The Spectrum of Children's Kidney Diseases—2403 Renal Biopsy-Proven Cases from a Single Centre in China Between 1999 and 2019

Background: This study aimed to investigate the clinical and pathological characteristics and the changes in glomerular diseases in 2403 pediatric renal biopsies from 1999 to 2019.Methods: Renal biopsies performed on children aged ≤18 years between 1999 and 2019 were analysed at our center. We analysed the clinical and histological characteristics, distribution of pediatric glomerular diseases with various clinical presentations, and changes in the glomerular disease patterns during the study period.Results: The most common primary glomerular disease was IgA nephropathy (IgAN) (24.3%), followed by minimal change disease (MCD) (15.3%) and membranous glomerulonephritis (MN) (13.1%). Henoch-Schonlein purpura nephritis (HSPN) (18.1%) and lupus nephritis (LN) (7.2%) were the most frequently recorded secondary glomerular diseases. Alport syndrome and thin basement membrane nephropathy (TBMN) were the most common inherited glomerular diseases, accounting for 1.2% and 0.6% of the total glomerular diseases in children, respectively. The number of boys with IgAN, MCD and IgM nephropathy (IgMN) was higher than that of girls, while the number of girls with MN and LN was higher than that of boys. The frequencies of MCD, MN, IgMN and endocapillary proliferative glomerulonephritis (EnPGN) in the 13-18-year-old group were higher than those in the 0-12-year-old group, while the frequencies of IgAN, mesangial proliferative glomerulonephritis (MsPGN) and focal proliferative glomerulonephritis (FPGN) were lower than those in the 0-12-year-old group. The ratio of Alport syndrome and TBMN in the 0-12-year-old group was higher than that in the 13-18-year-old group. The proportion of patients with MCD and MN in 2010-2019 was higher than that in 1999-2009, while the ratio of IgAN, MsPGN, IgMN, EnPGN, membranoproliferative glomerulonephritis (MPGN), HSPN and HBV-associated glomerulonephritis (HBV-GN) decreased. MCD (28.5%) was the most common cause of nephrotic syndrome (NS). In children with haematuria and proteinuria, HSPN (38.8%) and IgAN (36.9%) were more common than other glomerular diseases. IgAN (39.4%) was the most common cause of AKI. Sclerosing glomerulonephritis (SGN) (21.1%) was the main cause of progressive chronic kidney disease (CKD).Conclusions: Glomerular diseases in children were related to sex and age. From 1999 to 2019, the spectrum of children's kidney disease in our center changed significantly.

Evaluation of renal biopsies in various kidney diseases with reference to staining

Renal diseases of different origin and nature may produce essentially similar disturbances of renal functions and may have clinical similarities and hence there was a need to classify renal diseases more scientifically. The basic approach was to correlate clinical signs and symptoms with histological changes in the tissue, using both simple and special staining techniques so as to reach to a definitive diagnosis.The present study was conducted on renal biopsy referred to pathology department. Criteria for successful biopsy were as follows-Adequate biopsy sample size, correct processing of specimen, informed interpretation and issue of an accurate report. A total of 29 renal biopsies were examined. In minimal change disease, only in 4 patients the glomerulus was sclerosed. Membranous glomerulonephritis comprised of the maximum number of cases (9/30). Total of 3 cases of renal biopsies revealed amyloidosis. Focal amyloid deposits with deposits either near the hilum or perivascular areas were found in 33.3% of cases, while extensive amyloid deposits were found in 33.3% of the cases.It is necessary to determine both the type of renal disease and the cause of the primary disorder in order to make the diagnosis and various staining techniques play a very helpful role. The likelihood that the biopsy specimen accurately reflects the type and severity of the underlying disease is directly related to both the diffuseness of the disease process and the amount of tissue examined.

Discovery of Autoantibodies Targeting Nephrin in Minimal Change Disease Supports a Novel Autoimmune Etiology

Background Failure of the glomerular filtration barrier, primarily by loss of slit diaphragm architecture, underlies nephrotic syndrome in minimal change disease. The etiology remains unknown. The efficacy of B cell-targeted therapies in some patients, together with the known proteinuric effect of antinephrin antibodies in rodent models, prompted us to hypothesize that nephrin autoantibodies may be present in patients with minimal change disease. Methods We evaluated sera from patients with minimal change disease enrolled in the Nephrotic Syndrome Study Network (NEPTUNE) cohort and from our own institutions for circulating nephrin autoantibodies by indirect ELISA and by immunoprecipitation of full-length nephrin from human glomerular extract or a recombinant purified extracellular domain of human nephrin. We also evaluated renal biopsies from our institutions for podocyte-associated punctate IgG colocalizing with nephrin by immunofluorescence Results In two independent patient cohorts, we identified in a subset of patients with minimal change disease circulating nephrin autoantibodies during active disease that were significantly reduced or absent during treatment response. We correlated the presence of these autoantibodies with podocyte-associated punctate IgG in renal biopsies from our institutions. We also identified a patient with steroid-dependent childhood minimal change disease that progressed to end-stage kidney disease; she developed a massive posttransplant recurrence of proteinuria that was associated with high pretransplant circulating nephrin autoantibodies. Conclusions Our discovery of nephrin autoantibodies in a subset of adults and children with minimal change disease aligns with published animal studies and provides further support for an autoimmune etiology. We propose a new molecular classification of nephrin autoantibody minimal change disease to serve as framework for instigation of precision therapeutics for these patients.

Quality improvement Initiative to eliminate silver precipitate during Periodic Acid Silver Methenamine Stain (PAMS) automated protocol of renal biopsies at McGill University Health Centre

Introduction/Objective Annually, about 400 renal biopsies are processed at the McGill University Health Centre (MUHC) pathology laboratory located in Montreal, Canada. One of the stains used to visualize the glomerular basement membrane is Periodic Acid Silver Methenamine Stain (PAMS). In August 2020, a strong, granular precipitate of silver was noted during PAMS automated staining resulting in uninterpretable results and delay in the diagnosis. Based on a sample analysis, this problem affected 21 % of kidney biopsies. Methods/Case Report A cause-and-effect workflow was developed for systematic assessment of potential causes of the granular precipitate including pre-analytical and analytical factors. Some of the pre-analytical factors included length of time spent in transport before fixation and patient factors that predisposed precipitate formation. Analytical factors were categorized as fixation problems (temperature, pH, duration), embedding problems (parafilm temperature, cooling method, type of parafilm), slide preparation (temperature, water bath pH, dehydration and further processing steps), microtone parameters (microtone calibration, thickness, laboratory technologist expertise), automatic staining parameters (cartridge age, hematoxylin counterstain duration, wash-out period etc.) and coverslip placement (adhesive type, temperature, drying). Results (if a Case Study enter NA) Following our systematic approach, the cause of granular precipitate was identified as the timing of hematoxylin counterstain. A portion of renal biopsy tissue was taken from parafilm blocks of previouslly reported cases of patients with membranous glomerulonephritis to further test the hypothesis by introduction of various incubation times with the hematoxylin counterstain. Conclusion Best PAMS staining was attained when no hematoxylin counterstain was employed (instead, neutral red counterstain for 70 seconds was used). PAMS staining with hematoxylin counter stain for no more than 60 seconds was found to be acceptable for the interpretation of glomerular pathology.

Learning curve for the laparoscopy-guided kidney biopsy procedure in small corpses of dogs and pigs

The use of renal biopsy through laparoscopy is increasingly present both in human and veterinary medicine. However, both techniques require skill and training to make the operator capable to do it. The learning curve allows the quantitative and qualitative assessment of the number of attempts and minimum time for the surgical procedure. The objective included establish the learning curve for laparoscopy-guided kidney biopsy procedures in dog and pig corpses. Six dogs and six pigs corpses weighing less than 10 kg were used for this study. All corpses underwent kidney biopsy performed through laparoscopy. Twenty-four operators, two per animal, performed 20 renal biopsies each (10 for each kidney), with 480 collection-procedures in total. Duration and difficulty of the procedure and the biopsy sample quality were evaluated and statistical analysis was performed using a mixed regression model with a random effect of individuals and multivariate analysis of data. There were 91.5% of the samples that were adequate for evaluation. There was no significant difference in the number of glomeruli or cortex percentage considering the attempts in either species, demonstrating the operator’s ability since first collection. Swine samples showed higher amounts of renal cortex than canine samples. The procedure duration was shorter as more attempts were performed in dogs and pigs. From the fourth repetition, the professional reached a plateau for the variable related to ‘collection’, and from the second, the professional presented uniform duration for ‘sample storage’. Operators of the swine model acquired more agility than the dog ones. The variable ‘difficulty’ decreased as more repetitions were performed, reaching a plateau in the sixth attempt. Seven renal biopsies laparoscopy-guided are required for an operator to be considered ‘capable’ to perform the procedure in the referred species included. The learning curve for image-guided kidney biopsy procedures improves the implementation of this technique and benefits patients that undergo this procedure.

Determination of Anti-Phospholipase A2 and Anti-Thrombospondin Type 1 Domain-Containing Protein 7A in Latin Patients With Membranous Nephropathy

BACKGROUND Membranous nephropathy (MN) is caused by antibodies against podocyte antigens, of which the type M receptor of phospholipase A2 (PLA2R) and thrombospondin type-1 domain containing 7 A (THSD7A) are the mostly studied. The objectives of this study were to determine anti-PLA2R and anti-THSD7A serum antibodies and anti-PLA2R renal tissue prevalence in a Latin population with primary MN and to evaluate their role as biomarkers for disease activity. Additionally, the performance of the two available serum diagnostic methods - ELISA and indirect immunofluorescence - was evaluated for the diagnosis of MN. METHODS Fifty-nine patients, 29 MN, 18 lupus membranous nephropathy (LMN) and 12 focal and segmental glomerulosclerosis (FSGS) were evaluated for serum antibodies. Renal biopsies were also evaluated for the presence of anti-PLA2R. Twenty-one patients with MN were followed for 1 year. RESULTS Patients with LMN and FSGS were negative for both antibodies. All 29 MN were negative for anti-THSD7A; 16 MN were positive by ELISA and/or IFI, and 3 MN patients were positive only by IFI. Thus, ELISA test showed a 45% sensitivity and 97% specificity while the IFI showed a 55% and 100%, respectively. In patients with less than a year between biopsy and antibody collection, sensitivity increased to 79% and maintained specificity. Positive correlations were observed between the anti-PLA2R ELISA titer and proteinuria. Among the 28 MN renal biopsies, 20 presented anti-PLA2R positive staining, a 72% sensitivity. CONCLUSIONS The determination of anti-PLA2R antibodies in the Latin population showed similar rates as reported in other populations, and the IFI test presented greater sensitivity. A lower rate of remission was found among those with anti-PLA2R positive tests.

Clinical and Military Outcomes of Kidney Diseases Diagnosed in Active Duty Service Members

ABSTRACT Introduction Renal biopsy is a valuable tool for determining diagnosis, management, and prognosis of intrinsic kidney diseases. Indications for biopsy depend on the clinical presentation. Within the military, renal biopsies also enable medical review boards to make military service fitness assessments after diagnosis of a kidney disease. There are no recent studies evaluating kidney disease diagnoses and clinical outcomes after renal biopsy at military treatment facilities. Additionally, no studies have examined overall healthcare and military career outcomes following renal biopsy. Materials and Methods We retrospectively reviewed all native renal biopsies performed on active duty beneficiaries at the Walter Reed National Military Medical Center from 2005 to 2020. We determined the prevalence of those who progressed to end-stage kidney disease (ESKD), kidney transplantation, doubling of serum creatinine, nephrotic-range proteinuria (NRP; proteinuria >3.5 g/day), medical evaluation board (MEB) outcomes, and death. The Armed Forces Health Longitudinal Technology Application and the Joint Legacy Viewer electronic medical record systems were used to access clinical and laboratory data at the time of biopsy and subsequent outcomes. Death data were collected using the Defense Suicide Prevention Office database. Results There were 169 patients in the cohort, with a mean follow-up of 7.3 years. Mean age was 32 years; 79% male; 48% white; and 37% black. Sixty-seven percentage of them were junior or senior enlisted. The most common indication for renal biopsy was concomitant hematuria and proteinuria (31%). The most common histologic diagnoses were immunoglobulin A (IgA) nephropathy (23%), followed by focal segmental glomerulosclerosis (FSGS; 17%) and lupus nephritis (12%). Eleven percentage of them progressed to ESKD, of whom 87% received a kidney transplant (10% overall). Thirty percentage of the patients progressed to NRP and 5% died. Forty-seven percentage of our patients underwent MEB after diagnosis, and of these, 84% were not retained for further military service. Although IgA nephropathy was the most commonly diagnosed condition, FSGS and lupus nephritis diagnoses were significantly more likely to result in MEB. Conclusions and Implications Immunoglobulin A nephropathy was the most frequent histologic diagnosis in active duty service members undergoing renal biopsy between 2005 and 2020. Despite being largely young and previously healthy, 11% progressed to ESKD and 5% died. A confirmed histologic diagnosis was associated with separation from the service and the end of military careers for 84% of the patients in the cohort who underwent MEB.