Epidemiology of native kidney disease in Flanders: results from the FCGG kidney biopsy registry

[Diagnosis and treatment of focal-segmental glomerulosclerosis-2023]

The histopathological term focal-segmental glomerulosclerosis comprises different pathogenic processes with the unifying features of a high proteinuria and the name-giving glomerular lesion pattern seen on light microscopy. A differentiation according to the underlying cause into primary, secondary and genetic forms is therefore of utmost importance. The pathogenesis of primary focal-segmental glomerulosclerosis remains unknown but, like minimal-change disease, an autoimmune-mediated process leading to podocyte damage is assumed. Consequently, the unifying term "podocytopathy" is increasingly being used for both entities. Supportive treatment measures to preserve kidney function are important in all subtypes. In contrast, immunosuppressive treatment is only indicated in primary focal-segmental glomerulosclerosis. Steroid-dependence, steroid-resistance and frequently relapsing disease often complicate disease management and necessitate alternative treatment strategies. Here, the Austrian Society of Nephrology (ÖGN) provides consensus recommendations on how to best diagnose and manage patients with focal-segmental glomerulosclerosis.

Exploring hospital practice types and their impact on glomerular pathologic patterns: Insights from the largest kidney biopsy cohort in Thailand

BACKGROUND

This study aims to investigate the influence of different kidney biopsy practices on the prevalence of glomerular pathologic patterns in the largest kidney biopsy registry in Thailand.

METHODS

We conducted a retrospective review of kidney biopsy records from the period between 2000 and 2014. The records were obtained from 2 major institutions: King Chulalongkorn Memorial Hospital, a large university-based hospital, and the Kidney Center Bangkok Hospital, which provides pathology services to hospitals throughout Thailand. The study included native kidney biopsies from all provinces in Thailand, excluding paediatric patients, kidney transplant recipients, and cases of inadequate and repeated biopsies. Patient demographics, indications for biopsy, and final glomerular diagnoses were compared across different hospital practice settings: university (UVH), private (PVH) and public (PBH).

RESULTS

A total of 5893 eligible native kidney biopsies were identified from a pool of 7005 biopsies conducted over a 15-year period in 25 provinces throughout Thailand. The 3 most common indications for biopsy were suspected kidney involvement in systemic lupus erythematosus (SLE) (29%), nephrotic syndrome (NS) (29%), and acute glomerulonephritis (AGN)/rapidly progressive glomerulonephritis (RPGN) (13%). The leading indication for biopsy differed across practice types, with suspected kidney involvement in SLE being the primary indication in UVH, while NS took precedence in both PBH and PVH practices. Notably, UVH performed fewer kidney biopsies for asymptomatic urinary abnormalities and diabetes-related indications compared with PVH and PBH. The leading glomerular diagnoses correlated with the biopsy indications, with lupus nephritis (LN) being the most common diagnosis in UVH and PBH practices, whiles immunoglobulin A nephropathy was the predominant diagnosis in PVH practice.

CONCLUSION

Hospital practice types significantly impact the prevalence of glomerular pathologic diagnosis patterns in kidney biopsy data, highlighting the importance of considering this influence in epidemiological comparisons.

The Cleveland Clinic Kidney Biopsy Epidemiological Project

BACKGROUND

The kidney biopsy is the gold standard for diagnosing glomerular diseases. Large-scale, epidemiologic studies describing the prevalence of kidney diseases are lacking, especially in the United States. We aimed to determine the spectrum of biopsy-proven kidney disease across the Cleveland Clinic enterprise.

METHODS

We identified all patients with a native kidney biopsy performed or reviewed at the Cleveland Clinic from January 2015 to September 2021. Retrospective chart review was performed to obtain clinical and demographic characteristics. Results were stratified by age, sex, race, and location to determine epidemiologic trends.

RESULTS

Of >9600 patients, we excluded transplant and donor biopsies and unavailable records, and included 4128 patients with native kidney biopsy data. The median age was 60 years, with 46% female patients. Self-reported racial demographics included 73% White, 22% Black, 3% multiracial, and 2% Asian background, with 5% Hispanic. Common diagnoses were: FSGS (n=633, 15%), diabetic kidney disease (DKD) (n=602, 15%), IgA nephropathy (n=319, 8%), lupus nephritis (LN) (n=289, 7%), pauci-immune glomerulonephritis (n=275, 7%), membranous nephropathy (n=211, 5%), and amyloidosis (n=110, 3%). There were 3322 patients in Ohio, with 361 patients in Florida. Using multivariate analysis, those aged >70 years were more likely to have FSGS, whereas those <45 years were more likely to have IgA nephropathy or LN. Males were more likely to have FSGS or IgAN, and less likely to have LN. Black patients were more likely to have FSGS, DKD, or LN. Hispanic patients were more likely to have DKD. Finally, patients in Florida were more likely to have LN. There was no change in the disease spectrum before and during the COVID-19 pandemic.

CONCLUSION

Our study catalogs the spectrum of biopsy-proven kidney disease across the Cleveland Clinic enterprise. This lays the foundation for glomerular disease clinical trials, and highlights the need for a standardized national kidney biopsy registry to bolster glomerular and kidney disease research in the United States.

Epidemiology and clinicopathological characteristics of native kidney disease in children in Flanders, Belgium

BACKGROUND

The Flemish Collaborative Glomerulonephritis Group (FCGG) registry is a population-based kidney biopsy registry that has been including all native kidney biopsies performed in children in Flanders (Belgium), since 2017.

METHODS

From 2017 to 2020, 148 pediatric (< 18 years) native kidney biopsies were included. Each biopsy received a histopathological and final nephrological diagnosis, and concordance between both was assessed. Disease chronicity, summarized by the Mayo Clinic Chronicity Score, was determined on 122 biopsies with > 5 glomeruli.

RESULTS

Kidney biopsy rate was high (29.0 biopsies per million children per year), median age was 10.0 years (IQR 5.8-14.7), and boys predominated (56.1% males). A total of 140 biopsies (94.6%) showed a representative pathology result. Glomerular disease was most prevalent, with IgA nephropathy/IgA vasculitis (43 biopsies, 29.1%) and minimal change disease (MCD) (29 biopsies, 19.6%) being the overall most frequent diagnoses. In general, diagnostic concordance was high (80.7%). In Alport syndrome and focal segmental glomerulosclerosis (FSGS), concordance was lower, as the nephrological diagnosis was often determined by results of genetic analysis. Nephrotic syndrome was the most frequent indication for kidney biopsy (31.8%) and was mainly caused by MCD and FSGS. The degree of disease chronicity on kidney biopsies was generally low, although 27.3% of biopsies with a diagnosis of FSGS showed moderate-to-severe chronic damage.

CONCLUSIONS

The presented epidemiological findings validate data from previous European registry studies and may inspire kidney biopsy registries worldwide to implement novel features such as clinicopathological concordance and chronicity grading. A higher resolution version of the Graphical abstract is available as Supplementary information.

Clinicopathological characteristics and disease chronicity in native kidney biopsies in Flanders

Background

The Flemish Collaborative Glomerulonephritis Group (FCGG) registry provides complete population data on kidney disease epidemiology in the region of Flanders (Belgium), as it captures all native kidney biopsies performed in its population of 6.5 million inhabitants.

Methods

From 2017 until 2019, 2054 adult kidney biopsies were included from 26 nephrology centers (one biopsy per patient). Data on nephrotic and nephritic syndrome were available in 1992 and 2026 biopsies, respectively. In a subgroup of 898 biopsies containing ≥10 glomeruli from 2018 to 2019, disease chronicity was graded using the Mayo Clinic Chronicity Score (MCCS). The association between clinical variables and MCCS was determined using simple and multiple linear regression models.

Results

Nephrotic syndrome (present in 378 patients, 19.0%) was most frequently caused by minimal change disease in younger patients (18-44 years), membranous nephropathy in older patients (45-74 years) and amyloidosis in the elderly (>75 years). Nephritic syndrome (present in 421 patients, 20.8%) was most frequently caused by immunoglobulin A nephropathy (IgAN) in younger patients (18-64 years) and ANCA-associated vasculitis (AAV) in older patients (>64 years). AAV and IgAN were the most frequent underlying diagnoses in biopsies in which crescents were identified. In multivariable analysis, acute and chronic kidney disease and diagnoses of diabetic kidney disease, nephrosclerosis and hyperoxaluria/hypercalcemic nephropathy were associated with the highest MCCS increases.

Conclusions

The FCGG registry validates data from previous Western European registries and provides a snapshot of disease chronicity in the whole biopsied Flemish population.