Diagnosis and treatment of acute tubular necrosis

Patient selection has a strong impact on cystatin C and Modification of Diet in Renal Disease (MDRD) estimated glomerular filtration rate

OBJECTIVE

Estimation of the glomerular filtration rate (GFR) is essential for the evaluation of patients with kidney disease, and for correct dosage of drugs that are eliminated from the circulation by the kidneys. In most cases GFR is estimated based on serum creatinine and the Modification of Diet in Renal Disease (MDRD) formula. As both cystatin C and creatinine are used for the determination of GFR it is important to investigate if estimated GFR by the two methods differ in various patient groups.

DESIGN AND METHODS

We have compared cystatin C and MDRD estimated GFR calculated from the same request from primary care units (n=488), a cardiology ward (n=826), the cardiointensive care unit (n=1026), two oncology wards (n=919 and 1021), and the neurosurgical intensive care unit (n=1515) in an observational cross-sectional study.

RESULTS

We found better agreement between the two GFR estimates in samples from primary care patients and patients in the cardiology wards, than in samples from oncology wards or the neurosurgical intensive care unit. In the latter settings there was a pronounced difference between the two GFR estimates.

CONCLUSION

The comparisons show that differences in patient selections have a strong impact on the agreement between cystatin C and MDRD estimated glomerular filtration rate.

Technology Insight: biomarker development in acute kidney injury--what can we anticipate?

Early diagnosis has been the 'Achilles heel' of acute kidney injury (AKI) that has prevented successful implementation of treatment strategies. To date, pharmacological intervention has been largely unsuccessful or equivocal, and morbidity and mortality associated with AKI have remained unacceptably high. Despite their well-known limitations, the most widely used biomarkers for the early diagnosis of AKI are serum creatinine, blood urea nitrogen and urine output. Development of new biomarkers is imperative. A variety of methods have been employed to discover new biomarkers of AKI, including transcriptomics, proteomics, gene arrays, lipidomics and imaging technologies. Clinical trials are underway to establish the validity of the biomarkers discovered using these techniques. This Review summarizes the importance of biomarkers of AKI, from their discovery to clinical practice, from the current perspective and that of what to expect in the future. Great strides forward are being made in breaking down important barriers to the successful prevention and treatment of this devastating disorder.

Inhibition of bFGF-receptor type 2 increases kidney damage and suppresses nephrogenic protein expression after ischemic acute renal failure

Recovery from acute renal failure (ARF) requires the replacement of injured cells by new cells that are able to restore tubule epithelial integrity. We have recently described the expression of nephrogenic proteins [Vimentin, neural cell adhesion molecule, basic fibroblast growth factor (bFGF), Pax-2, bone morphogen protein-7, Noggin, Smad 1-5-8, p-Smad, hypoxia-inducible factor-1alpha, vascular endothelial growth factor], in a time frame similar to that observed in kidney development, after ischemic ARF induced in an ischemia-reperfusion (I/R) model. Furthermore, we show that bFGF, a morphogen involved in mesenchyme/epithelial transition in kidney development, induces a reexpression of morphogenic proteins in an earlier time frame and accelerates the recovery process after renal damage. Herein, we confirm that renal morphogenes are modulated by bFGF and hypothesized that a decrease in bFGF receptor 2 (bFGFR2) levels by the use of antisense oligonucleotides diminishes the expression of morphogenes. Male Sprague-Dawley rats submitted to ischemic injury were injected with 112 microg/kg bFGFR2 antisense oligonucleotide (bFGFR2-ASO) followed by reperfusion. Rats were killed, and the expression of nephrogenic proteins and renal marker damage was analyzed by immunohistochemistry and immunoblot. Animals subjected to I/R treated with bFGFR2-ASO showed a significant reduction in morphogen levels (P < 0.05). In addition, we observed an increase in markers of renal damage: macrophages (ED-1) and interstitial alpha-smooth muscle actin. These results confirm that bFGF participates in the recovery process and that treatment with bFGFR2-ASO induces an altered expression of morphogen proteins.

The L1 cell adhesion molecule is a potential biomarker of human distal nephron injury in acute tubular necrosis

The L1 cell adhesion molecule (CD171) is a multidomain membrane glycoprotein of the immunoglobulin superfamily. We evaluated its expression in human acute kidney injury and assessed its use as a tissue and urinary marker of acute tubular injury. Using immunohistochemical studies with antibodies to the extracellular or cytoplasmic domains, we compared L1 expression in normal kidneys in 24 biopsies taken from patients with acute tubular necrosis. L1 was found at the basolateral and the lateral membrane in all epithelial cells of the collecting duct in the normal kidney except for intercalated cells. In acute tubular necrosis, L1 lost its polarized distribution being found in both the basolateral and apical domains of the collecting duct. Further, it was induced in thick ascending limb and distal tubule cells. Apically expressed L1 found only when the cytoplasmic domain antibody was used in biopsy specimens of patients with acute tubular necrosis. The levels of urinary L1, normalized for creatinine, were significantly higher in all 24 patients with acute tubular necrosis compared to five patients with prerenal azotemia or to six patients with other causes of acute kidney injury. Our study shows that a soluble form of human L1 can be detected in the urine of patients with acute tubular necrosis and that this may be a marker of distal nephron injury.

The evaluation of effects of demographic features, biochemical parameters, and cytokines on clinical outcomes in patients with acute renal failure

AIM

To evaluate the effects of cytokines, biochemical parameters and demographic features on clinical outcomes of acute renal failure (ARF).

PATIENTS AND METHODS

59 patients with acute renal failure (28 men, 31 women) were enrolled to the study. Cytokines, biochemical parameters, and complete blood count were measured. Patients were divided into two groups: as survivors (group 1, n = 46) and nonsurvivors (group 2, n = 13).

RESULTS

Mean age of patients were 52.3 +/- 17.9 years. 46 patients survived (77.9%) and 13 patients died (22.1%). There was a statistically significant relationship between IL-2R, IL-6, and TNF-alpha levels and mortality rates (p = 0.004, p = 0.016, p = 0.020, respectively) and between TC levels and mortality rates (p = 0.041). In multivariable logistic regression analysis, the effects of proinflammatory cytokines (IL-1beta, IL-2R, IL-6, TNFalpha, CRP, and ESR) on the clinical outcomes in ARF was observed to be statistically significant (r = 0.341, p = 0.005).

CONCLUSION

We realized that in totally demographic features (male gender, advanced age, poor nutritional status), biochemical parameters (TC, albumin, and hemoglobin) and cytokine levels (IL-2R, IL-6, TNF-alpha), CRP and ESR may be predictive factors for mortality in patients with ARF.

A systematic review of urinary findings in experimental septic acute renal failure

OBJECTIVE

In experimental septic acute renal failure, urinary analysis is used to help diagnose and classify renal injury. However, the scientific basis for such use has not been systematically evaluated. Thus, we appraised the value of common urinary findings for the diagnosis and classification of experimental septic acute renal failure.

DESIGN

Systematic review.

SETTING

Academic medical center and university-based research laboratory.

SUBJECTS

Experimental studies describing urinary biochemistry, derived indexes, and microscopy in septic acute renal failure.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Twenty-seven articles fulfilled all inclusion criteria. Due to heterogeneity, no formal quantitative analysis was possible. The methods for induction of sepsis and models were variable. The urinary sodium, fractional excretion of sodium, and urine osmolality were reported in only four (15%), 21 (78%), and seven (26%) studies, respectively. The fractional excretion of sodium exhibited a decrease, no change, or an increase from baseline in 11 (52%), five (24%), and five (24%) studies, respectively. The urine osmolality decreased from baseline in all endotoxin-induced models but showed an early transient increase in six (22%) studies of cecal-ligation perforation. Proteinuria or urinary enzymuria was reported in only seven (26%) studies. Urinary microscopy was described in one study. Only ten studies (37%) simultaneously reported on histopathology. In all these studies, histology either was normal or showed minor ultrastructural changes on electron microscopy.

CONCLUSIONS

No conclusions are possible on how several urinary tests perform in diagnosing or classifying acute renal failure or in predicting the presence of acute tubular necrosis in experimental sepsis. Additional research is necessary to define the diagnostic and prognostic value of urinalysis in experimental sepsis.

Proteomics of S-(1, 2-dichlorovinyl)-L-cysteine-induced acute renal failure and autoprotection in mice

Previous studies (Vaidya VS, Shankar K, Lock EA, Bucci TJ, Mehendale HM. Toxicol Sci 74: 215-227, 2003; Korrapati MC, Lock EA, Mehendale HM. Am J Physiol Renal Physiol 289: F175-F185, 2005; Korrapati MC, Chilakapati J, Lock EA, Latendresse JR, Warbritton A, Mehendale HM. Am J Physiol Renal Physiol 291: F439-F455, 2006) demonstrated that renal repair stimulated by a low dose of S-(1,2-dichlorovinyl)l-cysteine (DCVC; 15 mg/kg i.p.) 72 h before administration of a normally lethal dose (75 mg/kg i.p.) protects mice from acute renal failure (ARF) and death (autoprotection). The present study identified the proteins indicative of DCVC-induced ARF and autoprotection in male Swiss Webster mice. Renal dysfunction and injury were assessed by plasma creatinine and histopathology, respectively. Whole-kidney homogenates were run on two-dimensional gel electrophoresis gels, and the expression of 18 common proteins was maximally changed (> or =10-fold) in all the treatment groups and they were conclusively identified by liquid chromatography tandem mass spectrometry. These proteins were mildly downregulated after low dose alone and in autoprotected mice in contrast to severe downregulation with high dose alone. Glucose-regulated protein 75 and proteasome alpha-subunit type 1 were further investigated by immunohistochemistry for their localization in the kidneys of all the groups. These proteins were substantially higher in the proximal convoluted tubular epithelial cells in the low-dose and autoprotected groups compared with high-dose alone group. Proteins involved in energetics were downregulated in all the three groups of mice, leading to a compromise in cellular energy. However, energy is recovered completely in low-dose and autoprotected mice. This study provides the first report on proteomics of DCVC-induced ARF and autoprotection in mice and reflects the application of proteomics in mechanistic studies as well as biomarker development in a variety of toxicological paradigms.

Effect of ischemic acute renal damage on the expression of COX-2 and oxidative stress-related elements in rat kidney

Acute renal failure (ARF) is a clinical syndrome characterized by deterioration of renal function over a period of hours or days. The principal causes of ARF are ischemic and toxic insults that can induce tissue hypoxia. Transcriptional responses to hypoxia can be inflammatory or adaptive with the participation of the hypoxia-inducible factor 1α and the expression of specific genes related to oxidative stress. The production of peroxynitrites and protein nitrotyrosylation are sequelae of oxidative stress. In several clinical and experimental conditions, inflammatory responses have been related to cyclooxygenase (COX)-2, suggesting that its activation might play an important role in the pathogenesis and progression of nephropathies such as ARF. In the kidney, renin and bradykinin participate on the regulation of COX-2 synthesis. With the hypothesis that in ARF there is an increase in the expression of agents involved in adaptive and inflammatory responses, the distribution pattern and abundance of COX-2, its regulators renin, kallikrein, bradykinin B2 receptor, and oxidative stress elements, heme oxygenase-1 (HO-1), erythropoietin (EPO), inducible nitric oxide synthase (iNOS), and nitrotyrosylated residues were studied by immunohistochemistry and immunoblot analysis in rat kidneys after bilateral ischemia. In kidneys with ARF, important initial damage was demonstrated by periodic acid-Schiff staining and by the induction of the damage markers α-smooth muscle actin and ED-1. Coincident with the major damage, an increase in the abundance of EPO, HO-1, and iNOS and an increase in renin and bradykinin B2 receptor were observed. Despite the B2 receptor induction, we observed an important decrease in COX-2 in the ischemic-reperfused kidney. These results suggest that COX-2 does not participate in inflammatory responses induced by hypoxia.

North East Italian Prospective Hospital Renal Outcome Survey on Acute Kidney Injury (NEiPHROS-AKI): Targeting the Problem with the RIFLE Criteria

Acute kidney injury (AKI) in the intensive care unit (ICU) is associated with an enhanced mortality. The Acute Dialysis Quality Initiative group has proposed the RIFLE (Risk-Injury-Failure-Loss-ESRD) classification to standardize the approach to AKI. This study was performed to estimate the AKI incidence in ICU patients in northeastern Italy and describe clinical characteristics and outcomes of patients with AKI on the basis of their RIFLE class. A prospective multicenter observational study was performed of patients who fulfilled AKI criteria in 19 ICU in northeastern Italy. Data were analyzed using multivariate logistic regression and survival curve analysis. Of 2164 ICU patients who were admitted during the study period, 234 (10.8%; 95% confidence interval 9.5 to 12.1%) developed AKI; 19% were classified as risk (R), 35% as injury (I), and 46% as failure (F). Preexisting kidney disease was present in 36.8%. The most common causes of AKI were prerenal causes (38.9%) and sepsis (25.6%). At diagnosis of AKI, median serum creatinine and urine output were 2.0 mg/dl and 1100 ml/d, respectively. ICU mortality was 49.5% in class F, 29.3% in I, and 20% in R. Independent risk factors for mortality included RIFLE class, sepsis, and need for renal replacement therapy, whereas a postsurgical cause of AKI, exposure to nephrotoxins, higher serum creatinine, and urine output were associated with lower mortality risk. In this study, AKI incidence in the ICU was between 9 and 12%, with 3.3% of ICU patients requiring renal replacement therapy. Sepsis was a significant contributing factor. Overall mortality was between 30 and 42%, and was highest among those in RIFLE class F.

N-acetylcysteine for patients with prolonged hypotension as prophylaxis for acute renal failure (NEPHRON)

BACKGROUND

Acute renal failure is a common complication in critically ill patients and carries an increased morbidity and mortality. N-acetylcysteine is an antioxidant and anti-inflammatory agent that may counteract some of the pathophysiologic derangements in shock states.

OBJECTIVE

To test whether the administration of N-acetylcysteine, compared with placebo, reduces the incidence of acute renal failure in hypotensive patients.

DESIGN

Prospective, randomized, double-blinded, placebo-controlled study.

SETTING

Intensive care units of a university tertiary care hospital.

PATIENTS

One hundred forty-two patients with new onset (within 12 hrs) of at least>or=30 consecutive minutes of hypotension and/or vasopressor requirement.

INTERVENTIONS

Patients were randomized to receive either N-acetylcysteine or placebo for 7 days, in addition to standard supportive therapy.

MEASUREMENTS AND MAIN RESULTS

Patients who received N-acetylcysteine had an incidence of acute renal failure (>or=0.5 mg/dL increase in creatinine) of 15.5%, compared with 16.9% in those receiving placebo (p=.82, not significant). There were no significant differences between treatment arms in any of the secondary outcomes examined, including incidence of a 50% increase in creatinine, maximal rise in creatinine, recovery of renal function, length of intensive care unit and hospital stay, requirement for renal replacement therapy, and mortality. Among patients receiving N-acetylcysteine, there were trends toward reduced incidence of acute renal failure in patients with baseline Sequential Organ Failure Assessment (SOFA) score>8 (p=.12), lower SOFA scores during the first 4 days of treatment (p=.28), and reduced mortality in patients<65 yrs of age (p=.20).

CONCLUSIONS

There were no significant differences in any of our primary or secondary end points between patients treated with N-acetylcysteine or placebo. Trends toward reduced incidence of acute renal failure in patients with baseline SOFA score >8, reduced SOFA scores during the first 4 days, and reduced mortality in patients<65 yrs of age are provocative but require further study to determine their clinical significance.

Pharmacologic treatment of acute kidney injury: why drugs haven't worked and what is on the horizon

Current strategies to limit the extent of injury in acute renal failure are based on extensive studies that identified cellular and molecular mechanisms of acute kidney injury. Despite successes in various animal models, translation to human studies has failed or studies are inconclusive. This review describes past failures and barriers to successful clinical trials. It also focuses on promising preclinical studies using novel compounds that currently are in or close to human investigation. Implementation of previous or novel compounds in well-designed clinical trials provides hope for the successful treatment of this devastating disorder.

[Renal replacement therapy in the intensive care unit]

Acute renal failure in critically ill patients in the intensive care unit is associated with high morbidity and mortality which is independent of the underlying etiology. Despite improvements in intensive care medicine and renal replacement therapy, patients with acute renal failure have much higher morbidity and mortality rates than patients without acute renal failure in the intensive care unit. In this overview, we summarize the literature on the incidence and mortality of patients with acute renal failure in the intensive care unit. Furthermore, we discuss timing of the initiation of renal replacement therapy, patient outcome with different renal replacement therapies and the adequate dialysis dose to be delivered.

Perioperative fluid management in renal transplantation: a narrative review of the literature

Adequate volume maintenance is essential to prevent acute renal failure during major surgery or to ensure graft function after renal transplantation. The various recommendations on the optimum fluid therapy are based, at best, on sparse evidence only from observational studies. This article reviews the literature on perioperative fluid management in renal transplantation. Crystalloid solutions not exerting any specific side-effects are the first choice for volume replacement in kidney transplantation. The use of colloids should be restricted to patients with severe intravascular volume deficits necessitating high volume restoration. The routine application of albumin, dopamine, and high dose diuretics is no longer warranted. Mannitol given immediately before removal of the vessel clamps reduces the requirement of post-transplant dialysis, but has no effects on graft function in the long term. There is insufficient evidence on the best use of dialysis, but it seems peritoneal dialysis pretransplant is associated with less delayed graft function, whereas the preference of dialysis post-transplant is not yet well-founded. This review article should provide better guidance for fluid management in kidney transplantation until best-evidence guidelines can be established based upon more research.

Prognosis of acute renal failure in children

Acute renal failure (ARF) is the acute loss of renal function over a period of hours or days. Given the poor prognosis of ARF among children, there is some urgency to identifying more effective prognostic indicators for detecting disease onset. Such indicators would help provide the means of selecting patients who would benefit the most from early aggressive treatment. In this study we assessed the etiologic and prognostic indicators of ARF, including several risk factors such as sepsis, respiratory distress, age, among others, in 300 children who were admitted to the Ali Asghar Children's Hospital, Tehran, Iran, from 1990 to 2003. Statistical analysis was performed using multiple regression and chi-square methods, and a score to determine the prognosis of ARF in children was developed.

RESULT

Based on the results of this study the three common causes of ARF are acute tubular necrosis (ATN, 38%), acute glumerulonephritis (24%) and hemolytic uremic syndrome (24.1%). The overall mortality rate among our patients was 24.7%, with the highest risk group being those patients suffering from ischemic ATN. In addition, the correlation (p<0.0005) between the etiology and mortality rate was particularly high in patients with ischemic ATN. Mortality was also high (68%) in children younger than 2 years. Multiple regression models revealed that among those factors that significantly differed between the survivors and nonsurvivors, only the necessity of dialysis (p<0.0005), the use of mechanical ventilation (p=0.05) and disseminated intravascular coagulation (p=0.038) can be regarded as independent determinants of ARF prognosis in children.

Urinary Biochemistry and Microscopy in Septic Acute Renal Failure: A Systematic Review

BACKGROUND

Biochemistry and microscopy of urine are widely published diagnostic activities in patients with acute renal failure (ARF). However, their scientific basis in patients with septic ARF has not been assessed systematically.

METHODS

We performed a systematic review of MEDLINE, EMBASE, CINHAL, and PubMed databases and bibliographies of retrieved articles for all studies describing urinary biochemistry, indices, and microscopy in patients with septic ARF.

RESULTS

We identified 27 articles (1,432 patients). Because of substantial heterogeneity, no formal quantitative analysis could be performed. Urinary biochemistry or derived indices were reported in 24 articles (89%), and microscopy, in 7 articles (26%). The majority were small single-center reports and had serious limitations. For example, only 52% of patients were septic, only 54% of patients had ARF, many studies failed to include a control group, time from diagnosis of sepsis or ARF to measure of urinary tests was variable, and there were numerous potential confounders. Urinary sodium, fractional excretion of sodium, urinary-plasma creatinine ratio, urinary osmolality, urinary-plasma osmolality ratio, and serum urea-creatinine ratio showed variable and inconsistent results. Low-molecular-weight proteinuria was described in only 22% of articles. A few reports of urinary microscopy described muddy brown/epithelial cell casts and renal tubular cells in patients with septic ARF, whereas others described normal urinary sediment.

CONCLUSION

The scientific basis for the use of urinary biochemistry, indices, and microscopy in patients with septic ARF is weak. More research is required to describe their accuracy, pattern, and time course in patients with septic ARF.

Biomarkers of acute renal injury and renal failure

Acute renal failure (ARF) is a frequent problem in the intensive care unit and is associated with a high mortality. Early recognition could help clinical management, but current indices lack sufficient predictive value for ARF. Therefore, there might be a need for biomarkers in detecting renal tubular injury and/or dysfunction at an early stage before a decline in glomerular filtration rate is noted by an increased serum creatinine. A MEDLINE/PubMed search was performed, including all articles about biomarkers for ARF. All publication types, human and animal studies, or subsets were searched in English language. An extraction of relevant articles was made for the purpose of this narrative review. These biomarkers include tubular enzymes (alpha- and pi-glutathione S-transferase, N-acetyl-glucosaminidase, alkaline phosphatase, gamma-glutamyl transpeptidase, Ala-(Leu-Gly)-aminopeptidase, and fructose-1,6-biphosphatase), low-molecular weight urinary proteins (alpha1- and beta2-microglobulin, retinol-binding protein, adenosine deaminase-binding protein, and cystatin C), Na+/H+ exchanger, neutrophil gelatinase-associated lipocalin, cysteine-rich protein 61, kidney injury molecule 1, urinary interleukins/adhesion molecules, and markers of glomerular filtration such as proatrial natriuretic peptide (1-98) and cystatin C. These biomarkers, detected in urine or serum shortly after tubular injury, have been suggested to contribute to prediction of ARF and need for renal replacement therapy. However, excretion of these biomarkers may also increase after reversible and mild dysfunction and may not necessarily be associated with persistent or irreversible damage. Large prospective studies in human are needed to demonstrate an improved outcome of biomarker-driven management of the patient at risk for ARF.

Effects of cigarette smoking on serum fluoride concentrations and renal function integrity after 1 MAC-h sevoflurane anaesthesia

BACKGROUND

Tobacco smoke contains various chemicals which may affect drug metabolism. Sevoflurane is metabolized to inorganic fluoride, and elevated serum fluoride concentrations (S-F(-)) may cause deterioration of renal function. Whether smokers develop high S-F(-) and associated disturbances in renal function is not known.

METHODS

We investigated sevoflurane metabolism in 25 non-smoking and 25 smoking (> 10 cigarettes/day) generally healthy women, aged 19-68 years, undergoing gynaecological elective surgery under one minimum alveolar concentration-hour (1 MAC-h) standardized sevoflurane anaesthesia. S-F(-) was measured for 24 h. Glomerular and tubular function was assessed by measuring serum and urine tumour-associated trypsin inhibitor (TATI), beta(2)-microglobulin and serum creatinine for 48 h after sevoflurane inhalation.

RESULTS

There were no differences between the two study groups with regard to S-F(-). It increased significantly in both groups: in non-smokers, from a baseline between 1.0 and 11 micromol/l (median, 1.6 micromol/l) to a maximum between 8.2 and 40 micromol/l (26 micromol/l) (P < 0.001) and, in smokers, from a baseline between 0.5 and 5.2 micromol/l (1.7 micromol/l) to a maximum between 19 and 71 micromol/l (25 micromol/l) (P < 0.001). In both groups, S-F(-) remained elevated for the entire sampling period (P < 0.001). In all five women (one non-smoker and four smokers) with a maximum S-F(-) of 40 micromol/l or higher and an area under the serum fluoride concentration-time curve (AUC(F0-24)) of 500 micromol/h/l or higher, serum TATI increased above the pathological concentration of 3.0 nmol/l, whereas only six of the 45 patients with S-F(-) below 40 micromol/l had serum TATI above 3.0 nmol/l (P < 0.001). Beta(2)-Microglobulin increased significantly (> 1 mg/l) in two patients with high S-F(-) relative to two of the 45 patients with S-F(-) below 40 micromol/l (P= 0.005). None of the patients developed clinically detectable renal dysfunction.

CONCLUSION

Smoking did not affect S-F(-) after sevoflurane anaesthesia. Glomerular dysfunction, seen as increased serum TATI, was noted in five women with S-F(-) above 40 micromol/l. Our results suggest that the renal toxic threshold of S-F(-) seems to be lower than the earlier reported value of 50 micromol/l.

bFGF induces an earlier expression of nephrogenic proteins after ischemic acute renal failure

Recovery from acute renal failure (ARF) requires the replacement of injured cells with new cells that restore tubule epithelial integrity. We described recently the expression of a wide range of nephrogenic proteins in tubular cells after ARF induced by ischemia-reperfusion (I/R) (Villanueva S, Cespedes C, and Vio CP. Am J Physiol Regul Integr Comp Physiol 290: R861-R870, 2006). These markers, namely, Vimentin, neural cell adhesion molecules (Ncam), basic fibroblast growth factor (bFGF), paired homeobox-2 (Pax-2), bone morphogene protein-7 (BMP-7), Noggin, Lim-1, Engrailed, Smad, phospho-Smad, hypoxia-induced factor-1alpha (HIF-1alpha), VEGF, and Tie-2, are expressed in a time frame similar to that observed in normal kidney development. bFGF participates in early kidney development as a morphogen involved in mesenchyme/epithelial transition, and it is reexpressed in the recovery phase of ARF. To test the hypothesis that bFGF can accelerate the regeneration after renal damage, we used recombinant bFGF and studied the expression pattern of the above described morphogens in ARF. Male Sprague-Dawley rats were subjected to 30 min of renal ischemic injury and were injected with bFGF 30 microg/kg followed by reperfusion. Rats were killed and the expression of nephrogenic proteins were analyzed by immunohistochemistry and Western blot analysis. In the animals subjected to I/R treated with bFGF, we observed a 12- to 24-h earlier and more abundant reexpression of the proteins Ncam, bFGF, Pax-2, BMP-7, Noggin, Lim-1, Engrailed, VEGF, and Tie-2 than the I/R untreated rats. In addition, we observed a reduction in renal damage markers ED-1 and alpha-smooth muscle actin. These results indicate that bFGF can participate in the regeneration process and suggest that the treatment with bFGF can induce an earlier regeneration process after ischemic acute renal failure.

Simvastatin improves sepsis-induced mortality and acute kidney injury via renal vascular effects

Acute kidney injury (AKI) occurs in about half of patients in septic shock and the mortality of AKI with sepsis is extremely high. An effective therapeutic intervention is urgently required. Statins are 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors that also have pleiotropic actions. They have been reported to increase the survival of septic or infectious patients. But the effect of simvastatin, a widely used statin, on sepsis-induced AKI is unknown. The effects of simvastatin and tumor necrosis factor (TNF)-alpha neutralizing antibody were studied in a clinically relevant model of sepsis-induced AKI using cecal ligation and puncture (CLP) in elderly mice. Simvastatin significantly improved CLP-induced mortality and AKI. Simvastatin attenuated CLP-induced tubular damage and reversed CLP-induced reduction of intrarenal microvascular perfusion and renal tubular hypoxia at 24 h. Simvastatin also restored towards normal CLP-induced renal vascular protein leak and serum TNF-alpha. Neither delayed simvastatin therapy nor TNF-alpha neutralizing antibody improved CLP-induced AKI. Simvastatin improved sepsis-induced AKI by direct effects on the renal vasculature, reversal of tubular hypoxia, and had a systemic anti-inflammatory effect.

Protection of HIF-1-deficient primary renal tubular epithelial cells from hypoxia-induced cell death is glucose dependent

Ischemic acute renal failure is a frequent clinical problem in hospitalized patients and is associated with significant mortality. Hypoxia-inducible factor 1 (HIF-1) mediates cellular adaptation to hypoxia by regulating biological processes important for cell survival, which include glycolysis, angiogenesis, erythropoiesis, apoptosis, and proliferation. To investigate the role of HIF-1 in hypoxia-induced renal epithelial cell death, we generated mice that allow inactivation of HIF-1α by tetracycline-inducible Cre-loxP-mediated recombination in primary renal proximal tubule cells (PRPTC), resulting in a suppression of HIF-1-mediated gene transcription during oxygen deprivation. In the absence of glucose, the onset and the degree of hypoxia-induced cell death in HIF-1-deficient PRPTC were comparable to wild-type cells. However, when glucose availability was limited, the onset of cell death was delayed in either PRPTC that were HIF-1 deficient or in wild-type PRPTC when glycolysis or glucose uptake was partially inhibited. Our findings suggest in an in vitro genetic model that 1) the generation of adequate energy levels for the maintenance of PRPTC viability under hypoxia does not require HIF-1 and 2) that HIF-1 regulates the timing of hypoxia-induced cell death and apoptosis onset through its effects on glucose consumption.

ApoSense: a novel technology for functional molecular imaging of cell death in models of acute renal tubular necrosis

Purpose

Acute renal tubular necrosis (ATN), a common cause of acute renal failure, is a dynamic, rapidly evolving clinical condition associated with apoptotic and necrotic tubular cell death. Its early identification is critical, but current detection methods relying upon clinical assessment, such as kidney biopsy and functional assays, are insufficient. We have developed a family of small molecule compounds, ApoSense, that is capable, upon systemic administration, of selectively targeting and accumulating within apoptotic/necrotic cells and is suitable for attachment of different markers for clinical imaging. The purpose of this study was to test the applicability of these molecules as a diagnostic imaging agent for the detection of renal tubular cell injury following renal ischemia.

Methods

Using both fluorescent and radiolabeled derivatives of one of the ApoSense compounds, didansyl cystine, we evaluated cell death in three experimental, clinically relevant animal models of ATN: renal ischemia/reperfusion, radiocontrast-induced distal tubular necrosis, and cecal ligature and perforation-induced sepsis.

Results

ApoSense showed high sensitivity and specificity in targeting injured renal tubular epithelial cells in vivo in all three models used. Uptake of ApoSense in the ischemic kidney was higher than in the non-ischemic one, and the specificity of ApoSense targeting was demonstrated by its localization to regions of apoptotic/necrotic cell death, detected morphologically and by TUNEL staining.

Conclusion

ApoSense technology should have significant clinical utility for real-time, noninvasive detection of renal parenchymal damage of various types and evaluation of its distribution and magnitude; it may facilitate the assessment of efficacy of therapeutic interventions in a broad spectrum of disease states.

Renal failure secondary to acute tubular necrosis: epidemiology, diagnosis, and management

Acute tubular necrosis (ATN) is a form of acute renal failure (ARF) that is common in hospitalized patients. In critical care units, it accounts for about 76% of cases of ARF. Despite the introduction of hemodialysis > 30 years ago, the mortality rates from ATN in hospitalized and ICU patients are about 37.1% and 78.6%, respectively. The purpose of this review is to discuss briefly the cause, diagnosis, and epidemiology of ARF, and to review in depth the clinical trials performed to date that have examined the influence of growth factors, hormones, antioxidants, diuretics, and dialysis. In particular, the role of the dialysis modality, dialyzer characteristics, and dosing strategies are discussed.

Ischemic acute renal failure induces the expression of a wide range of nephrogenic proteins

Ischemia-induced acute renal failure (ARF) is a disorder with high morbidity and mortality. ARF is characterized by a regeneration phase, yet its molecular basis is still under study. Changes in gene expression have been reported in ARF, and some of these genes are specific for nephrogenic processes. We tested the hypothesis that the regeneration process developed after ischemia-induced ARF can be characterized by the reexpression of important regulatory proteins of kidney development. The distribution pattern and levels of nephrogenic proteins in rat kidneys after ischemia were studied by immunohistochemistry and immunoblot analysis. Ischemic damage was assessed by conventional morphology, serum creatinine, and the apoptotic markers terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) and caspase 3. The hypoxia levels induced by ischemia were assessed by specific markers: hypoxia induced factor (HIF)-1alpha and 2-pimonidazole. In kidneys with ARF, an important initial damage was observed through periodic acid Schiff staining, by the induction of damage markers alpha-smooth muscle actin (alpha-SMA) and macrophages (ED-1) and by apoptosis induction. In agreement with diminishing renal damage at the initial reparation phase, the expression of the mesenchymal proteins vimentin, neural cell adhesion molecules (Ncam), and the epithelial markers, Pax-2, Noggin, and basic fibroblast growth factor was observed; after, in a second phase, the tubular markers bone morphogen protein 7, Engrailed, and Lim-1, as well as the transcription factors Smad and p-Smad, were observed. Additionally, the endothelial markers VEGF and Tie-2 were induced at the initial and middle stages of regeneration phase, respectively. The expression of these proteins was restricted in time and space, as well as spatially and temporally. Because all of these proteins are important in maintaining a functional kidney, these results suggest that during the regeneration process after induced hypoxia, these nephrogenic proteins can be reexpressed in a similar fashion to that observed during development, thus restoring mature kidney function.

Retrospective analysis on Chinese patients diagnosed with acute renal failure hospitalized during the last decade (1994-2003)

OBJECTIVES

To investigate the epidemiology, diagnosis and prognosis of acute renal failure (ARF) in hospitalized Chinese during the last decade.

METHODS

The diagnosis of patients with ARF in Peking University Third Hospital from January 1994 to December 2003 was reconfirmed and the data of epidemiology, etiology and prognosis were analyzed.

RESULTS

Only 209 discharged cases were diagnosed with ARF and all were reconfirmed. Two peak occurrences were found at ages of 35-45 and 60-80 with a male predominance of approximately 59.7%. Patients diagnosed with ARF accounted for 1.19 per thousand of the admissions in the same period and increased significantly in the last 5 years (p = 0.038). The creatinine level at diagnosis was 345.8 +/- 122.6 micromol/l and had no significant change (p > 0.05). The percent of hospital-acquired ARF (HA-ARF) demonstrated a significant increase in 1999-2003 compared to 1994-1998 (p = 0.008). Intrarenal ARF accounted for 73.69% and was multifactorial, with drugs, infections and operations as leading causes. Renal biopsy was performed in 37.32% (78/209) with 53.84% (42/78) having acute interstitial nephritis. Maintenance dialysis was discontinued in 46.41% because their renal function completely or partially recovered. The overall mortality was 37.91% without improvement over time. The mortality was 6.25% for patients in nephrology department, but 65.51% in ICU (p < 0.001), and was 21.6% for patients in community-acquired ARF (CA-ARF), but 63.1% in HA-ARF (p < 0.001).

CONCLUSIONS

During the past 10 years, the number of patients diagnosed with ARF has been rising in hospitalized Chinese. HA-ARF was the major source, and infections, drugs and operations were the leading causes. The diagnosis and prognosis of acute renal failure did not improve much in this population over the decade studied.

The diagnosis of acute renal failure in intensive care: mongrel or pedigree?

Acute renal failure is common in the intensive care unit; it is well recognised that patients who develop acute renal failure have a high mortality rate. While there have been improvements in the management of acute renal failure, the mortality remains high. Acute renal failure is easily diagnosed biochemically and clinically but it is not a single disease entity. It is a syndrome that affects a very heterogeneous population. Studies of acute renal failure and of the impact of renal replacement therapy in intensive care are usually inconclusive, which may be the natural consequence of studying a syndrome. This article focuses on the more uncertain features of acute renal failure, the problems of investigating acute renal failure as a disease and the difficulties of applying the results of a study of a heterogeneous population to the management of individuals.

Acute renal failure independently predicts mortality after myeloablative allogeneic hematopoietic cell transplant

BACKGROUND

Patients undergoing myeloablative allogeneic hematopoietic cell transplantation (HCT) have a high incidence of acute renal failure (ARF). However, it is unclear if ARF is independently associated with mortality after this procedure.

METHODS

We performed meta-analysis of published reports on ARF after myeloablative allogeneic HCT. Four databases (MEDLINE, Cochrane Library, PubMed, Web of Science) and hand searching of conference proceedings were used to identify the studies. ARF was defined as the doubling of serum creatinine occurring within the first 100 days after HCT. The absolute and the relative risks for death after ARF were calculated for every study. The combined relative risk was calculated using the random effects model. Also, multivariate analysis of patient level data was performed on patients from The University of Colorado to establish independent association between ARF and mortality.

RESULTS

One thousand two hundred and eleven patients were included in the meta-analysis from the 6 published reports in the literature. The overall incidence of ARF varied from 42% to 84% in these studies. On combining the studies by random-effects model, the relative risk of death after ARF was 2.22 (95%CI 1.38-3.5, P < 0.001). The analysis of patient level data from the University of Colorado demonstrated increasing mortality with worsening grades of ARF. After controlling for various demographic and clinical variables with logistic regression, patients who required dialysis had a 6.8-fold higher association with mortality.

CONCLUSION

ARF appears to independently influence mortality after myeloablative allogeneic HCT. Future studies should be aimed at interventions that can reduce the incidence and severity of ARF with this procedure.

Mechanical ventilation and acute renal failure

OBJECTIVE

To review the current literature on possible mechanisms by which mechanical ventilation may initiate or aggravate acute renal failure.

DATA SOURCE

A Medline database and references from identified articles were used to perform a literature search relating to mechanical ventilation and acute renal failure.

DATA SYNTHESIS

Acute renal failure may be initiated or aggravated by mechanical ventilation through three different mechanisms. First, strategies such as permissive hypercapnia or permissive hypoxemia may compromise renal blood flow. Second, through effects on cardiac output, mechanical ventilation affects systemic and renal hemodynamics. Third, mechanical ventilation may cause biotrauma-a pulmonary inflammatory reaction that may generate systemic release of inflammatory mediators. The harmful effects of mechanical ventilation may become more significant when a comorbidity is present. In these situations, it is more difficult to maintain normal gas exchange, and moderate arterial hypoxemia and hypercapnia are often accepted. Renal blood flow is compromised due to a decreased cardiac output as a consequence of high intrathoracic pressures. Furthermore, the effects of biotrauma are not limited to the lungs but may lead to a systemic inflammatory reaction.

CONCLUSIONS

The development of acute renal failure during mechanical ventilation likely represents a multifactorial process that may become more important in the presence of comorbidities. Development of optimal interventional strategies requires an understanding of physiologic principles and greater insight into the precise molecular and cellular mechanisms that may also play a role.

Utilizing physiological knowledge to care for acute renal failure

Nursing can play a pivotal role in promoting positive outcomes in patients who are both at risk of, and experiencing, an episode of acute renal failure (ARF). ARF is potentially recoverable to the extent that 94% of survivors have the potential to be dialysis independent. This article highlights the positive impact ward-based nurses can have on this group of patients through the use of a commonly encountered clinical scenario. Key aspects of renal physiology are utilized to ensure that the aetiology of ARF is clearly understood. Treatment and specific nursing care is discussed in order to enhance the quality of care delivered to this group of patients.

Early detection of acute renal failure by serum cystatin C

BACKGROUND

Acute renal failure (ARF) is associated with high mortality. Presently, no specific therapy for ARF exists. Therefore, early detection of ARF is critical to prevent its progression. However, serum creatinine, the standard marker to detect ARF, demonstrates major limitations. We prospectively evaluated whether serum cystatin C detected ARF earlier than serum creatinine.

METHODS

In 85 patients at high risk to develop ARF, serum creatinine and cystatin C were determined daily. ARF was defined according to the Risk of renal dysfunction, Injury to the kidney, Failure of kidney function, Loss of kidney function, and ESRD (RIFLE) classification when creatinine increased by >/=50% (R-criteria), by >/=100% (I-criteria), or by >/=200% (F-criteria). In analogy, ARF was detected when cystatin C increased by >/=50%, by >/=100%, or by >/=200%.

RESULTS

Forty-four patients developed ARF and 41 served as controls. In ARF by R-, I-, and F-criteria, the increase of cystatin C significantly preceded that of creatinine. Specifically, serum cystatin C increased already by >/=50% 1.5 +/- 0.6 days earlier compared to creatinine. Serum cystatin C demonstrated a high diagnostic value to detect ARF as indicated by area under the curve of the ROC analysis of 0.82 and 0.97 on the two days before the R-criteria was fulfilled by creatinine. Cystatin C detected ARF according to the R-criteria with a sensitivity of 55% and 82% on these days, respectively. Cystatin C also performed excellently, detecting ARF defined by the I- and F-criteria two days prior to creatinine, and moderately well predicting renal replacement therapy in the further course of ARF. Additionally, low T(3)- or T(3)/T(4) syndrome, glucocorticoid deficiency and excess did not affect cystatin C levels, adding to its usefulness in critically ill patients with ARF.

CONCLUSION

Serum cystatin C is a useful detection marker of ARF, and may detect ARF one to two days earlier than creatinine.

Acute renal failure: definitions, diagnosis, pathogenesis, and therapy

Acute renal failure (ARF), characterized by sudden loss of the ability of the kidneys to excrete wastes, concentrate urine, conserve electrolytes, and maintain fluid balance, is a frequent clinical problem, particularly in the intensive care unit, where it is associated with a mortality of between 50% and 80%. In this review, the epidemiology and pathophysiology of ARF are discussed, including the vascular, tubular, and inflammatory perturbations. The clinical evaluation of ARF and implications for potential future therapies to decrease the high mortality are described.

Ethyl pyruvate decreases sepsis-induced acute renal failure and multiple organ damage in aged mice

BACKGROUND

Sepsis is a common cause of acute renal failure (ARF). The incidence of sepsis increases dramatically after 50 years of age; however, most ARF studies are performed in young mice.

METHODS

We performed two common sepsis models, lipopolysaccharide (LPS) administration and cecal ligation puncture (CLP) in aged mice. We developed a fully treated CLP model in aged mice by treating mice with fluid resuscitation and antibiotics.

RESULTS

LPS induced renal injury in aged but not young mice. However, volume resuscitation starting within 6 hours decreased renal injury. We then used this fluid resuscitation scheme, along with antibiotics, to develop a fully treated CLP model in aged mice. Mice subjected to CLP developed functional and histologic ARF and multiple organ damage. Treatment with ethyl pyruvate, even when started 12 hours after surgery, decreased serum creatinine, tubular damage, and multiple organ injury at 24 hours. Ethyl pyruvate decreased plasma tumor necrosis factor-alpha (TNF-alpha), and kidney mRNA for TNF alpha, tissue factor, and plasminogen activator inhibitor-1 (PAI-1), and increased mRNA for urokinase-like plasminogen activator.

CONCLUSION

CLP in aged mice causes functional and histologic changes consistent with human ARF. A single dose of ethyl pyruvate inhibits renal and multiple organ damage, and is still effective when given 12 hours after surgery.

Clinical characteristics of patients developing ARF due to sepsis/systemic inflammatory response syndrome: results of a prospective study

BACKGROUND

Acute renal failure (ARF) in patients with sepsis provokes high mortality and financial cost. In this prospective study, we collected characteristics of patients in the intensive care unit (ICU) who developed sepsis/systemic inflammatory response syndrome (SIRS) to analyze differences between those who subsequently did or did not develop ARF.

METHODS

All patients admitted to the ICU of the University Hospital Gent, Belgium, between January 1, 2001, and December 31, 2001, who developed sepsis/SIRS were included if they had a serum creatinine level less than 2 mg/dL (<177 micromol/L).

RESULTS

Of 2,442 patients admitted to the ICU, 257 patients developed sepsis/SIRS. Of those, 29 patients (11%) developed ARF. In a univariate analysis, age, central venous pressure (CVP), and serum creatinine and blood urea nitrogen levels were greater (P = 0.003, P = 0.006, P < 0.001, and P < 0.001, respectively), whereas mean arterial and diastolic blood pressures, 24-hour urinary output, arterial pH, bicarbonate level, thrombocyte count, albumin level, and prothrombin time were lower (P = 0.05, P = 0.004, P = 0.005, P = 0.03, P = 0.009, P = 0.037, P = 0.05, and P = 0.006, respectively) in the ARF group. Prevalence of diabetes, sex, and need for ventilation were not different between the ARF and no-ARF groups, but in the ARF group, diuretic use, vasopressor use, and presence of primary hepatic failure were more prevalent (P = 0.001 for each). In a multivariate analysis, age, serum creatinine level, CVP, and presence of liver failure significantly contributed to a logistic regression model for ARF.

CONCLUSION

Several parameters already were disturbed at the first day of SIRS/sepsis in patients who later developed ARF. Older age, elevated serum creatinine level despite elevated CVP, and presence of hepatic failure are predictive for ARF in septic patients.

Drugs used to promote diuresis: a treatment for fluid balance charts?

Renal failure is a complex process characterized by the retention of nitrogenous waste products, electrolyte disturbances and decreased urine production. Diuretics are often prescribed as a treatment for decreased renal functioning. Diuretics induce urine production by different mechanisms of action. Diuretic therapy has not been found to decrease mortality nor decrease the need for further intervention. The current development of national framework standards will provide guidelines for the treatment of all patients suffering acute renal failure.

Prognostic value of tubular proteinuria and enzymuria in nonoliguric acute tubular necrosis

BACKGROUND

Acute tubular necrosis (ATN) has high mortality, especially in patients who require renal replacement therapy (RRT). We prospectively studied the diagnostic accuracy of the urinary excretion of low-molecular-weight proteins and enzymes as predictors of a need for RRT in ATN.

METHODS

In 73 consecutive patients with initially nonoliguric ATN, we measured urinary excretion of alpha(1)- and beta(2)-microglobulin, cystatin C, retinol-binding protein, alpha-glutathione S-transferase, gamma-glutamyltransferase, lactate dehydrogenase, and N-acetyl-beta-D-glucosaminidase early in the course of ATN.

RESULTS

Twenty-six patients (36%) required RRT a median of 4 (interquartile range, 2-6) days after detection of proteinuria and enzymuria. Patients who required RRT had higher urinary cystatin C and alpha(1)-microglobulin [median (interquartile range), 1.7 (1.2-4.1) and 34.5 (26.6-45.1) g/mol of creatinine] than patients who did not require RRT [0.1 (0.02-0.5) and 8.0 (5.0-17.5) g/mol of creatinine]. Urinary excretion of cystatin C and alpha(1)-microglobulin had the highest diagnostic accuracies in identifying patients requiring RRT as indicated by the largest areas under the ROC curves: 0.92 (95% confidence interval, 0.86-0.96) and 0.86 (0.78-0.92), respectively. Sensitivity and specificity were 92% (95% confidence interval, 83-96%) and 83% (73-90%), respectively, for urinary cystatin C >1 g/mol of creatinine, and 88% (78-93%) and 81% (70-88%) for urinary alpha(1)-microglobulin >20 g/mol of creatinine.

CONCLUSION

In nonoliguric ATN, increased urinary excretion of cystatin C and alpha(1)-microglobulin may predict an unfavorable outcome, as reflected by the requirement for RRT.

Critical issues in nephrology

Renal and electrolyte problems are common in patients in the ICU. Several advances that occurred in the recent past have been incorporated in the diagnosis and management of these disorders and were reviewed in this article. Unfortunately, many important questions remain unanswered, especially in the area of ARF, where new therapies are anxiously awaited to make the transition from bench to bedside. Better studies are sorely needed to define the best approach to dialysis in patients who have ARF.