSF-to-plasma ultrafiltrate concentration ratios. Levels of many of the uremic solutes were normally lower in the CSF than in the plasma ultrafiltrate, indicating exclusion of these solutes from the brain. CSF levels of the great majority of the uremic solutes increased in renal failure. The increase in the CSF was, however, relatively less than in the plasma ultrafiltrate for most solutes. In particular, for the 31 uremic solutes with CSF-to-plasma ultrafiltrate ratios of <0.25 in control rats, the average CSF-to-plasma ultrafiltrate ratio decreased from 0.13 ± 0.07 in control rats to 0.09 ± 0.06 in nephrectomized rats, revealing sustained ability to exclude these solutes from the brain. In summary, levels of many uremic solutes are normally kept lower in the CSF than in the plasma ultrafiltrate by the action of the blood-brain and blood-CSF barriers. These barriers remain functional but cannot prevent accumulation of uremic solutes in the CSF when the kidneys fail.

Alterations of default mode functional connectivity in individuals with end-stage renal disease and mild cognitive impairment

BACKGROUND

Mild cognitive impairment (MCI) occurs frequently in many end stage renal disease (ESRD) patients, may significantly worsen survival odds and prognosis. However, the exact neuropathological mechanisms of MCI combined with ESRD are not fully clear. This study examined functional connectivity (FC) alterations of the default-mode network (DMN) in individuals with ESRD and MCI.

METHODS

Twenty-four individuals with ESRD identified as MCI patients were included in this study; of these, 19 and 5 underwent hemodialysis (HD) and peritoneal dialysis (PD), respectively. Another group of 25 age-, sex- and education level-matched subjects were recruited as the control group. All participants underwent resting-state functional MRI and neuropsychological tests; the ESRD group underwent additional laboratory testing. Independent component analysis (ICA) was used for DMN characterization. With functional connectivity maps of the DMN derived individually, group comparison was performed with voxel-wise independent samples t-test, and connectivity changes were correlated with neuropsychological and clinical variables.

RESULTS

Compared with the control group, significantly decreased functional connectivity of the DMN was observed in the posterior cingulate cortex (PCC) and precuneus (Pcu), as well as in the medial prefrontal cortex (MPFC) in the ESRD group. Functional connectivity reductions in the MPFC and PCC/Pcu were positively correlated with hemoglobin levels. In addition, functional connectivity reduction in the MPFC showed positive correlation with Montreal Cognitive Assessment (MoCA) score.

CONCLUSION

Decreased functional connectivity in the DMN may be associated with neuropathological mechanisms involved in ESRD and MCI.

Neurological Complications After Renal Transplantation: A Systematic Review and Meta-Analysis

The aim of this systematic review and meta-analysis was to evaluate the prevalence of neurological complication after renal transplantation. The searches were conducted by two independent researchers in the international (PubMed, Web of Science, Scopus, and Google Scholar) and national databases (Magiran and SID) to find the relevant studies published in English and Persian languages since the creation of the databases until January 2019 (without time limitations). The keywords used in the search strategy were: neurologic complication, central nervous system, peripheral nervous system, tremor, CVA, encephalopathy, neurological complications, renal transplantation, renal failure, kidney transplantation, immunosuppression, neurotoxicity, opportunistic infections, CNS, cerebrovascular disease, chronic kidney disease, cognitive impairment, and end-stage renal disease, which were combined using the AND, OR, and NOT operators. Finally, a meta-analysis was conducted in STATA14 statistical software. Based on the random effect model, the total prevalence of neurologic complications in 4674 patients who had undergone the renal transplantation surgery was 7.9% (95% confidence interval [CI]:7.2%,8.7%, I² = 90.1%). The prevalence of infectious, non-infectious and treatment associated neurologic complications was 9.5% (95% CI -8.9, 10.2), 91.8% (95% CI -91.3, 92.4) and 97% (95% CI-95.7%,98.4%) of all neurologic complications in renal transplant patients, respectively. And according to the present subgroup analysis, peripheral neuropathy with a prevalence about 30% (29%) (95% CI -27.6%, 30.4%, I² = 99.4%) was the most common neurological disorder in renal transplant patients followed by tremor with a prevalence of 19.5% (CI -17.6%, 21.3%, I² = 97.1%), cerebrovascular events with a prevalence of 15.1% (95% CI -13.9%, 16.4%, I² = 96.5%), encephalopathy with the prevalence of 13% (95% CI -12%, 14%, I² = 99.3%), headache with a prevalence of 8.3% (95% CI -6.8%, 9.8%, I² = 97.3%) and seizure with a prevalence of 7.4% (CI - 6.5%, 8.3%, I² = 94.6%). The results of the present systematic review and meta-analysis, suggests that post-kidney transplantation neurological disorders, with a prevalence rate about 8%, are relatively common; most of them are caused by immunosuppressive drugs and can be treated by decreasing the dose or switching the immunosuppressive drugs. Neurological disorders are associated with increased mortality; thus, differential diagnosis should be conducted for each individual patient with neurological symptoms after transplantation. It is important for all health care providers to become familiar with the symptoms of neurological disorders that may occur after organ transplants. Recognizing and monitoring these symptoms can reduce the risk of death in kidney transplant recipients. Further research is needed to help the transplant community to identify these issues and problems better in order to achieve the ultimate goal of helping renal patients and sending them back into their normal lives.

Educational needs in families of pediatric liver and kidney transplant recipients: A quality improvement project

Parents of pediatric liver and kidney transplant recipients were surveyed regarding their current education plans (eg, Individualized Education Program, 504), satisfaction with these plans, and interest in educational support from the psychosocial transplant team. Survey results indicate high rates of IEP and 504 plans, academic and related services, and accommodations among this population. The majority of parents/guardians reported satisfaction with their child's current school plan and did not report need for additional transplant team support specific to school services on the survey measure. However, other information highlights the importance for pediatric transplant teams to consider other ways to support this population's educational needs.

Balance and fall risk in peritoneal dialysis patients

BACKGROUND

Vestibular, neurological and musculoskeletal functions are affected in patients with renal failure. These problems can in turn affect the balance system in peritoneal dialysis (PD) patients. Previously, postural balance changes were shown in hemodialysis patients. This is the first study that evaluates whether there are similar changes in patients with PD.

OBJECTIVE

This study aimed to compare balance and fall risk between patients undergoing PD treatment and healthy subjects, and aimed to determine the correlation between biochemical parameters and fall risk and balance assessments in PD patients.

METHODS

This controlled study included 58 patients receiving PD treatment (PD Group) and 75 healthy subjects (Control Group). The Berg Balance Scale (BBS) and Tetrax® Interactive Balance System were used for the comparison of balance between groups. For patients in the PD Group, duration of PD, blood pressure, Kt/Vurea (actual mass of urea removed via peritoneal dialysis), and serum biochemical parameters were recorded and correlation analysis was performed between these parameters and balance measurements.

RESULTS

There were no statistically significant differences between groups in terms of demographics or BBS scores (p> 0.05). The fall risk of patients in the PD Group was significantly higher than those in the Control Group (p< 0.0001) according to Tetrax measurements. Female gender, older age, higher BMI, and higher blood glucose levels were negatively correlated with balance parameters of PD patients (r> 0.3). There was no statistically significant correlation between duration of PD, blood pressure, and Kt/Vurea with balance parameters or fall risk.

CONCLUSIONS

Balance was impaired in patients undergoing PD in comparison to healthy subjects. Fall risk may be evaluated using the Tetrax® instead of BBS for this population. Serum glucose level, BMI and age appear to affect balance and fall risk. Therefore, optimization of body weight and normalization of serum glucose levels are important factors for improving balance. The duration of PD, blood pressure, and Kt/Vurea do not affect balance system.

A preliminary report of longitudinal white matter alterations in patients with end-stage renal disease: A three-year diffusion tensor imaging study

PURPOSE

End-stage renal disease (ESRD) patients exhibit silent white-matter alterations after long-term hemodialysis, which may be due to ESRD itself or the hemodialysis. The purpose of this study was to investigate the longitudinal white-matter alterations in the ESRD patients under 3-year long-term hemodialysis using voxel-wise analysis of diffusion tensor imaging (DTI).

MATERIALS AND METHODS

15 ESRD patients and 15 age-matched healthy controls participated in this study. Due to the development of abnormal brain lesions in some cases, 13 ESRD patients and 13 age-matched healthy controls were enrolled and underwent cognitive function assessment and DTI acquisition at two-time points separated by 3 years. Voxel-based analysis was performed to globally detect white-matter alterations between the two groups as well as between the two scans within the two groups.

RESULTS

In the ESRD patients, diffusivity indices were significantly increased and the fractional anisotropy was significantly decreased in both scans, as compared with healthy controls. Longitudinal comparisons showed significant white-matter alterations in healthy controls in three years, but little or no significant alterations were noted in the ESRD patients after additional 3-year hemodialysis.

CONCLUSION

Poorer white matter integrity and cognitive function are noted in ESRD patients and the toxic effect of ESRD may be the major factor of white matter alterations.

Is there a relationship between plantar foot sensation and static balance, physical performance, fear of falling, and quality of life in hemodialysis patients?

INTRODUCTION

This study was conducted to investigate the relationship between plantar foot sensation and static balance, physical performance, fear of falling, and quality of life in hemodialysis patients.

MATERIALS AND METHODS

The study involved 24 hemodialysis patients and 20 healthy volunteers. Light touch-pressure sensation (Semmes Weinstein Monofilament test kit), two-point discrimination sensation (esthesiometer) and vibration sensation (128 Hz diapason) were used to evaluate plantar foot sensation. Static balance was assessed by the one-leg standing balance test, physical performance by the Timed Up and Go test, fear of falling with the Fall Efficacy Scale, and quality of life with the Ferrans and Powers Quality of Life Index Dialysis Version.

FINDINGS

There was a significant difference in plantar foot sensation, static balance, and physical performance of the patients compared to the healthy controls (P < 0.05). There was a strong correlation between static balance and physical performance with foot sensation in the hemodialysis patients (P < 0.05). There was also a strong correlation between static balance, physical performance, and fear of falling in hemodialysis patients (P < 0.05). The correlation between static balance, physical performance, and quality of life in the hemodialysis patients was strong (P < 0.05).

DISCUSSION

The most important result of this study is that light touch-pressure sensation, vibration sensation, two-point discrimination sensation, static balance, and physical performance, all of which involve the activity of cutaneous sensory receptors on the sole of the foot, are reduced in individuals who undergo hemodialysis. The findings of this study suggest potential rehabilitation strategies that could be applied to this patient group.

The association between renal function and neurological diseases in type 2 diabetes: a multicenter nationwide cross-sectional study

BACKGROUND

The evidence for an association between renal function and neurological diseases among type 2 diabetes mellitus (T2DM) patients, particularly in the Asian population, is limited. This study aimed to assess the association between glomerular filtration rate (GFR) and various neurological diseases among T2DM patients in Thailand using a nationwide patient sample.

METHODS

We conducted a nationwide cross-sectional study based on the DM/HT study of the Medical Research Network of the Consortium of Thai Medical Schools. This study evaluated adult T2DM patients receiving care at public Thailand hospitals in the year 2014. GFR was categorized into ≥60, 30-59, and < 30 mL/min/1.73 m². Neurological diseases studied included ischemic stroke/transient ischemic attack (TIA), hemorrhagic stroke, dementia, all cerebrovascular disease, and peripheral neuropathy. Multivariate logistic regression was performed to assess the association between GFR and neurological diseases.

RESULTS

A total of 30,423 T2DM patients with available GFR data were included in the analysis. The mean GFR was 68.18 ± 26.45 mL/min/1.73 m². The prevalence of ischemic stroke/TIA, hemorrhagic stroke, dementia, any cerebrovascular diseases and peripheral neuropathy were 2.9%, 0.3%, 0.1%, 3.2%, and 3.1%, respectively. Patients with GFR of 30-59 and <30 mL/min/1.73 m² were significantly associated with increased rates of ischemic stroke/TIA, any cerebrovascular diseases, and peripheral neuropathy when compared with patients with GFR of ≥60 mL/min/1.73 m². This association remained significant after adjustment for potential confounders.

CONCLUSION

Decreased GFR was associated with increased ischemic stroke/TIA, all cerebrovascular diseases, and peripheral neuropathy. GFR should be monitored in diabetic patients for neurological disease awareness and prevention.

Effect of nocturnal hemodialysis on sleep parameters in patients with end-stage renal disease: a systematic review and meta-analysis

Introduction

Recently, a small but growing literature has depicted the beneficial effects of nocturnal hemodialysis (NHD) over conventional hemodialysis (CHD) in the fields of sleep disorders such as sleep apnea. The impact of various dialysis models on sleep disorders, however, has not been determined. The objective of our meta-analysis is to examine the potential effects of NHD, compared with CHD, on sleep disorders in HD patients.

Methods

Several electronic databases including PubMed, EMBASE, Cochrane Central Register of Controlled Trials, ClinicalTrials.gov and CNKI were searched, using the search terms “nocturnal” (or “nightly”) and “dialysis” (or “hemodialysis” or “renal dialysis”) from the earliest available date of indexing to March 2018. Two authors independently extracted data, evaluated the study quality, and conducted random-effects meta-analyses using STATA 12.0.

Results

Of 1789 potentially relevant citations, 9 fulfilled eligibility criteria, consisting of 6 single-arm studies (comparing pre- and post-intervention outcomes), 1 observational study, and 2 randomized controlled trials (a total of 286 participants). Regarding objective sleep assessments, conversion from CHD to NHD resulted in a significant reduction in the AHI (Mean difference was -14.90; 95% CI, -20.12 to -9.68), a significant increase of SaO2 (Mean difference was 1.38%; 95% CI, 0.35% to 2.42%), and a significant decrease of TST (Mean difference was -0.31; 95% CI, -0.47 to -0.15). The trends were even stronger in the HD patients with sleep disorders. However, regarding subjective sleep assessments, improved sleep quality was found in the prospective pre-post intervention studies and cohort studies, while no significant improvements were found in the randomized controlled trials.

Conclusion

Although a significant improvement of sleep apnea was observed by switching from CHD to NHD, it may not yield a net benefit in overall subjective sleep quality.

The specific impact of uremic toxins upon cognitive domains: a review

One of the mechanisms proposed for chronic kidney disease (CKD)-related cognitive impairment is the accumulation of uremic toxins due to the deterioration of the renal clearance function. Cognition can be categorized into five major domains according to its information processing functions: memory, attention, language, visual-spatial, and executive. We performed a review using the terms 'uric acid', 'indoxyl sulfate', 'p-cresyl sulfate', 'homocysteine', 'interleukins' and 'parathyroid hormone'. These are the compounds that were found to be strongly associated with cognitive impairment in CKD in the literature. The 26 selected articles point towards an association between higher levels of uric acid, homocysteine, and interleukin 6 with lower cognitive performance in executive, attentional, and memory domains. We also reviewed the hemodialysis effects on cognition. Hemodialysis seems to contribute to an amelioration of CKD-related encephalopathic dysfunction, although this improvement occurs more in some cognitive domains than in others.

Lower risk of musculoskeletal pain among patients with end-stage renal disease treated by hemodialysis: A frequency-matched retrospective cohort study

Musculoskeletal pain is experienced by 5%-14% of the general adult population, and it is highly common among patients with chronic kidney disease (CKD). Therefore, the purpose of the study was to decide the prevalent rate of musculoskeletal pain in end-stage renal disease (ESRD) patients and to analyze this relationship between myalgia and ESRD using clinical features and determinants.A total of 93,013 patients who received ESRD diagnoses during 2000 and 2010 and were followed up until December 31, 2011, were identified from the Longitudinal Health Insurance Database 2000 (LHID2000) of the National Health Research Institutes (NHRI); non-ESRD controls were also selected from the LHID2000.The results indicated that the risk of chronic musculoskeletal pain is significantly lower in the hemodialysis treated ESRD cohort (subhazard ratio = 0.52, P < .0001), despite of sex, age, or comorbidities. Older patients were discovered to be at lower risk of chronic musculoskeletal pain (subhazard ratio = 0.94, P = .0765), with those aged 40 to 64 years having the highest hazard ratios (subhazard ratio = 1.21, P < .0001), and the prevalence of chronic musculoskeletal pain in women was higher than that in men (vs female sex; subhazard ratio = 0.69, P < .0001). Kaplan-Meier analysis revealed a higher cumulative incidence of myalgia development in the non-ESRD cohort compared with the ESRD cohort (log-rank test, P < .001).Clinicians should assess the risk of chronic musculoskeletal pain in such patients and provide appropriate and timely support of hemodialysis.

Renal Disease and Neurology

PURPOSE OF REVIEW

Neurologic dysfunction is prevalent in patients with acute and chronic renal disease and may affect the central nervous system, peripheral nervous system, or both. Neurologic manifestations may result directly from the uremic state or as a consequence of renal replacement therapy. Early recognition of neurologic dysfunction may provide opportunities for intervention and reduced morbidity.

RECENT FINDINGS

Advances in the understanding of neurologic complications of renal disease and its treatments have led to more widespread recognition and earlier identification of encephalopathy syndromes such as cefepime neurotoxicity and posterior reversible encephalopathy syndrome (PRES), dramatic reductions in the incidence of dialysis disequilibrium syndrome and dialysis dementia, and improved survival in disorders such as von Hippel-Lindau disease and thrombotic thrombocytopenic purpura.

SUMMARY

This article summarizes the conditions that affect both the renal and the nervous systems, the effects of renal failure on the nervous system, and the neurologic complications of dialysis.

Distant Organ Dysfunction in Acute Kidney Injury: A Review

Acute kidney injury (AKI) is common in critically ill patients and is associated with increased morbidity and mortality. Dysfunction of other organs is an important cause of poor outcomes from AKI. Ample clinical and epidemiologic data show that AKI is associated with distant organ dysfunction in lung, heart, brain, and liver. Recent advancements in basic and clinical research have demonstrated physiologic and molecular mechanisms of distant organ interactions in AKI, including leukocyte activation and infiltration, generation of soluble factors such as inflammatory cytokines/chemokines, and endothelial injury. Oxidative stress and production of reactive oxygen species, as well as dysregulation of cell death in distant organs, are also important mechanism of AKI-induced distant organ dysfunction. This review updates recent clinical and experimental findings on organ crosstalk in AKI and highlights potential molecular mechanisms and therapeutic targets to improve clinical outcomes during AKI.

Uremic encephalopathy in a rhesus macaque (Macaca mulatta): A case report and a brief review of the veterinary literature

BACKGROUND

Uremic encephalopathy is uncommon yet is one of the most severe complications of renal failure. We present a case of acute renal failure and associated cerebral and vascular lesions consistent with uremic encephalopathy in a rhesus macaque (Macaca mulatta).

METHODS

A 14-year-old, female, specific-pathogen-free rhesus macaque presented in lateral recumbency, obtunded, severely dehydrated, and hypothermic, with severe azotemia, mild hyponatremia, hypokalemia, hypochloremia, increased anion gap, and hypercholesterolemia. Due to poor prognosis, the animal was euthanized and a complete necropsy was conducted.

RESULTS

The animal had diffuse proximal renal tubular epithelial necrosis and loss; regeneration of tubular epithelium was not observed. There was bilateral necrosis and loss of neurons and glial cells in the hippocampus and deep cerebral cortex with edema and multifocal areas of hemorrhage.

CONCLUSION

We present the first reported case of uremic encephalopathy in a rhesus macaque and describe the associated cerebral and vascular lesions.

Evaluation of Acute Kidney Injury and Mortality After Intensive Blood Pressure Control in Patients With Intracerebral Hemorrhage

Background

We sought to assess the risk of acute kidney injury (AKI) and mortality associated with intensive systolic blood pressure reduction in acute intracerebral hemorrhage.

Methods and Results

Patients with acute intracerebral hemorrhage had spontaneous cause and symptom onset within 24 hours. We excluded patients with structural causes, coagulopathy, thrombocytopenia, and preexisting end‐stage renal disease. We defined AKI using the Acute Kidney Injury Network criteria. Chronic kidney disease status was included in risk stratification and was defined by Kidney Disease Outcomes Quality Initiative staging. Maximum systolic blood pressure reduction was defined over a 12‐hour period and dichotomized using receiver operating characteristic curve analysis. Descriptive statistics were done using independent sample t tests, χ² tests, and Mann‐Whitney U tests, whereas multivariable logistic regression analysis was used to evaluate for predictors for AKI and mortality. A total of 448 patients with intracerebral hemorrhage met inclusion criteria. Maximum systolic blood pressure reduction was dichotomized to 90 mm Hg and found to increase the risk of AKI in patients with normal renal function (odds ratio, 2.1; 95% confidence interval, 1.19–3.62; P=0.010) and chronic kidney disease (odds ratio, 3.91; 95% confidence interval, 1.26–12.15; P=0.019). The risk of AKI was not significantly different in normal renal function versus chronic kidney disease groups when adjusted for demographics, presentation characteristics, and medications associated with AKI. AKI positively predicted mortality for patients with normal renal function (odds ratio, 2.41; 95% confidence interval, 1.11–5.22; P=0.026) but not for patients with chronic kidney disease (odds ratio, 3.13; 95% confidence interval, 0.65–15.01; P=0.154).

Conclusions

These results indicate that intensive systolic blood pressure reduction with a threshold >90 mm Hg in patients with acute intracerebral hemorrhage may be an independent predictor for AKI.

Aberrant cortical thickness in neurologically asymptomatic patients with end-stage renal disease

PURPOSE

The aim of this study is to investigate the morphology of cortical gray matter in patients with end-stage renal disease (ESRD) and the relationship between cortical thickness and kidney function.

PATIENTS AND METHODS

Three-dimensional high-resolution brain structural magnetic resonance imaging data were collected from 35 patients with ESRD (28 men, 18-61 years old) and 40 age- and gender-matched healthy controls (HCs, 32 men, 22-58 years old). Vertex-wise analysis was then performed to compare the brains of the patients with ESRD with those of HCs to identify abnormalities in the brains of the former. Multiple biochemical measures of renal metabolin, vascular risk factors, general cognitive ability, and dialysis duration were correlated with brain morphometry alterations for the patients.

RESULTS

Patients with ESRD showed lesser cortical thickness than the HCs. The most significant cluster with decreased cortical thickness was found in the right prefrontal cortex (P<0.05, random-field theory correction). In addition, the four local peak vertices in the prefrontal cluster were lateral prefrontal cortex (Peaks 1 and 2), medial prefrontal cortex (Peak 3), and ventral prefrontal cortex (Peak 4). Significant negative correlations were observed between the cortical thicknesses of all four peak vertices and blood urea nitrogen; a negative correlation, between the cortical thickness in three of four peaks and serum creatinine; and a positive correlation, between cortical thickness in the medial prefrontal cortex (Peak 3) and hemoglobin.

CONCLUSION

These results provided compelling evidence for cortical abnormality of ESRD patients and suggested that kidney function may be the key factor for predicting changes of brain tissue structure.

Human recombinant erythropoietin reduces sensorimotor dysfunction and cognitive impairment in rat models of chronic kidney disease

INTRODUCTION

Chronic kidney disease (CKD) can cause anaemia and neurological disorders. Recombinant human erythropoietin (rHuEPO) is used to manage anaemia in CKD. However, there is little evidence on the effects of rHuEPO on behaviour and cognitive function in CKD. This study aimed to evaluate the impact of rHuEPO in sensorimotor and cognitive functions in a CKD model.

METHODS

Male Wistar rats were randomly assigned to 4 groups: control and CKD, with and without rHuEPO treatment (1050 IU per kg body weight, once weekly for 4 weeks). The Morris water maze, open field, and adhesive removal tests were performed simultaneously to kidney damage induction and treatment. Markers of anaemia and renal function were measured at the end of the study.

RESULTS

Treatment with rHuEPO reduced kidney damage and corrected anaemia in rats with CKD. We observed reduced sensorimotor dysfunction in animals with CKD and treated with rHuEPO. These rats also completed the water maze test in a shorter time than the control groups.

CONCLUSIONS

rHuEPO reduces kidney damage, corrects anemia, and reduces sensorimotor and cognitive dysfunction in animals with CKD.

Differential associations between systemic markers of disease and white matter tissue health in middle-aged and older adults

Age-associated cerebrovascular disease impacts brain tissue integrity, but other factors, including normal variation in blood markers of systemic health, may also influence the structural integrity of the brain. This cross-sectional study included 139 individuals between 40 to 86 years old who were physically healthy and cognitively intact. Eleven markers (total-cholesterol, high-density lipoprotein, low-density lipoprotein, triglyceride, insulin, fasting glucose, glycated hemoglobin, creatinine, blood urea nitrogen, albumin, total protein) and five derived indicators (estimated glomerular filtration rate, creatinine clearance rate, insulin-resistance, average glucose, and cholesterol/high-density lipoprotein ratio) were obtained from blood sampling. Diffusion tensor imaging was used to evaluate white matter tissue health. Blood markers were clustered into five factors. The first factor (defined as insulin/high-density lipoprotein factor) was associated with markers of integrity in the deep white matter and projection fiber systems, while the third factor (defined as kidney function factor) was associated with different markers of integrity in the periventricular and watershed white matter regions. Differential segregated associations for insulin and high-density lipoprotein levels and serum markers of kidney function may provide information about distinct mechanisms of brain changes across the lifespan. These results emphasize the need to determine whether therapeutic modulation of systemic health and organ function may prevent decline in brain structural integrity.

[Life after Acute Kidney Injury : Long-term consequences and implications for clinical practice]

Acute kidney injury (AKI) is a common complication in critically ill patients and is accompanied by significantly increased mortality and morbidity. Those complications are not limited to the acute phase of the illness, but may also affect a patient's risk profile long after AKI. Recovery of renal function is observed in the majority of patients although this rate significantly deteriorates with increasing severity of the AKI. After an AKI episode, the long-term risk for the development of chronic kidney disease (CKD) is considerably increased, as well as the risk for cardiovascular and neurological complications. Follow-up of these patients should include general nephroprotective measures such as controlling hypertension as well as avoiding nephrotoxic drugs, as well as repeated evaluations of renal function.

Asymptomatic Brain Edema after Hemodialysis Initiation in a Patient with Severe Uremia

A 66-year-old man with severe renal insufficiency presented with mild confusion associated with uremia. Cranial magnetic resonance imaging (MRI) showed no remarkable changes. The patient was placed on short-duration hemodialysis (2 hours) with smaller surface area and low blood flow (100 mL/min) to avoid dialysis disequilibrium syndrome (DDS). His consciousness gradually improved and he did not develop apparent DDS symptoms. However, T2-weighted FLAIR MRI showed increased signal intensities bilaterally in the cortical and subcortical areas of the occipital lobe on day 15. In other words, cranial MRI showed cerebral edema, indicating asymptomatic DDS. On day 29, cranial MRI showed a return to findings on admission. In this case, because the patient did not have apparent DDS symptoms despite MRI changes, we diagnosed asymptomatic cerebral edema. The patient was discharged on regular intermittent HD without any neurological deficits. No further neurological disturbances were noted during 1-year follow-up. MRI findings in ESKD patients without DDS symptoms help to clarify the diagnosis of cerebral edema. In this case, the patient did not have apparent DDS symptoms and was therefore diagnosed with asymptomatic cerebral edema.

Cognitive Impairment in Chronic Kidney Disease: Vascular Milieu and the Potential Therapeutic Role of Exercise

Chronic kidney disease (CKD) is considered a model of accelerated aging. More specifically, CKD leads to reduced physical functioning and increased frailty, increased vascular dysfunction, vascular calcification and arterial stiffness, high levels of systemic inflammation, and oxidative stress, as well as increased cognitive impairment. Increasing evidence suggests that the cognitive impairment associated with CKD may be related to cerebral small vessel disease and overall impairment in white matter integrity. The triad of poor physical function, vascular dysfunction, and cognitive impairment places patients living with CKD at an increased risk for loss of independence, poor health-related quality of life, morbidity, and mortality. The purpose of this review is to discuss the available evidence of cerebrovascular-renal axis and its interconnection with early and accelerated cognitive impairment in patients with CKD and the plausible role of exercise as a therapeutic modality. Understanding the cerebrovascular-renal axis pathophysiological link and its interconnection with physical function is important for clinicians in order to minimize the risk of loss of independence and improve quality of life in patients with CKD.

Intradialytic exercise and postural control in patients with chronic kidney disease undergoing hemodialysis

Abstract Introduction: Exercise promotes physiological improvements that reflect better quality of life and survival among chronic kidney disease patients. However, little is known about the effect of exercise on postural control of hemodialysis patients. Objective: To evaluate the effect of intradialytic aerobic exercise on postural balance in patients on hemodialysis. Methods: a pilot study with seven individuals was conducted at the Hemodialysis Center of Bauru State Hospital. The Berg Balance Scale evaluated balance and postural balance was evaluated by the force platform Advance Mechanical Technology Inc. (AMTI - AccuGait). Trunk mean sway amplitude in the anterior-posterior (AP) and medial-lateral (ML) directions and mean velocity in the AP and ML directions were assessed. Secondary outcomes about functional capacity and body composition (DEXA) were evaluated. The aerobic exercise was performed with a ergometric bicycle during the first two hours of hemodialysis session for 50-60 minutes (BORG >12), three times a week for 12-weeks. Results: Four men and three women, 52.86 ± 11.08 years, participated in the study. There was no difference between pre and post-test of postural balance outcomes. Although the results were not statistically significant, except for the lean body mass and leg lean mass, the presented pilot study suggests improved functional balance and lower limb strength. Conclusion: The 12-weeks of aerobic exercise protocol during hemodialysis despite inducing gains in lean body mass and leg lean mass, was not able to promote improvements in postural control of chronic renal failure patients on hemodialysis.

Transport across the choroid plexus epithelium

The choroid plexus epithelium is a secretory epithelium par excellence. However, this is perhaps not the most prominent reason for the massive interest in this modest-sized tissue residing inside the brain ventricles. Most likely, the dominant reason for extensive studies of the choroid plexus is the identification of this epithelium as the source of the majority of intraventricular cerebrospinal fluid. This finding has direct relevance for studies of diseases and conditions with deranged central fluid volume or ionic balance. While the concept is supported by the vast majority of the literature, the implication of the choroid plexus in secretion of the cerebrospinal fluid was recently challenged once again. Three newer and promising areas of current choroid plexus-related investigations are as follows: 1) the choroid plexus epithelium as the source of mediators necessary for central nervous system development, 2) the choroid plexus as a route for microorganisms and immune cells into the central nervous system, and 3) the choroid plexus as a potential route for drug delivery into the central nervous system, bypassing the blood-brain barrier. Thus, the purpose of this review is to highlight current active areas of research in the choroid plexus physiology and a few matters of continuous controversy.

Evaluation of abrin induced nephrotoxicity by using novel renal injury markers

Abrin is a potent plant toxin analogous to ricin that is derived from the seeds of Abrus precatorius plant. It belongs to the family of type II ribosome-inactivating proteins and causes cell death by irreversibly inactivating ribosomes through site-specific depurination. In this study we examined the in vivo nephrotoxicity potential of abrin toxin in terms of oxidative stress, inflammation, histopathological changes and biomarkers of kidney injury. Animals were exposed to 0.5 and 1.0 LD50 dose of abrin by intraperitoneal route and observed for 1, 3, and 7 day post-toxin exposure. Depletion of reduced glutathione and increased lipid peroxidation levels were observed in abrin treated mice. In addition, abrin also induced inflammation in the kidneys as observed through expression of MMP-9 and MMP-9/NGAL complex in abrin treated groups by using zymography method. Nephrotoxicity was also evaluated by western blot analysis of kidney injury biomarkers including Clusterin, Cystatin C and NGAL, and their results indicate severity of kidney injury in abrin treated groups. Kidney histology confirmed inflammatory changes due to abrin. The data generated in the present study clearly prove the nephrotoxicity potential of abrin.

The immunologic considerations in human head transplantation

The idea of head transplantation appears at first as unrealistic, unethical, and futile. Here we discuss immunological considerations in human head transplantation. In a separate accompanying article we discuss surgical, ethical, and psychosocial issues concerned in body-to-head transplantation (BHT) [1]. The success of such an unusual allograft, where the donor and the recipient can reject each other, depends on prevention of complex immunologic reactions, especially rejection of the head by the body (graft-vs-host) or probably less likely, the possibility of the head rejecting the total body allograft (host-vs-graft). The technical and immunologic difficulties are enormous, especially since rapid nerve and cord connections and regeneration have not yet been possible to achieve. In this article we begin by briefly reviewing neuro-immunologic issues that may favor BHT such as the blood brain barrier (BBB) and point out its shortcomings. And we touch on the cellular and humoral elements in the brain proper that differ in some respects from those in other organs and in the periphery. Based on recent successes in vascular composite allografts (VCAs), we will elaborate on potential specific advantages and difficulties in BHT of various available immunosuppressive medications already utilized in VCAs. The risk/benefit ratio of these drugs will be emphasized in relation to direct brain toxicity such as seizure disorders, interference, or promotion of nerve regeneration, and potentiation of cerebral viral infections. The final portion of this article will focus on pre-transplant immunologic manipulation of the deceased donor body along with pretreatment of the recipient.

Neurologic emergencies in HIV-negative immunosuppressed patients

HIV-negative immunosuppressed patients comprise a heterogeneous group including transplant patients, patients undergoing treatment with immunosuppressors, uremic patients, alcoholics, undernourished patients, diabetics, patients on dialysis, elderly patients, and those diagnosed with severe or neoplastic processes. Epileptic seizures, focal neurologic signs, and meningoencephalitis are neurologic syndromes that require urgent action. In most of these situations, neuroimaging tests are necessary, but the findings can be different from those observed in immunocompetent patients in function of the inflammatory response. Infectious disease is the first diagnostic suspicion, and the identification of an opportunistic pathogen should be oriented in function of the type and degree of immunosuppression. Other neurologic emergencies include ischemic stroke, cerebral hemorrhage, neoplastic processes, and pharmacological neurotoxicity. This article reviews the role of neuroimaging in HIV-negative immunodepressed patients with a neurologic complication that requires urgent management.

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.

Spatial Disassociation of Disrupted Functional Connectivity for the Default Mode Network in Patients with End-Stage Renal Disease

PURPOSE

To investigate the aberrant functional connectivity of the default mode network (DMN) in patients with end-stage renal disease (ESRD) and their clinical relevance.

MATERIALS AND METHODS

Resting-state functional MRI data were collected from 31 patients with ESRD (24 men, 24-61 years) and 31 age- and gender-matched healthy controls (HCs, 21 men, 26-61years). A whole-brain seed-based functional connectivity analysis of these collected R-fMRI data was performed by locating the seeds in the posterior cingulate cortex (PCC) and ventromedial prefrontal cortex (vmPFC) to investigate the functional connectivity of the posterior and anterior DMN over the whole brain, respectively.

RESULTS

Compared to the HCs, the patients exhibited significantly decreased functional connectivity with the PCC in the left middle temporal gyrus, the right anterior cingulate gyrus, and the bilateral medial superior frontal gyrus. For the vmPFC seed, only the right thalamus showed significantly decreased functional connectivity in the patients with ESRD compared to HCs. Interestingly, functional connectivity between the PCC and right medial superior frontal gyrus exhibited a significantly positive correlation with the hemoglobin level in the patients.

CONCLUSION

Our findings suggest a spatially specific disruption of functional connectivity in the DMN in patients with ESRD, thereby providing novel insights into our understanding of the neurophysiology mechanism that underlies the disease.

Brain Microstructural Abnormalities Are Related to Physiological Alterations in End-Stage Renal Disease

PURPOSE

To study whole-brain microstructural alterations in patients with end-stage renal disease (ESRD) and examine the relationship between brain microstructure and physiological indictors in the disease.

MATERIALS AND METHODS

Diffusion tensor imaging data were collected from 35 patients with ESRD (28 men, 18-61 years) and 40 age- and gender-matched healthy controls (HCs, 32 men, 22-58 years). A voxel-wise analysis was then used to identify microstructural alterations over the whole brain in the ESRD patients compared with the HCs. Multiple biochemical measures of renal metabolin, vascular risk factors, general cognitive ability and dialysis duration were correlated with microstructural integrity for the patients.

RESULTS

Compared to the HCs, the ESRD patients exhibited disrupted microstructural integrity in not only white matter (WM) but also gray matter (GM) regions, as characterized by decreased fractional anisotropy (FA) and increased mean diffusivity (MD), axial diffusivity (AD) and radial diffusivity (RD). Further correlation analyses revealed that the in MD, AD and RD values showed significantly positive correlations with the blood urea nitrogen in the left superior temporal gyrus and significantly negative correlations with the calcium levels in the left superior frontal gyrus (orbital part) in the patients.

CONCLUSION

Our findings suggest that ESRD is associated with widespread diffusion abnormalities in both WM and GM regions in the brain, and microstructural integrity of several GM regions are related to biochemical alterations in the disease.

Association between troponin I level and cardiovascular risk factors in asymptomatic hemodialysis patients

Objective:

Patients on hemodialysis (HD) have a high risk for cardiovascular morbidity and mortality. Cardiac troponins are biomarkers for diagnosing acute myocardial injury or infarction. There is considerable controversy that exists in the frequency and significance of cardiac troponins in predicting cardiac injury and ischemia in HD patients.

Methods:

In this cross-sectional study, all HD patients more than 18-year-old, who were at least 3 months under HD, and had no sign and symptom of active cardiovascular disease (CVD), in two HD centers were enrolled. One hundred and one patients fulfilled the inclusion criteria. Blood sample for cardiac troponin I (cTnI) was drown before the initiation of HD session during their routine monthly blood testing from patients’ vascular access arterial line. cTnI levels were measured by a high-sensitivity assay, VIDAS troponin I Ultra kit, and correlated with patients’ demographic, clinical, and laboratory results.

Findings:

The patients’ different demographic and clinical characteristics had no statistically significant correlation with troponin levels except for marginal trend for past medical history of diabetes and hyperlipidemia with corresponding P values of 0.072 and 0.055. Twenty-six patients had cTnI level more than 0.01 ΅g/L and only two patients had cTnI level more than 0.11 ΅g/L. For laboratory results, only fasting blood sugar had statistically significant correlation with patients’ cTnI level (r = 0.357, P = 0.0001).

Conclusion:

Frequency of significant elevation of cTnI level in our asymptomatic HD patients was very low and if such elevation is found in this population, it may be considered as a sign of active CVD.