Retarding the progression of renal disease

Validation of the Kidney Failure Risk Equation in the Colombian Population

Introduction

Chronic kidney disease prevention programs must identify patients at risk of early progression to provide better treatment and prolong kidney replacement therapy-free survival. Risk equations have been developed and validated in cohorts outside of Colombia, so this study aims to evaluate the discrimination and calibration of the four-variable kidney failure risk equation in a Colombian population where it has yet to be validated.

Methods

External validation study of a kidney failure risk equation using a historical cohort of patients with CKD stages 3, 4, and 5, adults without a history of dialysis or kidney transplantation with a two-year follow-up, belonging to the Baxter Renal Care Services Colombia network. The discriminatory capacity of the model was evaluated by the concordance index using Harrell's C statistic, and the time-dependent area under the receiver operating characteristic (ROC) curve was estimated using the nearest neighbor method, as well as the optimal cut-off point for sensitivity and specificity. Calibration was determined by the degree of agreement between the observed outcome and the probabilities predicted by the model using the Hosmer-Lemeshow statistic.

Results

A total of 5,477 patients were included, with a mean age of 72 years, 36.4% diabetic, and a mean baseline eGFR of 36 ml/min/1.73 m2. The rate of dialysis initiation was three events per 100 patient-years, 95% CI (2.9-3.6). The optimal cutoff for sensitivity was 0.94, for specificity, 0.76, and the area under the ROC curve was 0.92. Harrell's C-statistic was 0.88 for the total population, 0.88 for diabetic patients, and 0.93 for those 65 years or older. The validation of the model showed good calibration.

Conclusions

In this Colombian cohort, the four-variable KFRE with a two-year prediction horizon has excellent calibration and discrimination, and its use in the care of CKD Colombian patients is recommended.

Can SGLT2 inhibitors answer unmet therapeutic needs in chronic kidney disease?

Chronic kidney disease (CKD) is a global health problem, affecting more than 850 million people worldwide. The number of patients receiving renal replacement therapy (dialysis or renal transplantation) has increased over the years, and it has been estimated that the number of people receiving renal replacement therapy will more than double from 2.618 million in 2010 to 5.439 million in 2030, with wide differences among countries. The main focus of CKD treatment has now become preserving renal function rather than replacing it. This is possible, at least to some extent, through the optimal use of multifactorial therapy aimed at preventing end-stage kidney disease and cardiovascular events. Sodium/glucose cotransporter 2 inhibitors (SGLT2i) reduce glomerular hypertension and albuminuria with beneficial effects on progression of renal damage in both diabetic and non-diabetic CKD. SGLT2 inhibitors also show great benefits in cardiovascular protection, irrespective of diabetes. Therefore, the use of these drugs will likely be extended to the whole CKD population as a new standard of care.

Chronic Kidney Disease Progression and Transition Probabilities in a Large Preventive Cohort in Colombia

BACKGROUND

Variability in chronic kidney disease (CKD) progression is a well-known phenomenon that underlines the importance of characterizing the said outcome in specific populations. Our objectives were to evaluate changes in the estimated glomerular filtration rate (eGFR) over time and determine the frequency of dialysis admission and factors associated with this outcome, to estimate the rate of program's loss-to-follow-up and the probability of transition between CKD stages over time.

METHODS

The study type was an observational analytic retrospective cohort in patients treated in a CKD prevention program in Bogota, Colombia, between January 1, 2009, and December 31, 2013, with follow-up until December 31, 2018. Adult participants of 18 years of age or older with diagnosed CKD stages G3 or G4 were enrolled into a prevention program. For each patient, the rate of progression of CKD in ml/min/1.73 m2/year was estimated using the ordinary least-squares method. Dialysis initiation and program's loss-to-follow-up rates were calculated. Heat maps were used to present probabilities of transitioning between various CKD stages over time. Survival model with competing risks was used to evaluate factors associated with dialysis initiation.

RESULTS

A total of 2752 patients met inclusion criteria and contributed with 14133 patient-years of follow-up and 200 dialysis initiation events, which represents a rate of 1.4 events per 100 patient-years (95% CI 1.2 to 1.6). The median change of the eGFR for the entire cohort was -0.47 ml/min/1.73 m2 per year, and in the diabetic population, it was -1.55 ml/min/1.73 m2 per year. The program's loss-to-follow-up rate was 2.6 events per 100 patient-years (95% CI 2.3 to 2.9). Probabilities of CKD stage transitions are presented in heat maps. Female sex, older age, baseline eGFR, and serum albumin were associated with lower risk of dialysis initiation while CKD etiology diabetes, cardiovascular disease history, systolic blood pressure, blood urea nitrogen, and LDL cholesterol were associated with a higher likelihood of dialysis initiation.

CONCLUSIONS

A CKD secondary prevention program's key indicator is reported here, such as dialysis initiation, progression rate, and program drop-out; CKD progression appears to be correlated with diabetic status and timing of referral into the preventive program.

Usefulness of urinary parameters in advanced chronic kidney disease

This review discusses the diagnostic value of urinary parameters in the setting of advanced chronic kidney disease and we present the key concepts that summarise the suggestions of the manuscript.

URINARY VOLUME

The amount of fluid intake may be a non-established risk factor for CKD. For these patients, a urinary output ≥2-3 l/day is a reasonable proposal. This recommendation is not applicable to patients with cardiorenal syndrome or fluid overload risk. NA: This determination is very useful to monitor salt intake. Reducing urinary Na<120 mEq/day (≅salt intake≤5-6g) is a reasonable objective.

URINARY UREA NITROGEN (UUN)

This parameter is useful to estimate protein intake (Maroni BJ equation). A protein intake between 48-72g (0.8-0.9g/kg/day according to weight) is equivalent to UUN 7-10g/day approximately.

ACID LOAD AND POTASSIUM

Acid load reduction may be an additional strategy in the nutritional management of this population. It may be estimated indirectly from a diet survey or by measuring the elimination of UUN and K_ur. The limits of this recommendation have not been established, but we propose a cautious and prudent diet of fruit and vegetables.

PHOSPHORUS

There is a significant positive correlation between phosphorus and protein, both in dietary records and urine elimination. Based on this information, we suggest a urinary P excretion<800mg/day or<600mg/day for patients with GFR<25ml/min or<15ml/min, respectively.

CONCLUSION

Urinary parameters provide sensitive and useful knowledge for clinical practice, provide information about the dietary habits of patients and the adherence to our recommendations.

Analysis of emergency Department Frequentation among patients with advanced CKD (chronic kidney disease): Lessons to optimise scheduled renal replacement therapy initiation

The decision to initiate renal replacement therapy (RRT) implies a wide margin of uncertainty. Glomerular filtration rate (GFR) tells us the magnitude of renal damage. Proteinuria indicates the speed of progression. However, nowadays more than 50% of patients are still initiating RRT hastily, and it is life threatening.

HYPOTHESIS

By analysing Emergency Department (ED) frequentation and causes of a hurried initiation, we can better schedule the timing of the start of RRT.

METHOD

Retrospective and observational study of all CKD patients in our outpatient clinic. ED frequentation and hospitalisation (Hos) time were reviewed during a 12-month period. We analysed: 1) time at risk, purpose (modality of RRT), previous comorbidity; 2) causes of ED frequentation and Hos; 3) type of initiation: «scheduled» vs. «non-scheduled», and within these «non-planned» vs. «potentially planned».

RESULTS

Of a total of 267 patients (time at risk 63.987 days, 70±13 years, 67% males, 38% diabetics), 68 (25%) patients came to hospital on 97 occasions: 39 only ED, 46 ED+Hos and 12 only Hos. ED frequentation was one patient every 4.3 days, and bed occupation was almost 3 per day. Main causes: 47% cardiopulmonary (1/3 heart failure), 11% vascular peripheral+cerebral, 11% gastrointestinal: 8/11 due to bleeding (all with anticoagulants/antiplatelet agents). Thirty-one (12%) patients initiated RRT: of these, 14 (45%) were scheduled (6 PD, 6 HD, and 2 living donor RTx), and 17 (55%) were not scheduled or were rushed, all with venous central catheter. Following the objectives of this study, the non-scheduled group were itemised into 2 groups: 9 non-planned (initial indication of conservative management or patient's refusal to undergo dialysis, and diverse social circumstances not controllable by the nephrologist) and 8 were considered potentially planned (6 heart failure, one gastrointestinal bleeding and one peripheral vascular complication). This last group (potentially planned), when compared with the 14 patients who started treatment in a scheduled manner, had significant differences in that they were older, with more previous cardiac events, and GFR almost double that of the other group. All of them started treatment in the ED.

CONCLUSION

This analysis provides us with knowledge on those patients who may benefit from an earlier preparation in RRT. We suggest that patients with previous cardiac events, especially with a risk of gastrointestinal bleeding, should start the preparation for RRT even with GFR rates of 20^-25ml/min. In spite of the retrospective nature of this study, and taking into account the difficulties of carrying out clinical trials in this population, we propose this suggestion as complementary to the current recommendations for a scheduled start using this technique.

Stage 5-CKD under nephrology care: to dialyze or not to dialyze, that is the question

Appropriate timing of starting chronic dialysis in patients with advanced chronic kidney disease (CKD) under nephrology care still is undefined. We systematically reviewed the most recent studies that have compared outcomes of stage 5-CKD under conservative versus substitutive treatment. Eleven studies, most in elderly patients, were identified. Results indicate no advantage of dialysis over conservative management in terms of survival, hospitalization or quality of life. This information is integrated with a case report on a middle-aged CKD patient followed in our clinic who has remained for 15 years in stage 5 despite severe disease. The patient is a diabetic woman who underwent right nephrectomy in 1994 because of renal tuberculosis. In 1999, she commenced regular nephrology care in our clinic and, since 2000, when she was 53 years old, her estimated glomerular filtration rate (eGFR) has been ≤15 ml/min/1.73 m(2). Over the last decade, despite, several episodes of acute kidney injury and placement of permanent percutaneous nephrostomy in 2001, renal function has remained remarkably stable, though severely impaired (eGFR 7.7-5.6 ml/min/1.73 m(2)). Our systematic analysis of the literature and this case report highlight the need for further studies, not limited exclusively to elderly patients, to verify the efficacy of non-dialysis treatment in stage 5-CKD patients. Meanwhile, nephrologists may consider that their intervention can safely prolong for several years the dialysis-free condition in ESRD independently of age.

Aldosterone antagonists for preventing the progression of chronic kidney disease

BACKGROUND

Treatment with angiotensin-converting enzyme inhibitors (ACEi) and angiotensin receptor blockers (ARB) is increasingly used to reduce proteinuria and retard the progression of chronic kidney disease (CKD). However, resolution of proteinuria may be incomplete with these therapies and the addition of an aldosterone antagonist may be added to further prevent progression of CKD. This is an update of a review first published in 2009.

OBJECTIVES

To evaluate the effect of aldosterone antagonists (both selective (eplerenone) and non-selective (spironolactone)) alone or in combination with ACEi or ARB in adults who have CKD with proteinuria (nephrotic and non-nephrotic range) on: patient-centred endpoints including major cardiovascular events, hospitalisation and all-cause mortality; kidney function (proteinuria, glomerular filtration rate (GFR), serum creatinine, and need for renal replacement therapy; and adverse events (including gynaecomastia and hyperkalaemia).

SEARCH METHODS

For this update, we searched the Cochrane Renal Group's Specialised Register to 30 January 2013 using search terms relevant to this review.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and quasi-RCTs that compared aldosterone antagonists alone or in combination with ACEi or ARB (or both) with other anti-hypertensive strategies or placebo.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed study quality and extracted data. Data were summarised using random effects meta-analysis. We tested for heterogeneity in estimated treatment effects using the Cochran Q test and I² statistic. We expressed summary treatment estimates as a risk ratio (RR) for dichotomous outcomes together with their 95% confidence intervals (CI) and mean difference (MD) for continuous outcomes, or standardised mean difference (SMD) when different scales were used.

MAIN RESULTS

We identified 27 studies (1549 participants) that were eligible for inclusion. These studies provided no data relating to aldosterone antagonists in addition to ACEi or ARB (or both) on patient-level outcomes including major cardiovascular events and mortality and progression to end-stage kidney disease (ESKD) requiring dialysis or transplantation.Compared with ACEi or ARB (or both), non-selective aldosterone antagonists (spironolactone) combined with ACEi or ARB (or both) significantly reduced 24-hour protein excretion (11 studies, 596 participants): SMD -0.61, 95% CI -1.08 to -0.13). There was a significant reduction in both systolic and diastolic blood pressure (BP) at the end of treatment with additional non-selective aldosterone antagonist therapy (systolic BP (10 studies, 556 participants): MD -3.44 mm Hg, 95% CI -5.05 to -1.83) (diastolic BP (9 studies, 520 participants): MD -1.73 mm Hg, 95% CI -2.83 to -0.62).However, we found that aldosterone antagonist treatment had imprecise effects at the end of treatment on GFR (9 studies, 528 participants; MD -2.55 mL/min/1.73 m², 95% CI -5.67 to 0.51), doubled the risk of hyperkalaemia (11 studies, 632 patients): RR 2.00, 95% CI 1.25 to 3.20; number needed to treat for an additional harmful outcome (NNTH): 7.2, 95% CI 3.4 to ∞) and increased the risk of gynaecomastia compared to ACEi or ARB (or both) (4 studies, 281 patients): RR 5.14, 95% CI 1.14 to 23.23; NNTH: 14.1, 95% CI 8.7 to 37.3).Most studies enrolled few patients (range 12 to 268) and were powered to observe differences in surrogate end points rather than patient-focused outcomes. Nine studies had a cross-over design and the majority of studies did not adequately report study methods to assess methods and study quality.

AUTHORS' CONCLUSIONS

Aldosterone antagonists reduced proteinuria and blood pressure in adults who had mild to moderate CKD and were treated with ACEi or ARB (or both), but increase hyperkalaemia and gynaecomastia. Whether adding aldosterone antagonists to ACEi or ARB (or both) reduced the risk of major cardiovascular events or ESKD in this population is unknown.

Predictors of proteinuria reduction by monotherapy with an angiotensin receptor blocker, olmesartan

INTRODUCTION

It is known that reduced glomerular filtration rate (GFR) is a crucial factor to limit the blood pressure lowering effect of antihypertensives. In the present study, we tested whether the effects of monotherapy with an angiotensin receptor blocker (ARB) to lower proteinuria could be restricted by reduced GFR.

MATERIALS AND METHODS

Thirty-five renal patients who had albuminuria more than 30 mg/day, but did not have diabetic nephropathy or nephrotic syndrome, were studied before and during eight weeks of monotherapy with ARB, olmesartan.

RESULTS

Blood pressure was lowered from 129 ± 18/79 ± 12 to 116 ± 18/72 ± 12 mmHg (p < 0.0001), while albuminuria was reduced from 614±630 to 343±472 mg/day (p < 0.0001). Albuminuria was inversely correlated with GFR both before and during treatment. Albuminuria reduction was enhanced as plasma renin activity (p = 0.047) and dose of olmesartan were increased (p = 0.04). Although the absolute reduction in proteinuria was not correlated with GFR (p = 0.56), the % reduction was significantly proportional with GFR (p = 0.027). Multiple regression analysis demonstrated that 64% of proteinuria reduction could be explained by baseline levels of albuminuria, GFR and renin activity.

CONCLUSIONS

The reduction in proteinuria by olmesartan may be roughly predicted using baseline GFR and other parameters. These findings clarify that the effect of ARB on proteinuria reduction is restricted by reduced GFR.

Chronic kidney disease epidemic: myth and reality

In recent years, an epidemic of chronic kidney disease (CKD) has emerged as one of the major public health problem. The prevalence of CKD is largely sustained by the inclusion of a substantial proportion of the elderly population within stage 3 CKD, according to the Kidney Disease Outcomes Quality Initiative staging system. However, some clarifications are necessary when interpreting these data. In fact, renal function "normally" declines with age, without bearing any unfavourable outcome; in addition, the Modification of Diet in Renal Disease formula used to calculate glomerular filtration rate (GFR) underestimates kidney function in the elderly and in women. Considerable interest in CKD has been generated by the evidence that predialysis CKD is associated with the increased risk of cardiovascular disease (CVD). Again, potential confounding factors must be ruled out. Age is thought to play a major role in this context. The most common causes of CKD, hypertension and diabetes mellitus, are also known to affect cardiovascular outcomes directly, thus preventing the recognition of an independent effect of kidney dysfunction on mortality by CVD. Taken together, these considerations point for a better definition of CKD. Early identification of patients at risk for accelerated decline in renal function is mandatory to plan strategies for screening and preventing CKD and its complications. At present, detection of CKD in the general population requires a multi-dimensional approach that should include the evaluation of clinical risk conditions, evaluation of albuminuria and sequential monitoring of GFR.

Novel therapies for resistant focal segmental glomerulosclerosis (FONT) phase II clinical trial: study design

Background

The lack of adequate randomized clinical trials (RCT) has hindered identification of new therapies that are safe and effective for patients with primary focal segmental glomerulosclerosis (FSGS), especially in patients who fail to respond to corticosteroids and immunosuppressive therapies. Recent basic science advances have led to development of alternative treatments that specifically target aberrant pathways of fibrosis which are relevant to disease progression in FSGS. There is a need for a flexible Phase II study design which will test such novel antifibrotic strategies in order to identify agents suitable for phase III testing.

Methods/Design

The Novel Therapies for Resistant Focal Segmental Glomerulosclerosis (FONT) project is a multicenter Phase I/II RCT designed to investigate the potential efficacy of novel therapies for resistant FSGS. Adalimumab and galactose will be evaluated against conservative therapy consisting of the combination of lisinopril, losartan and atorvastatin. The sample size is defined to assure that if one of the treatments has a superior response rate compared to that of the other treatments, it will be selected with high probability for further evaluation. Comparison of primary and secondary endpoints in each study arm will enable a choice to be made of which treatments are worthy of further study in future Phase III RCT.

Discussion

This report highlights the key features of the FONT II RCT including the two-step outcome analysis that will expedite achievement of the study objectives. The proposed phase II study design will help to identify promising agents for further testing while excluding ineffective agents. This staged approach can help to prevent large expenditures on unworthy therapeutic agents in the management of serious but rare kidney diseases

Trial Registration

ClinicalTrials.gov, NCT00814255

Timely referral to the nephrologist: essential to optimizing patient outcomes

Annual mortality on renal replacement therapy is about 10% in Western Europe and reaches 20% in the United States. The reasons responsible for this excess mortality include among others advanced age, high prevalence of diabetes and comorbid conditions, susceptibility to infections, and cancer. An additional cause that should be considered is late referral to overall renal care and for renal replacement therapy. It has been demonstrated recently that early referral may provide many advantages for the patient, such as prevention of organ damage secondary to uremia and even delay the onset of end-stage renal disease. These benefits prompted numerous recommendations for timely referral, both for dialysis and for long-term renal follow-up. Despite available guidelines for nephrology referral the current practice is still suboptimal, resulting in delayed initiation of dialysis and clinical outcomes that are not ideal. There is an urgent need in the renal community to change the current practice of referral. Beyond the benefits for patients, society may also expect potential cost effectiveness from early renal care.

Pharmacogenomics: a new paradigm to personalize treatments in nephrology patients

Although notable progress has been made in the therapeutic management of patients with chronic kidney disease in both conservative and renal replacement treatments (dialysis and transplantation), the occurrence of medication-related problems (lack of efficacy, adverse drug reactions) still represents a key clinical issue. Recent evidence suggests that adverse drug reactions are major causes of death and hospital admission in Europe and the United States. The reasons for these conditions are represented by environmental/non-genetic and genetic factors responsible for the great inter-patient variability in drugs metabolism, disposition and therapeutic targets. Over the years several genetic settings have been linked, using pharmacogenetic approaches, to the effects and toxicity of many agents used in clinical nephrology. However, these strategies, analysing single gene or candidate pathways, do not represent the gold standard, being the overall pharmacological effects of medications and not typically monogenic traits. Therefore, to identify multi-genetic influence on drug response, researchers and clinicians from different fields of medicine and pharmacology have started to perform pharmacogenomic studies employing innovative whole genomic high-throughput technologies. However, to date, only few pharmacogenomics reports have been published in nephrology underlying the need to enhance the number of projects and to increase the research budget for this important research field. In the future we would expect that, applying the knowledge about an individual's inherited response to drugs, nephrologists will be able to prescribe medications based on each person's genetic make-up, to monitor carefully the efficacy/toxicity of a given drug and to modify the dosage or number of medications to obtain predefined clinical outcomes.

Similar renal decline in diabetic and non-diabetic patients with comparable levels of albuminuria

BACKGROUND

Diabetes is the main cause of ESRD, and albuminuria is a major determinant of adverse renal outcome. Likewise, albuminuria is an intermediate risk factor of chronic kidney disease (CKD) progression in diabetic patients. Our aim was to compare the rate of renal decline in diabetic and non-diabetic CKD patients (GFR < 50 ml/min) with comparable levels of albuminuria.

METHODS

In this observational study, 333 patients (age 67 +/- 15 years, 46% diabetics) were included during a 7.5-year period. The mean follow-up was 30 +/- 18 months (range 4-79). The influence of study variables was evaluated applying a time-dependent Cox model and slope-based outcome using a linear regression model.

RESULTS

The diabetes condition was associated with adverse outcome in univariate analysis, and after adjusting for age, sex and systolic blood pressure. However, when controlling for albuminuria (a time-dependent covariate), diabetes did not show any association with outcome. In addition, the mean slope of renal decline was similar in diabetic and non-diabetic patients when controlling for albuminuria. The urinary albumin-creatinine ratio was a robust predictor of poor outcome in uni- and multivariate models. In the diabetic group, time-varying glycosilated haemoglobin did not influence renal outcome in the Cox model, and time-varying albuminuria remained a strong predictor of outcome.

CONCLUSIONS

Diabetic patients have a poorer renal outcome, but at comparable levels of albuminuria renal decline is similar in diabetic and non-diabetic patients. Albuminuria is a risk factor for renal decline, and the main target to delay progression in patients, diabetics or non-diabetics, with moderate to advanced CKD.

Aldosterone antagonists for preventing the progression of chronic kidney disease

BACKGROUND

Treatment with angiotensin converting enzyme inhibitors (ACEi) and angiotensin receptor blockers (ARB) is increasingly used to reduce proteinuria and retard the progression of chronic kidney disease (CKD). But some patients do not attain complete resolution of proteinuria and might have higher aldosterone levels within few months of treatment. The addition of aldosterone antagonists may be beneficial to these patients for reduction of progression of renal damage.

OBJECTIVES

We evaluated the benefits and harms of adding aldosterone antagonists in patients with CKD currently treated with ACEi and/or ARB.

SEARCH STRATEGY

We searched MEDLINE, EMBASE, CENTRAL, and hand-searched reference lists of textbooks, articles and scientific proceedings for relevant articles.

SELECTION CRITERIA

Randomised controlled trials (RCTs) and quasi-RCTs comparing aldosterone antagonists in addition to ACEi and/or ARB versus ACEi and/or ARB alone were included.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed study quality and extracted data. Statistical analyses were performed using a random effects model and heterogeneity was tested formally using the Cochran Q and I(2) statistic. Results were expressed as mean difference (MD) for continuous outcomes and risk ratio (RR) for dichotomous outcomes with 95% confidence intervals (CI).

MAIN RESULTS

Ten studies (845 patients) were included. Compared to ACEi and/or ARB plus placebo, non-selective aldosterone antagonists along with ACEi and/or ARB significantly reduced 24 hour proteinuria (7 studies, 372 patients; MD -0.80 g, 95% CI -1.23 to -0.38). There was a significant reduction in both systolic and diastolic blood pressure at the end of treatment with the addition of non-selective aldosterone antagonists to ACEi and/or ARB. This did not translate into an improvement in glomerular filtration rate (5 studies, 306 patients; MD -0.70 mL/min/1.73 m(2), 95% CI -4.73 to 3.34). There was a significant increase in the risk of hyperkalaemia with the addition of non-selective aldosterone antagonists to ACEi and/or ARB (8 studies, 436 patients; RR 3.06, 95% CI 1.26 to 7.41). In two studies, the addition of selective aldosterone antagonists to ACEi resulted in an additional reduction in 24 hour proteinuria but without any impact on BP and renal function. Data on cardiovascular outcomes, long-term renal outcomes and mortality were not available.

AUTHORS' CONCLUSIONS

Aldosterone antagonists contribute to reduction of proteinuria in patients with CKD who are already on ACEi and ARB but increase the risk of hyperkalaemia. Available studies are small and have short follow-up. Long-term effects on renal outcomes, mortality and safety are unknown.

Aldosterone antagonists for preventing the progression of chronic kidney disease: a systematic review and meta-analysis

BACKGROUND AND OBJECTIVES

Addition of aldosterone antagonists (AA) might provide renal benefits to proteinuric chronic kidney disease (CKD) patients over and above the inhibition of renin-angiotensin system blockers (RAS). We evaluated the benefits and harms of adding selective and nonselective AA in CKD patients already on RAS.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

MEDLINE, EMBASE, and Renal Health Library were searched for relevant randomized clinical trials in adult CKD patients. Results were summarized using the random-effects model.

RESULTS

Eleven trials (991 patients) were included. In comparison to angiotensin- converting enzyme inhibitors (ACEi) and/or angiotensin receptor blockers (ARB) plus placebo, nonselective AA along with ACEi and/or ARB significantly reduced 24 h proteinuria (seven trials, 372 patients, weighted mean difference [WMD] -0.80 g, 95% CI -1.27, -0.33) and BP. This did not translate into an improvement in GFR (WMD -0.70 ml/min/1.73m(2), 95% CI -4.73, 3.34). There was a significant increase in the risk of hyperkalemia with the addition of nonselective AA to ACEi and/or ARB (relative risk 3.06, 95% CI 1.26, 7.41). In two trials, addition of selective AA to ACEi resulted in an additional reduction in 24 h proteinuria, without any impact on BP and renal function. Data on cardiovascular outcomes, long-term renal outcomes and mortality were not available in any of the trials.

CONCLUSIONS

Aldosterone antagonists reduce proteinuria in CKD patients already on ACEis and ARBs but increase the risk of hyperkalemia. Long-term effects of these agents on renal outcomes, mortality, and safety need to be established.

Inhibition of the renin-angiotensin system and chronic kidney disease

Chronic kidney disease (CKD), a major worldwide public-health problem which affects about 10% of the population, has an increased annual incidence rate of about 5-8%. This increased incidence is mainly due to type 2 diabetes and hypertension and the increasing incidence of elderly patients with CKD. Although the progression to end-stage renal failure (ESRF) is mainly based upon the underlying disease, comorbid conditions such as an initial low renal function, severe proteinuria, and high levels of blood pressure also play important roles in the development of ESRF. Since experimental and clinical evidence suggest that angiotensin II plays a central role in the progression of CKD, pharmacological inhibition of the renin-angiotensin-aldosteron system (RAAS) with angiotensin converting enzyme inhibitors or angiotensin II receptor antagonists has been suggested as first-line treatment for hypertension and prevention of ESRF in these patients. Aliskiren, a novel renin inhibitor is also a promising medical intervention. However, independently of the category of the drugs used, low target blood pressure levels seem to be equally or more important for the delay or prevention of CKD. In this review the results of studies with pharmacological inhibition of the RAAS in patients with diabetic and nondiabetic nephropathy is discussed.

Care of elderly patients with chronic kidney disease

BACKGROUND

Providing optimal care to the growing number of chronic kidney disease (CKD) patients remains a significant problem in the United States. There is little known about the care of elderly CKD patients by primary care physicians as well as nephrologists.

METHODS

We performed a retrospective study of 377 elderly male CKD (serum creatinine >1.4 mg/dl on 2 separate occasions 3 months apart) patients referred to the Nephrology Clinic at the Buffalo Veterans Administration Medical Center between 1999 and 2002 to see if the pattern of care changed during this time.

RESULTS

The mean age of the patients was 75.9 years. Eighty-four percent were Caucasian, 15% were African-American, and 1% were of other race. Etiology of CKD included hypertensive nephrosclerosis (49%), diabetic nephropathy (23%), renovascular disease (18%), and others (10%). Sixty-five percent of patients had estimated glomerular filtration rate (eGFR) >30 ml/min. Overall angiotensin converting enzyme inhibitor (ACEI) was used in 51% of patients with CKD, and in 63% of patients with diabetic nephropathy. Twenty percent of patients had a hemoglobin <11 g/dl, darbepoietin/epogen was used in 31% of these patients. Screening for kidney related tests were done infrequently while lipid profile and hemoglobin A1C were done in the majority of patients because of clinical reminders in the VA computerized patient record system (CPRS).

CONCLUSION

These results emphasize the need for increased education of primary care physicians and nephrologists to improve the care of elderly CKD patients. Although there was a trend towards earlier referral, care did not change significantly between years 1999 and 2002.

Hyperfiltration, nitric oxide, and diabetic nephropathy

Early diabetes is often accompanied by an increased glomerular filtration rate (GFR). This hyperfiltration, which is significantly dependent upon increased nitric oxide activity, is believed to contribute to progression of diabetic nephropathy. In this article, a technique for the measurement of tubular fluid nitric oxide in vivo, in real time, is reviewed, and findings in three commonly used rodent models of diabetes are described. The mechanisms of altered tubuloglomerular feedback (TGF) in diabetes are also reviewed, with emphasis on hyperfiltration and the role of nitric oxide. New findings on the modulation of hyperfiltration in the classic type 2 diabetes db/db mouse are presented, showing suppression of the TGF mechanism and modulation of single-nephron GFR by a specific nitric oxide synthase inhibitor.

Proteinuria with and without renal glomerular podocyte effacement

Renal biopsies of patients with proteinuria and kidney disease most often are associated with podocyte foot process effacement. For several decades, nephrologists have wondered whether proteinuria is a result of podocyte foot process effacement or the cause of it. In the past few years, the author's laboratory has addressed this issue using different mouse models of proteinuria. Although in most cases, podocyte effacement is associated with proteinuria and glomerular disease, in three different mouse models, it was demonstrated that proteinuria can be observed without podocyte foot process effacement. The first model is generated by injection of antibodies to vascular endothelial growth factor or soluble vascular endothelial growth factor receptor 1. The second model is a mouse with deletion of type IV collagen alpha3 chain in the glomerular basement membrane. The third model was generated by genetic deletion of a slit diaphragm protein known as nephrin. Collectively, these experiments and the supporting evidence from several human studies demonstrate that severe defects in either the glomerular basement membrane or the glomerular endothelium can lead to proteinuria without foot process effacement.

Time to screen for proteinuria?

Screening for proteinuria in childhood is performed in some countries but remains a controversial subject. During the last decade, a greater understanding of the importance of proteinuria for the long-term prognosis of children with renal diseases has been gained. Exciting new data also show that proteinuria is a prognostic factor for long-term cardiovascular outcome.

CONCLUSION

In my opinion, there are still not strong enough reasons to support the routine screening of healthy children for proteinuria.

Acarbose treatment lowers generation and serum concentrations of the protein-bound solute p-cresol: a pilot study

Several protein-bound uremic retention solutes (including p-cresol) originate from colonic bacterial fermentation of protein. Higher colonic availability of carbohydrates drives this process towards lower production of toxic metabolites. Small intestinal alpha-glucosidase inhibitors like Acarbose (Glucobay) enhance the amount of undigested carbohydrates reaching the colon. We studied the effect of Acarbose on generation and serum concentrations of p-cresol. Nine healthy volunteers (age 25 (22-36) years) with a creatinine clearance of 89.6 ml/min/1.73 m(2) (85.5-116.4) were treated with Acarbose for 3 weeks. Dose was gradually increased to reach 300 mg/day after 1 week. Blood sampling, 24-h urine and stool collections on 3 consecutive days were performed before and during the last days of the treatment period. p-Cresol generation was estimated from mean 24-h urinary elimination. Gastrointestinal side effects, if present, were mild to moderate. Serum concentrations of p-cresol declined significantly after Acarbose treatment (before: 1.14 mg/l (0.93-3.03); after: 1.11 mg/l (0.31-1.82); P=0.047). Urinary excretion of p-cresol, reflecting its colonic generation rate, was significantly lower after treatment (before: 29.93 mg/day (6.79-75.19); after: 10.54 mg/day (1.08-30.85); P=0.031). The fecal excretion of nitrogen increased after treatment (before: 1.04 g/day (0.47-2.29); after: 1.99 g/day (0.76-3.08); P=0.047). This pilot study suggests that Acarbose treatment lowers generation and serum concentrations of the protein-bound uremic solute p-cresol. Although further confirmation is warranted, the data may point to a novel treatment option for chronic kidney disease patients in view of the potential toxic effects of p-cresol and related substances.

Progression of chronic kidney disease: can it be prevented or arrested?

Chronic kidney disease constitutes a highly prevalent health problem worldwide. Left untreated, it progresses inexorably to greater levels of severity at variable rates. The morbid impact of chronic kidney disease is heightened by its role as risk factor for cardiovascular disease. In the past two decades, considerable gains have been realized in retarding progression of chronic kidney disease by emphasizing blood pressure control and blockade of the renin-angiotensin system. Notwithstanding, the therapeutic goal of preventing or arresting chronic kidney disease progression remains unfulfilled. Currently attainable rates of decrease in glomerular filtration rate remain at 2 to 8 mL/min/y depending on the underlying disease. It is now believed that to achieve optimal therapeutic targets (proteinuria of <500 mg/day and decrease in glomerular filtration rate of 1 mL/min/y, the average age-related decline) we must introduce novel strategies and a multifaceted approach to treatment that interrupts multiple mechanisms of progression. To this end, and wherever relevant, new approaches to cause-specific treatment must be applied, such as targeted immunosuppression, intensive glycemic control, gene therapy, and enzyme replacement therapy. Furthermore, in all chronic kidney disease, we must interfere more effectively with the multitude of common mechanisms of progression. Established or putative, such approaches include aggressive blood pressure control; advanced renin-angiotensin system blockade; cytokine modulation and antifibrotic therapy; aldosterone blockade; endothelin blockade, nitric oxide modulation and vasopeptidase inhibition; antioxidant therapy; statin therapy; glycosaminoglycan therapy; anemia therapy; dietary restrictions; lifestyle changes; and pharmacogenomic profiling. Such a concerted, multifaceted approach to management might indeed prevent or arrest progression of chronic kidney disease, or even achieve regression of chronic kidney disease.

Primary and secondary prevention of chronic kidney disease

The incidence and prevalence of chronic kidney disease (CKD) is on the rise worldwide. End-stage renal disease (ESRD) is the most advanced form of CKD, requiring some form of renal replacement therapy to ensure survival. Interventions to prevent or slow the progression of CKD, irrespective of the original cause, are thus of significant importance. The most effective of these interventions is based on the inhibition of the renin-angiotensin system (RAS) and is the main focus of this review.

Different regional dynamics of end-stage renal disease in Japan by different causes

BACKGROUND

We recently showed that there were clear regional differences in the dynamics of end-stage renal disease (ESRD) within Japan, which has an ethnically homogenous population. We speculate on the reason for these regional differences by correlating the regional distributions in the incidence of ESRD due to each of the following individual causes of ESRD: chronic glomerulonephritis (CGN), diabetic nephropathy (DMN) and polycystic kidney disease (PKD).

METHODS

The number of ESRD patients entering maintenance dialysis therapy due to individual causes of renal disease in each prefecture was reported annually for a 6-year period by the Japanese Society for Dialysis Therapy. After combining data from several prefectures into 11 geopolitical regions in Japan, the mean annual incidence of ESRD across the 11 regions was correlated among the three causes of ESRD.

RESULTS

There were significant regional differences in the incidence of ESRD due to CGN (P<0.0001) and DMN (P=0.0015), the distributions of which were similar to each other across the 11 regions. In contrast, no regional differences were found in the incidence of ESRD due to PKD (P=0.6) as the major genetic disorder of the kidneys, suggesting that genetic backgrounds are relatively uniform throughout Japan. The regional distributions due to PKD were not correlated with those due to other causes: CGN and DMN.

CONCLUSION

Risk factors common to nephropathy progression, rather than an underlying disease incidence and genetic predisposition, might contribute to regional differences in the overall ESRD incidence in Japan. Other possibilities such as the prevalence of underlying diseases, and acceptance or rejection rates into treatment programmes must be considered further for better explanations.

Glomerular function reserve and sodium sensitivity

In clinical nephrology, the glomerular filtration rate (GFR) has been recognized as the golden standard to assess renal function. However, a normal GFR does not necessarily mean normal filtration capability of the kidneys, because impaired filtration capability can be compensated for by elevating glomerular hydraulic pressure. Therefore, an early phase of glomerular dysfunction cannot be detected by the baseline GFR alone. On the other hand, glomerular capillary hypertension is widely recognized as one of the strong risk factors for the progression of nephropathies. Now, it is very important to imagine glomerular hemodynamics in each patient with nephropathy for detecting early dysfunction, as well as for evaluating risk factors. Here, I would like to summarize the current status of how an early phase of renal dysfunction can be detected in clinical practice. I truly anticipate that new methods to assess glomerular hemodynamics in humans will be developed in the near future.

Strategies to retard the progression of chronic kidney disease

Chronic kidney disease (CKD) is a common and, in advanced cases, highly morbid disorder. The most severe form of CKD is end-stage renal disease (ESRD), in which the patient requires some form of renal replacement therapy to survive. The increasing incidence, prevalence, and costs of ESRD are major national health care concerns; interventions that may prevent or slow the progression of CKD towards ESRD are extremely important and the focus of this article.

Diabetic nephropathy: the proteinuria hypothesis

BACKGROUND/AIMS

Proteinuria, nearly a universal finding in progressive kidney disease, has been the subject of frequent recent analyses in the renal literature. Proteinuria is a hallmark of diabetic nephropathy: microalbuminuria is the principal early predictor for progression of diabetic glomerulopathy, and proteinuria may be viewed as a measure of the severity and promoter of progression of nephropathy.

METHODS

This article critically reviews for the first time the full scope of diabetic proteinuria--complex molecular mechanisms, natural history, and analysis of treatment trials--in order to address the validity of 'the proteinuria hypothesis', i.e., that diabetic proteinuria is a modifiable determinant of renal progression. This hypothesis is analyzed in detail, including recent studies on the primary therapy of diabetic nephropathy, renin-angiotensin blockade.

RESULTS

As fully developed, this hypothesis consists of three postulates: that higher amounts of proteinuria predict progressive loss of function, that proteinuria reduction correlates with slowing progression, and that proteinuria is a surrogate endpoint for clinical trials. The latter postulate has not before been adequately linked to growing information about the first two postulates as they apply to diabetic kidney disease.

CONCLUSION

While diabetic nephropathy is a disease model for the potential use of proteinuria as a surrogate marker for renal progression, this shift in perspective will require prospective data from additional clinical trials, particularly of non-renin-angiotensin blocking drugs, to be complete.

Proteinuria and microalbuminuria in adults: significance, evaluation, and treatment

This paper reviews current concepts regarding the pathophysiology, diagnostic evaluation, and treatment of microalbuminuria and proteinuria in adults. Microalbuminuria (in diabetics) and proteinuria are early markers for potentially serious renal disease, and are associated with increased risk of atherosclerotic cardiovascular disease. Proteinuria also contributes to renal scarring, and accelerates the progression of chronic kidney disease to end-stage renal failure. Screening of diabetics for microalbuminuria, and the initial workup of proteinuria, should occur in the primary care setting. Reduction of microalbuminuria in diabetics may retard its progression to overt diabetic nephropathy. Therapy of renal diseases should aim for optimal blood pressure control and the maximum possible reduction in urinary protein excretion. Angiotensin-converting enzyme inhibitor (ACE-I) and/or angiotensin-receptor blocker (ARB) therapy is the most effective measure to achieve this. These drugs also provide protection against the cardiovascular problems that are highly prevalent in this patient population.

Albuminuria: Marker or target in indigenous populations

BACKGROUND

Australian Aborigines in remote areas are experiencing an epidemic of renal disease, type 2 diabetes, hypertension, and cardiovascular disease. Adult deaths are increased 3- to 6-fold, and renal failure more than 20-fold. Renal disease is marked by albuminuria. We describe its distributions and correlations in two remote communities in the Northern Territory.

METHODS

Observations in Community 1 included a screen of 939 adult participants (18+ years, 90% recruitment), a treatment program, and 8 to 11 years of follow-up. In Community 2, a screen of 259 people, or 60% of adults, included HbA1c, homocysteine, C-reactive protein (CRP), CMV serology, and carotid intimal media thickness (CIMT). Albumin/creatinine ratio (ACR) was measured by immunoassay in g/mol on random urine, with microalbuminuria defined as 3.4 to 33, and overt albuminuria as ACR 34+.

RESULTS

Dipstick urine protein trace+ correctly classified 76% of people with ACR 3.4+, and dipstick protein 1+ correctly classified 82% of people with ACR 34+. ACR was stable to glucose loading and water diuresis in subsets of people in Community 1. ACR levels rose steeply with age. Rates of micro- and overt albuminuria in Community 1 were 28% and 21%, and in Community B were 31% and 13%. ACR correlated inversely with estimated glomerular filtration rate (GFR). ACR also correlated directly with weight, blood pressure, cholesterol, triglycerides, random glucose, HbA1c, homocysteine, and GGT levels, and inversely with HDL cholesterol. ACR correlated with skin sores, scabies, high titer antibodies to Helicobacter pylori, high-titer CMV antibodies, with CRP over a greatly elevated range and, inversely, with birth weight. Finally, ACR correlated with CIMT. Baseline ACR predicted loss of GFR over time. ACR 3.4+ predicted all-cause and cardiovascular hospitalization, while ACR 34+ predicted all renal failure developing over 11 years and all-cause natural deaths and cardiovascular disease deaths. ACEi treatment for people with ACR 34+ reduced renal failure and natural deaths, but the hierarchical effect of higher ACRs within that group for renal and nonrenal deaths was maintained.

CONCLUSION

Random urine ACR is a stable and robust marker of renal disease, which is multideterminant. A broad base of shared risk factors probably explains the simultaneous emergence of the excessive renal and nonrenal chronic disease morbidities from which these populations suffer. Thus, albuminuria is a unifying marker for the harmful effects of the spectrum of chronic disease, and perhaps beyond. Dipstick urine protein is a useful surrogate for ACR when resources are constrained and disease burdens high.

Slowing the Progression of Adult Chronic Kidney Disease

When kidney disease of any aetiology results in substantial loss of nephrons, a common clinical syndrome, characterised by hypertension, proteinuria and a progressive decline in renal function, ensues. This observation suggests that common mechanisms may contribute to progressive renal injury and that therapeutic interventions that inhibit these common pathways may afford renal protection. Research to date has identified several mechanisms that may contribute to progressive renal injury including glomerular haemodynamic changes, multiple effects of angiotensin II and detrimental effects of excessive filtration of plasma proteins by injured glomeruli. Clinical trials over the past decade have identified several interventions that are effective in slowing the rate of progression of chronic kidney disease (CKD). The use of ACE inhibitors, angiotensin receptor antagonists or a combination of the two should be regarded as fundamental to any therapy for slowing the rate of CKD progression. Hypertension should be treated aggressively to achieve a blood pressure target of < 130/80 mm Hg. Reduction of proteinuria to < 0.5 g/day should be regarded as an independent therapeutic goal. Although inconclusive, there is some evidence to support moderate dietary protein restriction to 0.6 g/kg/day in appropriate patients. Hyperlipidaemia may contribute to CKD progression and should be treated to reduce cardiovascular risk and potentially improve renal protection. Smoking cessation should be encouraged and, where necessary, assisted. Among diabetic patients tight glycaemic control should be achieved (glycosylated haemoglobin < 7%). These interventions are simple and relatively inexpensive. If applied to all patients with CKD they will result in substantial slowing of renal function decline in many patients and thereby reduce the number who progress to end-stage renal disease and require renal replacement therapy.