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About 37 million people in the United States have chronic kidney disease, a disease that encompasses multiple causes. About 10% or more of kidney diseases in adults and as many as 70% of selected chronic kidney diseases in children are expected to be explained by genetic causes. Despite the advances in genetic testing and an increasing understanding of the genetic bases of certain kidney diseases, genetic testing in nephrology lags behind other medical fields. More understanding of the benefits and logistics of genetic testing is needed to advance the implementation of genetic testing in chronic kidney diseases. Accordingly, the National Kidney Foundation convened a Working Group of experts with diverse expertise in genetics, nephrology, and allied fields to develop recommendations for genetic testing for monogenic disorders and to identify genetic risk factors for oligogenic and polygenic causes of kidney diseases. Algorithms for clinical decision making on genetic testing and a road map for advancing genetic testing in kidney diseases were generated. An important aspect of this initiative was the use of a modified Delphi process to reach group consensus on the recommendations. The recommendations and resources described herein provide support to nephrologists and allied health professionals to advance the use of genetic testing for diagnosis and screening of kidney diseases.

Background:Chronic kidney disease (CKD) continues to be a significant global public health issue. The escalating burden of CKD is probably driven by the aging population and the rising prevalence of diabetes. CKD not only adversely impacts an individual’s health and well-being, but also poses significant challenge on the economy of the society. Summary:Experts from ten countries and regions around the world (Australia, Canada, China, Hong Kong, Malaysia, New Zealand, Singapore, Taiwan, United Kingdom, and United States) convened in the 4th International Congress of Chinese Nephrologists on December 1, 2023 to discuss the global dialysis burden. Although the cost of kidney replacement therapy (KRT) accounts for 2–3% of total healthcare expenditure in developed countries, patients with end stage kidney disease (ESKD) only represent a small percentage (<0.5%) of the population. Importantly, the economic impact of ESKD is not limited to direct medical costs, but extends to indirect societal costs, such as productivity loss by patients and caregivers. Primary prevention of CKD, early screening and treatment to delay progression to ESKD (where treatment costs rise dramatically), and utilization of home-based dialysis therapy (including peritoneal dialysis and home hemodialysis) shall be implemented as part of cost-containment strategy. Kidney transplant provides better outcomes than dialysis and is cost-effective in long run, whereas conservative kidney management should be considered for elderly frail patients. Key Messages:Implementation of preventive measures and cost-effective treatment strategies are the cornerstone to combat the global CKD epidemic.

While autosomal dominant polycystic kidney disease (ADPKD) is a dichotomous diagnosis, substantial variability in disease severity exists. Identification of inherited risk through family history, genetic testing, and environmental risk factors through clinical assessment are important components of risk assessment for optimal management of patients with ADPKD. Genetic testing is especially helpful in cases with diagnostic uncertainty, particularly in cases with no apparent family history, in young cases (age less than 25 years) where a definitive diagnosis is sought, or in atypical presentations with early, severe, or discordant findings. Currently, risk assessment in ADPKD may be performed with the use of age-adjusted estimated glomerular filtration rate thresholds, evidence of rapid estimated glomerular filtration rate decline on serial measurements, age- and height-adjusted total kidney volume by Mayo Clinic Imaging Classification, or evidence of early hypertension and urological complications combined with PKD1or PKD2mutation class; however, caveats exist with each of these approaches. Fine-tuning of risk stratification with advanced imaging features and biomarkers is the subject of research but is not yet ready for general clinical practice. While conservative treatment strategies will be advised for all patients, those with the greatest rate of disease progression will have the most benefit from aggressive disease-modifying therapy. In this narrative review, we will summarize the evidence behind the clinical assessment and risk stratification of patients with ADPKD.

Background: Age- and height-adjusted total kidney volume is currently considered the best prognosticator in patients with autosomal dominant polycystic kidney disease. We tested the ratio of urinary epidermal growth factor and monocyte chemotactic peptide 1 for the prediction of the Mayo Clinic Imaging Classes. Methods: Urinary epidermal growth factor and monocyte chemotactic peptide 1 levels were measured in two independent cohorts (discovery, n= 74 and validation set, n= 177) and healthy controls (n= 59) by immunological assay. Magnetic resonance imaging parameters were used for total kidney volume calculation and the Mayo Clinic Imaging Classification defined slow (1A–1B) and fast progressors (1C–1E). Microarray and quantitative gene expression analysis were used to test epidermal growth factor and monocyte chemotactic peptide 1 gene expression. Results: Baseline ratio of urinary epidermal growth factor and monocyte chemotactic peptide 1 correlated with total kidney volume adjusted for height (r= − 0.6, p&lt; 0.001), estimated glomerular filtration rate (r= 0.69 p&lt; 0.001), discriminated between Mayo Clinic Imaging Classes (p&lt; 0.001), and predicted the variation of estimated glomerular filtration rate at 10 years (r= − 0.51, p&lt; 0.001). Conditional Inference Trees identified cut-off levels of the ratio of urinary epidermal growth factor and monocyte chemotactic peptide 1 for slow and fast progressors at > 132 (100% slow) and &lt; 25.76 (89% and 86% fast, according to age), with 94% sensitivity and 66% specificity (p= 6.51E−16). Further, the ratio of urinary epidermal growth factor and monocyte chemotactic peptide 1 at baseline showed a positive correlation (p= 0.006, r= 0.36) with renal outcome (delta-estimated glomerular filtration rate per year, over a mean follow-up of 4.2 ± 1.2 years). Changes in the urinary epidermal growth factor and monocyte chemotactic peptide 1 were mirrored by gene expression levels in both human kidney cysts (epidermal growth factor: − 5.6-fold, fdr = 0.001; monocyte chemotactic peptide 1: 3.1-fold, fdr = 0.03) and Pkd1knock-out mouse kidney (Egf: − 14.8-fold, fdr = 2.37E-20, Mcp1: 2.8-fold, fdr = 6.82E−15). Conclusion: The ratio of urinary epidermal growth factor and monocyte chemotactic peptide 1 is a non-invasive pathophysiological biomarker that can be used for clinical risk stratification in autosomal dominant polycystic kidney disease.

The omission of outcomes that are of relevance to patients, clinicians, and regulators across trials in autosomal dominant polycystic kidney disease (ADPKD) limits shared decision making. The Standardized Outcomes in Nephrology–Polycystic Kidney Disease (SONG-PKD) Initiative convened an international consensus workshop on October 25, 2018, to discuss the identification and implementation of a potential core outcome set for all ADPKD trials. This article summarizes the discussion from the workshops and the SONG-PKD core outcome set. Key stakeholders including 11 patients/caregivers and 47 health professionals (nephrologists, policy makers, industry, and researchers) attended the workshop. Four themes emerged: “Relevance of trajectory and impact of kidney function” included concerns about a patient’s prognosis and uncertainty of when they may need to commence kidney replacement therapy and the lack of an early prognostic marker to inform long-term decisions; “Discerning and defining pain specific to ADPKD” highlighted the challenges in determining the origin of pain, adapting to the chronicity and repeated episodes of pain, the need to place emphasis on pain management, and to have a validated measure for pain; “Highlighting ADPKD consequences” encompassed cyst-related complications and reflected patient’s knowledge because of family history and the hereditary nature of ADPKD; and “Risk for life-threatening but rare consequences” such as cerebral aneurysm meant considering both frequency and severity of the outcome. Kidney function, mortality, cardiovascular disease, and pain were established as the core outcomes for ADPKD.

Trials in autosomal dominant polycystic kidney disease (ADPKD) have increased, but their impact on decision making has been limited. Because heterogeneity in reported outcomes may be responsible, we assessed their range and variability in ADPKD trials.

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by the progressive growth of renal cysts, leading to the loss of functional nephrons. Recommendations for individuals with ADPKD to maintain a healthy diet and lifestyle are largely similar to those for the general population. However, recent evidence from preclinical models suggests that more tightly specified dietary regimens, including caloric restriction, intermittent fasting, and ketogenic diets, hold promise to slow disease progression, and the results of ongoing human clinical trials are eagerly awaited. These dietary interventions directly influence nutrient signaling and substrate availability in the cystic kidney, while also conferring systemic metabolic benefits. The present review focuses on the importance of local and systemic metabolism in ADPKD and summarizes current evidence for dietary interventions to slow disease progression and improve quality of life.

CKD is a global problem that causes significant burden to the healthcare system and the economy in addition to its impact on morbidity and mortality of patients. Around the world, in both developing and developed economies, the nephrologists and governments face the challenges of the need to provide a quality and cost-effective kidney replacement therapy for CKD patients when their kidneys fail. In December 2019, the 3rd International Congress of Chinese Nephrologists was held in Nanjing, China, and in the meeting, a symposium and roundtable discussion on how to deal with this CKD burden was held with opinion leaders from countries and regions around the world, including Australia, Canada, China, Hong Kong, Singapore, Taiwan, the UK, and the USA. The participants concluded that an integrated approach with early detection of CKD, prompt treatment to slow down progression, promotion of home-based dialysis therapy like peritoneal dialysis and home HD, together with promotion of kidney transplantation, are possible effective ways to combat this ongoing worldwide challenge.

Autosomal dominant polycystic kidney disease is the most common monogenic cause of ESKD. Genetic studies from patients and animal models have informed disease pathobiology and strongly support a “threshold model” in which cyst formation is triggered by reduced functional polycystin dosage below a critical threshold within individual tubular epithelial cells due to (1) germline and somatic PKD1and/or PKD2mutations, (2) mutations of genes (e.g., SEC63, SEC61B, GANAB, PRKCSH, DNAJB11, ALG8, and ALG9) in the endoplasmic reticulum protein biosynthetic pathway, or (3) somatic mosaicism. Genetic testing has the potential to provide diagnostic and prognostic information in cystic kidney disease. However, mutation screening of PKD1is challenging due to its large size and complexity, making it both costly and labor intensive. Moreover, conventional Sanger sequencing–based genetic testing is currently limited in elucidating the causes of atypical polycystic kidney disease, such as within-family disease discordance, atypical kidney imaging patterns, and discordant disease severity between total kidney volume and rate of eGFR decline. In addition, environmental factors, genetic modifiers, and somatic mosaicism also contribute to disease variability, further limiting prognostication by mutation class in individual patients. Recent innovations in next-generation sequencing are poised to transform and extend molecular diagnostics at reasonable costs. By comprehensive screening of multiple cystic disease and modifier genes, targeted gene panel, whole-exome, or whole-genome sequencing is expected to improve both diagnostic and prognostic accuracy to advance personalized medicine in autosomal dominant polycystic kidney disease.

Outcomes reported in trials involving patients with autosomal dominant polycystic kidney disease (ADPKD) are heterogeneous and rarely include patient-reported outcomes. We aimed to identify critically important consensus-based core outcome domains to be reported in trials in ADPKD.

MicroRNAs (miRNAs) play an important role in regulating gene expression in health and disease but their role in modifying disease expression in Autosomal Dominant Polycystic Kidney Disease (ADPKD) remains uncertain. Here, we profiled human urinary exosome miRNA by global small RNA-sequencing in an initial discovery cohort of seven patients with ADPKD with early disease (eGFR over 60ml/min/1.73m2), nine with late disease (eGFR under 60ml/min/1.73m2), and compared their differential expression with six age and sex matched healthy controls. Two kidney-enriched candidate miRNA families were identified (miR-192/miR-194-2 and miR-30) and selected for confirmatory testing in a 60 patient validation cohort by quantitative polymerase chain reaction. We confirmed that miR-192-5p, miR-194-5p, miR-30a-5p, miR-30d-5p and miR-30e-5p were significantly downregulated in patient urine exosomes, in murine Pkd1cystic kidneys and in human PKD1cystic kidney tissue. All five miRNAs showed significant correlations with baseline eGFR and ultrasound-determined mean kidney length and improved the diagnostic performance (area under the curve) of mean kidney length for the rate of disease progression. Finally, inverse correlations of these two miRNA families with increased expression in their predicted target genes in patient PKD1cystic tissue identified dysregulated pathways and transcriptional networks including novel interactions between miR-194-5p and two potentially relevant candidate genes, PIK3R1and ANO1. Thus, our results identify a subset of urinary exosomal miRNAs that could serve as novel biomarkers of disease progression and suggest new therapeutic targets in ADPKD.

Tubulointerstitial injury is an important determinant of chronic kidney disease progression, yet treatment is limited. Accordingly, we derived a chronic kidney disease progression signature based on aging and disease in Col4a3–/–mice, a model associated with proteinuria and progressive loss of kidney function. Computational drug repurposing with the Connectivity Map identified vorinostat, a lysine deacetylase inhibitor, as a candidate treatment to reverse progression signature gene expression. Vorinostat administration significantly increased the lifespan of Col4a3–/–mice and attenuated tubulointerstitial fibrosis and JNK phosphorylation in the kidneys of Col4a3–/–mice. In vitro, vorinostat reduced albumin- and angiotensin II-induced activation of canonical mitogen-activated protein kinases in kidney tubular epithelial cells. Finally, a subset of murine progression signature genes was differentially expressed across kidney transcriptomic data from patients with focal segmental glomerulosclerosis, IgA nephropathy, and diabetic nephropathy. Thus, our findings suggest that lysine deacetylase inhibition may be a novel treatment to chronic kidney disease associated with proteinuria and progressive tubulointerstitial injury.

There are an estimated 14,000 randomized trials published in chronic kidney disease. The most frequently reported outcomes are biochemical endpoints, rather than clinical and patient-reported outcomes including cardiovascular disease, mortality, and quality of life. While many trials have focused on optimizing kidney health, the heterogeneity and uncertain relevance of outcomes reported across trials may limit their policy and practice impact. The international Standardized Outcomes in Nephrology (SONG) Initiative was formed to identify core outcomes that are critically important to patients and health professionals, to be reported consistently across trials. We convened a SONG Implementation Workshop to discuss the implementation of core outcomes. Eighty-two patients/caregivers and health professionals participated in plenary and breakout discussions. In this report, we summarize the findings of the workshop in two main themes: socializing the concept of core outcomes, and demonstrating feasibility and usability. We outline implementation strategies and pathways to be established through partnership with stakeholders, which may bolster acceptance and reporting of core outcomes in trials, and encourage their use by end-users such as guideline producers and policymakers to help improve patient-important outcomes.

Alport syndrome is a rare hereditary disorder caused by rare variants in 1 of 3 genes encoding for type IV collagen. Rare variants in COL4A5on chromosome Xq22 cause X-linked Alport syndrome, which accounts for ∼80% of the cases. Alport syndrome has a variable clinical presentation, including progressive kidney failure, hearing loss, and ocular defects. Exome sequencing performed in 2 affected related males with an undefined X-linked glomerulopathy characterized by global and segmental glomerulosclerosis, mesangial hypercellularity, and vague basement membrane immune complex deposition revealed a COL4A5sequence variant, a substitution of a thymine by a guanine at nucleotide 665 (c.T665G; rs281874761) of the coding DNA predicted to lead to a cysteine to phenylalanine substitution at amino acid 222, which was not seen in databases cataloguing natural human genetic variation, including dbSNP138, 1000 Genomes Project release version 01-11-2004, Exome Sequencing Project 21-06-2014, or ExAC 01-11-2014. Review of the literature identified 2 additional families with the same COL4A5variant leading to similar atypical histopathologic features, suggesting a unique pathologic mechanism initiated by this specific rare variant. Homology modeling suggests that the substitution alters the structural and dynamic properties of the type IV collagen trimer. Genetic analysis comparing members of the 3 families indicated a distant relationship with a shared haplotype, implying a founder effect.

Cai et al. identified the Hippo signaling effector YAP and its transcriptional target, c-Myc, as promoters of cystic kidney pathogenesis. A comprehensive kinase inhibitor screen identified a signaling pathway involving the RhoGEF LARG, the small GTPase RhoA, and the RhoA effector Rho-associated kinase (ROCK) as a critical signaling module between PKD1 and YAP.

Polycystic kidney disease (PKD) is a life-threatening disorder, commonly caused by defects in polycystin-1 (PC1) or polycystin-2 (PC2), in which tubular epithelia form fluid-filled cysts. A major barrier to understanding PKD is the absence of human cellular models that accurately and efficiently recapitulate cystogenesis. Previously, we have generated a genetic model of PKD using human pluripotent stem cells and derived kidney organoids. Here we show that systematic substitution of physical components can dramatically increase or decrease cyst formation, unveiling a critical role for microenvironment in PKD. Removal of adherent cues increases cystogenesis 10-fold, producing cysts phenotypically resembling PKD that expand massively to 1-centimetre diameters. Removal of stroma enables outgrowth of PKD cell lines, which exhibit defects in PC1 expression and collagen compaction. Cyclic adenosine monophosphate (cAMP), when added, induces cysts in both PKD organoids and controls. These biomaterials establish a highly efficient model of PKD cystogenesis that directly implicates the microenvironment at the earliest stages of the disease.

Rare kidney diseases encompass at least 150 different conditions, most of which are inherited. Although individual rare kidney diseases raise specific issues, as a group these rare diseases can have overlapping challenges in diagnosis and treatment. These challenges include small numbers of affected patients, unidentified causes of disease, lack of biomarkers for monitoring disease progression, and need for complex care. To address common clinical and patient issues among rare kidney diseases, the KDIGO Controversies Conference entitled, Common Elements in Rare Kidney Diseases, brought together a panel of multidisciplinary clinical providers and patient advocates to address five central issues for rare kidney diseases. These issues encompassed diagnostic challenges, management of kidney functional decline and progression of chronic kidney disease, challenges in clinical study design, translation of advances in research to clinical care, and provision of practical and integrated patient support. Thus, by a process of consensus, guidance for addressing these challenges was developed and is presented here.

Angiotensin-converting enzyme 2 (ACE2) is a monocarboxypeptidase in the renin-angiotensin system that catalyzes the breakdown of angiotensin II to angiotensin 1-7. We have reported that ACE2 expression in the kidney is reduced in experimental Alport syndrome but the impact of this finding on disease progression has not been studied. Accordingly, we evaluated effects of murine recombinant ACE2 treatment in Col4a3knockout mice, a model of Alport syndrome characterized by proteinuria and progressive renal injury. Murine recombinant ACE2 (0.5 mg/kg/day) was administered from four to seven weeks of age via osmotic mini-pump. Pathological changes were attenuated by murine recombinant ACE2 treatment which ameliorated kidney fibrosis as shown by decreased expression of COL1α1 mRNA, less accumulation of extracellular matrix proteins, and inhibition of transforming growth factor-β signaling. Further, increases in proinflammatory cytokine expression, macrophage infiltration, inflammatory signaling pathway activation, and heme oxygenase-1 levels in Col4a3knockout mice were also reduced by murine recombinant ACE2 treatment. Lastly, murine recombinant ACE2 influenced the turnover of renal ACE2, as it suppressed the expression of tumor necrosis factor-α converting enzyme, a negative regulator of ACE2. Thus, treatment with exogenous ACE2 alters angiotensin peptide metabolism in the kidneys of Col4a3knockout mice and attenuates the progression of Alport syndrome nephropathy.

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by the formation of multiple kidney cysts that leads to growth in total kidney volume (TKV) and progression to kidney failure. Venglustat is a glucosylceramide synthase inhibitor that has been shown to inhibit cyst growth and reduce kidney failure in preclinical models of ADPKD.

Autosomal dominant polycystic kidney disease (ADPKD) is a spectrum of disease severity based on genetic and morphologic features, and radiologists play an important role in establishing the diagnosis by using US criteria, predicting future renal function decline, and identifying complications of ADPKD.

Background:Cyst infection is one of the complications of autosomal dominant polycystic kidney disease and polycystic liver disease. The diagnosis is typically made on a mix of clinical, laboratory and imaging abnormalities but the importance of individual items is uncertain. We aimed to perform a Delphi survey amongst physicians to achieve consensus on diagnostic criteria. Methods:We retrieved diagnostic items from the literature and conducted physician and patient interviews. All items were combined to create the online questionnaire. Participants rated each item during 3 consecutive rounds. Items were rated for diagnostic helpfulness for hepatic and renal cyst infection on a 9-point scale with anchors, from extremely unimportant (n = 1) to extremely important (n = 9). We determined consensus with the disagreement index. The median rating of each item was calculated and categorized into inappropriate (≤3.4), uncertain (3.5-6.4) or appropriate (≥6.5). By combining all items that reached an appropriate consensus rating, we developed a diagnostic algorithm based on expert consensus. Results:We invited 58 physicians to participate in the survey. In total, 35 (60%) responded to round 1 of which 91% (n = 32) and 86% (n = 30) responded to round 2 and 3, respectively. The final panel included 23 nephrologists, 5 hepatologists, a nuclear medicine specialist and an infectious disease physician from 11 countries (male 67%, mean age 47 ± 11 years, median clinical experience 21 years). The panel rated the diagnostic helpfulness of 59 potential items. Ultimately, 22 hepatic and 26 renal items were rated appropriate, including positive blood cultures and fluorodeoxyglucose positron-emission CT imaging. Ultrasonography and absence of intracystic bleeding were amongst those deemed uncertain or inappropriate. Subsequently, by combining items rated appropriate, we developed a clinical tool to diagnose hepatic and renal cyst infection. Conclusions:We identified diagnostic items for hepatic and renal cyst infection and developed an expert-based diagnostic algorithm, which may aid physicians in the diagnostic work-up. A prospective study is necessary to validate this algorithm.

Blockade of the renin-angiotensin system attenuates the progression of experimental and clinical Alport syndrome (AS); however, the underlying mechanism(s) remains largely unknown. We evaluated the renin-angiotensin system in 4- and 7-week-old homozygous for collagen, type IV, α3 gene (Col4A3−/−) and wild-type mice, a model of AS characterized by proteinuria and progressive renal injury. Renal angiotensin (Ang) II levels increased, whereas renal Ang-(1–7) levels decreased in 7-week-old Col4a3−/−mice compared with age-matched controls; these changes were partially reversed by recombinant angiotensin-converting enzyme 2 (ACE2) treatment. The expression of both the angiotensinogen and renin protein increased in Col4a3−/−compared with wild-type mice. Consistent with the Ang-(1–7) levels, the expression and activity of kidney ACE2 decreased in 7-week-old Col4a3−/−mice. The urinary excretion rate of ACE2 paralleled the decline in tissue expression. Expression of an Ang II-induced gene, heme oxygenase-1, was up-regulated in the kidneys of 7-week-old Col4a3−/−mice compared with wild-type mice by microarray analysis. Heme oxygenase-1 (HO-1) protein expression was increased in kidneys of Col4a3−/−mice and normalized by treatment with ACE inhibitor. Urinary HO-1 excretion paralleled renal HO-1 expression. In conclusion, progressive kidney injury in AS is associated with changes in expression of intrarenal renin Ang system components and Ang peptides. HO-1 and ACE2 may represent novel markers of AS-associated kidney injury, whereas administration of recombinant ACE2 and/or Ang-(1–7) may represent novel therapeutic approaches in AS.

How renal epithelial cells respond to increased pressure and the link with kidney disease states remain poorly understood. Pkd1knockout or expression of a PC2 pathogenic mutant, mimicking the autosomal dominant polycystic kidney disease, dramatically enhances mechanical stress-induced tubular apoptotic cell death. We show the presence of a stretch-activated K+channel dependent on the TREK-2 K2Psubunit in proximal convoluted tubule epithelial cells. Our findings further demonstrate that polycystins protect renal epithelial cells against apoptosis in response to mechanical stress, and this function is mediated through the opening of stretch-activated K2Pchannels. Thus, to our knowledge, we establish for the first time, both in vitro and in vivo, a functional relationship between mechanotransduction and mechanoprotection. We propose that this mechanism is at play in other important pathologies associated with apoptosis and in which pressure or flow stimulation is altered, including heart failure or atherosclerosis.