Acute renal failure in the elderly: particular characteristics

Renin-angiotensin-aldosterone system blockers effect in chronic kidney disease progression in hypertensive elderly patients without proteinuria: PROERCAN trial

INTRODUCTION

Evidence about nefroprotective effect with RAAS blockers in elderly patients with chronic kidney disease (CKD) without proteinuria is lacking. The primary outcome of our study is to evaluate the impact of RAAS blockers in CKD progression in elderly patients without proteinuria.

MATERIALS AND METHODS

Multicenter open-label, randomized controlled clinical trial including patients over 65 year-old with hypertension and CKD stages 3-4 without proteinuria. Patients were randomized in a 1:1 ratio to either receive RAAS blockers or other antihypertensive drugs and were followed up for three years. Primary outcome is estimated glomerular filtration rate (eGFR) decline at 3 years. Secondary outcome measures include BP control, renal and cardiovascular events and mortality.

RESULTS

88 patients were included with a mean age of 77.9±6.1 years and a follow up period of 3 years: 40 were randomized to RAAS group and 48 to standard treatment. Ethiology of CKD was: 53 vascular, 16 interstitial and 19 of unknown ethiology. In the RAAS group eGFR slope during follow up was -4.3±1.1ml/min, whereas in the standard treatment group an increase on eGFR was observed after 3 years (+4.6±0.4ml/min), p=0.024. We found no differences in blood pressure control, number of antihypertensive drugs, albuminuria, potassium serum levels, incidence of cardiovascular events nor mortality during the follow up period.

CONCLUSIONS

In elderly patients without diabetes nor cardiopathy and with non proteinuric CKD the use of RAAS blockers does not show a reduction in CKD progression. The PROERCAN (PROgresión de Enfermedad Renal Crónica en ANcianos) trial (trial registration: NCT03195023).

Use of renin-angiotensin-aldosterone system blockade in controversial chronic kidney disease populations

Renin-angiotensin-aldosterone system blockers have shown to be effective in controlling blood pressure and proteinuria, slowing the progression to end stage renal disease and reducing cardiovascular risk, so they are the mainstream treatment of hypertension in chronic kidney disease. Their beneficial effects have been proven in multiple randomized clinical trials on different study populations, but there has recently been some controversial data on its use in some subgroups of patients, especially those with advanced chronic kidney disease. In some other populations such as patients with non-proteinuric nephropathies or the elderly, who can be more susceptible to its adverse events, their benefits have also been questioned. The aim of the present review is to collect available published data on the effect of renin-angiotensin-aldosterone system blockers in some controversial populations and provide perspective on future research areas in this field.

The Effect of Aging Physiology on Critical Care

Older patients experience a decline in their physiologic reserves as well as chronic low-grade inflammation named "inflammaging." Both of these contribute significantly to aging-related factors that alter the acute, subacute, and chronic response of these patients to critical illness, such as sepsis. Unfortunately, this altered response to stressors can lead to chronic critical illness followed by dismal outcomes and death. The primary goal of this review is to briefly highlight age-specific changes in physiologic systems majorly affected in critical illness, especially because it pertains to sepsis and trauma, which can lead to chronic critical illness and describe implications in clinical management.

Excessive Oxidative Stress Contributes to Increased Acute ER Stress Kidney Injury in Aged Mice

The aged kidney is susceptible to acute injury due presumably to its decreased ability to handle additional challenges, such as endoplasmic reticulum (ER) stress. This was tested by giving tunicamycin, an ER stress inducer, to either old or young mice. Injection of high dose caused renal failure in old mice, not in young mice. Moreover, injection of low dose resulted in severe renal damage in old mice, confirming the increased susceptibility of aged kidney to ER stress. There existed an abnormality in ER stress response kinetics in aged kidney, characterized by a loss of XBP-1 splicing and decreased PERK-eIF2α phosphorylation at late time point. The presence of excessive oxidative stress in aged kidney may play a role since high levels of oxidation increased ER stress-induced cell death and decreased IRE1 levels and XBP-1 splicing. Importantly, treatment with antioxidants protected old mice from kidney injury and normalized IRE1 and XBP-1 responses. Furthermore, older mice (6 months old) transgenic with antioxidative stress AGER1 were protected from ER stress-induced kidney injury. In conclusion, the decreased ability to handle ER stress, partly due to the presence of excessive oxidative stress, may contribute to increased susceptibility of the aging kidney to acute injury.

Evaluation of changes in renal function in PARAMOUNT: a phase III study of maintenance pemetrexed plus best supportive care versus placebo plus best supportive care after induction treatment with pemetrexed plus cisplatin for advanced nonsquamous non-small-cell lung cancer

OBJECTIVES

To assess the effect of long-term pemetrexed maintenance therapy on patients' renal function.

METHODS

In the PARAMOUNT phase III trial (NCT 00789373), pemetrexed was compared with placebo as maintenance treatment in advanced nonsquamous non-small-cell lung cancer patients who completed 4 cycles of pemetrexed plus cisplatin induction therapy. To evaluate changes in renal function during pemetrexed continuation maintenance treatment, we retrospectively analyzed changes in serum creatinine (sCr), treatment-emergent adverse events, dose delays and treatment discontinuations associated with impaired renal function.

RESULTS

Creatinine clearance ≥45 mL/min was required before the start of any cycle. Patients on pemetrexed maintenance had a significantly higher percentage maximum increase in sCr over baseline versus placebo for the range of ≥10% to ≥90% increase (p < .05). The risk of experiencing renal events leading to dose delays and discontinuations was higher with higher increases in sCr but reversible in most patients. sCr increases of ≥30% and ≥40% were associated with gender (female), age (<70 years) and longer exposure to pemetrexed compared with placebo. Sixteen (4%) pemetrexed patients and 1 (1%) placebo patient discontinued treatment due to drug-related renal events; 13/16 (81%) of those pemetrexed patients had sCr increases ≥30% and 7/13 (54%) had pre-existing conditions and/or were receiving nephrotoxic drugs.

CONCLUSIONS

The appearance of renal events leading to dose delays and/or treatment discontinuations was associated with sCr increase of at least 30%. However, it was difficult to identify patients at a higher risk of treatment discontinuation due to a drug-related renal event based only on changes in pre-maintenance laboratory values.

Estimating renal function in old people: an in-depth review

Estimates of glomerular filtration rate (eGFR) should provide accurate measure of an individual's kidney function because important clinical decisions such as timing of renal replacement therapy and drug dosing may be dependent on eGFR. Formulae from which eGFR is derived are generally based on serum creatinine measurement, such as Cockcroft-Gault, MDRD and CKD-EPI. More recently, calculation of eGFR using other laboratory biomarkers such as cystatin C has emerged with apparent greater accuracy. In old people, there is age-related physiological change in the kidney, which could lead to reduced GFR. Likewise, physiological changes in body composition that occur with the ageing process impede the use of a single creatinine-based calculation of eGFR across all adult age groups. Studies have shown differences in the prevalence of CKD based on the type of equation used to estimate GFR. This review discusses the evolution of eGFR calculations and the relative accuracy of such equations in older population.

Risk factors for developing acute kidney injury in older people with diabetes and community-acquired pneumonia: a population-based UK cohort study

Background

Acute kidney injury (AKI) is being increasingly recognised in ageing populations. There are a paucity of data about AKI risk factors among older individuals with diabetes and infections, who are at particularly high risk of AKI. The objective of this study was to evaluate the risk factors for developing acute kidney injury (AKI) amongst older patients with diabetes and community-acquired pneumonia (CAP) in England, and whether the impact of underlying kidney function varied with age.

Methods

This was a population-based retrospective cohort study over 7 years (01/04/2004–31/3/2011) using electronic health records from the Clinical Practice Research Datalink linked to Hospital Episode Statistics. The study population comprised individuals with diabetes aged ≥65 years with CAP. Associations between demographic, lifestyle factors, co-morbidities and medications and development of AKI within 28 days of CAP were explored in a logistic regression model.

Results

Among 3471 patients with CAP and complete covariate data, 298 patients developed subsequent AKI. In multivariable analyses, factors found to be independently associated with AKI included: male sex (adjusted odds ratio, aOR: 1.56 95% confidence interval (CI): 1.20–2.04), hypertension (aOR1.36 95% CI 1.01–1.85), being prescribed either angiotensin-converting-enzyme inhibitors or angiotensin-II-receptor-blockers (aOR: 1.59 95% CI: 1.19–2.13), or insulin (aOR: 2.27 95% CI: 1.27–4.05), presence of proteinuria (aOR 1.27 95% CI 0.98–1.63), and low estimated glomerular filtration rate (eGFR). The odds of AKI were more graded amongst older participants aged ≥80 years compared to those of younger age: for eGFR of ≤29 mL/min/1.73m² (vs 60 ml/min/1.73m²) aOR: 5.51 95% CI 3.28–9.27 and for eGFR 30–59 mL/min/1.73m² 1.96 95% CI 1.30–2.96, whilst any eGFR < 60 ml/min/1.73m² was associated with approximately 3-fold increase in the odds of AKI amongst younger individuals (p-value for interaction = 0.007).

Conclusions

The identified risk factors should help primary care and hospital providers identify high risk patients in need of urgent management including more intensive monitoring, and prevention of AKI following pneumonia.

Acute kidney injury in elderly intensive care patients from a developing country: clinical features and outcome

AIM

The elderly are at high risk of acute kidney injury (AKI) because of structural and functional degeneration over time and with the aging of the population, the demand for intensive care unit (ICU) admission for older patients has risen recently. However, data from developing countries are scarce. This study aimed to describe the incidence of AKI in elderly patients admitted to ICU from a developing country, to determine the most frequent etiologies for renal impairment and identify its risk factors and outcome.

METHODS

All patients admitted to the ICU at a Brazilian teaching hospital for 12 consecutive months were followed prospectively from the time of admission until ICU discharge. Elderly was defined as aged >60 years and AKI was defined according to the Kidney Disease Improving Global Outcomes 2012 criteria. Multivariable logistic regression was used to adjust confounding and selection bias.

RESULTS

Two hundred elderly patients were included in the study. AKI incidence was 27% and the main etiology was sepsis (48.1%). At logistic regression, baseline creatinine (odds ratio [OR]=5.17, p<0.0001), Acute Physiology and Chronic Health Evaluation (APACHE) II (OR=1.20, p<0.0001), sepsis (OR=2.96, p<0.0001), and longer ICU stay (OR=1.68, p<0.0001) were associated with AKI in elderly patients. Baseline creatinine (OR=1.97, p=0.018), APACHE II (OR=1.29, p<0.0001), sepsis (OR=1.87, p<0.0001), and AKI severity (OR=2.57, p=0.027) were identified as predictors of death.

CONCLUSION

AKI was frequent in elderly patients admitted to ICU from a developing country, and it was identified as a risk factor for death. Sepsis was an important risk factor for both AKI and mortality, similar to developed countries and in younger populations.

The Impact of Renin-Angiotensin System Blockade on Renal Outcomes and Mortality in Pre-Dialysis Patients with Advanced Chronic Kidney Disease

Renin-angiotensin-system (RAS) blockade is thought to slow renal progression in patients with chronic kidney disease (CKD). However, it remains uncertain if the habitual use of RAS inhibitors affects renal progression and outcomes in pre-dialysis patients with advanced CKD. In this multicenter retrospective cohort study, we identified 2,076 pre-dialysis patients with advanced CKD (stage 4 or 5) from a total of 33,722 CKD patients. RAS blockade users were paired with non-users for analyses using inverse probability of treatment-weighted (IPTW) and propensity score (PS) matching. The outcomes were renal death, all-cause mortality, hospitalization for hyperkalemia, and interactive factors as composite outcomes. RAS blockade users showed an increased risk of renal death in PS-matched analysis (hazard ratio [HR], 1.381; 95% CI, 1.071–1.781; P = 0.013), which was in agreement with the results of IPTW analysis (HR, 1.298; 95% CI, 1.123–1.500; P < 0.001). The risk of composite outcomes was higher in RAS blockade users in IPTW (HR, 1.154; 95% CI, 1.016–1.310; P = 0.027), but was marginal significance in PS matched analysis (HR, 1.243; 95% CI, 0.996–1.550; P = 0.054). The habitual use of RAS blockades in pre-dialysis patients with advanced CKD may have a detrimental effect on renal outcome without improving all-cause mortality. Further studies are warranted to determine whether withholding RAS blockade may lead to better outcomes in these patients.

The characteristics and mortality risk factors for acute kidney injury in different age groups in China-a cross sectional study

AIM

Age is an independent risk factor for acute kidney injury (AKI). The causes and outcomes of AKI in children, middle-aged, and older patients are different. The objective of this country-based study was to identify the characteristics and mortality factors for AKI in different age groups in China.

METHODS

Using data from 374,286 adult patients (≥18 years) admitted to 44 study hospitals, we investigated the characteristics and mortality risk factors for AKI in four different age groups: 18-39 years of age, 40-59 years of age, 60-79 years of age, and ≥80 years of age. The identification criteria for AKI included the 2012 KDIGO AKI definition and an expanded criterion.

RESULTS

The country-based survey included 7604 AKI patients (7604/374,286, 2.03%). The proportions of AKI in the four age groups were 11.52%, 30.79%, 41.03%, and 16.66%, respectively. In any age group, the patients with AKI stage 1 were the majority (43.4%, 42.4%, 46.4%, and 52.2%, respectively), and the most common classification of AKI was pre-renal AKI (44.3%, 51.3%, 52.3%, and 56.4%, respectively). The higher AKI peak stage occurred for the in-hospital mortality factors for AKI in all age groups; except for the AKI stage 2 patients in the 18-39 age group.

CONCLUSION

The characteristics and mortality factors for AKI vary by age in China. Elderly patients were the primary population with AKI, and the most common type of AKI was pre-renal AKI. Special caution should be taken to the old population in hospitalized patients to prevent the pre-renal AKI.

Syndrome of rapid onset end stage renal disease in incident Mayo Clinic chronic hemodialysis patient

Despite decades of research, a full understanding of chronic kidney disease (CKD)-end stage renal disease (ESRD) progression remains elusive. The common consensus is a predictable, linear, progressive and time-dependent decline of CKD to ESRD. Acute kidney injury (AKI) on CKD is usually assumed to be transient, with recovery as the expected outcome. AKI-ESRD association in current nephrology literature is blamed on the so-called "residual confounding." We had previously described a relationship between AKI events and rapid onset yet irreversible ESRD happening in a continuum in a high-risk CKD cohort. However, the contribution of the syndrome of rapid onset-ESRD (SORO-ESRD) to incident United States ESRD population remained conjectural. In this retrospective analysis, we analyzed serum creatinine trajectories of the last 100 consecutive ESRD patients in 4 Mayo Clinic chronic hemodialysis units to determine the incidence of SORO-ESRD. Excluding 9 patients, 31 (34%) patients, including two renal transplant recipients, had SORO-ESRD: 18 males and 13 females age 72 (range 50-92) years. Precipitating AKI followed pneumonia (8), acutely decompensated heart failure (7), pyelonephritis (4), post-operative (5), sepsis (3), contrast-induced nephropathy (2), and others (2). Time to dialysis was shortest following surgical procedures. Concurrent renin angiotensin aldosterone system blockade was higher with SORO-ESRD - 23% versus 5%, P = 0.0113. In conclusion, SORO-ESRD is not uncommon among the incident general US ESRD population. The implications for ESRD care planning, AV-fistula-first programs, general CKD care and any associations with renal ageing/senescence warrant further study.

Derivation and validation of a risk score for contrast-induced nephropathy after cardiac catheterization in Chinese patients

BACKGROUND

To derive and validate a risk score for prediction of contrast-induced nephropathy (CIN) in the Chinese patients undergoing cardiac catheterization.

METHODS

The hospital medical records of 3945 patients undergoing coronary angiography or percutaneous coronary intervention were reviewed. Patients were randomly assigned into two cohorts: one was for derivation of risk score (n = 2764) and another for validation (n = 1181). The CIN was defined as an increase of serum creatinine level ≥44.2 μmol/L or ≥25 % and beyond its upper limit of normal value within 72 h following the procedure. On the basis of the odds ratio obtained from multivariate logistic regression, risk score of CIN was built up. The discrimination of the risk score was assessed using the area under the receiver operating characteristic curve and the calibration was assessed using the Hosmer-Lemeshow goodness-of-fit test.

RESULTS

The incidences of CIN in the derivation and validation cohorts were 4.6 and 4.2 %, respectively. Independent predictors included age >60 years, hypertension, acute myocardial infarction, heart failure, use of intra-aortic balloon pump, decreased glomerular filtration rate and contrast volume >100 mL. The incidence of CIN was increased with increment of risk score. Both the derivation and validation cohorts showed adequate discrimination (an area under the ROC curve, 0.76 and 0.71, respectively) and good calibration (Hosmer-Lemeshow statistic test, P = 0.50 and P = 0.54, respectively).

CONCLUSION

A simple risk score for prediction of CIN development after cardiac catheterization in Chinese patients was built up by this study. Use of this risk score may help clinicians to perform early preventative strategies to minimize the risk of CIN.

Relationship between urinary fractional excretion of sodium and life prognosis in liver cirrhosis patients

AIM

Renal vasoconstriction in generalized vasodilatation with blood pooling and the consequent reduction in effective arterial volume is the pathophysiological basis of liver cirrhosis (LC). Low levels of fractional excretion of sodium (FENa) are an effective marker of hypoperfusion of the renal artery. However, the relationship between levels of FENa, LC severity and life prognosis has not yet been elucidated.

METHODS

We examined 57 LC patients (39 men and 18 women; mean age, 70.5 ± 8.8 years; underlying liver disease, type B hepatitis in eight patients, type C hepatitis in 37, alcoholic hepatitis in four and others in eight) with renal dysfunction (estimated glomerular filtration rate (eGFR) <60 mL/min) who were admitted to our hospital.

RESULTS

Nine patients died because of uremia, liver failure, gastrointestinal bleeding and infection. No differences were found in patient background and blood pressure. However, in addition to differences in the levels of aspartate aminotransferase (AST), cholinesterase, albumin, prothrombin time (PT), eGFR and Model for End-Stage Liver Disease (MELD) score, the patients who died had significant differences in levels of FENa. The levels of FENa were significantly and inversely correlated with blood urea nitrogen, total bilirubin, AST, Child-Pugh score and MELD score, and were significantly and positively correlated with cholinesterase, albumin and PT. Moreover, the sensitivity (88%) and specificity (93%) of the levels of FENa of less than 0.4% to predict death were remarkably high.

CONCLUSION

Levels of FENa may reflect LC severity and may be associated with the life prognosis of LC patients.

Therapeutic apheresis in the elderly: an update

Therapeutic apheresis medicine comprises many procedures, the most common being therapeutic plasma exchange (TPE). There is wide acceptance and use of TPE in the treatment of disease conditions that cut across several organ systems in the body and affect patients of various age groups. Patients that are 65 years or older form a significant cohort with increasing need for TPE. This brief report addresses special considerations in this cohort with useful comparisons made with younger cohorts as presented in the Therapeutic Apheresis Academy at the University of Virginia in September 2012.

The effect of antihypertensive drugs on chronic kidney disease: a comprehensive review

Data from randomized clinical trials and epidemiological evidence identify systemic hypertension as the second most common modifiable risk factor for chronic kidney disease (CKD) progression after diabetes mellitus. CKD may progress silently over the years and early diagnosis and control of hypertension is of major importance in delaying renal function decline. Recent guidelines for the treatment of hypertension suggest the use of a variety of antihypertensive drugs in order to achieve the desired blood pressure levels. Renin-angiotensin system inhibitors have been undoubtedly studied the most and are suggested by guidelines and experts as first choice in patients with hypertension and renal injury, particularly in those with diabetes, as they have repeatedly shown to significantly reduce proteinuria. Other classes of antihypertensive drugs have been studied to a lesser extent and they have their own unique properties and effects. However, it is now common knowledge that adequate blood pressure control is the most important factor for the preservation of renal function, so every drug that effectively lowers hypertension is believed to be renoprotective. The present article will review the latest data on the role and properties of each class of antihypertensive drugs on CKD.

Elderly patients with acute kidney injury (AKI): clinical features and risk factors for mortality

PURPOSE

Elderly patients with AKI are associated with considerable mortality. The clinical features and risk factors predicting poor outcomes of these patients are not known. The aim of this study is to investigate the clinical features and risk factors affecting mortality in elderly patients with AKI.

METHODS

A prospective study on the elderly patients with AKI (age ≥65 years old) was conducted. A consecutive sample of 99 elderly patients with AKI was evaluated. These patients were divided into survivor group and non-survivor group according their outcomes. Factors including clinical characteristics and laboratory features were compared between these two groups. Analysis of correlations between death and categorized risk factors was done by means of Pearson's chi-squared test (or Fisher's exact test). Multivariate logistic regression was performed to analyze the possible risk factors for death.

RESULTS

The main causes of the elderly patients with AKI were ischemia (53.34%), surgery (33.33%), sepsis/infection (10.10%), nephrotoxic drug (3.03%). The mortality rate of the elderly patients with AKI was 42%. Significant differences were found between the survival group and non-survival group of the elderly patients in concomitant disease, complicated with multiple organ dysfunction syndrome (MODS), albumin, etc. Concomitant disease and MODS were found to be the independent risk factors for death of the elderly patients with AKI after adjusting for age, sex, pre-albumin, sepsis/infection, and serum creatinine (SCr).

CONCLUSION

This study found that concomitant disease and MODS were the independent risk factors for the death of elderly patients with AKI.

[Acute renal failure in the elderly]

Acute renal failure in elderly patients is common and likely to become more so as life expectancy in France continues to grow. The chances of acute renal failure occurring in the elderly are increased by changes in renal function and the effects of various chronic diseases such as diabetes, hypertension and obstructive urological disorders, all of which increase in incidence with age. The elderly may develop all types of the disease but are most prone to drug-related acute renal failure. The diagnostic and therapeutic strategies adopted are the same as those for adult patients but should take into account the potential risks and benefits in this specific age group. However, age should no longer be considered as the sole determining factor in diagnostic and therapeutic decisions. The elderly are among those who benefit most from preventive measures against acute renal failure.

Use of renal biopsy in the elderly

Renal biopsy is an essential tool in the management of kidney disease. A biopsy provides a diagnosis, guides therapy and aids in prognosis, and this is true for persons of all ages. For a variety of reasons, nephrologists are sometimes hesitant to perform a biopsy in an older person. There is the major issue of a lack of perceived benefit that the biopsy will not show a treatable lesion and that therapy may not be possible in an older person. Additionally, concerns of safety may also influence the decision to biopsy. In this review, we will address these issues in the context of clinical renal syndromes and common kidney diseases in the elderly and weigh the benefit of biopsy in various situations. In general, the indications are the same as in the adult population, as is the risk associated with the biopsy procedure. Therapy, as for adults, is often successful, although further assessment of risk-benefit ratio is necessary. Age, by itself, is not a contraindication to biopsy.

Acute kidney injury in the elderly population

The elderly population is more prone to acute kidney injury (AKI) than younger populations. Older patients have less renal reserve because of reduced glomerular filtration rates due to anatomic/functional changes, and concomitant diseases such as hypertension, diabetes, atherosclerosis, heart failure, ischemic renal disease, and obstructive uropathy. The risk of AKI may also increase as a result of aggressive diagnostic and therapeutic procedures, which include medical agents, radiology, and surgical intervention. AKI in the elderly has a multifactorial physiopathology due to different etiologies. Studies that have specifically compared prognosis of AKI in elderly versus young over the recent years suggest that age is a predictor of long-term outcome. In most cases, the treatment of AKI is similar for all age groups. The majority of critically ill patients with AKI will eventually need renal replacement therapy (RRT). The influence of RRT on renal outcome remains a subject of intense investigation and debate. Avoiding situations that could damage the kidney is an important strategy to prevent AKI development in the elderly, besides medical and interventional therapeutics.

The human urinary proteome reveals high similarity between kidney aging and chronic kidney disease

Aging induces morphological changes of the kidney and reduces renal function. We analyzed the low molecular weight urinary proteome of 324 healthy individuals from 2-73 years of age to gain insight on human renal aging. We observed age-related modification of secretion of 325 out of over 5000 urinary peptides. The majority of these changes were associated with renal development before and during puberty, while 49 peptides were related to aging in adults. We therefore focussed the remainder of the study on these 49 peptides. The majority of these 49 peptides were also markers of chronic kidney disease, suggesting high similarity between aging and chronic kidney disease. Blinded evaluation of samples from healthy volunteers and diabetic nephropathy patients confirmed both the correlation of biomarkers with aging and with renal disease. Identification of a number of these aging-related peptides led us to hypothesize that reduced proteolytic activity is involved in human renal aging. Finally, among the 324 supposedly healthy individuals, some had urinary aging-related peptide excretion patterns typical of an individual significantly older than their actual age. In conclusion, these aging-related biomarkers may allow noninvasive detection of renal lesions in healthy persons and show high resemblance between human aging and chronic kidney disease. This similarity has to be taken into account when searching for biomarkers of renal disease.

Creatinine reabsorption by the aged kidney

AIM

The handling of renal creatinine in human beings has classically been described as the result of two particular physiological processes: glomerular filtration and proximal tubular secretion. However, there are particular physiological situations in which tubular creatinine reabsorption has been documented, such as in the case of healthy newborns and premature babies. We performed a prospective study in order to evaluate if there is tubular creatinine reabsorption in healthy elderly people.

PATIENTS AND METHOD

We studied prospectively nine healthy volunteers, four of them young (20-33 years old) and the remaining five, old (65-73 years old). Since creatinine is secreted in the proximal tubules, and its secretion can be completely blocked by cimetidine administration, a creatinine clearance with cimetidine reliably represents the glomerular filtration rate. Therefore, if the ratio creatinine clearance (Ccr)/creatinine clearance with cimetidine (CcrWC) is higher than one, this would indicate net creatinine secretion, whereas a ratio lower than one would indicate a net renal creatinine tubular reabsorption; a ratio equal to one indicates creatinine filtration. Finally, the Ccr, CcrWC, and Ccr/CcrWC ratios were compared between the young and old group.

STATISTICAL TESTS

Mann-Whitney and Wilcoxon tests were used.

RESULTS

As expected, creatinine clearance in the elderly was significantly lower than in the young [Ccr: 74.4 ml/min (47.9-100.9) (old) vs. 153.8 ml/min (108.3-199.2) (young), p = 0.014]. Similarly, the creatinine clearance with cimetidine (CcrWC) was significantly lower in the elderly compared to the young [CcrWC: 81.8 ml/min (69.2-94.5) (old) vs. 122.5 ml/min (82.6-162.4) (young), p = 0.028]. The ratio of Ccr/CcrWC was 0.9 in the elderly vs. 1.26 in the young (p = 0.014), indicating net creatinine reabsorption in the elderly and net creatinine secretion in the young.

CONCLUSION

Our findings indicate that there seems to be a net reabsorption of creatinine in the renal tubules of healthy old persons.

Renal senescence in 2008: progress and challenges

Kidneys are significantly affected by profound anatomic and functional changes with senescence. These changes lead to decline in glomerular filtration rate, decreased urinary concentrating and diluting ability, diminished urinary acidification, and impaired potassium clearance, to list a few. Such changes make the elderly prone to drug toxicity and serious fluid and electrolyte imbalance. While the entire mystery of aging is far from being clear, the role of oxidative stress, telomere length, Klotho gene expression, and the renin angiotensin system seem to be the key mechanisms involved in aging. Aging, being a complex process, involves an array of intertwined molecular pathways. Simultaneous study of multiple molecular pathways in parallel could provide invaluable information in understanding the clinical course of kidney aging and elucidating mechanisms that play key roles in the aging process. A better understanding of these mechanisms may help to preserve renal function, improve morbidity and mortality, and hopefully reduce healthcare costs for the aging population.