A large-scale retrospective study enabled deep-learning based pathological assessment of frozen procurement kidney biopsies to predict graft loss and guide organ utilization.

Lesion scores on procurement donor biopsies are commonly used to guide organ utilization for deceased-donor kidneys. However, frozen sections present challenges for histological scoring, leading to inter- and intra-observer variability and inappropriate discard. Therefore, we constructed deep-learning based models to recognize kidney tissue compartments in hematoxylin & eosin-stained sections from procurement needle biopsies performed nationwide in years 2011-2020. To do this, we extracted whole-slide abnormality features from 2431 kidneys and correlated with pathologists' scores and transplant outcomes. A Kidney Donor Quality Score (KDQS) was derived and used in combination with recipient demographic and peri-transplant characteristics to predict graft loss or assist organ utilization. The performance on wedge biopsies was additionally evaluated. Our model identified 96% and 91% of normal/sclerotic glomeruli respectively; 94% of arteries/arterial intimal fibrosis; 90% of tubules. Whole-slide features of Sclerotic Glomeruli (GS)%, Arterial Intimal Fibrosis (AIF)%, and Interstitial Space Abnormality (ISA)% demonstrated strong correlations with corresponding pathologists' scores of all 2431 kidneys, but had superior associations with post-transplant estimated glomerular filtration rates in 2033 and graft loss in 1560 kidneys. The combination of KDQS and other factors predicted one- and four-year graft loss in a discovery set of 520 kidneys and a validation set of 1040 kidneys. By using the composite KDQS of 398 discarded kidneys due to "biopsy findings", we suggest that if transplanted, 110 discarded kidneys could have had similar survival to that of other transplanted kidneys. Thus, our composite KDQS and survival prediction models may facilitate risk stratification and organ utilization while potentially reducing unnecessary organ discard.

Anti-slit diaphragm antibodies on kidney biopsy identify pediatric patients with steroid-resistant nephrotic syndrome responsive to second-line immunosuppressants.

Podocytopathies represent a group of glomerular disorders associated with minimal changes (MC) or focal segmental glomerulosclerosis (FSGS) lesion patterns at biopsy and heterogeneous responses to steroids. Anti-nephrin antibodies were previously found in such patients, suggesting an autoimmune form of podocytopathy. High resolution confocal microscopy on kidney biopsies of a cohort of 128 pediatric patients revealed localization of IgG along the slit diaphragm in 30% of patients with MC and 25% of those with FSGS, but not in other lesion patterns. Anti-nephrin IgG ELISA assay in the serum and stimulated emission depletion microscopy of kidney biopsies showed IgG-nephrin co-localization only in 77.8% of cases. Similar observations were obtained in a cohort of 48 adult patients with MC or FSGS at kidney biopsy, where IgG-nephrin colocalization was only 44.4%, suggesting the existence of autoantibodies binding to other slit proteins. Patients with anti-slit antibodies showed nephrotic syndrome at onset in 94.4% of cases. Patients with primary steroid-resistance had anti-slit antibodies in 27%, while those with secondary steroid-resistance in 87.5% of cases, irrespective of the histopathological lesion pattern. Steroid-resistant patients with anti-slit antibodies responded to second-line immunosuppressants in 92.3% vs. only 20% of patients that were anti-slit negative. No patient with anti-slit antibodies developed kidney failure vs. 51.7% of those negative for antibodies (66.7% with a genetic cause and 41.2% with a non-genetic cause). Thus, the detection of anti-slit antibodies can identify patients with an autoimmune podocytopathy responsive to treatment with second-line immunosuppressants, irrespective of the histopathological lesion pattern at biopsy.

Transcriptomic signatures of chronic active antibody-mediated rejection deciphered by RNA sequencing of human kidney allografts.

Natural killer (NK) cells mediate spontaneous cell-mediated cytotoxicity and antibody-dependent cell-mediated cytotoxicity. This dual functionality could enable their participation in chronic active antibody-mediated rejection (CA-ABMR). Earlier microarray profiling studies have not subcategorized antibody-mediated rejection into CA-ABMR and active-ABMR, and the gene expression pattern of CA-ABMR has not been compared with that of T cell-mediated rejection (TCMR). To fill these gaps, we RNA sequenced human kidney allograft biopsies categorized as CA-ABMR, active-ABMR, TCMR, or No Rejection (NR). Among the 15,910 genes identified in the biopsies, 60, 114, and 231 genes were uniquely overexpressed in CA-ABMR, TCMR, and active-ABMR, respectively; compared to NR, 50 genes were shared between CA-ABMR and active-ABMR, and 164 genes between CA-ABMR and TCMR. The overexpressed genes were annotated to NK cells and T cells in CA-ABMR and TCMR, and to neutrophils and monocytes in active-ABMR. The NK cell cytotoxicity and allograft rejection pathways were enriched in CA-ABMR. Genes encoding perforin, granzymes, and death receptor were overexpressed in CA-ABMR versus active-ABMR but not compared to TCMR. NK cell cytotoxicity pathway gene set variation analysis score was higher in CA-ABMR compared to active-ABMR but not in TCMR. Principal component analysis of the deconvolved immune cellular transcriptomes separated CA-ABMR and TCMR from active-ABMR and NR. Immunohistochemistry of kidney allograft biopsies validated a higher proportion of CD56+ NK cells in CA-ABMR than in active-ABMR. Thus, CA-ABMR was exemplified by the overexpression of the NK cell cytotoxicity pathway gene set and, surprisingly, molecularly more like TCMR than active-ABMR.

Unbiased kidney-centric molecular categorization of chronic kidney disease as a step towards precision medicine.

Current classification of chronic kidney disease (CKD) into stages using indirect systemic measures (estimated glomerular filtration rate (eGFR) and albuminuria) is agnostic to the heterogeneity of underlying molecular processes in the kidney thereby limiting precision medicine approaches. To generate a novel CKD categorization that directly reflects within kidney disease drivers we analyzed publicly available transcriptomic data from kidney biopsy tissue. A Self-Organizing Maps unsupervised artificial neural network machine-learning algorithm was used to stratify a total of 369 patients with CKD and 46 living kidney donors as healthy controls. Unbiased stratification of the discovery cohort resulted in identification of four novel molecular categories of disease termed CKD-Blue, CKD-Gold, CKD-Olive, CKD-Plum that were replicated in independent CKD and diabetic kidney disease datasets and can be further tested on any external data at kidneyclass.org. Each molecular category spanned across CKD stages and histopathological diagnoses and represented transcriptional activation of distinct biological pathways. Disease progression rates were highly significantly different between the molecular categories. CKD-Gold displayed rapid progression, with significant eGFR-adjusted Cox regression hazard ratio of 5.6 [1.01-31.3] for kidney failure and hazard ratio of 4.7 [1.3-16.5] for composite of kidney failure or a 40% or more eGFR decline. Urine proteomics revealed distinct patterns between the molecular categories, and a 25-protein signature was identified to distinguish CKD-Gold from other molecular categories. Thus, patient stratification based on kidney tissue omics offers a gateway to non-invasive biomarker-driven categorization and the potential for future clinical implementation, as a key step towards precision medicine in CKD.

Association of Implantation Biopsy Findings in Living Donor Kidneys With Donor and Recipient Outcomes.

RATIONALE & OBJECTIVE: Some living donor kidneys are found to have biopsy evidence of chronic scarring and/or glomerular disease at implantation, but it is unclear if these biopsy findings help predict donor kidney recovery or allograft outcomes. Our objective was to identify the prevalence of chronic histological changes and glomerular disease in donor kidneys, and their association with donor and recipient outcomes. STUDY DESIGN: Retrospective cohort study. SETTING & PARTICIPANTS: Single center, living donor kidney transplants from January 2010 to July 2022. EXPOSURE: Chronic histological changes, glomerular disease in donor kidney implantation biopsies. OUTCOME: For donors, single-kidney estimated glomerular filtration rate (eGFR) increase, percent total eGFR loss, ≥40% eGFR decline from predonation baseline, and eGFR<60mL/min/1.73m2 at 6 months after donation; for recipients, death-censored allograft survival. ANALYTICAL APPROACH: Biopsies were classified as having possible glomerular disease by pathologist diagnosis or chronic changes based on the percentage of glomerulosclerosis, interstitial fibrosis/tubular atrophy, and vascular disease. We used logistic regression to identify factors associated with the presence of chronic changes, linear regression to identify the association between chronic changes and single-kidney estimated glomerular filtration rate (eGFR) recovery, and time-to-event analyses to identify the relationship between abnormal biopsy findings and allograft outcomes. RESULTS: Among 1,104 living donor kidneys, 155 (14%) had advanced chronic changes on implantation biopsy, and 12 (1%) had findings suggestive of possible donor glomerular disease. Adjusted logistic regression showed that age (odds ratio [OR], 2.44 per 10 years [95% CI, 1.98-3.01), Hispanic ethnicity (OR, 1.87 [95% CI, 1.15-3.05), and hypertension (OR, 1.92 [95% CI, 1.01-3.64), were associated with higher odds of chronic changes on implantation biopsy. Adjusted linear regression showed no association of advanced chronic changes with single-kidney eGFR increase or relative risk of eGFR<60mL/min/1.73m2. There were no differences in time-to-death-censored allograft failure in unadjusted or adjusted Cox proportional hazards models when comparing kidneys with chronic changes to kidneys without histological abnormalities. LIMITATIONS: Retrospective, absence of measured GFR. CONCLUSIONS: Approximately 1 in 7 living donor kidneys had chronic changes on implantation biopsy, primarily in the form of moderate vascular disease, and 1% had possible donor glomerular disease. Abnormal implantation biopsy findings were not significantly associated with 6-month donor eGFR outcomes or allograft survival. PLAIN-LANGUAGE SUMMARY: Kidney biopsies are the gold standard test to identify the presence or absence of kidney disease. However, kidneys donated by healthy living donors-who are extensively screened for any evidence of kidney disease before donation-occasionally show findings that might be considered "abnormal," including the presence of scarring in the kidney or findings suggestive of a primary kidney disease. We studied the frequency of abnormal kidney biopsy findings among living donors at our center. We found that about 14% of kidneys had chronic abnormalities and 1% had findings suggesting possible glomerular kidney disease, but the presence of abnormal biopsy findings was not associated with worse outcomes for the donors or their recipients.

Clinicopathologic Characteristics of Crystalglobulin-Induced Nephropathy: A Case Series.

RATIONALE & OBJECTIVE: Crystalglobulinemia is a rare syndrome characterized by intravascular crystallization of monoclonal immunoglobulins (MIg). Data on kidney involvement are limited to case reports. This series characterizes the clinicopathologic spectrum of crystalglobulin-induced nephropathy (CIN). STUDY DESIGN: Case series. SETTING & PARTICIPANTS: Nineteen CIN cases identified from the nephropathology archives of Mayo Clinic and Columbia University. CIN was defined by intravascular (extracellular) MIg crystals visible by light microscopy (LM) and electron microscopy (EM). RESULTS: Among the cases, 68% were male, and 65% were Caucasian (median age, 56 years). Most patients presented with severe acute kidney injury (AKI) (median creatinine, 3.5mg/dL), hematuria, and mild proteinuria (median, 1.1g/day). Common extrarenal manifestations were constitutional (67%), cutaneous (56%), and rheumatologic (50%). Fifty percent of cases had hypocomplementemia. The hematologic disorders were monoclonal gammopathy of renal significance (MGRS) (72%), lymphoma (17%), or myeloma (11%), with 65% of these disorders discovered concomitantly with CIN. All patients had MIg identified on serum protein electrophoresis/immunofixation (IgGκ in 65%). The serum free light chain ratio was outside the renal range in 40%, and bone marrow biopsy detected the responsible clone in 67%. On LM, crystals involved glomeruli (100%) and vessels (47%), often with an inflammatory reaction (89%) and fibrin (58%). All cases exhibited crystal substructures (mostly paracrystalline) by EM. Immunofluorescence on paraffin-embedded tissue was more sensitive than frozen tissue (92% vs 47%) for demonstrating the crystal composition (IgGκ in 63%). Follow-up observation (median, 20 months) was available in 16 patients. Eighty-one percent received steroids, 44% plasmapheresis, 38% hemodialysis, and 69% chemotherapy. Ninety-percent of patients who received clone-directed therapy achieved kidney recovery versus 20% of those who did not (P=0.02). LIMITATIONS: Retrospective design, small sample size. CONCLUSIONS: CIN is a rare cause of nephropathy associated with lymphoplasmacytic disorders (mostly MGRS) and typically presents with severe AKI and extrarenal manifestations. Diagnosis often requires immunofluorescence performed on paraffin-embedded kidney tissue. Prompt initiation of clone-directed therapy, coupled with corticosteroids and plasmapheresis, may lead to recovery of kidney function.

Atypical Anti-Glomerular Basement Membrane Nephritis: A Case Series From the French Nephropathology Group.

RATIONALE & OBJECTIVE: Atypical anti-glomerular basement membrane (GBM) nephritis is characterized by a bright linear immunoglobulin staining along the GBM by immunofluorescence without a diffuse crescentic glomerulonephritis nor serum anti-GBM antibodies by conventional enzyme-linked immunosorbent assay (ELISA). We characterized a series of patients with atypical anti-GBM disease. STUDY DESIGN: Case series. SETTING & PARTICIPANTS: Patients identified by the French Nephropathology Group as having atypical anti-GBM nephritis between 2003 and 2022. FINDINGS: Among 38 potential cases, 25 were included, of whom 14 (56%) were female and 23 (92%) had hematuria. The median serum creatinine at diagnosis was 150 (IQR, 102-203) µmol/L and median urine protein-creatinine ratio (UPCR) was 2.4 (IQR, 1.3-5.2) g/g. Nine patients (36%) had endocapillary proliferative glomerulonephritis (GN), 4 (16%) had mesangial proliferative GN, 4 (16%) had membranoproliferative GN, 2 (8%) had pure and focal crescentic GN, 1 (4%) had focal segmental glomerulosclerosis, and 5 had glomeruli that were unremarkable on histopathology. Nine patients (36%) had crescents, involving a median of 9% of glomeruli. Bright linear staining for IgG was seen in 22 cases (88%) and for IgA in 3 cases (12%). The 9 patients (38%) who had a monotypic staining pattern tended to be older with less proteinuria and rarely had crescents. Kidney survival rate at 1 year was 83% and did not appear to be associated with the light chain restriction. LIMITATIONS: Retrospective case series with a limited number of biopsies including electron microscopy. CONCLUSIONS: Compared with typical anti-GBM disease, atypical anti-GBM nephritis frequently presents with an endocapillary or mesangial proliferative glomerulonephritis pattern and appears to have a slower disease progression. Further studies are needed to fully characterize its pathophysiology and associated clinical outcomes. PLAIN-LANGUAGE SUMMARY: Atypical anti-glomerular basement membrane (GBM) nephritis is characterized histologically by bright linear immunoglobulin staining along the GBM without diffuse crescentic glomerulonephritis or circulating anti-GBM antibodies. We report a case series of 25 atypical cases of anti-GBM nephritis in collaboration with the French Nephropathology Group. Compared with typical anti-GBM disease, we observed a slower disease progression. Patients frequently presented with heavy proteinuria and commonly had evidence of endocapillary or mesangial proliferative glomerulonephritis. About half of the patients displayed a monotypic immune staining pattern; they tended to be older, with less proteinuria, and commonly without glomerular crescents in biopsy specimens. No concomitant circulating monoclonal gammopathy was detected. Further studies are needed to fully characterize its pathophysiology and associated clinical outcomes.

Development and validation of a nomogram for predicting the interstitial fibrosis and tubular atrophy in patients with lupus nephritis.

OBJECTIVE: Interstitial fibrosis and tubular atrophy (IFTA) were frequent histologic features of lupus nephritis (LN), and LN patients with IFTA have poor renal outcomes. In this study, we aimed to construct prediction models for the IFTA in LN patients. METHODS: This retrospective study included 303 patients with biopsy proven LN at the Affiliated Hospital of Qingdao University and Union Hospital of Fujian Medical University. The participants were randomly divided into development and validation cohorts. They were further divided into IFTA and non-IFTA groups. The least absolute shrinkage and selection operator (LASSO) regression model with laboratory test results collected at the time of kidney biopsy was used to optimize feature selection for the risk model. Multivariable logistic regression analysis was applied to build a predicting model incorporating the feature selected in the LASSO regression model. Discrimination, calibration, and clinical usefulness of the predicting model were assessed using the C-index, calibration plot, and ROC curve analysis. Internal validation was assessed using the bootstrapping validation. A nomogram for individual assessment was constructed based on the preferable model. RESULTS: Predictors contained in the prediction nomogram included age, body mass index (BMI), mean arterial pressure (MAP), logANA, C3, eGFR and serum uric acid. The model displayed good discrimination with a C-index of 0.794 (95% CI 0.734-0.854) and good calibration. High C-index value of 0.857 (95% CI 0.776-0.938) could still be reached in the interval validation. A nomogram model based on the LASSO model was created for producing a probability score of IFTA in LN patients. CONCLUSION: With excellent predictive abilities, the nomogram may provide a simple and reliable tool to distinguish LN patients with IFTA and helps physicians make clinical decisions in their comprehensive assessment.

A nomogram predicting the histologic activity of lupus nephritis from clinical parameters.

BACKGROUND: The 2021 clinical guidelines of the Kidney Disease: Improving Global Outcomes emphasize the importance of the histological activity index (AI) in the management of lupus nephritis (LN). Patients with LN and a high AI have poor renal outcomes and high rates of nephritic relapse. In this study we constructed prediction models for the AI in LN. METHODS: The study population comprised 337 patients diagnosed with LN using kidney biopsy. The participants were randomly divided into training and testing cohorts. They were further divided into high-activity (AI >2) and low-activity (AI ≤2) groups. This study developed two clinical prediction models using logistic regression and least absolute shrinkage and selection operator (LASSO) analyses with laboratory test results collected at the time of kidney biopsy. The performance of models was assessed using 5-fold cross-validation and validated in the testing cohort. A nomogram for individual assessment was constructed based on the preferable model. RESULTS: Multivariate analysis showed that higher mean arterial pressure, lower estimated glomerular filtration rate, lower complement 3 level, higher urinary erythrocytes count and anti-double-stranded DNA seropositivity were independent risk factors for high histologic activity in LN. Both models performed well in the testing cohort regarding the discriminatory ability to identify patients with an AI >2. The average area under the curve of 5-fold cross-validation was 0.855 in the logistic model and 0.896 in the LASSO model. A webtool based on the LASSO model was created for clinicians to enter baseline clinical parameters to produce a probability score of an AI >2. CONCLUSIONS: The established nomogram provides a quantitative auxiliary tool for distinguishing LN patients with a high AI and helps physicians make clinical decisions in their comprehensive assessment.

Impact of hyperparathyroidism on allograft histology and function after kidney transplantation: Rethinking its causal role in graft dysfunction.

INTRODUCTION: The causal relationship between hyperparathyroidism and kidney graft dysfunction remains inconclusive. Applying Bradford-Hill's temporality and consistency causation principles, we assessed the effect of parathyroid hormone (iPTH) on graft histology and eGFR trajectory on kidney transplant recipients (KTRs) with normal time-zero graft biopsies. METHODS: Retrospective cohort study evaluating the effect of hyperparathyroidism on interstitial fibrosis and tubular atrophy (IF/TA) development in 1232 graft biopsies. Pre-transplant hyperparathyroidism was categorized by KDIGO or KDOQI criteria, and post-transplant hyperparathyroidism by iPTH >1× and >2× the URL 1 year after transplantation. RESULTS: We included 325 KTRs (56% female, age 38 ± 13 years, follow-up 4.2 years [IQR: 2.7-5.8]). Based on pre-transplant iPTH levels, 26% and 66% exceeded the KDIGO and KDOQI targets, respectively. There were no significant differences in the development of >25% IF/TA between KTRs with pre-transplant iPTH levels above and within target range according to KDIGO (53% vs. 62%, P = .16, HR.94 [95% CI:.67-1.32]) and KDOQI (60% vs. 60%, P = 1.0, HR 1.19 [95% CI:.88-1.60]) criteria. Similarly, there were no differences when using 1 year post-transplant iPTH cut-offs > 88 pg/mL (58% vs. 64%, P = .33) and > 176 pg/mL (55% vs. 62%, P = .19). After adjusting for confounders, no significant differences were observed in eGFR trajectories among the iPTH strata. CONCLUSION: In young KTRs who received a healthy graft, no association was found between increased pre- and post-transplant iPTH levels and graft dysfunction, as assessed histologically and through eGFR trajectory. The concept of hyperparathyroidism as a risk factor for graft dysfunction in recipients at low risk requires reevaluation.

Spectrum of Nondiabetic Kidney Diseases in Patients with Type 2 Diabetes Mellitus Who Underwent Kidney Biopsy in Egypt.

INTRODUCTION: Diabetic kidney disease (DKD) affects 30-40% of patients with diabetes. The prevalence of nondiabetic kidney disease (NDKD) in patients with type 2 diabetes mellitus (T2D) in Egypt is unknown. This study aimed to assess the prevalence of NDKD in patients with T2D in Egypt. METHODS: In this cross-sectional study, we searched the data of patients with T2D who underwent a native kidney biopsy between January 2010 and December 2020 in a kidney pathology laboratory in Egypt. RESULTS: Of 12,006 patients who underwent kidney biopsy, 677 patients had T2D. NDKD was found in 285 patients (42.7%), DKD in 220 patients (33%), and mixed DKD and NDKD in 162 patients (24.3%). The total prevalence of NDKD was 67% in patients with T2D in our study group. Membranous nephropathy was the most common histopathological disease in patients with NDKD (20.6%) followed by acute tubular injury (ATI) (19.2%) and focal segmental glomerulosclerosis (15.2%). The presence of ATI in a kidney biopsy was associated with a significantly higher mean serum creatine level (p < 0.001). Minimal change disease was associated with a significantly higher proteinuria level (p < 0.001). In binary logistic regression analysis, combining NDKD and mixed groups, the duration of diabetes was a negative predictor of NDKD, with a longer duration decreasing the likelihood of NDKD. CONCLUSION: NDKD is prevalent among patients with T2D who underwent a kidney biopsy. Kidney biopsy remains the gold standard for diagnosing NDKD in patients with T2D.

Cyanotic Nephropathy in an Adult Patient with Eisenmenger Syndrome: A Case Report and Literature Review.

INTRODUCTION: Cyanotic nephropathy, a rare disease characterized by proteinuria, decreased estimated glomerular filtration rate, thrombocytopenia, polycythemia, and hyperuricemia, may occasionally be secondary to cyanotic congenital heart disease (CHD). There are currently no detailed diagnostic criteria or treatments for cyanotic nephropathy, owing to its extremely low incidence. Eisenmenger syndrome (ES) was initially defined by Paul Wood in pathophysiologic terms as "pulmonary hypertension (PH) at the systemic level, caused by a high pulmonary vascular resistance, with a reversed or bidirectional shunt at the aorto-pulmonary, ventricular, or atrial level." It typically develops in the presence of large, unrepaired atrial or ventricular septal defects, arterial shunts, or complex forms of CHD and is the most severe hemodynamic phenotype of pulmonary arterial hypertension associated with CHD. This study aimed to outline the case of an ES patient who developed cyanotic nephropathy and successfully achieved clinical remission through primary disease treatment and symptomatic management. Overall, this case expands our understanding of cyanotic nephropathy and lays a theoretical reference for the treatment of ES. CASE PRESENTATION: A 33-year-old Chinese female attended the outpatient department with abnormal urine test results over the past two and a half years. Following a comprehensive medical history collection, she underwent the necessary tests. Cardiac color ultrasound displayed a significant widening of the pulmonary artery and PH (severe), as well as mild tricuspid regurgitation and patent ductus arteriosus. The results of the kidney biopsy, combined with clinical findings, suggested a high risk of polycythemia-related kidney disease. She was eventually diagnosed with cyanotic nephropathy and ES. Her symptoms were relieved following symptomatic treatment, such as the administration of ambrisentan, febuxostat, and home oxygen therapy. Her follow-up visit at 6 months demonstrated improvements in hyperuricemia and a significant increase in physical strength. CONCLUSION: Cyanotic nephropathy is a rare condition in adults. Kidney biopsy remains the gold standard of diagnosis for various nephropathies. Active treatment of CHD and alleviating hypoxia may be pivotal for the treatment of cyanotic nephropathy.

IgA nephropathy in children with minimal proteinuria: to biopsy or not to biopsy?

BACKGROUND: Tubulointerstitial lesions and glomerular inflammation severity have been shown to correlate with proteinuria in children with IgA nephropathy (cIgAN). However, there is a lack of data regarding severity of histopathologic findings in cIgAN in patients with minimal to absent proteinuria since kidney biopsy indications are not well defined in these cases. METHODS: Twenty-eight cIgAN patients with kidney biopsy from 4 different centers in Paris (France) and Montreal (Canada) with a urine protein/creatinine ratio (UPCr) ≤ 0.03 g/mmol and a normal estimated glomerular filtration rate (eGFR > 90 ml/min/1.73 m2) on the day of kidney biopsy prior to treatment were included. RESULTS: Median age was 11.82 (9.32-13.45) years, and median follow-up was 4 years (2.87-6.53). At time of biopsy, median eGFR was 116 (102.3-139.7) ml/min/1.73 m2, and median UPCr was 0.02 (0.011-0.03) g/mmol. Microscopic or macroscopic hematuria was present in 35.7% and 64.3% of cases, respectively. Kidney biopsy microscopy analysis showed mesangial (M1), endocapillary (E1), or extracapillary (C1) hypercellularity in 53.5%, 32.1%, and 7.1% of patients, respectively. Chronic histological lesions were also present: glomerulosclerosis (S1) in 42.8% and tubular atrophy/interstitial fibrosis in 7.1%. Podocytopathic features were detected in 21.4%. An ACE inhibitor or immunosuppressive therapy (IS) was prescribed in 42.8% and 21.4% of these patients respectively. One-third (35.7%) received no treatment. At last follow-up, median eGFR was 111.9 (90.47-136.1) ml/min/1.73 m2, and median UPCr was 0.028 (0.01-0.03) g/mmol. CONCLUSION: cIgAN with minimal proteinuria at time of biopsy might be linked with acute and chronic glomerular lesions.

Kidney biopsy findings in children with diabetes mellitus.

BACKGROUND: Diabetic nephropathy may begin in childhood, but clinical kidney disease ascribable to this is uncommon in children with type 1 (insulin dependent) diabetes mellitus. METHODS: We reviewed our experience of kidney biopsies in children with type 1 diabetes mellitus. RESULTS: Between 1995 and 2022, there were biopsies in 17 children, with various clinical indications for kidney biopsy, making this the largest series of biopsies in diabetic children with clinical kidney abnormalities. Four biopsies showed diabetic nephropathy, three showed the combination of diabetic nephropathy and IgA nephropathy, and ten showed a variety of conditions other than diabetic nephropathy: minimal change disease (2), membranous nephropathy (2), thin glomerular basement membrane lesion (2), non-glomerular chronic damage in Wolcott-Rallison syndrome (2), acute pauciimmune necrotizing crescentic glomerulonephritis (1) and IgA nephropathy (1). Clinical clues of something other than diabetic nephropathy included acute kidney injury, microscopic haematuria or chronic kidney impairment with little or no proteinuria and the nephrotic syndrome after a short duration of diabetes. CONCLUSIONS: We confirm that changes better known in adults with either type 1 or type 2 diabetes mellitus can occur in children with type 1 diabetes mellitus: overt diabetic nephropathy either on its own or combined with other conditions and kidney disorders other than diabetic nephropathy.

Biomarkers of histologic severity in children with severe or atypical acute post-streptococcal glomerulonephritis.

BACKGROUND: Acute post-streptococcal glomerulonephritis (APSGN) is a common cause of acute kidney injury (AKI) in children; however, in a small subgroup, the presentation is one of rapidly progressive glomerulonephritis (RPGN) deteriorating kidney function associated with severe oligo-anuria or a mixed nephritic-nephrotic picture. This study reviewed potential clinical and laboratory factors which may assist the treating clinician to identify patients at high risk of severe disease. METHODS: All kidney biopsies for APSGN performed between 1996 and 2020 were obtained from a departmental biopsy database. Clinical and laboratory data were extracted from the patients' clinical records. Kidney biopsies were reviewed and scored independently by a renal histopathologist. RESULTS: Thirty of 53 (56.6%) patients had stage 3 AKI at initial presentation with a median estimated glomerular filtration rate (eGFR) 27 (IQR 11-41), falling to 20 ml/min/1.73 m2 (IQR 13.3-43) at time of biopsy. Patients who had either a pre-biopsy eGFR < 35 ml/min/1.73 m2 or a ≥ 25% fall in eGFR between admission and biopsy were more likely to have glomerular crescents (p = 0.004). Multivariate regression analysis and receiver operating curve showed the pre-biopsy eGFR most accurately predicted glomerular crescents (p = 0.047, ROC 0.757). There were no significant predictors of nephrotic proteinuria or nephrotic syndrome during the acute phase. CONCLUSIONS: Severe APSGN is associated with a pronounced reduction in eGFR. Calculation of eGFR in this small group of patients may assist in identifying which patient should have an urgent kidney biopsy to facilitate a more accurate clinical diagnosis and management plan.

Multinucleated podocytes as a clue to diagnosis of juvenile nephropathic cystinosis.

BACKGROUND  : Cystinosis is a rare autosomal recessive lysosomal disorder that mainly affects the kidney and eye. Early treatment with cysteamine significantly improves the prognosis. However, early diagnosis of cystinosis, especially the juvenile nephropathic form, remains challenging because typical symptoms only become apparent in adulthood. We herein describe a 13-year-old girl who presented with proteinuria only but was diagnosed with juvenile nephropathic cystinosis based on multinucleated podocytes in her kidney biopsy specimen. We also studied the nephropathology of another case to determine the features of the multinucleated podocytes. CASE DIAGNOSIS: A previously healthy 13-year-old girl presented to our hospital because proteinuria had been detected in her school urine screening. She had been noted to have proteinuria on her school urine screening when she was 11 years of age but there was no consultation with her physician at that time. She was asymptomatic and had no other abnormalities on examination other than a relatively high urinary ß-2 microglobulin level. Her kidney biopsy showed 15 multinucleated podocytes in 34 glomeruli, and the mean number of nuclei per multinucleated podocyte was 4.4. Ophthalmological examination showed cystine crystals in her cornea. Her white blood cell cystine level was high, and she was diagnosed with juvenile nephropathic cystinosis. She started oral cysteamine treatment and showed almost no progression of the disease after 2 years. In another patient with juvenile nephropathic cystinosis, there were 25 multinucleated podocytes in 63 glomeruli, and the mean number of nuclei per multinucleated podocyte was 2.9. CONCLUSION: Early diagnosis is crucial to improve the prognosis of patients with cystinosis. This report emphasizes the importance of recognizing the unique pathological feature of multinucleated podocytes as an essential clue to the diagnosis of cystinosis.

To biopsy or not to biopsy a teenager with idiopathic nephrotic syndrome? Biopsy first.

Kidney biopsy plays a crucial role in the diagnosis and management of several glomerular diseases. While it is generally considered a routine and safe procedure in children, it should be conducted with the primary objective of addressing the following question: do the prognosis and treatments vary based on the findings of kidney biopsy? In children presenting with idiopathic nephrotic syndrome (INS), guidelines suggest to consider kidney biopsy for individuals older than 12 years, primarily due to the possible increased incidence of different glomerulonephritis compared to younger patients, who predominantly manifest with minimal change disease. However, these guidelines also advocate for uniform therapeutic strategies, typically steroids, irrespective of the age or histological findings. Whether the age of more than 12 years may be a recommendation for performing kidney biopsy at presentation of INS is debatable. Instead, kidney biopsy could be reserved for steroid-resistant cases. On the other hand, when kidney biopsy is performed in INS, particularly in focal segmental glomerulosclerosis, histology may reveal additional lesions, that are strongly associated with a poorer response to treatment and worse clinical outcomes. Therefore, current guidelines on treatments of nephrotic syndrome may appear overly restrictive, despite the relevant findings provided by kidney biopsy. Therefore, in the present manuscript, which is part of a pro-con debate on the management of nephrotic syndrome in adolescents, we emphasize the potential role of performing a kidney biopsy before initiating corticosteroid treatment.

Pediatric contributions and lessons learned from the NEPTUNE cohort study.

Primary glomerular diseases are rare entities. This has hampered efforts to better understand the underlying pathobiology and to develop novel safe and effective therapies. NEPTUNE is a rare disease network that is focused on patients of all ages with minimal change disease, focal segmental glomerulosclerosis, and membranous nephropathy. It is a longitudinal cohort study that collects detailed demographic, clinical, histopathologic, genomic, transcriptomic, and metabolomic data. The goal is to develop a molecular classification for these disorders that supersedes the traditional pathological features-based schema. Pediatric patients are important contributors to this ongoing project. In this review, we provide a snapshot of the children and adolescents enrolled in NEPTUNE and summarize some key observations that have been made based on the data accumulated during the study. In addition, we describe the development of NEPTUNE Match, a program that aims to leverage the multi-scalar information gathered for each individual patient to provide guidance about potential clinical trial participation based on the molecular characterization and non-invasive biomarker profile. This represents the first organized effort to apply principles of precision medicine to the treatment of patients with primary glomerular disease. NEPTUNE has proven to be an invaluable asset in the study of glomerular diseases in patients of all ages including children and adolescents.

Nephrotic Syndrome in a Child With NPHS2 Mutation.

Steroid resistant nephrotic syndrome (SRNS) accounts for 30% of all cases of nephrotic syndrome (NS) in children and frequently leads to end stage kidney disease (ESKD). About 30% of children with SRNS demonstrate causative mutations in podocyte- associated genes. Early identification of genetic forms of SRNS is critical to avoid potentially harmful immunosuppressive therapy. A 2-year-old male patient with NS and no family history of renal disease did not respond to 4-week steroid treatment. Kidney biopsy demonstrated mesangial proliferative glomerulopathy with basement membrane dysmorphism. Tacrolimus and Lisinopril were added to therapy pending results of genetic testing. Kidney Gene panel showed a NPHS2 c.413G>A (p.Arg138Gln) homozygous pathogenic variant. This missense variant is considered a common pathogenic founder mutation in European populations. A diagnosis of autosomal-recessive form of nonsyndromic SRNS due to NPHS2 causative variant was made. Immunosuppresive therapy was stopped, Lizinopril dose was increased and weekly infusions of Albumin/furosemide were initiated to manage edema. This case demonstrates that early genetic testing in children with SRNS avoids prolonged potentially harmful immunosuppressive therapy, allows for timely genetic family counseling, and allows earlier consideration for future living related donor kidney transplantation.

Straightforward and immediate ultrasound-guided kidney biopsy using a guide needle technique to get adequate tissue with reduced procedural time.

BACKGROUND: A streamlined and effective renal biopsy technique is essential for all nephrologists, particularly those who are less experienced, such as residents. Herein, we report the efficacy of a Straightforward and Immediate ultrasound-guided kidney biopsy using a Guide Needle (SIGN) technique, which allows operators to insert a biopsy gun through a guide needle placed into the fascia of the posterior abdominal wall. METHODS: A retrospective cross-sectional study was conducted at a nephrology training institution to compare the time spent on the procedure and the number of glomeruli obtained between a group using the SIGN (n = 81) and a group using the conventional ultrasound-guided kidney biopsy technique with a needle guide device (n = 143). RESULTS: The median procedure time in the SIGN group (2 min, interquartile range [IQR]: 1-3 min) was significantly shorter than that in the conventional group (3 min, IQR: 2-4 min) (P < 0.001). Multivariable linear regression and logistic regression analyses adjusted for covariates, including operators (board-certificated nephrologists or nephrology residents), showed that the use of the SIGN technique was independently associated with a high number of glomeruli obtained and a procedure time above 2 min as the median value (odds ratio: 0.17, 95% confidence interval CI 0.09-0.34). The prevalence of complications was comparable between the two groups (P = 0.681). CONCLUSION: The SIGN technique reduces the procedure time and obtains adequate biopsy tissue regardless of the operator's experience. SIGN can be applied in nephrology training programs and used as a standard biopsy technique.