Renal disease progression in autosomal dominant polycystic kidney disease

Kidney Measurement and Glomerular Filtration Rate Evolution in Children with Polycystic Kidney Disease

Autosomal dominant polycystic kidney disease (ADPKD) is an inherited disorder characterized by renal tubular cystic dilatations. The cysts can develop anywhere along the nephron, and over time the cystic dilatation leads to kidney enlargement. On the other hand, the cysts begin to reduce the number of functional nephrons as a consequence of cystic expansion that further contributes to the decline in renal function over the years. The pressure exerted by the dilated cysts leads to compensatory mechanisms that further contribute to the decline in renal function. These structural changes are responsible of glomerular hyperfiltration states, albuminuria, proteinuria, and hematuria. However, the presentation of ADPKD varies in children, from a completely asymptomatic child with incidental ultrasound detection of cysts to a rapidly progressive disease. There have been reports of early onset ADPKD in children younger than 2 years that showed a more rapid decline in renal function. ADPKD is caused by a mutation in PKD1 and PKD2 genes. Today, the PKD1 gene mutation seems to account for up to 85% of the cases worldwide, and it is associated with worse renal outcomes. Individuals with PKD2 gene mutation seem to present a milder form of the disease, with a more delayed onset of end-stage kidney disease. The cardinal sign of ADPKD is the presence of renal cysts during renal ultrasound. The current guidelines provide clinicians the recommendations for genetic testing in children with a positive family history. Given that the vast majority of children with ADPKD present with normal or supra-normal kidney function, we explored the glomerular filtration rates dynamics and the renal ultrasound-adjusted percentiles. In total, 14 out of 16 patients had kidney percentiles over 90%. The gene mutations were equally distributed among our cohort. In addition, we compared the modified Schwartz formula to the quadratic equation after adjusting the serum creatinine measurements. It seems that even though children with ADPKD have enlarged kidneys, the renal function is more likely normal or near normal when the quadratic estimation of glomerular filtration rate is used (qGFR tended to be lower, 111.95 ± 12.43 mL/min/1.73 m2 when compared to Schwartz eGFR 126.28 ± 33.07 mL/min/1.73 m2, p = 0.14). Also, when the quadratic equation was employed, not even a single patient reached the glomerular hyperfiltration threshold. The quadratic formula showed that glomerular filtration rates are linear or slightly decreasing after 1 year of follow-up (quadratic ΔeGFR = -0.32 ± 5.78 mL/min/1.73 m2), as opposed to the Schwartz formula that can falsely classify children in a hyperfiltration state (ΔeGFR = 7.51 ± 19.46 mL/min/1.73 m2), p = 0.019.

Cyst Fraction as a Biomarker in Autosomal Dominant Polycystic Kidney Disease

Autosomal dominant polycystic kidney disease (ADPKD) is the most common monogenic kidney disease. Patients at high risk of severe disease progression should be identified early in order to intervene with supportive and therapeutic measures. However, the glomerular filtration rate (GFR) may remain within normal limits for decades until decline begins, making it a late indicator of rapid progression. Kidney volumetry is frequently used in clinical practice to allow for an assessment of disease severity. Due to limited prognostic accuracy, additional imaging markers are of high interest to improve outcome prediction in ADPKD, but data from clinical cohorts are still limited. In this study, we examined cyst fraction as one of these parameters in a cohort of 142 ADPKD patients. A subset of 61 patients received MRIs in two consecutive years to assess longitudinal changes. All MRIs were analyzed by segmentation and volumetry of the kidneys followed by determination of cyst fraction. As expected, both total kidney volume (TKV) and cyst fraction correlated with estimated GFR (eGFR), but cyst fraction showed a higher R² in a univariate linear regression. Besides, only cyst fraction remained statistically significant in a multiple linear regression including both htTKV and cyst fraction to predict eGFR. Consequently, this study underlines the potential of cyst fraction in ADPKD and encourages prospective clinical trials examining its predictive value in combination with other biomarkers to predict future eGFR decline.

Health Disparities in Kidney Failure Among Patients With Autosomal Dominant Polycystic Kidney Disease: A Cross-Sectional Study

Rationale & Objective

Understanding potential differences in patterns of kidney failure among patients with autosomal dominant polycystic kidney disease (ADPKD) may provide insights into improving disease management. We sought to characterize patients with ADPKD and kidney failure across different race/ethnicities.

Study Design

Cross-sectional study.

Setting & Participants

Kaiser Permanente Southern California members diagnosed with ADPKD between January1, 2002, and December 31, 2018.

Exposure

ADPKD.

Outcome

Kidney failure, dialysis, or receipt of kidney transplant.

Analytical Approach

Differences in characteristics by race/ethnicity were assessed using analysis of variance F test and χ² test. To compare the range and distribution of the average age at onset of kidney failure by race/ethnicity and sex, we used box plots and confidence intervals. Multivariable logistic regression was used to estimate OR for kidney transplant.

Results

Among 3,677 ADPKD patients, 1,027 (27.3%) had kidney failure. The kidney failure cohort was comprised of Black (n=138; 30.7%), White (n=496; 30.6%), Hispanic (n=306; 24.7%), and Asian (n=87; 23.6%) patients. Hispanic patients had the youngest mean age of kidney failure onset (50 years) compared to Black (56 years) and White (57 years) patients. Black (44.2%; OR, 0.72) and Hispanic (49.7%; OR, 0.65) patients had lower rates of kidney transplantation compared to White (53.8%) patients. Preemptive kidney transplantations occurred in 15.0% of patients.

Limitations

Retrospective study design and possible misclassification of ADPKD cases. Kidney function calculations were based on equations incorporating race, potentially overestimating kidney function in African Americans. The study was conducted within a single, integrated health care system in 1 geographic region and may not be generalizable to all ADPKD patients.

Conclusions

Among a large diverse ADPKD population, we observed racial/ethnic differences in rates of kidney failure, age of kidney failure onset, and rates of kidney transplantation. Our real-world ADPKD cohort provides insight into racial/ethnic variation in clinical features of disease and potential disparities in care, which may affect ADPKD outcomes.

Outcomes from the Northeast England cohort of autosomal dominant polycystic kidney disease (ADPKD) patients on tolvaptan

Autosomal dominant polycystic kidney disease (ADPKD) is a cause of end-stage kidney disease (ESKD). The vasopressin V2-receptor antagonist tolvaptan has been shown within randomized clinical trials to slow down decline of kidney function in patients with ADPKD at risk of rapid progression. We performed a retrospective review of a Northeast England cohort of adult ADPKD patients who had been established on tolvaptan therapy to determine its efficacy in a real-world clinic setting. Other inclusion criteria involved a pre-treatment decline in greater than 2.5 ml/min/1.73m2/year based on readings for a 3 year period, and ability to tolerate and maintain tolvaptan treatment for at least 12 months. We calculated based on eGFR slopes, predicted time to reach ESKD with and without tolvaptan therapy. The cohort of patients included 21 from the Northeast of England. The mean rate of eGFR decline prior to treatment was -6.02 ml/min/1.73m2/year for the cohort. Following tolvaptan treatment, the average decline in eGFR was reduced to -2.47 ml/min/1.73m2/year, gaining a mean 8 years and 4 months delay to reach ESKD. The majority of patients (n=19) received and tolerated full dose tolvaptan (90 mg/30 mg). The real-life use of tolvaptan gave a dramatic improvement in eGFR slopes, much more than previously reported in clinical studies. These effects may be in part due to careful patient identification, selection and inclusion of patients who were able to tolerate tolvaptan therapy, excellent compliance with medication and a "tolvaptan clinic" effect where great personal care was given to these patients.

Association of autosomal dominant polycystic kidney disease with cardiovascular disease: a US-National Inpatient Perspective

PURPOSE

Data on the epidemiology of cardiovascular diseases (CVD) in patients with autosomal dominant polycystic kidney disease (ADPKD) are limited. In this study, we assess the prevalence of CVD in patients with ADPKD and evaluate associations between these two entities.

METHODS

Using the National Inpatient Sample database, we identified 71,531 hospitalizations among adults aged ≥ 18 years with ADPKD, from 2006 to 2014 and collected relevant clinical data.

RESULTS

The prevalence of CVD in the study population was 42.6%. The most common CVD were ischemic heart diseases (19.3%), arrhythmias (14.2%), and heart failure (13.1%). The prevalence of CVD increased with the severity of renal dysfunction (RD). We found an increase in hospitalizations of patients with ADPKD and CVD over the years (p_trend < 0.01), irrespective of the degree of RD. CVD was the greatest independent predictor of mortality in these patients (OR: 3.23; 95% CI 2.38-4.38 [p < 0.001]). In a propensity matched model of hospitalizations of patients with CKD with and without ADPKD, there was a significant increase in the prevalence of atrial fibrillation/flutter (AF), pulmonary hypertension (PHN), non-ischemic cardiomyopathy (NICM), and hemorrhagic stroke among patients with ADPKD when compared to patients with similar degree of RD without ADPKD.

CONCLUSIONS

The prevalence of CVD is high among patients with ADPKD, and the most important risk factor associated with CVD is severity of RD. We found an increase in the trend of hospitalizations of patients with ADPKD associated with increased risk of AF, PHN, NICM, and hemorrhagic stroke. History of CVD is the strongest predictor of mortality among patients with ADPKD.

Factors predicting decline in renal function and kidney volume growth in autosomal dominant polycystic kidney disease: a prospective cohort study (Japanese Polycystic Kidney Disease registry: J-PKD)

BACKGROUND

Factors affecting decline in renal function and cyst growth in patients with autosomal polycystic kidney disease (ADPKD) are not fully described, particularly in Japan.

METHODS

This was the first multi-facility, prospective, observational cohort study conducted in ADPKD patients at 14 centers in Japan. Patients in the J-PKD registry were assessed from December 2009 to June 2012 (follow-up until June 2017). Patients' data including estimated glomerular filtration rate (eGFR) and total kidney volume (TKV) were assessed initially and a maximum of five times annually. Contributing factors to eGFR decline and TKV growth were identified using multiple linear regression analysis.

RESULTS

Of the 340 patients in the J-PKD registry, data analysis was performed for 192 patients in whom serial changes for both eGFR and TKV were obtained. eGFR slope, eGFR change, and TKV change values were as follows: - 2.7 (- 4.2 to - 1.5) (ml/min/1.73 m²/year), - 5.0 (- 9.6 to - 2.3) (%/year), and 4.78 (0.86-8.22) (%/year), respectively. Lower high-density lipoprotein (HDL) cholesterol was an independent predictor of eGFR decline, using both eGFR slope and change (P = 0.04, P = 0.02, respectively), whereas lower hemoglobin and higher uric acid were significantly associated with greater eGFR change only (P = 0.02, P = 0.002, respectively). Younger age and higher fasting blood sugar were independent predictors of greater TKV change (P = 0.01, P = 0.02, respectively).

CONCLUSIONS

This real-world study in Japan identified risk factors for renal function decline in ADPKD patients. These included lower HDL cholesterol, lower hemoglobin and higher uric acid for eGFR decline, and youth and higher blood sugar levels for TKV growth.

Comparison of annual eGFR decline among primary kidney diseases in patients with CKD G3b-5: results from a REACH-J CKD cohort study

BACKGROUND

Disease-specific trajectories of renal function in advanced chronic kidney disease (CKD) are not well defined. Here, we compared these trajectories in the estimated glomerular filtration rate (eGFR) by CKD stages.

METHODS

Patients with multiple eGFR measurements during the 5-year preregistration period of the REACH-J study were enrolled. Mean annual eGFR declines were calculated from linear mixed effect models with the adjustment variables of baseline CKD stage, age, sex and the current CKD stage and the level of proteinuria (CKDA1-3).

RESULTS

Among 1,969 eligible patients with CKDG3b-5, the adjusted eGFR decline (ml/min/1.73 m²/year) was significantly faster in diabetic kidney disease (DKD) patients and polycystic kidney disease (PKD) patients than in patients with other kidney diseases (DKD, - 2.96 ± 0.13; PKD, - 2.82 ± 0.17; and others, - 1.95 ± 0.05, p < 0.01). The declines were faster with higher CKD stages. In DKD patients, the eGFR decline was significantly faster in CKDG5 than CKDG4 (- 4.10 ± 0.18 vs - 2.76 ± 0.20, p < 0.01), while these declines in PKD patients were similar. The eGFR declines in PKD patients were significantly faster than DKD patients in CKDG4 (- 2.92 ± 0.23 vs - 2.76 ± 0.20, p < 0.01) and in CKDA2 (- 3.36 ± 0.35 vs - 1.40 ± 0.26, p < 0.01).

CONCLUSION

Our study revealed the disease-specific annual eGFR declines by CKD stages and the level of proteinuria. Comparing to the other kidney diseases, the declines in PKD patients were getting faster from early stages of CKD. These results suggest the importance of CKD managements in PKD patients from the early stages.

The value of genotypic and imaging information to predict functional and structural outcomes in ADPKD

BACKGROUNDA treatment option for autosomal dominant polycystic kidney disease (ADPKD) has highlighted the need to identify rapidly progressive patients. Kidney size/age and genotype have predictive power for renal outcomes, but their relative and additive value, plus associated trajectories of disease progression, are not well defined.METHODSThe value of genotypic and/or kidney imaging data (Mayo Imaging Class; MIC) to predict the time to functional (end-stage kidney disease [ESKD] or decline in estimated glomerular filtration rate [eGFR]) or structural (increase in height-adjusted total kidney volume [htTKV]) outcomes were evaluated in a Mayo Clinic PKD1/PKD2 population, and eGFR and htTKV trajectories from 20-65 years of age were modeled and independently validated in similarly defined CRISP and HALT PKD patients.RESULTSBoth genotypic and imaging groups strongly predicted ESKD and eGFR endpoints, with genotype improving the imaging predictions and vice versa; a multivariate model had strong discriminatory power (C-index = 0.845). However, imaging but not genotypic groups predicted htTKV growth, although more severe genotypic and imaging groups had larger kidneys at a young age. The trajectory of eGFR decline was linear from baseline in the most severe genotypic and imaging groups, but it was curvilinear in milder groups. Imaging class trajectories differentiated htTKV growth rates; severe classes had rapid early growth and large kidneys, but growth later slowed.CONCLUSIONThe value of imaging, genotypic, and combined data to identify rapidly progressive patients was demonstrated, and reference values for clinical trials were provided. Our data indicate that differences in kidney growth rates before adulthood significantly define patients with severe disease.FUNDINGNIDDK grants: Mayo DK058816 and DK090728; CRISP DK056943, DK056956, DK056957, and DK056961; and HALT PKD DK062410, DK062408, DK062402, DK082230, DK062411, and DK062401.

RAPID-ADPKD (Retrospective epidemiological study of Asia-Pacific patients with rapId Disease progression of Autosomal Dominant Polycystic Kidney Disease): study protocol for a multinational, retrospective cohort study

INTRODUCTION

Patients with autosomal dominant polycystic kidney disease (ADPKD) reach end-stage renal disease in their fifth decade on average. For effective treatment and early intervention, identifying subgroups with rapid disease progression is important in ADPKD. However, there are no epidemiological data on the clinical manifestations and disease progression of patients with ADPKD from the Asia-Pacific region.

METHODS AND ANALYSIS

The RAPID-ADPKD (Retrospective epidemiological study of Asia-Pacific patients with rapId Disease progression of Autosomal Dominant Polycystic Kidney Disease) study is a multinational, retrospective, observational cohort study of patients with ADPKD in the Asia-Pacific region (Australia, China, Hong Kong, South Korea, Taipei and Turkey). This study was designed to identify the clinical characteristics of patients with ADPKD with rapid disease progression. Adult patients with ADPKD diagnosed according to the unified ultrasound criteria and with an estimated glomerular filtration rate (eGFR) ≥45 mL/min/1.73 m² at baseline will be included. The cohort will include patients with ≥2 records of eGFR and at least 24 months of follow-up data. Demographic information, clinical characteristics, comorbidities, medications, eGFR, radiological findings that allow calculation of height-adjusted total kidney volume, ADPKD-related complications and the Predicting Renal Outcomes in autosomal dominant Polycystic Kidney Disease (PRO-PKD) score will be collected. Rapid progression will be defined based on the European Renal Association - European Dialysis and Transplant Association (ERA-EDTA) guideline. All other patients without any of these criteria will be classified to be of slow progression. Clinical characteristics will be compared between patients with rapid progression and those with slow progression. The incidence of complications and the effects of race and water intake on renal progression will also be analysed. The planned sample size of the cohort is 1000 patients, and data from 600 patients have been collected as of 30 May 2019.

ETHICS AND DISSEMINATION

This study was approved or is in the process of approval by the institutional review boards at each participating centre. The results will be presented in conferences and published in a journal, presenting data on the clinical characteristics, risk factors for disease progression and patterns of complications of ADPKD in Asian populations.

Oxidative stress in autosomal dominant polycystic kidney disease: player and/or early predictor for disease progression?

Autosomal dominant polycystic kidney disease (ADPKD), caused by mutations in PKD1 or PKD2 genes, is the most common hereditary renal disease. Renal manifestations of ADPKD are gradual cyst development and kidney enlargement ultimately leading to end-stage renal disease. ADPKD also causes extrarenal manifestations, including endothelial dysfunction and hypertension. Both of these complications are linked with reduced nitric oxide levels related to excessive oxidative stress (OS). OS, defined as disturbances in the prooxidant/antioxidant balance, is harmful to cells due to the excessive generation of highly reactive oxygen and nitrogen free radicals. Next to endothelial dysfunction and hypertension, there is cumulative evidence that OS occurs in the early stages of ADPKD. In the current review, we aim to summarize the cardiovascular complications and the relevance of OS in ADPKD and, more specifically, in the early stages of the disease. First, we will briefly introduce the link between ADPKD and the early cardiovascular complications including hypertension. Secondly, we will describe the potential role of OS in the early stages of ADPKD and its possible importance beyond the chronic kidney disease (CKD) effect. Finally, we will discuss some pharmacological agents capable of reducing reactive oxygen species and OS, which might represent potential treatment targets for ADPKD.

Long-term trajectory of kidney function in autosomal-dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by cyst and kidney growth, which is hypothesized to cause loss of functioning renal mass and eventually end-stage kidney disease. However, the time course of decline in glomerular filtration rate (GFR) is poorly defined. The Consortium for Radiologic Imaging Studies of Polycystic Kidney Disease study is a 14-year observational cohort study of 241 adults with ADPKD. As an estimate of the rate of kidney growth, participants were stratified into 5 subclasses based on baseline age and magnetic resonance imaging measurements of total kidney volume (TKV) according to the method of Irazabal. GFR trajectories spanning over four decades of life were reconstructed and fitted using mixed polynomial models, which were validated using data from the HALT-PKD study. GFR trajectories were nonlinear, with a period of relative stability in most participants, followed by accelerating decline. The shape and slope of these trajectories were strongly associated with baseline Irazabal class. Patients with PKD1 mutations had a steeper GFR decline than patients with PKD2 mutations or with no detected mutation, largely mediated by the effect of genotype on Irazabal class. Thus, GFR decline in ADPKD is nonlinear, and its trajectory throughout adulthood can be predicted from a single measurement of kidney volume. These models can be used for clinical prognostication, clinical trial design, and patient selection for clinical interventions. Our findings support a causal link between growth in kidney volume and GFR decline, adding support for the use of TKV as a surrogate endpoint in clinical trials.

Urinary Biomarkers to Identify Autosomal Dominant Polycystic Kidney Disease Patients With a High Likelihood of Disease Progression

Introduction

The variable disease course of autosomal dominant polycystic kidney disease (ADPKD) makes it important to develop biomarkers that can predict disease progression, from a patient perspective and to select patients for renoprotective treatment. We therefore investigated whether easy-to-measure urinary biomarkers are associated with disease progression and have additional value over that of conventional risk markers.

Methods

At baseline, inflammatory, glomerular, and tubular damage markers were measured in 24-hour urine collections (albumin, IgG, kidney injury molecule−1 (KIM-1), N-acetyl-β-d-glucosaminidase (NAG), β2 microglobulin (β2MG), heart-type fatty acid binding protein (HFABP), macrophage migration inhibitory factor (MIF), neutrophil gelatinase-associated lipocalin (NGAL), and monocyte chemotactic protein−1 (MCP-1). Disease progression was expressed as annual change in estimated glomerular filtration rate (eGFR, Chronic Kidney Disease EPIdemiology equation), measured glomerular filtation rate (mGFR, using ¹²⁵I-iothalamate), or height-adjusted total kidney volume (htTKV). Multivariable linear regression was used to assess associations of these markers independent of conventional risk markers.

Results

A total of 104 ADPKD patients were included (40 ± 11 years, 39% female, eGFR 77 ± 30, mGFR 79 ± 30 ml/min per 1.73 m² and htTKV 852 [510−1244] ml/m). In particular, β2MG and MCP-1 were associated with annual change in eGFR, and remained associated after adjustment for conventional risk markers (standardized β = −0.35, P = 0.001, and standardized β = −0.29, P = 0.009, respectively). Adding β2MG and MCP-1 to a model containing conventional risk markers that explained annual change in eGFR significantly increased the performance of the model (final R² = 0.152 vs. 0.292, P = 0.001). Essentially similar results were obtained when only patients with an eGFR ≥ 60 ml/min per 1.73 m² were selected, or when change in mGFR was studied. Associations with change in htTKV were less strong.

Conclusion

Urinary β2MG and MCP-1 excretion were both associated with GFR decline in ADPKD, and had added value beyond that of conventional risk markers. These markers therefore have the potential to serve as predictive tools for clinical practice.

Clinical Manifestation and Management of ADPKD in Western Countries

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary kidney disease in Western countries. The prevalence is between 2.4/10,000 and 3.9/10,000. ADPKD represents a systemic disease resulting in deterioration in renal function. Until now, mutations in two genes (PKD1 and PKD2) have been identified. Recently, the European Medicines Agency (EMA) approved the use of the vasopressin V2 receptor antagonist tolvaptan to slow the progression of cyst development and renal insufficiency connected with ADPKD in adult patients with chronic kidney disease stages 1-3 at initiation of treatment with evidence of rapidly progressing disease. Whereas the EMA approved the release of tolvaptan, the US Food and Drug Administration (FDA) requested further data on side effects and the selection of patient cohorts who may benefit from treatment.

SUMMARY

This review focused on advances in the management and treatment of ADPKD in Western countries.

KEY MESSAGE

ADPKD represents the fourth most common cause of end-stage renal disease (ESRD) in Western countries. ADPKD is a multisystemic disease characterized by the progressive development of bilateral renal cysts, resulting in enlargement of the kidney volume due to cystic formations, hypertension, hematuria, and loss of renal function. ADPKD is associated with high inter- and intrafamilial variability in disease appearance and progression. Patients with PKD1 mutations typically have a more severe phenotype than those with PKD2 mutations. ADPKD is under intensive investigation. Vasopressin and the associated cyclic adenosine monophosphate-related signaling pathways have been demonstrated to be important contributors to cyst growth in ADPKD. Supportive treatments are recommended with the aim of reducing morbidity and mortality associated with disease manifestations. In the past years, several agents have been investigated in ADPKD patients, including mTOR inhibitors, somatostatin analogs, statins, and vasopressin V2 receptor antagonists.

FACTS FROM EAST AND WEST

(1) ADPKD is diagnosed globally by ultrasound detection of kidney enlargement and presence of cysts. Recent analyses of variants of the PKD1 and PKD2 genes by next-generation sequencing in Chinese and Western ADPKD patients might lead to the development of reliable genetic tests. (2) Besides lifestyle changes (low-salt diet, sufficient fluid intake, and no smoking), blood pressure control is the primary nonspecific treatment recommended by Kidney Disease - Improving Global Outcomes (KDIGO) for ADPKD patients. How low the blood pressure target should be and what the means of achieving it are remain open questions depending on the severity of chronic kidney disease and the age of the patients. In a recent Chinese study, diagnostic needle aspiration and laparoscopic unroofing surgery successfully improved infection, pain, and hypertension. Peritoneal dialysis was found to be a feasible treatment for most Chinese ADPKD patients with ESRD. In most Western centers, patients without contraindication are selected for peritoneal dialysis. Kidney transplantation with concurrent bilateral nephrectomy was successful in relieving hypertension and infection in Chinese ADPKD patients. In Western countries, sequential surgical intervention with kidney transplantation after nephrectomy, or the other way round, is preferred in order to reduce risks. (3) The vasopressin 2 receptor antagonist tolvaptan was approved in Europe, Canada, Japan, and Korea to slow down progression of kidney disease in ADPKD patients. Tolvaptan is not yet approved in the USA or in China. mTOR pathway-targeting drugs are currently under evaluation: mTOR inhibitors could slow down the increase in total kidney volume in a cohort of Western and Japanese ADPKD patients. Western studies as well as an ongoing study in China failed to show benefit from rapamycin. A study performed in Italy indicates protective effects of the somatostatin analog octreotide in ADPKD patients. Western and Chinese studies revealed a potential beneficial effect of triptolide, the active substance of the traditional Chinese medicine Tripterygium wilfordii (Lei Gong Teng) to prevent worsening in ADPKD patients.

The importance of total kidney volume in evaluating progression of polycystic kidney disease

The rate at which autosomal dominant polycystic kidney disease (ADPKD) progresses to end-stage renal disease varies widely and is determined by genetic and non-genetic factors. The ability to determine the prognosis of children and young adults with ADPKD is important for the effective life-long management of the disease and to enable the efficacy of emerging therapies to be determined. Total kidney volume (TKV) reflects the sum volume of hundreds of individual cysts with potentially devastating effects on renal function. The sequential measurement of TKV has been advanced as a dynamic biomarker of disease progression, yet doubt remains among nephrologists and regulatory agencies as to its usefulness. Here, we review the mechanisms that lead to an increase in TKV in ADPKD, and examine the evidence supporting the conclusion that TKV provides a metric of disease progression that can be used to assess the efficacy of potential therapeutic regimens in children and adults with ADPKD. Moreover, we propose that TKV can be used to monitor treatment efficacy in patients with normal levels of renal function, before the pathologic processes of ADPKD cause extensive fibrosis and irreversible loss of functioning renal tissue.

Recommendations for the use of tolvaptan in autosomal dominant polycystic kidney disease: a position statement on behalf of the ERA-EDTA Working Groups on Inherited Kidney Disorders and European Renal Best Practice

Recently, the European Medicines Agency approved the use of the vasopressin V2 receptor antagonist tolvaptan to slow the progression of cyst development and renal insufficiency of autosomal dominant polycystic kidney disease (ADPKD) in adult patients with chronic kidney disease stages 1–3 at initiation of treatment with evidence of rapidly progressing disease. In this paper, on behalf of the ERA-EDTA Working Groups of Inherited Kidney Disorders and European Renal Best Practice, we aim to provide guidance for making the decision as to which ADPKD patients to treat with tolvaptan. The present position statement includes a series of recommendations resulting in a hierarchical decision algorithm that encompasses a sequence of risk-factor assessments in a descending order of reliability. By examining the best-validated markers first, we aim to identify ADPKD patients who have documented rapid disease progression or are likely to have rapid disease progression. We believe that this procedure offers the best opportunity to select patients who are most likely to benefit from tolvaptan, thus improving the benefit-to-risk ratio and cost-effectiveness of this treatment. It is important to emphasize that the decision to initiate treatment requires the consideration of many factors besides eligibility, such as contraindications, potential adverse events, as well as patient motivation and lifestyle factors, and requires shared decision-making with the patient.

Progression of autosomal dominant kidney disease: measurement of the stage transitions of chronic kidney disease

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is a progressive genetic disorder characterized by the development of numerous kidney cysts that result in kidney failure. Little is known regarding the key patient characteristics and utilization of healthcare resources for ADPKD patients along the continuum of disease progression. This observational study was designed to describe the characteristics of ADPKD patients and compare them with those of patients with other chronic kidney diseases.

METHODS

This retrospective cohort study involved patients with a claim for ADPKD or PKD unspecified from 1/1/2000-2/28/2013 and ≥6 months of previous continuous enrollment (baseline) within a large database of administrative claims in the USA. A random sample of chronic kidney disease (CKD) patients served as comparators. For a subset of ADPKD patients who had only a diagnosis code of unspecified PKD, abstraction of medical records was undertaken to estimate the proportion of patients who had medical chart-confirmed ADPKD. In patients with linked electronic laboratory data, the estimated glomerular filtration rate was calculated via serum creatinine values to determine CKD stage at baseline and during follow-up. Proportions of patients transitioning to another stage and the mean age at transition were calculated.

RESULTS

ADPKD patients were, in general, younger and had fewer physician visits, but had more specific comorbidities at observation start compared with CKD patients. ADPKD patients had a longer time in the milder stages and longer duration before recorded transition to a more severe stage compared with CKD patients. Patients with ADPKD at risk of rapid progression had a shorter time-to-end-stage renal disease than patients with CKD and ADPKD patients not at risk, but stage duration was similar between ADPKD patients at risk and those not at risk.

CONCLUSIONS

These results suggest that distribution of patients by age at transition to next stage may be useful for identification of ADPKD patients at risk of rapid progression. The results also suggest that medical claims with diagnosis codes for "unspecified PKD", in absence of a diagnosis code for autosomal recessive polycystic kidney disease, may be a good proxy for ADPKD.

Sirolimus for treatment of autosomal-dominant polycystic kidney disease: a meta-analysis of randomized controlled trials

BACKGROUND

Autosomal-dominant polycystic kidney disease (ADPKD) is the most common form of cystic kidney disease. The mammalian target of rapamycin (mTOR) pathway is associated with progressive kidney enlargement. The drug sirolimus suppresses mTOR signaling but plays an uncertain role in the treatment of ADPKD. The objective of our study was to conduct a meta-analysis of randomized controlled trials (RCTs) to present an objective appraisal of the efficacy and safety of sirolimus therapy in patients with ADPKD.

METHODS

We conducted a meta-analysis of RCTs performed in adults with ADPKD, and compared the effect of sirolimus on total kidney volume (TKV), glomerular filtration rate (GFR), cyst volume, and daily urinary protein excretion. Safety was evaluated based on analysis of blood pressure, lipid profile, complete blood count, infection, and other reported adverse events.

RESULTS

Four RCTs were included. The sirolimus therapy group had smaller TKV than the control group. The mean difference (MD) of TKV post-treatment compared with the control group was -234.74 (P = .01). However, GFR did not reach a statistically significant difference between groups. Standard mean difference (SMD) of GFR after therapy was 0.24 (95% confidence interval [CI], 0.05-0.52; P = .11), but sirolimus seemed to increase urine protein excretion (P = .002). There was no statically significant difference in leukocytes, hemoglobin, platelets, and blood pressure between groups. Aphthous stomatits and pharyngitis are reported more commonly in the sirolimus therapy group compared with the control group (P < .000001).

CONCLUSIONS

In ADPKD patients, treatment with sirolimus is safe and can effectively slow kidney growth, but it seems not to slow down the decrease of GFR.

Survival after arterial embolization therapy in patients with polycystic kidney and liver disease

BACKGROUND

Transcatheter arterial embolization (TAE) has become a therapeutic option for symptomatic polycystic kidney disease (PKD) and polycystic liver disease (PLD). However, factors affecting survival with renal TAE remain unknown.

METHODS

All symptomatic patients with severe PKD and/or PLD who received renal and/or hepatic TAE at our center from October 1996 through March 2013 (n = 1,028) were followed until death. Their survival was compared with that of the general PKD population on dialysis in Japan. Factors affecting survival were analyzed using the Cox hazard model.

RESULTS

After renal TAE, 5- and 10-year survival was, respectively, 0.78 (95% confidence interval, 0.74-0.82) and 0.56 (0.49-0.63); with hepatic TAE, 0.69 (0.58-0.77) and 0.41 (0.22-0.60); and with dual TAE (renal and hepatic), 0.82 (0.72-0.88) and 0.45 (0.31-0.59). Survival after dialysis initiation was better among patients with renal TAE than among general PKD patients. Factors affecting survival after renal TAE were age [hazard ratio (HR) 3.02 (1.44-6.33) for every 10 years] and albumin [HR 0.70 (0.55-0.89) per 0.1 g/dl]. Kidney volume was not associated with patient death after TAE. The main causes of death among patients after renal TAE were similar to those of the general PKD population on dialysis whereas, after hepatic TAE, the main cause was cyst infection with liver failure (12.5% with PLD and 5.9% with PKD, p < 0.01).

CONCLUSION

Survival after renal TAE with severe PKD was better than for the general PKD population on dialysis, suggesting that renal TAE could overcome the disadvantage due to huge organ size.

Peroxisome proliferator-activated receptor agonists in a battle against the aging kidney

As aging is a complex phenomenon characterized by intraindividual and interindividual diversities in the maintenance of the homeostatic condition of cells and tissues, changes in renal function are not uniform and depend on associated diseases and environmental factors. Multiple studies have investigated the possible underlying mechanisms of age-related decline in kidney function. Evolutionary, molecular, cellular and systemic theories have been postulated to explain the primary disease independent age-related changes and adaptive responses. As peroxisome proliferator-activated receptors (PPARs) are involved in a broad spectrum of biological processes, PPAR activation might have an effect on the prevention of cell senescence. In this review, we will focus on the experimental and clinical evidence of PPAR agonists in a battle against the aging kidney.

Renal replacement therapy in ADPKD patients: a 25-year survey based on the Catalan registry

Background

Some 7-10% of patients on replacement renal therapy (RRT) are receiving it because of autosomal dominant polycystic kidney disease (ADPKD). The age at initiation of RRT is expected to increase over time.

Methods

Clinical data of 1,586 patients (7.9%) with ADPKD and 18,447 (92.1%) patients with other nephropathies were analysed from 1984 through 2009 (1984–1991, 1992–1999 and 2000–2009).

Results

The age at initiation of RRT remained stable over the three periods in the ADPKD group (56.7 ± 10.9 (mean ± SD) vs 57.5 ± 12.1 vs 57.8 ± 13.3 years), whereas it increased significantly in the non-ADPKD group (from 54.8 ± 16.8 to 63.9 ± 16.3 years, p < 0.001). The ratio of males to females was higher for non-ADPKD than for ADPKD patients (1.6–1.8 vs 1.1–1.2). The prevalence of diabetes was significantly lower in the ADPKD group (6.76% vs 11.89%, p < 0.001), as were most of the co-morbidities studied, with the exception of hypertension. The survival rate of the ADPKD patients on RRT was higher than that of the non-ADPKD patients (p < 0.001).

Conclusions

Over time neither changes in age nor alterations in male to female ratio have occurred among ADPKD patients who have started RRT, probably because of the impact of unmodifiable genetic factors in the absence of a specific treatment.

Kidney volume and function in autosomal dominant polycystic kidney disease

Background

The significance of total kidney volume (TKV) as a biomarker of kidney function in autosomal dominant polycystic kidney disease (ADPKD) is controversial and has been reappraised.

Methods

Between 2007 and 2012, 64 patients were followed with a mean 39.7-month observation period. TKV measurements by magnetic resonance imaging and estimation of renal function with estimated glomerular filtration rate (eGFR) using the Modification of Diet in Renal Disease equation and 24-h urine creatinine clearance were repeated annually.

Results

TKV and its adjusted parameters (height-adjusted, body surface area-adjusted and log-converted TKV [log-TKV]) correlated with eGFR significantly. Among them, the correlation coefficient of log-TKV was most significant (r = −0.6688, p < 0.001). The eGFR slope correlated negatively with TKV slope (p < 0.05). TKV increased faster and became larger as chronic kidney disease (CKD) stage advanced. As age advanced, eGFR declined significantly (p < 0.001), but the eGFR slope remained constant. There was no significant correlation between TKV and age, but the log-TKV slope became smaller as age advanced. If baseline TKV was large, the eGFR slope was steeper (p < 0.05), which suggests that eGFR declines faster in patients with larger kidney volume.

Conclusions

TKV is confirmed as a clinically meaningful surrogate marker in ADPKD. Log-TKV correlates with eGFR most significantly. Higher rates of kidney enlargement and larger kidney volume are associated with a more rapid decrease in kidney function. Kidney function decreased faster as CKD stage advanced, but its declining slope did not change significantly by age, at least after ~30 years of age.

The natural history of autosomal dominant polycystic kidney disease: 30-year experience from a single centre

BACKGROUND AND AIM

Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited kidney disease. The major objective of this study was to analyse the natural history of disease progression in all patients with ADPKD seen at the Sheffield Kidney Institute between 1978 and 2012.

METHODS

A retrospective analysis was performed based on recorded renal function up to 30 years prior to analysis. The rate of estimated glomerular filtration rate (eGFR) decline (ΔeGFR) was determined by linear regression, based on a minimum of 5 years of renal function prior to the study or renal replacement therapy. Patients who had reached end-stage renal disease (ESRD) (n = 113) were compared with those under follow-up in a dedicated polycystic kidney disease (PKD) clinic (n = 88).

RESULTS

The two groups were comparable in age and gender though the mean follow-up duration was longer in the PKD clinic group. Overall, ΔeGFR was significantly higher in the ESRD group compared with the PKD clinic group (4.19 ± 1.66 vs. 1.71 ± 1.36 ml/min/1.73 m(2)/year). Retrospective analysis for each 5-year period prior to ESRD or analysis showed a significant difference in ΔeGFR between both groups 10 years before with an increasing trend in ΔeGFR 20 years before especially in the ESRD group. In the PKD clinic group, the age of diagnosis and mean kidney length were also predictors of ΔeGFR.

CONCLUSION

This is one of the longest natural history studies in ADPKD. The difference in ΔeGFR can be predicted at least 10 years prior to the onset of ESRD and thus will enable higher risk patients to be identified early for treatment.

Genomic instability in patients with autosomal-dominant polycystic kidney disease

OBJECTIVE

Autosomal-dominant polycystic kidney disease (ADPKD) is a systemic disorder affecting multiple organs that results in renal and extrarenal cysts. Patients with ADPKD may have genomic instability, making them more vulnerable to developing cancer. This study aimed to investigate latent genomic instability in patients with ADPKD, using single-cell gel electrophoresis (comet assay).

METHODS

The susceptibility of peripheral blood lymphocytes to DNA damage induced by X-ray treatment (0.5 Gy) was tested in 20 patients with ADPKD using single-cell gel electrophoresis. The percentage of DNA in the comet tail (TDNA%) before and after irradiation was compared between patients with ADPKD and 20 sex- and age-matched healthy control subjects.

RESULTS

Renal and extrarenal cysts were observed in patients with ADPKD. A significantly higher mean TDNA% was determined in patients with ADPKD compared with control subjects (8.85% versus 7.50%). After in vitro irradiation, DNA damage was significantly increased in all participants, but the increase was significantly greater in patients with ADPKD compared with control subjects.

CONCLUSION

These data suggest that patients with ADPKD have genomic instability, which may trigger renal and extrarenal cyst formation.