Dahl, Neera K

Background: Total kidney volume (TKV), a prognostic biomarker in ADPKD, is used to stratify high risk individuals. eGFR measures may carry significant error in ADPKD compared to measured GFR(mGFR). This retrospective study investigates the association between height adjusted TKV (htTKV) and eGFR derived from race-free CKD-EPI equations utilizing creatinine and cystatin C. Methods: eGFR was calculated using 3 race-free CKD-EPI formulas: creatinine-based (CKD-EPI creatinine), cystatin C (CKD-EPI cys), and creatinine-cystatin C (CKD-EPI creatinine-cystatin C) equations on 697 Mayo Clinic ADPKD patients. Correlations between eGFR and TKV measures were estimated and stratified by MIC class risk groups and CKD. Linear regression models were computed to predict ln(htTKV) from the 3 eGFR data sets. The eGFR measures were compared to iothalamate-based mGFR in a subset of patients (n=50). Results: A correlation between eGFR measures and htTKV (Pearson correlation r of -0.53 to -0.54), varied by MIC stratification. Pearson correlation was -0.47 to -0.48 for MIC 1A and 1B, -0.67 to -0.71 for MIC 1C, and -0.67 to -0.68 for MIC 1D and 1E. All equations were significantly associated with htTKV levels, with similar adjusted beta values (95% CI) of -0.15 (-0.17 to -0.13), -0.14 (-0.16 to -0.12), -0.15 (-0.16 to -0.13), for CKD-EPI creatinine, CKD-EPI cystatin C, and CKD-EPI creatinine-cystatin C, respectively. Compared to mGFR, the CKD-EPI creatinine-cystatin C equation was the least biased (mean -0.86 (95% CI: -3.09 to 1.37)) versus CKD-EPI creatinine (2.31 (-0.73 to 5.34)) or CKD-EPI cystatin C (-3.54 (-5.86 to -1.21)), and most precise, with 1-P30 of 16% (95% CI 7.2% to 29.1%), compared to 18% (8.6% to 31.4%) for CKD-EPI creatinine, or 20% (10.0% to 33.7%) for CKD-EPI cystatin C. Conclusion: A moderate correlation between eGFR and htTKV associated with MIC stratification. Associations between htTKV and all 3 CKD-EPI equations were similar. CKDEPIcrcys tended to be the least biased and most precise equation when compared to mGFR and may be a reasonable alternative.

Key Points In a cohort of children, 79% of families with kidney cysts had a monogenic diagnosis. Resolved cases were more likely to have a family history of kidney cysts and unresolved cases more often had unilateral cysts. Broad genetic testing revealed genetic diversity and informed prognosis and clinical management in childhood kidney cysts. Background Pediatric kidney cysts may indicate an underlying genetic disorder, yet the full spectrum of causes remains incompletely defined. With advances in genetic testing enabling broader evaluation, this study assessed the diagnostic utility of comprehensive genetic testing in a broad pediatric cohort with kidney cysts and characterized the underlying etiological diversity. Methods This observational cohort study included patients younger than 18 years enrolled between January 2020 and June 2024 at a single tertiary center. Genetic testing used targeted multigene or custom curated exome/genome sequencing panels, with segregation analysis when available. Eligible participants had at least two cysts without family history, one cyst with positive family history, or enlarged echogenic kidneys on prenatal ultrasound; those with congenital anomalies of the kidney and urinary tract associated with cysts were excluded. Clinical presentation was categorized as symptomatic, incidental, prenatal, or family screening. Primary outcomes were diagnostic yield and distribution of pathogenic variants. Results Among 109 patients (median age 7.6 years, 53% female), genetic testing identified a definitive diagnosis in 81 of 100 tested patients (81%) from 72 families (79%; 14 disorders). PKD1 variants were most common (45%), while PKD2 accounted for 7%. Other causes included HNF1B or 17q12 deletions (13%), minor autosomal dominant polycystic kidney disease genes (11%; GANAB, NEK8, IFT140 ), monoallelic PKHD1 (3%), and biallelic PKHD1 (8%), while syndromic ciliopathy genes accounted for 5%. A positive family history of cystic kidney disease was more common among patients with a genetic diagnosis (54% versus 11%; P = 0.008). Patients without an identified genetic diagnosis more often had unilateral cysts (26% versus 4%; P = 0.53). Diagnosis by clinical symptoms was the most genetically diverse category. Conclusions Comprehensive genetic testing in pediatric kidney cysts achieved high diagnostic yield in a selected cohort and identified diverse causes beyond major autosomal dominant polycystic kidney disease/autosomal recessive polycystic kidney disease genes, supporting early evaluation to improve diagnostic accuracy, inform prognosis, and guide management, even in the absence of family history.

Key Points Genetic testing in CKD showed diagnostic and clinical utility in the year following reporting of test results. Genetic testing was helpful for or changed management in 86% of patients with a positive finding and 42% with a negative finding. Clinical utility was seen across 12 clinical cohorts, including CKD of unknown etiology and hypertension or diabetes-related nephropathy. Background CKD is a significant public health burden, affecting >800 million people worldwide with significant cost to the health care system. CKD is a disease process with substantial genetic and phenotypic heterogeneity that can obscure a definitive diagnosis, resulting in suboptimal management. Recent guidelines support greater adoption of genetic testing in CKD. We assessed the diagnostic and clinical utility in the year following broad-panel CKD genetic testing. Methods The Renasight Clinical Application, Review, and Evaluation (RenaCARE) study (NCT05846113) was a single-arm, interventional, prospective, multicenter study evaluating the utility of genetic testing with a 385-gene panel on the diagnosis and management of CKD. Clinical history was collected before testing, and nephrologists responded to questionnaires at both 1 month and 1 year after testing. The impact of genetic testing on CKD diagnosis and management were assessed in active study patients at the 1-year time point. Results In a cohort of 1388 CKD patients with 13 pretest clinical categories of CKD, 335 (24%) patients had a positive genetic finding; 1174 had a questionnaire completed at 1 year and were included in the analysis. Genetic testing was reported helpful for clinical management and/or led to a change in management in 86% of patients with a positive test finding and 42% of patients with a negative test finding. In addition, genetic testing resulted in a change in the physician estimation of the 5-year prognosis for 55% of patients with a positive test finding and 18% of those with a negative test finding. Conclusions Supporting the previous results of the RenaCARE study at 1 month, this report demonstrated that genetic testing was helpful in the clinical management and estimated prognosis of patients with CKD. Clinical Trial registry name and registration number: ClinicalTrials.gov, NCT05846113.

Key Points Automated cyst segmentation in autosomal dominant polycystic kidney disease could transform care by enabling precise monitoring of cyst progression with minimal manual effort. This technology can facilitate more consistent assessments of cyst burden across patients. Translating these segmentation models from magnetic resonance imaging to computed tomography is crucial for providing comprehensive, modality-independent evaluations. Background Total kidney and liver volumes are key image-based biomarkers to predict the severity of kidney and liver phenotype in autosomal dominant polycystic kidney disease (ADPKD). However, magnetic resonance (MR) imaging-based advanced biomarkers like total cyst number and cyst parenchyma surface area have been shown to more accurately assess cyst burden and improve the prediction of disease progression. The main aim of this study was to extend the calculation of advanced biomarkers to other imaging modalities; thus, we propose a fully automated model to segment kidney and liver cysts in computed tomography (CT) images. Methods Abdominal CTs of patients with ADPKD were gathered retrospectively between 2001 and 2018. A three-dimensional deep learning method using the nnU-Net architecture was trained to learn cyst edges-cores and the noncystic kidney/liver parenchyma. Separate segmentation models were trained for kidney cysts in contrast-enhanced CTs and liver cysts in noncontrast CTs using an active learning approach. Two experienced research fellows manually generated the reference standard segmentation, which were reviewed by an expert radiologist for accuracy. Results Two-hundred CT scans from 148 patients (mean age, 51.2±14.1 years; 48% male) were used for model training (80%) and testing (20%). In the test set, both models showed good agreement with the reference standard segmentations, similar to the agreement between two independent human readers (model versus reader: TCN kidney/liver r =0.96/0.97 and CPSA kidney r =0.98, inter-reader: TCN kidney/liver r =0.96/0.98 and CPSA kidney r =0.99). Conclusions Our study demonstrates that automated models can segment kidney and liver cysts accurately in CT scans of patients with ADPKD.

Key Points The growing knowledge of single-gene causes of pediatric-onset kidney diseases necessitates a structured application of genetic testing in practice. The clinical application of a combined nephrogenetics approach for management of kidney diseases is not well described in pediatric settings. Real-world application of a kidney genetics workflow highlights clinical value and challenges to be addressed for its successful implementation. Background The expanding knowledge of identifiable genetic contributions to pediatric inherited kidney diseases, and the increasing availability of genetic testing resources necessitates a combined nephrogenetics clinical approach. Although such models are described for adults, the effect of a structured nephrogenetics workflow on children with inherited kidney disease has not been rigorously evaluated. Methods Clinical and genetic data of patients aged younger than 1–21 years over a 10-year period between 2014 and 2024 from a single-center pediatric inherited kidney disease outpatient program were evaluated. Genetic variants were classified as pathogenic/likely pathogenic and variants of uncertain significance (VUS). Patients were grouped into “informative” or “uninformative” groups based on the effect of genetic test results on disease management and outcomes. Results Of the N =356 patients evaluated for a known or suspected inherited kidney disease, N =188 received clinical genetic testing. Of these, N =147 had an “informative” genetic test affecting at least one positive clinical outcome. Patients with an “informative” genetic test mostly harbored a pathogenic/likely pathogenic variant ( N =122). An additional N =25 had a VUS reclassified as a “VUS-of-interest” affecting a positive outcome measure. Genetic test results led to change in clinical diagnosis (reverse phenotyping, 46%), informed specific diagnosis-based treatment (46%), avoided unnecessary immunosuppression (27%) or kidney biopsy (18%), and guided extrarenal evaluation (72%) in patients with an informative test. Patients with a glomerular (odds ratio [OR]=5.23; 95% confidence interval [CI], 1.96 to 13.96) or a tubular functional disease (OR=2.17; 95% CI, 1.31 to 5.59) were more likely and those with a structural kidney disease (OR=0.39; 95% CI, 0.25 to 0.60) were less likely to receive a genetic test when compared with all other disease categories combined. Conclusions This workflow integrated multidisciplinary care for children with inherited kidney disease and describes a model for actionable clinical care plans after genetic testing. Informative genetic tests were associated with positive outcomes, and notable challenges include access to combined nephrology and genetics expertise for informed testing and an effective result return including VUS interpretation.

Importance Autosomal dominant polycystic kidney disease (ADPKD) is characterized by progressive development of kidney cysts and is the most common inherited kidney disorder worldwide. ADPKD accounts for 5% to 10% of kidney failure in the US and Europe, and its prevalence in the US is 9.3 per 10 000 individuals. Observations ADPKD is typically diagnosed in individuals aged 27 to 42 years and is primarily caused by pathogenic variants in the PKD1 (78%) or PKD2 (15%) genes. Most persons with ADPKD have an affected parent, but de novo disease is suggested in 10% to 25% of families. More than 90% of patients older than 35 years have hepatic cysts, which may cause abdominal discomfort and occasionally require medical or surgical intervention. Hypertension affects 70% to 80% of patients with ADPKD, and approximately 9% to 14% develop intracranial aneurysms, which have a rupture rate of 0.57 per 1000 patient-years. Approximately 50% of individuals with ADPKD require kidney replacement therapy by 62 years of age. The severity of kidney disease can be quantified using the Mayo Imaging Classification (MIC), which stratifies patients based on total kidney volume adjusted for height and age and ranges from 1A to 1E. Patients with MIC 1C to MIC 1E have larger kidneys because of more rapid growth (6%-10% per year) compared with those with MIC 1A and 1B (1%-5% per year) and have earlier progression to kidney replacement therapy, which occurs at a mean age of 58.4 years for MIC 1C, 52.5 years for MIC 1D, and 43.4 years for MIC 1E. Optimal management of ADPKD includes systolic blood pressure lower than 120 mm Hg for most patients, but lower than 110/75 mm Hg for patients with MIC 1C to 1E who have an estimated glomerular filtration rate (eGFR) greater than 60 mL/min/1.73 m 2 and are younger than 50 years, dietary sodium restriction (<2000 mg/d), weight management, and adequate hydration (>2.5 L daily). The vasopressin type 2 receptor antagonist tolvaptan reduces the annual rate of eGFR decline by 0.98 to 1.27 mL/min/1.73 m 2 and is indicated for patients with MIC 1C to 1E or an eGFR decline greater than 3 mL/min/1.73 m 2 per year to slow disease progression and delay the onset of kidney failure. Conclusion ADPKD is the most common genetic kidney disease worldwide and is characterized by progressive development of kidney cysts. Patients typically have hypertension and liver cysts, and 9% to 14% develop intracranial aneurysms. First-line treatment includes blood pressure control, dietary and weight management, and adequate hydration. Tolvaptan reduces the rate of eGFR decline for those at high risk of rapid progression to kidney failure.

Key Points Loss-of-function ALG8 and ALG9 variants were enriched in polycystic kidney/liver groups and International Classification of Diseases–coded cystic individuals in population cohorts. The ALG8 and ALG9 kidney phenotypes were usually mild to moderate, and lower eGFR or kidney failure was rare. ALG8 pathogenic variants sometimes resulted in severe polycystic liver disease. Background Autosomal dominant polycystic kidney disease (ADPKD) is a common, inherited nephropathy often resulting in kidney failure. It is genetically heterogeneous; along with the major genes, PKD1 and PKD2 , at least eight others have been suggested. ALG8 pathogenic variants have been associated with autosomal dominant polycystic liver disease and implicated in ADPKD, while ALG9 has been suggested as an ADPKD gene, but details of the phenotypes and penetrance are unclear. Methods We screened >3900 families with cystic kidneys and/or livers using global approaches to detect ALG8 or ALG9 pathogenic variants. In addition, population cohorts with sequence data (Genomics England 100K Genomics Project, UK Biobank, and Mayo Clinic Biobank [MCBB]) were screened for ALG8 / ALG9 pathogenic variants. Results Multicenter screening of individuals with polycystic kidney and/or liver disease identified 51 (1.3%) ALG8 (7 multiplex) and 23 (0.6%) ALG9 (5 multiplex) families—frequencies that were approximately 10× and approximately 24× greater than nonpolycystic kidney disease controls. Analysis of individuals with polycystic kidney disease phenotypes in 100K Genomics Project, UK Biobank, and MCBB identified nine ALG8 (0.39%) and nine ALG9 (0.39%) families, an enriched frequency over controls. Two individuals had PKD1 and ALG8 pathogenic changes. Eighty-nine percent of individuals with ALG8 mutations with imaging in the entire MCBB had kidney cysts (50%, >10 cysts), with greater median kidney and liver cyst numbers than controls. For ALG9, 78% had kidney cysts (27%, >10 cysts). Individuals with ALG8 mutations typically had mild cystic kidneys with limited enlargement. Liver cysts were common (71%), with enlarged livers (>2L) found in 11 of 62 patients, although surgical intervention was rare. The ALG9 kidney phenotype was also of mild cystic kidneys, but enlarged livers were rare; for both genes, CKD or kidney failure were rare. Conclusions ALG8 and ALG9 are defined as cystic kidney/liver genes but with limited penetrance for lower eGFR.