One step forward in the early detection of acute renal failure

Past, present, and future biomarkers of kidney function and injury: The relationship with antibiotics

Routinely used kidney biomarkers of injury and function such as serum creatinine and urine albumin to creatinine ratio, are neither sensitive nor specific. Future biomarkers are being developed for clinical use and have already been included in guidance from groups such as the U.S. Food and Drug Administration and the Predictive Safety Testing Consortium. These biomarkers have important implications for early identification of kidney injury and more accurate measurement of kidney function. Many antibiotics are either eliminated by the kidney or can cause clinically significant nephrotoxicity. As a result, clinicians should be familiar with new biomarkers of kidney function and injury, their place in clinical practice, and applications for antibiotic dosing.

Acute kidney injury in the acute care surgery patient: What you need to know

ABSTRACT

Acute kidney injury is associated with poor outcomes in the trauma and emergency general surgery population, and recent consensus definitions have allowed for significant advances in defining the burden of disease. The current definitions rely on overall functional measures (i.e., serum creatinine and urine output), which can be confounded by a variety of clinical factors. Biomarkers are increasingly being investigated as more direct diagnostic assays for the diagnosis of acute kidney injury and may allow earlier detection and more timely therapeutic intervention. Etiologies fall into two general categories: disorders of renal perfusion and exposure to nephrotoxic agents. Therapy is largely supportive, and prevention offers the best chance to decrease clinical impact.

Substantial Downregulation of Mitochondrial and Peroxisomal Proteins during Acute Kidney Injury revealed by Data-Independent Acquisition Proteomics

Acute kidney injury (AKI) manifests as a major health concern, particularly for the elderly. Understanding AKI-related proteome changes is critical for prevention and development of novel therapeutics to recover kidney function and to mitigate the susceptibility for recurrent AKI or development of chronic kidney disease. In this study, mouse kidneys were subjected to ischemia-reperfusion injury, and the contralateral kidneys remained uninjured to enable comparison and assess injury-induced changes in the kidney proteome. A fast-acquisition rate ZenoTOF 7600 mass spectrometer was introduced for data-independent acquisition (DIA) for comprehensive protein identification and quantification. Short microflow gradients and the generation of a deep kidney-specific spectral library allowed for high-throughput, comprehensive protein quantification. Upon AKI, the kidney proteome was completely remodeled, and over half of the 3,945 quantified protein groups changed significantly. Downregulated proteins in the injured kidney were involved in energy production, including numerous peroxisomal matrix proteins that function in fatty acid oxidation, such as ACOX1, CAT, EHHADH, ACOT4, ACOT8, and Scp2. Injured mice exhibited severely declined health. The comprehensive and sensitive kidney-specific DIA assays highlighted here feature high-throughput analytical capabilities to achieve deep coverage of the kidney proteome and will serve as useful tools for developing novel therapeutics to remediate kidney function.

Urinay neutrophil gelatinase-associated lipocalin as a biomarker in different renal problems

Background/aim

Neutrophil gelatinase-associated lipocalin (NGAL) is used previously to estimate the etiology, severity, and clinical outcomes of acute kidney injury (AKI). However, the role of urinary NGAL (uNGAL) in the postrenal setting is not clear. In our study, we aimed to discover the cut-off value of uNGAL that can be used in the differential diagnosis of underlying AKI etiologies.

Materials and methods

In this prospective cross-sectional study, we examined 82 subjects in four groups: patients that had (1) postrenal AKI; (2) AKI other than postrenal etiologies; (3) stable chronic kidney disease; and (4) healthy subjects. A renal function assessment was carried out by measuring serum creatinine (sCr) and uNGAL at the time of diagnosis [0th min (T0)]. We followed the study group for three months.

Results

At the time of diagnosis, sCr (T0) was highest in the postrenal AKI and AKI groups in contrast to stable chronic kidney disease patients and healthy subjects (P < 0.001), as expected. T0 median uNGAL was highest in the postrenal group (P < 0.001). Area under curve (AUC) of uNGAL to estimate postrenal AKI presence was 0.957 (95% CI, 0.897–1.000; P < 0.001). The cut-off point of uNGAL was 42.625 ng/mL for this estimation.

Conclusion

Patients with AKI must be classified according to the underlying etiologies as soon as possible. uNGAL may be useful to estimate the etiologies, and whether the problem is acute or chronic in the course. In postrenal kidney problems, to plan the urgency of the urologic procedures, it is crucial.

Prognostic Value of Urinary Neutrophil Gelatinase-Associated Lipocalin on the First Day of Admission for Adverse Events in Patients With Acute Decompensated Heart Failure

BACKGROUND

Urinary neutrophil gelatinase-associated lipocalin (U-NGAL) is an early predictor of acute kidney injury and adverse events in various diseases; however, in acute decompensated heart failure patients, its significance remains poorly understood. This study aimed to investigate the prognostic value of U-NGAL on the first day of admission for the occurrence of acute kidney injury and long-term outcomes in acute decompensated heart failure patients.

METHODS AND RESULTS

We studied 260 acute decompensated heart failure patients admitted to our department between 2011 and 2014 by measuring U-NGAL in 24-hour urine samples collected on the first day of admission. Primary end points were all-cause death, cardiovascular death, and heart failure admission. Patients were divided into 2 groups according to their median U-NGAL levels (32.5 μg/gCr). The high-U-NGAL group had a significantly higher occurrence of acute kidney injury during hospitalization than the low-U-NGAL group (P=0.0012). Kaplan-Meier analysis revealed that the high-U-NGAL group exhibited a worse prognosis than the low-U-NGAL group in all-cause death (hazard ratio 2.07; 95%CI 1.38-3.12, P=0.0004), cardiovascular death (hazard ratio 2.29; 95%CI 1.28-4.24, P=0.0052), and heart failure admission (hazard ratio 1.77; 95%CI 1.13-2.77, P=0.0119). The addition of U-NGAL to the estimated glomerular filtration rate significantly improved the predictive accuracy of all-cause mortality (P=0.0083).

CONCLUSIONS

In acute decompensated heart failure patients, an elevated U-NGAL level on the first day of admission was related to the development of clinical acute kidney injury and independently associated with poor prognosis.

Changes in Urinary and Serum Levels of Novel Biomarkers after Administration of Gadolinium-based Contrast Agents

OBJECTIVE

The aim of our study is to describe the changes in urinary and serum levels of novel biomarkers after gadolinium contrast administration in patients with normal renal function.

METHODS

We measured four biomarkers in 28 volunteers: interleukin-18 (IL-18), N-acetyl-glucosaminidase (NAG), neutrophil gelatinase-associated lipocalin, and cystatin C. Urinary and serum samples were collected at 0, 3, and 24 hours following gadolinium administration.

RESULTS

Baseline serum creatinine was 57.8 ± 34.5 µmol/L and remained stable. Urinary IL-18 levels increased significantly at three hours (10.7 vs. 7.3 ng/mg creatinine; P < 0.05). Similarly, urinary NAG levels increased significantly at three hours (3.9 vs. 2.2 IU/mg creatinine; P < 0.001). For both these markers, the difference was no longer significant at 24 hours. No statistically significant differences were observed for urinary and serum neutrophil gelatinase-associated lipocalin levels and for serum cystatin C levels.

CONCLUSIONS

Urinary IL-18 and NAG levels increased transiently after administration of gadolinium-based contrast agents in patients with normal renal function.

Importance of neutrophil gelatinase-associated lipocalin in differential diagnosis of acute and chronic renal failure

Background:

Neutrophil Gelatinase-associated Lipocalin (NGAL) protein is easily detected in the blood and urine soon after acute renal injury. NGAL gains features of an early, sensitive and noninvasive biomarker for acute renal injury. Recent evidences suggest that its expression is also increased in CRF reflecting the severity of disease.

Objectives:

In the present study, we aimed to investigate whether blood NGAL level plays a role in the differential diagnosis of acute and chronic renal failure.

Patients and Methods:

This was a prospective case-control study. Fifty patients presented to emergency department with acute renal failure (ARF), 30 with chronic renal failure (CRF) and 20 healthy individuals as control group were included in this study. Blood pH, HCO3^-, BUN, creatinine and potassium values were evaluated in all patients. Blood NGAL values were evaluated in all groups. BUN, serum creatinine and NGAL values were statistically compared between patients and controls.

Results:

Median NGAL levels in patients was 304.50 (29), and 60 (0) in control, which was statistically significant between the two groups (Z = -6.477, P < 0.001). The median NGAL values were 261.50 ± 291 in ARF group and 428.50 ± 294 in CRF group. There was a significant difference in NGAL level between ARF and CRF groups (Z = -2.52, P = 0.012). Median BUN values were 153.46 ± 82.47 in ARF group and 169.40 ± 93.94 in CRF group. There was no significant difference in BUN value between ARF and CRF groups (P > 0.05). Median creatinine values were 2.84 ± 2.95 in ARF group and 4.78 ± 4.32 in CRF group. In serum creatinine values, a significant difference was found between ARF and CRF groups (P < 0.05).

Conclusions:

Serum NGAL levels of ARF and CRF patients were significantly higher than healthy individuals. In addition, NGAL values of patients with CRF were significantly higher than those of ARF. Serum NGAL values can be used to detect renal injury and differentiate ARF and CRF.

Severity of acute kidney injury and two-year outcomes in critically ill patients

BACKGROUND

The association between levels of acute kidney injury (AKI) during ICU admission and long-term mortality are not well defined.

METHODS

We examined medical records of adult patients admitted to a large tertiary medical center with no history of end-stage renal disease who survived 60 days from ICU admission between 2001 and 2007. Demographic, clinical, physiologic, and date of death data were extracted.

RESULTS

Among 15,048 patients, 12,399 (82.4%) survived 60 days from ICU admission and comprised the study population. AKI did not develop in 5,663 (45.7%) during ICU admission, whereas progressively severe levels of AKI as defined by Acute Kidney Injury Network (AKIN) criteria AKIN 1, AKIN 2, and AKIN 3 developed in 4,589 (37.0%), 1,613 (13.0%), and 534 (4.3%), respectively. Only 42.5% of patients with AKIN 3 survived 2 years from ICU admission. Patients with AKIN 3 had a 61% higher mortality risk 2 years from ICU discharge compared with patients in whom AKI did not develop. Patients with AKIN 1 and AKIN 2 had similar increased mortality risk 2 years from ICU admission (hazard ratio, 1.26 and 1.28, respectively). The level of estimated glomerular filtration rate on ICU discharge and chronic kidney disease were associated with long-term mortality.

CONCLUSIONS

Patients in whom AKI develops during ICU admission have significantly increased risks of death that extend beyond their high ICU mortality rates. These increased risks of death continue for at least 2 years after the index ICU admission.

New biomarkers of acute kidney injury and the cardio-renal syndrome

Changes in renal function are one of the most common manifestations of severe illness. There is a clinical need to intervene early with proven treatments in patients with potentially deleterious changes in renal function. Unfortunately progress has been hindered by poor definitions of renal dysfunction and a lack of early biomarkers of renal injury. In recent years, the definitional problem has been addressed with the establishment of a new well-defined diagnostic entity, acute kidney injury (AKI), which encompasses the wide spectrum of kidney dysfunction, together with clearer definition and sub-classification of the cardio-renal syndromes. From the laboratory have emerged new biomarkers which allow early detection of AKI, including neutrophil gelatinase-associated lipocalin (NGAL) and cystatin C. This review describes the new concepts of AKI and the cardio-renal syndromes as well as novel biomarkers which allow early detection of AKI. Panels of AKI biomarker tests are likely to revolutionise the diagnosis and management of critically ill patients in the coming years. Earlier diagnosis and intervention should significantly reduce the morbidity and mortality associated with acute kidney damage.

Iron behaving badly: inappropriate iron chelation as a major contributor to the aetiology of vascular and other progressive inflammatory and degenerative diseases

BACKGROUND

The production of peroxide and superoxide is an inevitable consequence of aerobic metabolism, and while these particular 'reactive oxygen species' (ROSs) can exhibit a number of biological effects, they are not of themselves excessively reactive and thus they are not especially damaging at physiological concentrations. However, their reactions with poorly liganded iron species can lead to the catalytic production of the very reactive and dangerous hydroxyl radical, which is exceptionally damaging, and a major cause of chronic inflammation.

REVIEW

We review the considerable and wide-ranging evidence for the involvement of this combination of (su)peroxide and poorly liganded iron in a large number of physiological and indeed pathological processes and inflammatory disorders, especially those involving the progressive degradation of cellular and organismal performance. These diseases share a great many similarities and thus might be considered to have a common cause (i.e. iron-catalysed free radical and especially hydroxyl radical generation).The studies reviewed include those focused on a series of cardiovascular, metabolic and neurological diseases, where iron can be found at the sites of plaques and lesions, as well as studies showing the significance of iron to aging and longevity. The effective chelation of iron by natural or synthetic ligands is thus of major physiological (and potentially therapeutic) importance. As systems properties, we need to recognise that physiological observables have multiple molecular causes, and studying them in isolation leads to inconsistent patterns of apparent causality when it is the simultaneous combination of multiple factors that is responsible.This explains, for instance, the decidedly mixed effects of antioxidants that have been observed, since in some circumstances (especially the presence of poorly liganded iron) molecules that are nominally antioxidants can actually act as pro-oxidants. The reduction of redox stress thus requires suitable levels of both antioxidants and effective iron chelators. Some polyphenolic antioxidants may serve both roles.Understanding the exact speciation and liganding of iron in all its states is thus crucial to separating its various pro- and anti-inflammatory activities. Redox stress, innate immunity and pro- (and some anti-)inflammatory cytokines are linked in particular via signalling pathways involving NF-kappaB and p38, with the oxidative roles of iron here seemingly involved upstream of the IkappaB kinase (IKK) reaction. In a number of cases it is possible to identify mechanisms by which ROSs and poorly liganded iron act synergistically and autocatalytically, leading to 'runaway' reactions that are hard to control unless one tackles multiple sites of action simultaneously. Some molecules such as statins and erythropoietin, not traditionally associated with anti-inflammatory activity, do indeed have 'pleiotropic' anti-inflammatory effects that may be of benefit here.

CONCLUSION

Overall we argue, by synthesising a widely dispersed literature, that the role of poorly liganded iron has been rather underappreciated in the past, and that in combination with peroxide and superoxide its activity underpins the behaviour of a great many physiological processes that degrade over time. Understanding these requires an integrative, systems-level approach that may lead to novel therapeutic targets.

Plasma neutrophil gelatinase-associated lipocalin predicts acute kidney injury, morbidity and mortality after pediatric cardiac surgery: a prospective uncontrolled cohort study

Introduction

Acute kidney injury (AKI) is a frequent complication of cardiopulmonary bypass (CPB). The lack of early biomarkers has impaired our ability to intervene in a timely manner. We previously showed in a small cohort of patients that plasma neutrophil gelatinase-associated lipocalin (NGAL), measured using a research enzyme-linked immunosorbent assay, is an early predictive biomarker of AKI after CPB. In this study we tested whether a point-of-care NGAL device can predict AKI after CPB in a larger cohort.

Methods

First, in a cross-sectional pilot study including 40 plasma samples (NGAL range 60 to 730 ng/ml) and 12 calibration standards (NGAL range 0 to 1,925 ng/ml), NGAL measurements by enzyme-linked immunosorbent assay and by Triage^® NGAL Device (Biosite Inc., San Diego, CA, USA) were highly correlated (r = 0.94). Second, in a subsequent prospective uncontrolled cohort study, 120 children undergoing CPB were enrolled. Plasma was collected at baseline and at frequent intervals for 24 hours after CPB, and analyzed for NGAL using the Triage^® NGAL device. The primary outcome was AKI, which was defined as a 50% or greater increase in serum creatinine.

Results

AKI developed in 45 patients (37%), but the diagnosis using serum creatinine was delayed by 2 to 3 days after CPB. In contrast, mean plasma NGAL levels increased threefold within 2 hours of CPB and remained significantly elevated for the duration of the study. By multivariate analysis, plasma NGAL at 2 hours after CPB was the most powerful independent predictor of AKI (β = 0.004, P < 0.0001). For the 2-hour plasma NGAL measurement, the area under the curve was 0.96, sensitivity was 0.84, and specificity was 0.94 for prediction of AKI using a cut-off value of 150 ng/ml. The 2 hour postoperative plasma NGAL levels strongly correlated with change in creatinine (r = 0.46, P < 0.001), duration of AKI (r = 0.57, P < 0.001), and length of hospital stay (r = 0.44, P < 0.001). The 12-hour plasma NGAL strongly correlated with mortality (r = 0.48, P = 0.004) and all measures of morbidity mentioned above.

Conclusion

Accurate measurements of plasma NGAL are obtained using the point-of-care Triage^® NGAL device. Plasma NGAL is an early predictive biomarker of AKI, morbidity, and mortality after pediatric CPB.

CRITICAL CARE ISSUES FOR THE NEPHROLOGIST: The Epidemiology and Outcome of Acute Renal Failure and the Impact on Chronic Kidney Disease

Acute renal failure (ARF) is a common condition, especially among the critically ill, and confers a high mortality. Recent publications have highlighted changes in the epidemiology and improvement in mortality that was long thought to be static despite improvements in clinical care. The incidence of ARF is increasing. Efforts, such as the Acute Dialysis Quality Initiative, are being undertaken to establish a consensus definition of ARF, and to distinguish between varying degrees of acute kidney injury. Data are emerging to allow comparison of the epidemiology of ARF across institutions internationally. There is ongoing recognition of the important interaction between ARF and chronic kidney disease. Two brief case reports are offered to help frame the context and clinical impact of this disorder, followed by a review of some of the recent literature that addresses these points.