Risk Severity Model for Pediatric Autosomal Dominant Polycystic Kidney Disease Using 3D Ultrasound Volumetry

Autosomal dominant polycystic kidney disease: an overview of recent genetic and clinical advances

Autosomal Dominant Polycystic Kidney Disease (ADPKD) is the most common inherited kidney disease, characterized by the progressive development of multiple kidney cysts, leading to a gradual decline in kidney function. ADPKD is also the fourth leading cause of kidney failure (KF) in adults. In addition to kidney manifestations, ADPKD is associated with various extrarenal features, including liver cysts, cardiovascular abnormalities, intracranial aneurysms, and chronic pain with significant impact on patients' quality of life. While several disease-modifying agents have been tested in ADPKD, tolvaptan remains the only approved drug by the US Food and Drug Administration. The Mayo Imaging Classification is currently the most practical tool for predicting rate of kidney disease progression in ADPKD. This review provides a comprehensive overview of ADPKD, focusing on its genetics, pathophysiology, clinical presentation, management, and prognostic tools. Advances in diagnostic imaging and genetic testing have improved the early detection of ADPKD, allowing better classification of patients and prediction of KF. The review also discusses current therapeutic approaches to ADPKD, including tolvaptan, a vasopressin V2-receptor antagonist. Additionally, we address specific issues in children and pregnant individuals with ADPKD. Despite substantial progress in understanding ADPKD, there is a large need for additional effective treatments and prognostic markers to provide a more personalized care for these patients.

Characteristics of patients with autosomal polycystic kidney disease reaching kidney failure by age 40

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) demonstrates broad genetic and phenotypic variability, with kidney failure (KF) occurring across a wide age spectrum. Despite several predictor tools, there remains a need to identify factors associated with rapid disease progression. This study describes the phenotypic characteristics of a multicentric cohort experiencing early-onset KF by age 40.

METHODS

This retrospective, multicenter cohort study analyzed longitudinal data of rapidly progressive ADPKD patients (n = 199). The prevalence of established risk factors was compared to nine existing ADPKD cohorts (ntotal = 6782) with KF after 40 years of age. We examined the longitudinal impact of early hypertension and urological events on the risk of developing KF.

RESULTS

The median age at ADPKD diagnosis was 22.3 years (IQR, 16.5-28.6) and median age of KF was 35.6 years (31.7-38.0). Hypertension was observed in 68.1% of cases, with early-onset hypertension being more common among those with accelerated progression towards KF. Urological events were present in 60.1% of cases, with a high burden of gross hematuria (30.4%). Existing ADPKD cohorts had a mean age of 45.5 years, with weighted prevalences of hypertension (71.1%), kidney stones (22.4%), hematuria (22.9%), and urinary tract infections (22.8%). Extrarenal manifestations were less prevalent compared to other ADPKD cohorts.

CONCLUSION

This study outlines a cohort of ADPKD patients with accelerated disease progression, reaching KF before age 40. Hypertension and urological events were highly prevalent at a young age, emphasizing the importance of early and regular blood pressure monitoring.

Insights from ADPedKD, ERKReg and RaDaR registries provide a multi-national perspective on the presentation of childhood autosomal dominant polycystic kidney disease in high- and middle-income countries

Data on the presentation of Autosomal Dominant Polycystic Kidney Disease (ADPKD) in children have been based on small/regional cohorts and practices regarding both asymptomatic screening in minors and genetic testing differ greatly between countries. To provide a global perspective, we analyzed over 2100 children and adolescents with ADPKD from 32 countries in six World Health Organization regions: 1060 children from the multi-national ADPedKD registry were compared to 269 pediatric patients from the United Kingdom (RaDaR) and 825 from the European Rare Kidney Disease Registry (ERKReg). Asymptomatic family screening was a common mode of presentation (48% in ADPedKD, 62% in ERKReg) with broad international variability (19%-75%), but fairly stable temporal trends in both registries with no correlation to genetic testing. The national rates of genetic testing varied and correlated significantly with healthcare expenditure (odds ratio 1.030 per 100 United States Dollars/capita/year, in the ERKReg cohort), with little variation over time. Diagnosis due to prenatal abnormalities was more common than anticipated at 14% increasing steadily from 2000 onward in both registries. Realistically, a high proportion of children were diagnosed with ADPKD by active screening, underlining that families affected by ADPKD have a high need for counselling on the complex issues around presymptomatic diagnosis. Regional variations in rate of genetic testing appeared to be driven by economic factors. However, large differences in rate of active screening were not correlated to healthcare spending and probably reflect the influence of different of cultural, legal and ethical frameworks on families and clinicians in different healthcare systems.

Polycystic Kidney Disease in Children: The Current Status and the Next Horizon

Autosomal dominant polycystic kidney disease (ADPKD) and autosomal recessive polycystic kidney disease (ARPKD) are inherited disorders that share many features such as kidney cysts, hypertension, urinary concentrating defects, and progressive chronic kidney disease. Underlying pathogenic mechanisms for both include cilia dysfunction and dysregulated intracellular signaling. ADPKD has been traditionally regarded as an adult-onset disease, whereas ARPKD has been classically described as an infantile or childhood condition. However, clinicians must recognize that both disorders can present across all age groups ranging from fetal life and infancy to childhood and adolescence, as well as adulthood. Here we highlight the points of overlap and distinct features for these disorders with respect to pathogenesis, diagnostic modalities (radiological and genetic), clinical assessment, and early therapeutic management. In particular, we consider key issues at two critical points for transition of care, i.e., fetal life to infancy and adolescence to adulthood. These timepoints are poorly covered in the extant literature. Therefore, we recommend guiding principles for transitions of clinical care at these critical junctures in the lifespan. While there is no cure for polycystic kidney disease (PKD), recent insights into pathogenic mechanisms have identified promising therapeutic targets that are currently being evaluated in a growing portfolio of clinical trials. We summarize the key findings from these largely adult-based trials and discuss the implications for designing child-focused studies. Finally, we look forward to the next horizon for childhood PKD, highlighting gaps in our current knowledge, and discussing future directions and strategies to attenuate the full burden of disease for children affected with PKD.

Ultrasound versus magnetic resonance imaging for calculating total kidney volume in patients with ADPKD: a real-world data analysis

BACKGROUND AND OBJECTIVES

This study aimed to compare Total kidney volume (TKV) measurements using US-ellipsoid (US-EL) and MRI-ellipsoid (MRI-EL) in patients with autosomal-dominant-polycystic-kidney-disease (ADPKD). It also evaluated whether the agreement between right (RKV) and left (LKV) kidney volume measurements differed.

METHODS

Retrospective analysis of a prospective data-base that included consecutive patients diagnosed with ADPKD. Total kidney volumes by 3D-US-EL were compared with those by MRI-EL. Bland-Altman-plots, Passing-Bablok-regression, and the concordance-correlation-coefficient (CCC) were used to compare right (RKV), left (LKV), and TKV measurements.

RESULTS

Thirty-two ADPKD patients, 14(43.7%) women, were included. Mean measured (mGFR) and estimated (eGFR) glomerular-filtration-rate (GFR) were 86.5 ± 23.9 mL/min and 78.9 ± 23.6 mL/min, respectively. Compared with MRI-EL, TKV (Mean difference: - 85.9 ± 825.6 mL; 95%CI - 498.5 to 326.7 mL; p = 0.6787), RKV (Mean difference: - 58.5 ± 507.7 mL; 95%CI - 312.2 to 195.2 mL; p = 0.6466), and LKV (Mean difference: - 27.4 ± 413.5 mL; 95%CI - 234.1 to 179.2 mL; p = 0.7918) were lower with US-EL than with MRI-EL, although without significant differences. According to Passing and Bablok-regression analysis, the Spearman correlation-coefficient was 0.96 (95%CI 0.92 to 0.98); 0.91 (95%CI 0.82 to 0.96), and 0.94 (95%CI 0.87 to 0.97) in the RKV, LKV, and TKV, respectively; p < 0.0001 each, respectively. CCC of RKV, LKV, and TKV measurements were 0.95, 0.89, and 0.94, respectively. The mGFR and eGFR showed statistically significant negative correlations with TKV measured by both MRI-EL (p = 0.0281 and p = 0.0054, respectively) and US-EL (p = p = 0.0332 and p = 0.0040, respectively).

CONCLUSIONS

This study found that ultrasound-based ellipsoid kidney volume measurements strongly correlated with MRI-based measurements, suggesting that ultrasound is a reliable, accessible alternative for assessing kidney volume, particularly when MRI is unavailable.

Biomarkers of Kidney Disease Progression in ADPKD

Autosomal dominant polycystic kidney disease (ADPKD) is the most common monogenic kidney disorder and the fourth leading cause of kidney failure (KF) in adults. Characterized by a reduction in glomerular filtration rate (GFR) and increased kidney size, ADPKD exhibits significant variability in progression, highlighting the urgent need for reliable and predictive biomarkers to optimize management and treatment approaches. This review explores the roles of diverse biomarkers-including clinical, genetic, molecular, and imaging biomarkers-in evaluating disease progression and customizing treatments for ADPKD. Clinical biomarkers such as biological sex, the predicting renal outcome in polycystic kidney disease (PROPKD) score, and body mass index are shown to correlate with disease severity and progression. Genetic profiling, particularly distinguishing between truncating and non-truncating pathogenic variants in the PKD1 gene, refines risk assessment and prognostic precision. Advancements in imaging significantly enhance our ability to assess disease severity. Height-adjusted total kidney volume (htTKV) and the Mayo imaging classification (MIC) are foundational, whereas newer imaging biomarkers, including texture analysis, total cyst number (TCN), cyst-parenchyma surface area (CPSA), total cyst volume (TCV), and cystic index, focus on detailed cyst characteristics to offer deeper insights. Molecular biomarkers (including serum and urinary markers) shed light on potential therapeutic targets that could predict disease trajectory. Despite these advancements, there is a pressing need for the development of response biomarkers in both the adult and pediatric populations, which can evaluate the biological efficacy of treatments. The holistic evaluation of these biomarkers not only deepens our understanding of kidney disease progression in ADPKD, but it also paves the way for personalized treatment strategies aiming to significantly improve patient outcomes.

Improved predictions of total kidney volume growth rate in ADPKD using two-parameter least squares fitting

Mayo Imaging Classification (MIC) for predicting future kidney growth in autosomal dominant polycystic kidney disease (ADPKD) patients is calculated from a single MRI/CT scan assuming exponential kidney volume growth and height-adjusted total kidney volume at birth to be 150 mL/m. However, when multiple scans are available, how this information should be combined to improve prediction accuracy is unclear. Herein, we studied ADPKD subjects ( n = 36 ) with 8+ years imaging follow-up (mean = 11 years) to establish ground truth kidney growth trajectory. MIC annual kidney growth rate predictions were compared to ground truth as well as 1- and 2-parameter least squares fitting. The annualized mean absolute error in MIC for predicting total kidney volume growth rate was 2.1 % ± 2 % compared to 1.1 % ± 1 % ( p = 0.002 ) for a 2-parameter fit to the same exponential growth curve used for MIC when 4 measurements were available or 1.4 % ± 1 % ( p = 0.01 ) with 3 measurements averaging together with MIC. On univariate analysis, male sex ( p = 0.05 ) and PKD2 mutation ( p = 0.04 ) were associated with poorer MIC performance. In ADPKD patients with 3 or more CT/MRI scans, 2-parameter least squares fitting predicted kidney volume growth rate better than MIC, especially in males and with PKD2 mutations where MIC was less accurate.

Estimating risk of rapid disease progression in pediatric patients with autosomal dominant polycystic kidney disease: a randomized trial of tolvaptan

BACKGROUND

Tolvaptan preserves kidney function in adults with autosomal dominant polycystic kidney disease (ADPKD) at elevated risk of rapid progression. A trial (NCT02964273) evaluated tolvaptan safety and pharmacodynamics in children (5-17 years). However, progression risk was not part of study eligibility criteria due to lack of validated criteria for risk assessment in children. As risk estimation is important to guide clinical management, baseline characteristics of the study participants were retrospectively evaluated to determine whether risk of rapid disease progression in pediatric ADPKD can be assessed and to identify parameters relevant for risk estimation.

METHODS

Four academic pediatric nephrologists reviewed baseline data and rated participant risk from 1 (lowest) to 5 (highest) based on clinical judgement and the literature. Three primary reviewers independently scored all cases, with each case reviewed by two primary reviewers. For cases with discordant ratings (≥ 2-point difference), the fourth reviewer provided a secondary rating blinded to the primary evaluations. Study participants with discordant ratings and/or for whom data were lacking were later discussed to clarify parameters relevant to risk estimation.

RESULTS

Of 90 evaluable subjects, primary reviews of 69 (77%) were concordant. The proportion considered at risk of rapid progression (final mean rating ≥ 3.5) by age group was: 15-17 years, 27/34 (79%); 12- < 15, 9/32 (28%); 4- < 12, 8/24 (33%). The panelists agreed on characteristics important for risk determination: age, kidney imaging, kidney function, blood pressure, urine protein, and genetics.

CONCLUSIONS

High ratings concordance and agreement among reviewers on relevant clinical characteristics support the feasibility of pediatric risk assessment.

Update on the Application of Ultrasonography in Understanding Autosomal Dominant Polycystic Kidney Disease

With an estimated prevalence of 1 in 1000 individuals globally, autosomal dominant polycystic kidney disease (ADPKD) stands as the most prevalent inherited renal disorder. Ultrasonography (US) is the most widely used imaging modality in the diagnosis and monitoring of ADPKD. This review discusses the role of US in the evaluation of ADPKD, including its diagnostic accuracy, limitations, and recent advances. An overview of the pathophysiology and clinical manifestations of ADPKD has also been provided. Furthermore, the potential of US as a noninvasive tool for the assessment of disease progression and treatment response is examined. Overall, US remains an essential tool for the management of ADPKD, and ongoing research efforts are aimed at improving its diagnostic and prognostic capabilities.

Single-Center Experience of Pediatric Cystic Kidney Disease and Literature Review

INTRODUCTION

Pediatric cystic kidney disease (CyKD) includes conditions characterized by renal cysts. Despite extensive research in this field, there are no reliable genetics or other biomarkers to estimate the phenotypic consequences. Therefore, CyKD in children heavily relies on clinical and diagnostic testing to predict the long-term outcomes.

AIM

A retrospective study aimed to provide a concise overview of this condition and analyze real-life data from a single-center pediatric CyKD cohort followed during a 12-year period.

METHODS AND MATERIALS

Medical records were reviewed for extensive clinical, laboratory, and radiological data, treatment approaches, and long-term outcomes.

RESULTS

During the study period, 112 patients received a diagnosis of pediatric CyKD. Male patients were more involved than female (1:0.93). Fifty-six patients had a multicystic dysplastic kidney; twenty-one of them had an autosomal dominant disorder; fifteen had an isolated renal cyst; ten had been diagnosed with autosomal recessive polycystic kidney disease; three had the tuberous sclerosis complex; two patients each had Bardet-Biedl, Joubert syndrome, and nephronophthisis; and one had been diagnosed with the trisomy 13 condition. Genetic testing was performed in 17.9% of the patients, revealing disease-causing mutations in three-quarters (75.0%) of the tested patients. The most commonly presenting symptoms were abdominal distension (21.4%), abdominal pain (15.2%), and oligohydramnios (12.5%). Recurrent urinary tract infections (UTI) were documented in one-quarter of the patients, while 20.5% of them developed hypertension during the long-term follow-up. Antibiotic prophylaxis and antihypertensive treatment were the most employed therapeutic modalities. Seventeen patients progressed to chronic kidney disease (CKD), with thirteen of them eventually reaching end-stage renal disease (ESRD). The time from the initial detection of cysts on an ultrasound (US) to the onset of CKD across the entire cohort was 59.0 (7.0-31124.0) months, whereas the duration from the detection of cysts on an US to the onset of ESRD across the whole cohort was 127.0 (33.0-141.0) months. The median follow-up duration in the cohort was 3.0 (1.0-7.0) years. The patients who progressed to ESRD had clinical symptoms at the time of initial clinical presentation.

CONCLUSION

This study is the first large cohort of patients reported from Croatia. The most common CyKD was the multicystic dysplastic kidney disease. The most common clinical presentation was abdominal distention, abdominal pain, and oliguria. The most common long-term complications were recurrent UTIs, hypertension, CKD, and ESRD.

Magnetic resonance imaging based kidney volume assessment for risk stratification in pediatric autosomal dominant polycystic kidney disease

Introduction

In the pediatric context, most children with autosomal dominant polycystic kidney disease (ADPKD) maintain a normal glomerular filtration rate (GFR) despite underlying structural kidney damage, highlighting the critical need for early intervention and predictive markers. Due to the inverse relationship between kidney volume and kidney function, risk assessments have been presented on the basis of kidney volume. The aim of this study was to use magnetic resonance imaging (MRI)-based kidney volume assessment for risk stratification in pediatric ADPKD and to investigate clinical and genetic differences among risk groups.

Methods

This multicenter, cross-sectional, and case-control study included 75 genetically confirmed pediatric ADPKD patients (5-18 years) and 27 controls. Kidney function was assessed by eGFR calculated from serum creatinine and cystatin C using the CKiD-U25 equation. Blood pressure was assessed by both office and 24-hour ambulatory measurements. Kidney volume was calculated from MRI using the stereological method. Total kidney volume was adjusted for the height (htTKV). Patients were stratified from A to E classes according to the Leuven Imaging Classification (LIC) using MRI-derived htTKV.

Results

Median (Q1-Q3) age of the patients was 6.0 (2.0-10.0) years, 56% were male. There were no differences in sex, age, height-SDS, or GFR between the patient and control groups. Of the patients, 89% had PKD1 and 11% had PKD2 mutations. Non-missense mutations were 73% in PKD1 and 75% in PKD2. Twenty patients (27%) had hypertension based on ABPM. Median htTKV of the patients was significantly higher than controls (141 vs. 117 ml/m, p = 0.0003). LIC stratification revealed Classes A (38.7%), B (28%), C (24%), and D + E (9.3%). All children in class D + E and 94% in class C had PKD1 variants. Class D + E patients had significantly higher blood pressure values and hypertension compared to other classes (p > 0.05 for all).

Discussion

This study distinguishes itself by using MRI-based measurements of kidney volume to stratify pediatric ADPKD patients into specific risk groups. It is important to note that PKD1 mutation and elevated blood pressure were higher in the high-risk groups stratified by age and kidney volume. Our results need to be confirmed in further studies.