The changing epidemiology of acute renal failure

Hydrogen-rich saline solution attenuates renal ischemia-reperfusion injury

PURPOSE

Renal ischemia-reperfusion (I/R), an important cause of acute kidney injury, is unavoidable during various types of operations, including renal transplantation, surgical revascularization of the renal artery, partial nephrectomy, and treatment of suprarenal aortic aneurysms. Exacerbation of I/R injury is mediated by reactive oxygen species (ROS). A recent study has shown that hydrogen has antioxidant properties. In this study, we tested the hypothesis that a hydrogen-rich saline solution (HRSS) attenuates renal I/R injury in a rodent model.

METHODS

Rats were treated with an intravenous injection of HRSS or control saline solution followed by renal I/R. After 24 h of treatment, we performed a histological examination and transmission electron microscopy, and measured serum levels of 8-OHdG.

RESULTS

Histological analysis revealed a marked reduction of interstitial congestion, edema, inflammation, and hemorrhage in renal tissue harvested 24 h after HRSS treatment compared to saline administration. Renal I/R injury, which led to altered mitochondrial morphology, was also inhibited by HRSS. Furthermore, serum 8-OHdG levels were significantly lower in rats treated with HRSS and subjected to renal I/R.

CONCLUSIONS

These protective effects were likely due to the antioxidant properties of HRSS. These results suggest that HRSS is a potential therapeutic candidate for treating various I/R diseases.

Acute kidney injury in the elderly: problems and prospects

Acute kidney injury (AKI) usually is defined as a decline in glomerular filtration rate over hours to days that can occur either in a person with previously normal kidney function, or in the setting of pre-existing chronic kidney disease. The incidence of AKI has increased steadily in recent years, and this increase is associated strongly with advancing age in the population because epidemiologic data indicate that AKI is much more common in the elderly. In the aging population there is heightened susceptibility to drug toxicity, partially owing to altered drug pharmacokinetics and pharmacodynamics. Furthermore, the elderly consume twice as many medications overall, including nephrotoxic agents, compared with younger patients. The vasodilatory increase in the renal plasma flow and glomerular filtration rate that constitutes renal functional reserve is reduced markedly in healthy elderly individuals, compromising renal adaptation after acute ischemia, and heightening susceptibility to AKI. Age-related alterations in renal tubular function also may heighten susceptibility to AKI because renal sodium conservation in response to dietary sodium restriction is attenuated in the elderly. A recently published study showed that elderly subjects with AKI, particularly those with chronic kidney disease, are more likely to develop end-stage renal disease. The increasing prevalence and extended clinical consequences of AKI in the elderly are of great concern from a clinical and public health perspective.

Rapid detection of acute kidney injury by plasma cystatin C in the intensive care unit

BACKGROUND

Plasma cystatin C (pCysC) has been proposed as an alternative to plasma creatinine (pCr) as a measure of renal function. We compared the detection of functional change by both biomarkers in critically ill patients.

METHODS

pCysC and pCr were measured on admission to one of two intensive care units (ICU) and then daily over 7 days. Patients were classified according to the analyte that first increased by either ≥25 or ≥50% above the admission value. The proportion of patients in each class was compared using McNemar's chi-square test. Sustained acute kidney injury (AKI, a ≥50% increase in pCr from baseline for ≥24 h), dialysis and death within 30 days were recorded. The ability of pCysC and pCr on admission to predict sustained AKI, dialysis or death was assessed from the area under the receiver operator characteristic curve (AUC).

RESULTS

Of 442 patients, 83 had a ≥50% increase in one analyte, 17 in both and 342 in neither. Comparable numbers for a ≥25% increase were 163 in one analyte, 45 in both and 234 in neither. pCysC increased prior to pCr more frequently than vice versa in both the cohort with a ≥50% increase (P < 0.0001) and with a ≥25% increase (P < 0.0001). pCysC predicted sustained AKI with an AUC of 0.80 [95% confidence interval (CI) = 0.71-0.88]. pCysC and pCr were similarly moderately predictive of death or dialysis with AUCs of 0.61 [95% CI = 0.53-0.68] and 0.60 [95% CI = 0.51-0.67], respectively.

CONCLUSION

pCysC was an effective and earlier surrogate marker of decreased renal function than pCr in a general ICU population.

Decreased cytochrome c mediates an age-related decline of oxidative phosphorylation in rat kidney mitochondria

Kidney function declines with advancing age and mitochondria have been implicated. In the present study we have examined the integrated function of mitochondria isolated from kidneys of 6- and 24-month-old Fischer 344 rats. OXPHOS (oxidative phosphorylation) of intact mitochondria and cytochrome c oxidase activity in permeabilized mitochondria were determined with polarographic assays. The activities of the ETC (electron transport chain) complexes and the cytochrome content in solubilized mitochondria were measured using spectrophotometric methods. The respiratory complexes were evaluated with blue native gel electrophoresis. Mitochondrial preparations were evaluated by immunoblotting for cytochrome c, Smac/Diablo and VDAC (voltage-dependent anion channel). Mitochondrial morphology was examined by electron microscopy. OXPHOS of mitochondria isolated from 24-month-old animals was decreased 15-25% with complexes I, II, III and IV, and fatty acid substrates. The electron microscopic appearance of mitochondria, the activity of the ETC complexes and the protein abundance of individual complexes and supercomplexes were unchanged. The content of cytochrome c was decreased by 37% in aged mitochondria, as determined by spectrophotometric methods and confirmed with immunoblotting. Polarographic determination of cytochrome c oxidase activity with endogenous cytochrome c demonstrated a 23% reduction in aged mitochondria, which was corrected with the addition of exogenous cytochrome c. Renal mitochondrial OXPHOS decreased with aging in the Fischer 344 rat. Decreased mitochondrial cytochrome c content is a major factor contributing to the OXPHOS defect of mitochondria isolated from kidneys of elderly animals.

Interaction of oxidative stress, nitric oxide and peroxisome proliferator activated receptor gamma in acute renal failure

Oxidative stress has been reported to play a critical role in the pathology of acute renal failure (ARF). An interaction between different reactive species and/or their sources have been the focus of extensive studies. The exact sources of reactive species generated in biological systems under different disease states are always elusive because they are also a part of physiological processes. Exaggerated involvement of different oxidation pathways including NAD(P)H oxidase has been proposed in different models of ARF. An interaction between oxygen species and nitrogen species has drawn extensive attention because of the deleterious effects of peroxynitrite and their possible effects on antioxidant systems. Recent advances in molecular biology have allowed us to understand glomerular function more precisely, especially the organization and importance of the slit diaphragm. Identification of slit diaphragm proteins came as a breakthrough and a possibility of therapeutic manipulation in ARF is encouraging. Transcriptional regulation of the expression of slit diaphragm protein is of particular importance because their presence is crucial in the maintenance of glomerular function. This review highlights the involvement of oxidative stress in ARF, sources of these reactive species, a possible interaction between different reactive species, and involvement of PPARgamma, a nuclear transcription factor in this process.

ETS-GS, a new antioxidant, ameliorates renal ischemia-reperfusion injury in a rodent model

BACKGROUND

Ischemia-reperfusion (I/R) contributes to acute kidney injury (AKI). On the other hand, anti-oxidative drugs help to prevent renal injury caused by I/R. The current study examined whether a new antioxidant, ETS-GS, inhibits reactive oxygen species (ROS) generation and thereby prevents renal I/R injury in rodent models.

METHODS

Rats with experimentally-induced renal I/R injury were treated concurrently with an intravenous injection of either ETS-GS or saline. Anesthesia was induced with sevoflurane.

RESULTS

Histologic examination revealed marked reduction of interstitial congestion, edema, inflammation, and hemorrhage in kidney tissue harvested 24 h after ETS-GS treatment. Renal I/R-induced secretion of nitric oxide (NO) in serum was inhibited by ETS-GS treatment. Furthermore, malondialdehyde (MDA) levels in the kidney were significantly lower in ETS-GS-treated rats with renal I/R. Moreover, when murine macrophage-like RAW264.7 cells were stimulated with antimycin A in the presence or absence of simultaneous ETS-GS treatment, ETS-GS decreased ROS levels.

CONCLUSIONS

Thus, ETS-GS lowered ROS levels in cultured cells, reduced serum NO levels, decreased renal MDA levels, and protected rats against I/R-induced kidney injury. Given these in vitro and in vivo findings, ETS-GS is a strong candidate for future exploration of therapeutic potential in various human I/R diseases.

Mediators of inflammation in acute kidney injury

Acute kidney injury (AKI) remains to be an independent risk factor for mortality and morbidity. Inflammation is now believed to play a major role in the pathopathophysiology of AKI. It is hypothesized that in ischemia, sepsis and nephrotoxic models that the initial insult results in morphological and/or functional changes in vascular endothelial cells and/or in tubular epithelium. Then, leukocytes including neutrophils, macrophages, natural killer cells, and lymphocytes infiltrate into the injured kidneys. The injury induces the generation of inflammatory mediators like cytokines and chemokines by tubular and endothelial cells which contribute to the recruiting of leukocytes into the kidneys. Thus, inflammation has an important role in the initiation and extension phases of AKI. This review will focus on the mediators of inflammation contributing to the pathogenesis of AKI.

HIV and kidney disease in sub-Saharan Africa

A wide clinical spectrum of renal diseases affects individuals with HIV. These conditions include acute kidney injury, electrolyte and acid-base disturbances, HIV-associated glomerular disease, acute-on-chronic renal disease and adverse side effects related to treatment of HIV. Studies employing varying criteria for diagnosis of kidney disease have reported a variable prevalence of these diseases in patients with HIV in sub-Saharan Africa: 6% in South Africa, 38% in Nigeria, 26% in Côte d'Ivoire, 28% in Tanzania, 25% in Kenya, 20-48.5% in Uganda and 33.5% in Zambia. Results from these studies also suggest that a broader spectrum of histopathological lesions in HIV-associated kidney disease exists in African populations than previously thought. Strategies to prevent or retard progression to end-stage renal disease of HIV-associated kidney conditions should include urinalysis and measurement of kidney function of all people with HIV at presentation. Renal replacement in the form of dialysis and transplantation should be implemented as appropriate. This Review focuses on the available evidence of renal diseases in patients with HIV infection in sub-Saharan Africa and offers practical guidelines to treat these conditions that also take into consideration challenges and obstacles that are specific to sub-Saharan Africa.

Outcome definitions in non-dialysis intervention and prevention trials in acute kidney injury (AKI)

BACKGROUND

The risk, injury, failure, loss-of-function, end-stage-renal-failure (RIFLE) and acute kidney injury network (AKIN) consensus definitions of acute kidney injury (AKI) were established in part to facilitate comparison of trials. Contrast-induced nephropathy (CIN) has traditionally used a less demanding definition.

OBJECTIVES

To review use of RIFLE and AKIN as AKI trial outcome variables and contrast these with outcomes for CIN.

METHODS

We conducted a search of PubMed from 1 January 2005 to 31 December 2008 and 9 trial registries for randomized control trials for preventional or interventional treatment of AKI and CIN.

RESULTS

RIFLE or AKIN were outcome variables in 36% (n = 8) of the published (n = 22) and 18% (n = 4) of the current (n = 22) AKI trials. RIFLE was used to triage to intervention in three trials. The urine output definition of RIFLE and AKIN was an outcome in only two trials. In 18% (n = 8) of AKI trials, the CIN definition (increase in serum creatinine of > or =25% and/or > or =44 micromol/l) was the primary outcome. This was also the primary outcome in 56% (n = 13) of published (n = 12) and current (n = 11) CIN trials. Three published CIN trials used RIFLE or AKIN as an outcome (13%). The duration over which outcomes were determined varied from 24 h to 7 days.

CONCLUSIONS

Considerable heterogeneity remains in outcome variables of AKI and CIN clinical trials. Even when the RIFLE or AKIN criteria were used, they were not applied consistently. There is a need for further consensus on surrogate outcome variables.

Acute renal failure in the State of Qatar: presentation and outcome

Despite major improvements in health care, acute renal failure is still one of the main prognostic factors in terms of patient mortality and long-term morbidity. This cohort prospective study to evaluate the patterns and outcomes of renal failure in Qatar was performed between January and June 2005. Of the 213 patients followed prospectively from referral to the end of their hospitalization, 66.7% were males and 33.3% females. Their overall mean age was 60 years; the majority were referred from critical care units. Comorbidity was present in 87% of all patients. Volume depletion, hypotension, and sepsis were the main predisposing factors for renal failure. Eighty three patients (39%) needed renal replacement treatment and 130 (61%) were treated conservatively. The majority of critical care patients needed dialysis. Overall mortality was 23.9%, 7% needed chronic dialysis, and 69.1% were discharged with normal or mild renal impairment. This study showed that acute renal failure was a major factor affecting patient mortality in Qatar. Early treatment of predisposing factors may improve overall patient outcomes.

Evaluation of trial outcomes in acute kidney injury by creatinine modeling

BACKGROUND AND OBJECTIVES

Clinical trials of acute kidney injury (AKI) use changes in creatinine as outcome metrics. This study investigated how outcome metrics and baseline creatinine affect trial outcome.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A one-compartment pharmacokinetic model of creatinine change resulting from a decrease in GFR was applied to a population of 10,000 simulated virtual inpatients. Treatment was simulated as an amelioration of GFR decrease by a specified percentage, the treatment efficacy, in 50%. Three categorical and two continuous outcome metrics were calculated and compared. Outcomes were compared for measured and estimated baseline creatinine levels that were back-calculated assuming a GFR of 100 or 75 ml/min.

RESULTS

The continuous metrics, the average value of creatinine and the average value of creatinine relative to baseline decreased approximately linearly with increase in treatment efficacy. The categorical metrics displayed a sigmoidal decrease and erroneously suggested perfect treatment when GFR decrease was ameliorated by only 60 to 80%. Using an estimate of baseline creatinine increased the number of patients who were classified as having AKI.

CONCLUSIONS

When used to determine clinical trial outcome, continuous metrics correctly detected the extent of intervention. At low treatment efficacy, categorical metrics underestimated and at high treatment efficacy overestimated the effect of treatment. These effects were exaggerated when the population contained a high proportion of patients with more severe AKI. An estimated baseline creatinine level will overestimate AKI prevalence compared with a measured baseline value. Clinical trials of AKI should use a continuous outcome metric and a measured baseline and report baseline median and interquartile range.

Searching for genes that matter in acute kidney injury: a systematic review

BACKGROUND AND OBJECTIVES

Identifying patients who may develop acute kidney injury (AKI) remains challenging, as clinical determinants explain only a portion of individual risk. Another factor that likely affects risk is intrinsic genetic variability. Therefore, a systematic review of studies was performed that related the development or prognosis of AKI to genetic variation.

DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENTS

MEDLINE, EMBASE, HuGEnet, SCOPUS, and Web of Science were searched for articles from 1950 to Dec 2007. Two independent researchers screened articles using predetermined criteria. Studies were assessed for methodological quality via an aggregate scoring system.

RESULTS

The 16 included studies were of cohort or case-cohort design and investigated 35 polymorphisms in 21 genes in association with AKI. Fifteen gene-gene interactions were also investigated in four separate studies. Study populations were primarily premature infants or adults who were critically ill or postcardiac bypass patients. Among the studies, five different definitions of AKI were used. Only one polymorphism, APO E e2/e3/e4, had greater than one study showing a significant impact (P < 0.05) on AKI incidence. The mean quality score of 5.8/10 (range four to nine), heterogeneity in the studies, and the dearth of studies precluded additional meta-analysis of the results.

CONCLUSIONS

Current association studies are unable to provide definitive evidence linking genetic variation to AKI. Future success will require a narrow consensus definition of AKI, rigorous epidemiologic techniques, and a shift from a priori hypothesis-driven to genome-wide association studies.

Therapeutic and predictive targets of AKI

Acute kidney injury (AKI) is a very common condition encountered in a hospital setting. AKI is an independent risk factor for in-hospital mortality. In this review, we discuss in detail about the tubular, inflammatory and vascular molecular targets of AKI which may result in therapies to improve mortality and biomarkers for earlier diagnosis of AKI.

Acute renal problems in the critically ill cancer patient

PURPOSE OF REVIEW

This review addresses three major topics relevant for the management of renal problems in the critically ill cancer patient; the assessment of kidney function in patients with cancer, serious water and electrolyte metabolism disturbances and acute kidney injury secondary to hematological and nonhematological malignancies.

RECENT FINDINGS

In all cancer patients, renal function (urinalysis for proteinuria or albuminuria and serum creatinine to estimate glomerular filtration rate) should be tested when they first present, at initiation and change of cancer therapy as well as during follow-up. However, the different proposed formulae for estimation of the glomerular filtration rate should be used with caution. Electrolyte abnormalities associated with the refeeding syndrome are common, yet underappreciated, and occur typically in acutely ill, malnourished hospitalized patients who are administered intravenous or enteral nutrition. Currently available data on acute kidney injury and its consequences suggest that acute kidney injury has the potential to substantially alter the outcome of patients with cancer and jeopardize their chances of receiving optimal cancer treatment and a potential cure.

SUMMARY

The complex management of the numerous renal complications of the critically ill cancer patient needs a multidisciplinary approach in which the nephrologist, intensivist and oncologist all play a pivotal role.

Protective effect of 20-HETE analogues in experimental renal ischemia reperfusion injury

While it is known that the arachidonic acid metabolite 20-hydroxyeicosatetraenoic acid (20-HETE) contributes to ischemic injury in the heart and brain, its role in kidney injury is unclear. Here we determined the effects on ischemia-reperfusion injury of the 20-HETE analogues, 20-hydroxyeicosa-5(Z), 14(Z)-dienoic acid (5,14-20-HEDE), and N-[20-hydroxyeicosa-5(Z),14(Z)-dienoyl]glycine (5,14-20-HEDGE), and of the inhibitor of 20-HETE synthesis N-hydroxy-N-(4-butyl-2 methylphenyl) formamidine (HET0016). Using Sprague-Dawley rats we found that while treatment with the inhibitor exacerbated renal injury, infusion of both 5,14-20-HEDE and 5,14-20-HEDGE significantly attenuated injury when compared to vehicle or inhibitor-treated rats. Medullary blood flow, measured by laser-Doppler flowmetry, decreased to half of the baseline one hour after reperfusion in the control rats, but 5,14-20-HEDGE completely prevented this. Treatment of control animals with 5,14-20-HEDGE increased urine output and sodium excretion without altering their mean arterial pressure or glomerular filtration rate. Our results suggest that 20-HETE analogues protect the kidney from ischemia-reperfusion injury by inhibiting renal tubular sodium transport and preventing the post-ischemic fall in medullary blood flow. Analogues of 20-HETE may be useful in the treatment of acute ischemic kidney injury.

Hyperbaric oxygen treatment improves GFR in rats with ischaemia/reperfusion renal injury: a possible role for the antioxidant/oxidant balance in the ischaemic kidney

BACKGROUND

Ischaemic kidney injury continues to play a dominant role in the pathogenesis of acute renal failure (ARF) in many surgical and medical settings. A major event in the induction of renal injury is related to the generation of oxygen-free radicals. Hyperbaric oxygen therapy (HBO) is indicated for treatment of many ischaemic events but not for ARF. Therefore, the present study examined the effects of HBO on kidney function and renal haemodynamics in rats with ischaemic ARF.

METHODS

Renal ischaemia was induced by unilateral renal artery clamping (45 min) in rats. Within 24 h following ischaemia, rats were treated twice with HBO of 100% O(2) at 2.5 absolute atmospheres for 90 min each (+HBO). Untreated rats (-HBO) served as a control. Forty-eight hours later, GFR, RBF and endothelial-dependent vasorelaxation were measured. In addition, the immunoreactive staining of 4-hydroxy-2-noneal (4-HNE), a major product of endogenous lipid peroxidation, and superoxide dismutase (SOD) were assessed.

RESULTS

In the -HBO group, GFR was reduced by 94% compared with the untouched normal kidney (ischaemic: 0.06 +/- 0.03 ml/min, normal: 1.02 +/- 0.13 ml). In contrast, in the +HBO group, GFR of the ischaemic kidney (0.36 +/- 0.07 ml/min) was reduced only by 68% compared with the contralateral normal kidney (1.12 +/- 0.12 ml/min). In line with these findings, HBO improved the vasodilatory response to ACh as expressed in enhancement of both total and regional renal blood flow. In addition, HBO reduced the formation of 4-HNE by 33% and 76% and increased SOD by 30% and 70% in the cortex and outer stripe region of the medulla of the ischaemic kidney, respectively.

CONCLUSION

HBO attenuates the decline in GFR following renal ischaemia, and improves endothelial-dependent vasorelaxation, suggesting that treatment with HBO may be beneficial in the setting of ischaemic ARF.

HIV care and the incidence of acute renal failure

BACKGROUND

The clinical epidemiology of acute renal failure (ARF) in human immunodeficiency virus (HIV)-infected patients remains poorly defined.

METHODS

We conducted a retrospective analysis of patients who developed ARF while attending King's College Hospital (London, United Kingdom) during January 1998-December 2005. Serum creatinine level and estimated glomerular filtration rate were used to identify ARF. ARF episodes were classified as early onset if they occurred <3 months after initiation of HIV care and as late onset if they occurred > or =3 months after initiation of HIV care.

RESULTS

During the study period, 130 (5.7%) of 2274 patients developed 144 episodes of ARF. The incidences of early-onset and late-onset ARF were 19.3 episodes per 100 person-years (95% confidence interval [CI], 15.4-24.1 episodes per 100 person-years) and 1.1 episodes per 100 person-years (95% CI, 0.83-1.49 episodes per 100 person-years), respectively (rate ratio, 17.4; P<0.001). In multivariate analysis, nadir CD4 T cell count <100 x 10(9) cells/L (odds ratio [OR], 6.7; 95% CI, 2.5-18.3) and acquired immunodeficiency syndrome (OR, 6.7; 95% CI, 3.4-13.3) were associated with early-onset ARF, whereas injection drug use (OR, 4.8; 95% CI, 1.3-17.7), hepatitis C virus coinfection (OR, 3.4; 95% CI, 1.3-8.6), and nadir CD4 T cell count <100 x 10(9) cells/L (OR, 5.8; 95% CI, 2.5-13.4) were associated with late-onset ARF.

CONCLUSIONS

ARF was common and was associated with advanced immunodeficiency. The incidence of ARF decreased >10-fold in patients who had received HIV care for > or =3 months.

Using proteomics to identify preprocedural risk factors for contrast induced nephropathy

Contrast induced nephropathy (CIN) is the third leading cause of hospital acquired acute kidney injury (AKI). We conducted a cross-sectional study in children undergoing elective cardiac catheterization to determine if there is a distinct preprocedural urinary proteomic profile in subjects who subsequently develop CIN. Of 90 patients enrolled, AKI due to CIN (defined as a 50% or greater increase in serum creatinine) occurred in 10 participants by the 24 h postcontrast time point. Seven patients who did not develop AKI served as age and gender matched controls. SELDI-TOF-MS was performed using Protein Chips with different chromatographic surfaces. A 4480 Da biomarker displayed significantly greater peat intensities on three chromatographic surfaces (p = 0.02-0.001) in control patients at time = 0 with an area under the curve (AUC) of 0.89-0.99. This biomarker was identified as the 41 amino acid (a.a.) variant of human beta-defensin-1. Another biomarker of 4631 Da was found to have a significantly greater peak intensity (p = 0.03) in AKI patients at time = 0, with an AUC of 0.84. Thus, the presence of a 4631 Da peptide, as well as the absence of the 41 a.a. variant of human beta-defensin-1 in the pre-procedural urine, may prove to be useful biomarkers for the early prediction of CIN.

Biomarkers of acute kidney injury

The diagnosis of acute kidney injury (AKI) is usually based on measurements of blood urea nitrogen (BUN) and serum creatinine. BUN and serum creatinine are not very sensitive or specific for the diagnosis of AKI because they are affected by many renal and nonrenal factors that are independent of kidney injury or kidney function. Biomarkers of AKI that are made predominantly by the injured kidney have been discovered in preclinical studies. In clinical studies of patients with AKI, some of these biomarkers (eg, interleukin-18, neutrophil gelatinase-associated lipocalin, and kidney injury molecule-1) have been shown to increase in the urine before the increase in serum creatinine. These early biomarkers of AKI are being tested in different types of AKI and in larger clinical studies. Biomarkers of AKI may also predict long-term kidney outcomes and mortality.

Early detection of acute kidney injury: emerging new biomarkers

Acute kidney injury (AKI) has recently become the preferred term to describe the syndrome of acute renal failure (ARF) with 'failure' or 'ARF' restricted to patients who have AKI and need renal replacement therapy.(1) This allows capture of the broader clinical spectrum of modest reductions in creatinine, which are themselves known to be associated with major increases in both short- and long-term mortality risk.(2-5) It is hoped that this change in nomenclature will facilitate an expansion of our understanding of the underlying pathophysiology and also facilitate definitions of AKI, which allow comparisons among clinical trials of patients with similar duration and severity of illness. This review will cover the need for early detection of AKI and the role of urinary and plasma biomarkers, including enzymuria. The primary message is that use of existing criteria to diagnose AKI, namely elevation of the serum creatinine with or without oliguria, results in identification that is too late to allow successful intervention. New biomarkers are essential to change the dire prognosis of this common condition.

Atypical Plasmodium vivax malaria in a traveler: bilateral hydronephrosis, severe thrombocytopenia, and hypotension

We report a case of Plasmodium vivax infection manifested as severe thrombocytopenia, bilateral hydronephrosis, and hypotension in a returning traveler from a malaria-endemic area in Venezuela. While most of the efforts to prevent malaria in travelers focus on the life-threatening consequences of Plasmodium falciparum malaria, nonimmune travelers who encounter infection with P vivax may also develop serious complications. This case highlights the importance of preventing malaria cases among nonimmune or semi-immune individuals traveling to P vivax-endemic areas.

Delayed recovery of renal regional blood flow in diabetic mice subjected to acute ischemic kidney injury

Ischemic acute kidney injury in experimental diabetes mellitus (DM) is associated with a more severe deterioration in renal function than shown in nondiabetic animals. We evaluated whether the early recovery phase from acute kidney injury is associated with a more prolonged and sustained decrease in renal perfusion in diabetic mice, which could contribute to the impaired recovery of renal function. Perfusion to the renal cortex and medulla was evaluated by laser-Doppler flowmetry in 10- to 12-wk-old anesthetized mice with type 2 DM (db/db), heterozygous mice (db/m), and nondiabetic (control) mice (C57BL/6J). After baseline measurements were obtained, the right renal artery was clampedfor 20 min followed by reperfusion for 60 min. The data demonstrated that, in all three groups studied, the reperfusion phase was characterized by a significant increase in the medullary-to-cortical blood flow ratio. Moreover, during recovery from ischemia, there was a marked prolongation in the time (in min) required to reach peak reperfusion in the cortex (db/db: 20.7 +/- 4.0, db/m: 12.92 +/- 1.9, C57BL/6J: 9.3 +/- 1.3) and the medulla (db/db: 20.8 +/- 3.2, db/m: 12.88 +/- 1.89, C57BL/6J: 11.2 +/- 1.2). Additionally, the slope of the recovery phase was lower in db/db mice (cortex: 61.9 +/- 23.1%/min, medulla: 16.3 +/- 3.6%/min) than in C57BL/6J mice (cortex: 202.2 +/- 41.6%/min, medulla: 42.1 +/- 7.2%/min). Our findings indicate that renal ischemia is associated with a redistribution of blood flow from cortex to medulla, not related to DM. Furthermore, renal ischemia in db/db mice results in a marked impairment in reperfusion of the renal cortex and medulla during the early postischemic period.

Predictors of mortality in acute renal failure in a developing country: a prospective study

Acute renal failure (ARF) occurs in wide range of conditions, making the evaluation of its prognosis a difficult task. Data regarding prognostic factors in ARF in a general population in developing countries are scarce. The objective of the study was to describe predictors of mortality in ARF that are relevant in the developing world. This prospective study was carried out over a one-year period; all hospitalized adults with ARF were included in the study. Predictors of mortality studied included causes of ARF, pre-existing diseases, and severity as well as complications of ARF. Of 33,301 patients admitted during the study period, 294 (0.88%) were either admitted with or developed ARF after hospitalization. Mean age was 43.9 +/- 16.9 (18-86 yrs). Sepsis was the most common cause (63.26%). Pre-existing diseases like cardiovascular disease (CVSD), respiratory system disease (RSD), central nervous system disease (CNSD), hypertension, diabetes mellitus (DM), and malignancy were significantly higher in elderly as compared to younger patients. On univariate analysis sepsis, hypoperfusion as a cause of ARF and hospital-acquired ARF were associated with higher mortality. Pre-existing diseases viz. RSD, CVSD, CNSD, and DM had higher mortality. Among the severity and complications of ARF, oliguria, bleeding and infection during the course of ARF and critical illness were predictors of poor outcome. Age > 60 yrs was associated with significantly higher mortality. However, on multivariate analysis, only critical illness (odds ratio 37.3), age > 60 years (odds ratio of 5.6), and sepsis as cause of ARF (odds ratio of 2.6) were found to be independent predictors of mortality.

The kidney in the critically ill

Acute kidney injury (AKI) is a common and serious complication in the intensive care setting. It seldom occurs in isolation, but is mostly part of a multiple organ dysfunction syndrome. The pathogenesis is frequently multifactorial, with sepsis contributing to 50% of the cases.The development of AKI in critically-ill patients is "bad news": patients with AKI have a high morbidity and mortality. In addition, AKI, even in its mildest from, is not only a marker of illness severity but appears to be independently associated with mortality. Prevention of AKI is therefore a major goal to improve outcome of critically-ill patients. Treatment of established AKI is largely supportive. The optimal modality for renal replacement therapy in critically-ill patients still remains a matter of debate). The majority of survivors recover renal function.

Acute kidney injury: changing lexicography, definitions, and epidemiology

In recent years, there have been numerous advances in understanding the molecular determinants of functional kidney injury after ischemic and/or toxic exposure. However, translation of successful novel therapies designed to attenuate kidney functional injury from animal models to the clinical sphere has had modest results. This lack of translatability is at least in part due to lack of sufficient standardization in definitions and classification of cases of acute kidney injury (AKI), an incomplete understanding of the natural history of human AKI, and a limited understanding of how kidney injury interacts with other organ system failure in the context of systemic metabolic abnormalities. A concerted effort is now being made by nephrologists and intensivists to arrive at standardized terminology and classification of AKI. There have also been dramatic advances in our understanding of the epidemiology and natural history of AKI, particularly in the hospital and intensive care unit setting. Promising strategies are now being developed which may ultimately lead to improved outcomes for patients at risk for or who have developed AKI, which should be readily testable in the coming decade.

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.

Prevention and Treatment of Contrast-Induced Nephropathy

Contrast-induced nephropathy (CIN) is a well-known complication of therapeutic and diagnostic procedures requiring contrast administration and accounts for 10 to 12% of acute renal failure in hospitalized patients. Although the incidence of this complication is relatively low, its consequences can be catastrophic. The development of CIN is associated with increased hospital length of stay, an increased requirement for acute dialysis, and an increased risk of death. Preexisting renal dysfunction, age, diabetes, congestive heart failure, and volume of administered contrast are all associated with a risk of developing CIN. Despite a large number of clinical trials that have evaluated prophylaxis strategies for CIN, only the use of hemofiltration and N-acetylcysteine (NAC) in specific subgroups of patients have been shown to reduce dialysis requirement and mortality in patients undergoing angiographic procedures. In this review we will discuss the epidemiology and the risk factors for CIN and the evidence for commonly employed prophylaxis strategies, and we will provide general recommendations with respect to CIN prevention and management.