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Atypical hemolytic uremic syndrome (aHUS) is a subtype of thrombotic microangiopathy (TMA) characterized by a dysregulation of the alternative complement pathway. Here, we report a previously healthy 38-year-old woman in whom aHUS developed after a COVID-19 vaccine booster. One day after receipt of a booster dose of mRNA-1273 vaccine, she felt ill. Because of persistent headache, nausea, and general malaise, she went to her general practitioner, who referred her to the hospital after detecting hypertension and acute kidney injury. A diagnosis of TMA was made. Her treatment consisted of blood pressure control, hemodialysis, plasma exchange, and respiratory support. Kidney biopsy confirmed the diagnosis of acute TMA. The patient was referred for treatment with eculizumab, and kidney function improved after initiation of this therapy. Genetic analysis revealed a pathogenic C3 variant. SARS-CoV-2 infection as a trigger for complement activation and development of aHUS has been described previously. In addition, there is one reported case of aHUS occurring after receipt of the adenovirus-based COVID-19 vaccine ChAdOx1 nCoV-19, but, to our knowledge, this is the first case of aHUS occurring after a booster dose of an mRNA COVID-19 vaccine in a patient with an underlying pathogenic variant in complement C3. Given the time frame, we hypothesize that the vaccine probably was the trigger for development of aHUS in this patient. ispartof: AMERICAN JOURNAL OF KIDNEY DISEASES vol:81 issue:3 pages:364-367 ispartof: location:United States status: published

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. Graphical abstract: [Figure not available: see fulltext.]

Percutaneous kidney biopsy is essential for diagnosing various kidney diseases. However, insufficient glomerular yield leads to misdiagnosis, a critical problem. We retrospectively investigated the risk of insufficient glomerular yield in percutaneous kidney biopsies. We included 236 patients who underwent percutaneous kidney biopsies between April 2017 and September 2020. We retrospectively analyzed the relationship between glomerular yield and patient characteristics. After the biopsy, 31 patients produced insufficient glomerular yields (cases with yielded glomeruli

Background and objectives: C3 glomerulopathy and idiopathic Ig-associated membranoproliferative GN are kidney diseases characterized by abnormal glomerular complement C3 deposition. These conditions are heterogeneous in outcome, but approximately 50% of patients develop kidney failure within 10 years. Design, setting, participants, & measurements: To improve identification of patients with poor prognosis, we performed a detailed analysis of percutaneous kidney biopsies in a large cohort of patients. Using a validated histologic scoring system, we analyzed 156 native diagnostic kidney biopsies from a retrospective cohort of 123patients with C3 glomerulopathy and 33 patients with Ig-associated membranoproliferative GN. We used linear regression, survival analysis, and Cox proportional hazards models to assess the relationship between histologic and clinical parameters with outcome. Results: Frequent biopsy features were mesangial expansion and hypercellularity, glomerular basement membrane double contours, and endocapillary hypercellularity. Multivariable analysis showed negative associations between eGFR and crescents, interstitial inflammation, and interstitialfibrosis/tubular atrophy. Proteinuria positively associated with endocapillary hypercellularity and glomerular basement membrane double contours. Analysis of second native biopsies did not demonstrate associations between immunosuppression treatment and improvement in histology. Using a composite outcome, risk of progression to kidney failure associated with eGFR and proteinuria at the time of biopsy, cellular/fibrocellular crescents, segmental sclerosis, and interstitial fibrosis/tubular atrophy scores. Conclusions: Our detailed assessment of kidney biopsy data indicated that cellular/fibrocellular crescents and interstitial fibrosis/tubular atrophy scores were significant determinants of deterioration in kidney function.

Background The known risks and benefits of native kidney biopsies are mainly based on the findings of retrospective studies. The aim of this multicentre prospective study was to evaluate the safety of percutaneous renal biopsies and quantify biopsy-related complication rates in Italy. Methods The study examined the results of native kidney biopsies performed in 54 Italian nephrology centres between 2012 and 2020. The primary outcome was the rate of major complications 1 day after the procedure, or for longer if it was necessary to evaluate the evolution of a complication. Centre and patient risk predictors were analysed using multivariate logistic regression. Results Analysis of 5304 biopsies of patients with a median age of 53.2 years revealed 400 major complication events in 273 patients (5.1%): the most frequent was a ≥2 g/dL decrease in haemoglobin levels (2.2%), followed by macrohaematuria (1.2%), blood transfusion (1.1%), gross haematoma (0.9%), artero-venous fistula (0.7%), invasive intervention (0.5%), pain (0.5%), symptomatic hypotension (0.3%), a rapid increase in serum creatinine levels (0.1%) and death (0.02%). The risk factors for major complications were higher plasma creatinine levels [odds ratio (OR) 1.12 for each mg/dL increase, 95% confidence interval (95% CI) 1.08–1.17], liver disease (OR 2.27, 95% CI 1.21–4.25) and a higher number of needle passes (OR for each pass 1.22, 95% CI 1.07–1.39), whereas higher proteinuria levels (OR for each g/day increase 0.95, 95% CI 0.92–0.99) were protective. Conclusions This is the first multicentre prospective study showing that percutaneous native kidney biopsies are associated with a 5% risk of a major post-biopsy complication. Predictors of increased risk include higher plasma creatinine levels, liver disease and a higher number of needle passes.

BackgroundMembranous nephropathy is an uncommon cause of nephrotic syndrome in pediatrics.MethodsWe reviewed our kidney biopsy records for patients ≤ 20 years of age with membranous nephropathy without evidence of systemic lupus erythematosus within 6 months of biopsy (January 1995-September 2020). Staining for PLA2R, NELL1, THSD7A, SEMA3B, EXT2 (3 biopsies), and IgG-subclass were performed.ResultsSixteen children (≤ 12 years) and 25 adolescents (13-20 years) were identified. Four children and 15 adolescents showed autoantigen positivity: PLA2R+/SEMA3B- (13), SEMA3B+/PLA2R+ (2), SEMA3B+/PLA2R- (1), NELL1 (1),EXT2+ (2), and THSD7A (0). Co-morbidities associated with PLA2R positivity included IPEX syndrome, active hepatitis B, Von Hippel Lindau syndrome, solitary kidney, type 1 diabetes, hyperuricemia, pregnancy (1), obesity (3), type II diabetes, H. pylori, viral prodrome, and nephrolithiasis. The SEMA3B+/PLA2R- adolescent was pregnant, the NELL1+ adolescent was obese, and the two EXT2+ adolescents eventually met the clinical criteria for lupus (4, 9 years post-biopsy). Co-morbidities among the remaining 24 patients included remote hepatitis B (2), Down's syndrome, lysinuric protein intolerance, recurrent UTIs, hypothyroidism, pregnancy (3), and obesity (2). Follow-up data was available for 12 children and 16 adolescents. Of the 12 children, 6 achieved complete remission, 4 achieved partial remission, and 2 had no response to treatment (1 transplant). Of the 16 adolescents, 4 achieved complete remission, 4 achieved partial remission, and 8 had no response to treatment (3 transplants). A child with "full-house" immunofluorescence staining achieved spontaneous disease remission.ConclusionOur non-lupus membranous nephropathy cohort represents one of the largest pediatric studies to date. A higher resolution version of the Graphical abstract is available as Supplementary information.

Acute kidney injury (AKI) frequently complicates corona virus disease 2019 (COVID-19) and is associated with significant mortality. Kidney disease in COVID-19 is usually due to acute tubular injury, but a variety of glomerular processes, especially collapsing glomerulopathy, have been increasingly described. Until recently, proliferative glomerulonephritis with monoclonal immunoglobulin deposits (PGNMID) had not been reported in the setting of COVID-19. We present a case of dialysis-dependent AKI developing soon after symptomatic COVID-19 which, on kidney biopsy, was found to be due to PGNMID with IgG3 kappa deposits. As is typical of PGNMID, a search for evidence of extra-renal monoclonal immunoglobulin or clonal lymphocyte population was negative. However, the patient had a favorable response to anti-plasma cell therapy and was ultimately able to stop hemodialysis. Though monoclonal gammopathy of renal significance (MGRS) is usually not associated with infection, other cases of post-viral MGRS, including PGNMID, have been previously reported. PGNMID has recently been linked specifically to COVID-19, with this representing one of only four cases reported thus far. Though causality between the preceding viral infection and the subsequent glomerulonephritis cannot be proven in these reports, nephrologists should be aware that not all kidney disease occurring in the aftermath of COVID-19 is due to tubular injury or collapsing glomerulopathy. As such, kidney biopsy should be routinely considered in the setting of COVID-19-associated glomerular disease as findings may change management. In the case of COVID-19-associated PGNMID data to guide treatment are limited, but our report suggests that anti-plasma cell therapy may be effective.

Introduction: Nephrologists have recently recognized the heterogeneity of kidney diseases among patients with diabetes and begun to actively perform percutaneous renal biopsies (PRBs). Nevertheless, the association between diabetes and major bleeding complications of PRB remains unclear. Methods: In this retrospective cohort study using the Diagnosis Procedure Combination database in Japan, we identified patients who underwent an elective PRB from July 2010 to March 2018. The primary outcome was the occurrence of major bleeding complications, defined as red blood cell transfusion within 7 days after PRB or invasive hemostasis after PRB. Multivariable regression analysis was performed to analyze the association between diabetes and major bleeding complications with adjustment for patient and hospital characteristics. Results: We identified 76,302 patients, including 8245 with diabetes. The proportion of PRBs performed for patients with diabetes continuously increased over time. Major bleeding complications occurred in 678 patients (0.9%), including 622 (0.8%) with red blood cell (RBC) transfusion and 109 (0.1%) with invasive hemostasis. Diabetes was significantly associated with major bleeding complications (relative risk [RR] = 2.41; 95% CI 2.00–2.90). Among patients with diabetes, multiagent or insulin treatment had significant association with major bleeding complications (RR = 1.57; 95% CI 1.18–2.10), compared with single-agent diabetes treatment. Conclusion: Diabetes is significantly associated with major bleeding complications of PRBs. Moreover, severity of diabetes has association with increases in major bleeding complications. Thus, nephrologists should carefully judge whether the anticipated benefits outweigh the relatively high risk of major bleeding complications when considering PRB for patients with diabetes.

Background: C3 glomerulopathies (C3GN) are a group of rare kidney diseases associated with impaired complement regulation. The effects of this disease include the accumulation of complement C3 in the kidneys. Based on the clinical data, as well as light, fluorescence, and electron microscopy results, the diagnoses were verified. The study group consisted of biopsy specimens, which were obtained from 332 patients who were diagnosed with C3 glomerulopathy. In all cases, histopathological examinations were performed; deposits of complement C3 and C1q components, as well as the immunoglobulins IgA, IgG, and IgM, were identified using immunofluorescence. Furthermore, electron microscopy was also performed. Results: The histopathological examination results presented cases of C3GN (n = 111) and dense deposit disease (DDD; n = 17). The non-classified (NC) group was the most numerous (n = 204). The lack of classification was due to the poor severity of the lesions, even on the electron microscopic examination or in the presence of intense sclerotic lesions. Conclusions: In cases of suspected C3 glomerulopathies, we believe an electron microscopy examination is necessary. This examination is beneficial in mild-to-extremely-severe cases of this glomerulopathy, where the lesions are barely discernible when using immunofluorescence microscopy.

Introduction. IgA nephropathy is the most common form of glomerulonephritis that associated with the presence of mesangial deposits of IgA. This nephropathy may be associated with other diseases: Henoch-Schonlein purpura, hepatitis, Crohn's disease, celiac disease, psoriasis, HIV infection, spondyloarthritis, rheumatoid arthritis, Reiter's syndrome, Behcet's disease, scleritis, and uveitis. A case report. A case of a 29-year-old man diagnosed with axial SpA and IgA-nephropaty is reported. The patient first developed pain in the joints at the age of 13, achillitis was found a year later. At the age of 15 a symptoms of kidney damage were developed; a diagnosis of interstitial nephritis was established (clinically). Two years later the patient was hospitalized in the rheumatology department where the diagnosis of ankylosing spondylitis was established, it was confirmed by MRI. At the age of 26 in the nephrology department diagnosed with "Chronic kidney disease (CKD) Stage 2, Chronic glomerulonephritis". No pathogenetic therapy for CKD during all this time was administred, a nephrobiopsy was not performed. When contacting a rheumatologist in 2020: BASDAI (Bath ankylosing spondylitis disease activity index) - 7,0, BASFI (Bath Ankylosing Spondylitis Functional Index) – 7,7. Laboratory abnormalities: HLA B27 positive, Hematology: Hemoglobin 118 g/l (ranges 127 g/l -181 g/l), RBC 3.9 × 10 12/L (ranges 4.5 × 10 12/L - 6.4 ×10 12/L), Chemistry: C-reactive protein 1.59 mg/l, GRF (MDRD) - 52.297 ml/min/1.73 m2. Uinalysis: protein + 1, blood + 2, erythrocytes - 41 in the field (ranges 0 in the field - 3 in the field). From 2011 to 2018 the patient received sulfasalazine as disease modifying therapy, then the drug was discontinued and the patient switched to rheumoxicam at a dose of 7.5 mg. However, rheumoxicam was discontinued by a nephrologist and the patient started treatment with a tumor necrosis factor-alpha inhibitor. One year later on examination: BASDAI 2.8, BASFI 1,2. Laboratory abnormalities: Hematology: Hemoglobin 123 g/l (ranges 127 g/l - 181 g/l), RBC 4.1 × 10 12/L (ranges 4.5 × 10 12/L - 6.4 × 10 12/L), Chemistry: C-reactive protein 1.2 mg/l, GRF (MDRD) - 36.573 ml/min/1.73 m2. Uinalysis: protein + 1, blood + 3, erythrocytes - 38 in the field (ranges 0 in the field – 3 in the field). Thus, the patient's SpA symptoms improve and the GRF continues to decrease. The patient agreed to a kidney biopsy and a pathomorphological diagnosis was: pathomorphological, histochemical, immunohistochemical data indicate IgA nephropathy with a pronounced tubulo-interstitial component, a large number of positive B-lymphocytes in cells infiltrates. MEST-score -M1, E1, S1, T1, G2 - JgA-nephropathy Oxford classification 2009, 2016. Chronic stage (2017, Sethi et al) - CG3 (moderate chronic change - total renal chronic score TRCS 6 points): glomerulosclerosis (GS) 2, interstitial fibrosis (IF) 1, tubular atrophy (TA) 2, arteriosclerosis (CV) 1. Based on these results the patient was prescribed with methylprednisolone 32 mg per day, with following correction, and discontinued TNFα inhibitor. Here are the results of the examination after 5 months. BASDAI 2.8, BASFI 1,2. Laboratory abnormalities: Hematology: Hemoglobin 100 g/l (ranges 130 g/l - 160 g/l), RBC 3.21 × 10 12/L (ranges 4.0 × 10 12/L - 5.0 × 10 12/L), Chemistry: C-reactive protein 0.56 mg/l, GRF (MDRD) - 41.537 ml/min/1.73 m2. Uinalysis: protein + 1, blood + 2, erythrocytes - 30 in the field (ranges 0 in the field - 3 in the field). Conclusion. This observation shows an urgent need for close interaction between nephrologists and rheumatologists in cases where an association of symptoms of both profiles presents, active collaboration with a patient, and the search for a personalized approach to treatment. It seems important to unite the efforts of the medical community in various countries to obtain more complete information about the features of the association of IgA nephropathy and SpA., {"references":["Berger J, Hinglais N. Les depots intercapillaires d IgA-IgG. Intern. J. Urol Nephol. 1968.74. 9. Р.694-695.","Dyadyk E.A., Suliman Yu.V., Vasilenko I.V., et all. IGA nephropathy: clinical and morphological features. Newspaper \"News of Medicine and Pharmacy\". Nephrology. 2009. 297. URL: http://www.mif-ua.com/archive/article/10721","He D, Wang R, Liang S., et all. Comparison of secondary IgA nephropathy in patients with ankylosing spondylitis and rheumatoid arthritis. Intern. J. Mod Rheumatol. 2020. 30. 4. 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BACKGROUND: The goal of the Artificial Intelligence in Renal Scarring (AIRS) study is to develop machine learning tools for noninvasive quantification of kidney fibrosis from imaging scans. METHODS: We conducted a retrospective analysis of patients who had one or more abdominal computed tomography (CT) scans within 6 months of a kidney biopsy. The final cohort encompassed 152 CT scans from 92 patients, which included images of 300 native kidneys and 76 transplant kidneys. Two different convolutional neural networks (slice-level and voxel-level classifiers) were tested to differentiate severe versus mild/moderate kidney fibrosis (≥50% versus

Background Transplant nephropathology is a highly specialized field of pathology comprising both the evaluation of organ donor biopsy for organ allocation and post-transplant graft biopsy for assessment of rejection or graft damage. The introduction of digital pathology with whole-slide imaging (WSI) in clinical research, trials and practice has catalyzed the application of artificial intelligence (AI) for histopathology, with development of novel machine-learning models for tissue interrogation and discovery. We aimed to review the literature for studies specifically applying AI algorithms to WSI-digitized pre-implantation kidney biopsy. Methods A systematic search was carried out in the electronic databases PubMed-MEDLINE and Embase until 25th September, 2021 with a combination of the key terms “kidney”, “biopsy”, “transplantation” and “artificial intelligence” and their aliases. Studies dealing with the application of AI algorithms coupled with WSI in pre-implantation kidney biopsies were included. The main theme addressed was detection and quantification of tissue components. Extracted data were: author, year and country of the study, type of biopsy features investigated, number of cases, type of algorithm deployed, main results of the study in terms of diagnostic outcome, and the main limitations of the study. Results Of 5761 retrieved articles, 7 met our inclusion criteria. All studies focused largely on AI-based detection and classification of glomerular structures and to a lesser extent on tubular and vascular structures. Performance of AI algorithms was excellent and promising. Conclusion All studies highlighted the importance of expert pathologist annotation to reliably train models and the need to acknowledge clinical nuances of the pre-implantation setting. Close cooperation between computer scientists and practicing as well as expert renal pathologists is needed, helping to refine the performance of AI-based models for routine pre-implantation kidney biopsy clinical practice.

Background TAFRO syndrome is a rare clinical subtype of idiopathic multicentric Castlemans disease characterised by thrombocytopenia, anasarca, myelofibrosis, renal dysfunction, and organomegaly. Renal involvement is common, sometimes requiring temporary renal replacement therapy. Due to the associated thrombocytopenia, renal biopsies are rarely performed limiting descriptions of the renal histopathology in this condition. This case describes a patient with TAFRO syndrome and the associated renal histology. Case presentation A 49-year-old Caucasian man presented to a tertiary hospital in Sydney with a six- week history of malaise, non-bloody diarrhoea, progressive shortness of breath, and drenching night sweats. A progressive bicytopenia and renal function decline necessitating temporary dialysis prompted a bone marrow aspirate and trephine, as well as a renal biopsy respectively. This noted a hypercellular bone marrow with increased granulopoiesis, reduced erythropoiesis, and fibrosis, with renal histology suggesting a thrombotic microangiopathic-like glomerulopathy. Alternate conditions were excluded, and a diagnosis of TAFRO syndrome was made. Glucocorticoids and rituximab were initiated with rapid renal recovery, and normalisation of his haematologic parameters achieved at six months. Conclusion This case describes an atypical thrombotic microangiopathy as the predominant histologic renal lesion in a patient with TAFRO syndrome. This was responsive to immunosuppression with glucocorticoids and rituximab, highlighting the importance of early recognition of this rarely described condition.

BACKGROUND Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can result in clinically significant multi-system disease including involvement in the kidney. The underlying histopathological processes were unknown at the start of the pandemic. As case reports and series have been published describing the underlying renal histopathology from kidney biopsies, we have started to gain an insight into the renal manifestations of this novel disease. AIM To provide an overview of the current literature on the renal histopathological features and mechanistic insights described in association with coronavirus disease 2019 (COVID-19) infection. METHODS A systematic review was performed by conducting a literature search in the following websites-‘PubMed’, ‘Web of Science’, ‘Embase’ and ‘Medline-ProQuest’ with the following search terms-“COVID-19 AND kidney biopsy”, “COVID-19 AND renal biopsy”, “SARS-CoV-2 AND kidney biopsy” and “SARS-CoV-2 AND renal biopsy”. We have included published data up until February 15, 2021, which includes kidney biopsies (native, transplant and postmortem) from patients with COVID-19. Data on clinical presentation, histopathological features, management and outcome was extracted from the reported studies. RESULTS The total number of biopsies reported on here is 288, of which 189 are postmortem, 84 native and 15 transplants. The results are varied and show underlying pathologies ranging from collapsing glomerulopathy and acute tubular injury (ATI) to anti-nuclear cytoplasmic antibody associated vasculitis and pigment nephropathy. There was variation in the specific treatment used for the various renal conditions, which included steroids, hydroxychloroquine, eculizumab, convalescent plasma, rituximab, anakinra, cyclophosphamide and renal replacement therapy, amongst others. The pathological process which occurs in the kidney following COVID-19 infection and leads to the described biopsy findings has been hypothesized in some conditions but not others (for example, sepsis related hypoperfusion for ATI). It is important to note that this represents a very small minority of the total number of cases of COVID-19 related kidney disease, and as such there may be inherent selection bias in the results described. Further work will be required to determine the pathogenetic link, if any, between COVID-19 and the other renal pathologies. CONCLUSION This report has clinical relevance as certain renal pathologies have specific management, with the implication that kidney biopsy in the setting of renal disease and COVID-19 should be an early consideration, dependent upon the clinical presentation.

Ipilimumab is a human monoclonal antibody targeting cytotoxic T-lymphocyte-associated protein 4 approved for the treatment of non-small-cell lung cancer (NSCLC) and other malignancies. Despite a high prevalence of other immune-related adverse events (irAEs), checkpoint inhibitor (CPI)-related nephrotoxicity has been reported less frequently. In this clinical case report, we describe the evaluation of a 70-year-old female with stage IV NSCLC who presented with nephrotic range proteinuria 4 weeks after receiving her first cycle of ipilimumab. She underwent a renal biopsy and was found to have IgA nephropathy that was presumed to be secondary to ipilimumab use, given recent initiation of therapy and clinical history. Unfortunately, despite prompt initiation of corticosteroids, her acute kidney injury progressed and she required hemodialysis, later transitioning to hospice. To our knowledge, this is one of few reported cases of IgA nephropathy secondary to CPI use. With increasing use of CPIs, this case further emphasizes the need for continued surveillance for irAEs, which can occur at any point in a patient’s treatment course.

Rationale & Objective Although kidney biopsy is a useful tool, nephrologists’ approach toward biopsies is inconsistent for reasons incompletely understood, including lack of established clinical guidelines. We examined contemporary clinical decision-making patterns among nephrologists to perform native kidney biopsy. Study Design Qualitative study using semistructured interviews. Setting & Participants Purposive sampling was used to select nephrologists from different regions in the United States. Semistructured interviews were continued until thematic saturation. Analytical Approach A modified grounded theory was used to identify dominant themes reflecting the nephrologists’ decision-making styles about kidney biopsy. Results Twenty nephrologists were interviewed: 16 (80%) were from academic centers, 3 (15%) performed their own biopsies, and 7 (35%) had been in practice for less than 10 years. The median time of practice was 14 years. We found substantial variability among the nephrologists in their attitude toward using kidney biopsy, which reflected individual differences in weighing the risks and benefits of the procedure for an individual patient. Five overarching themes were identified: operator comfort with biopsy and availability of interventional radiologist, exposure to biopsy during training and years of experience, concerns about the invasiveness of biopsy and inflicting harm, perception of evidence base and limited treatment options, and patient characteristics and preference. Limitations Generalizability was limited because the nephrologists sampled may not have been broadly representative. Conclusions Multiple factors influence nephrologists’ decision to pursue kidney biopsy, with substantial variability among nephrologists that can have meaningful clinical implications. This suggests the need to establish consensus guidelines to make biopsy practice more standardized., Kidney biopsy is the gold standard for diagnosis of most kidney diseases, but practice patterns vary widely, and no consensus guidelines exist. Studies are lacking on how nephrologists go about deciding which patients to biopsy with acute or chronic kidney disease. To address this gap in the literature, we conducted a qualitative study amongst nephrologists to examine and understand the reasons for variabilities in practice patterns. We found that the biopsy decision is complex and that multiple factors inform the decision to biopsy including nephrologist’s experience with the biopsy procedure, nephrologists’ varying perspectives on indications, the ease of scheduling biopsies, and patient preference. Development of consensus guidelines may assist nephrologists in making complex clinical decisions that balance risks and benefits.

The authors report a case of a 57-year-old woman who was successfully treated with a percutaneous embolization procedure for a renal arteriovenous fistula that developed as a complication of a kidney biopsy. An acute kidney injury that failed to resolve with medical management prompted further investigation with a renal biopsy. Five hours after the kidney biopsy, the patient became hemodynamically unstable with a blood pressure of 77 of 52 mm Hg. A stat abdominal computed tomography scan without contrast discovered a large left-sided perinephric hematoma that measured up to 11.5 cm with a moderate amount of perinephric blood. An angiogram subsequently demonstrated the presence of an arteriovenous fistula at the inferior pole of the left kidney. Several 2 × 3 mm and 3 × 3 mm coils were deployed into two separate segmental branches of the inferior pole, and the post embolization angiogram confirmed resolution of the previously visualized arteriovenous fistula.

A 67-year-old female with Type 2 diabetes mellitus developed nephrotic syndrome within 1 week of receiving the first dose of severe acute respiratory syndrome coronavirus 2 CoronaVac vaccine. A kidney biopsy was consistent with minimal change nephrotic syndrome and treatment was symptomatic with antiproteinuric therapy and improvement in proteinuria. Oedema returned within 1 week of the second dose of CoronaVac. On this occasion, acute kidney injury and massive proteinuria were noted. In kidney biopsy, glomeruli were normal, but tubulointerstitial inflammation consistent with acute tubulointerstitial nephritis was noted. Pulse followed by oral steroids was followed by recovery of kidney function. Proteinuria decreased after initiation of cyclosporine A.

Background Percutaneous kidney biopsy is the gold standard investigation for the diagnosis of kidney diseases. The associated risks of the procedure depend on the skill and experience of the proceduralist as well as the characteristics of the patient. The Kidney Health Australia – Caring for Australasians with Renal Impairment (KHA-CARI) guidelines on kidney biopsies, published in 2019, are the only published national kidney biopsy guidelines. As such, this study surveys current kidney biopsy practices in Australasia and examines how they align with the Australian guidelines, as well as international biopsy practice. Methods A cross-sectional, multiple-choice questionnaire was developed examining precautions prior to kidney biopsy; rationalisation of medications prior to kidney biopsy; technical aspects of kidney biopsy; complications of kidney biopsy; and indications for kidney biopsy. This was distributed to all members of the Australian and New Zealand Society of Nephrology (ANZSN). Results The response rate for this survey is approximately 21.4 % (182/850). Respondents found agreement (> 75.0 %) in only six out of the twelve questions (50.0 %) which assessed their practice against the KHA-CARI guidelines. Conclusions This is the first study of its kind where kidney biopsy practices are examined against a clinical guideline. Furthermore, responses showed that practices were incongruent with guidelines and that there was a lack of consensus on many issues.

Background Histological findings of kidney involvement have been rarely reported in pediatric patients with SARS-CoV-2 infection. Here, we describe clinical, laboratory, and histological findings of two pediatric cases with almost exclusive kidney involvement by SARS-CoV-2. Results A 10-year-old girl with IgA vasculitis nephritis underwent kidney biopsy, showing diffuse and segmental mesangial-proliferative glomerulonephritis, and steroid therapy was initiated. After the worsening of the clinical picture, including an atypical skin rash, she was diagnosed with SARS-CoV-2. The re-evaluation of initial biopsy showed cytoplasmatic blebs and virus-like particles in tubular cells at electron microscopy. Despite SARS-CoV-2 clearance and the intensification of immunosuppression, no improvement was observed. A second kidney biopsy showed a crescentic glomerulonephritis with sclerosis, while virus-like particles were no longer evident. The second patient was a 12-year-old girl with a 3-week history of weakness and weight loss. Rhinitis was reported the month before. No medications were being taken. Blood and urine analysis revealed elevated serum creatinine, hypouricemia, low molecular weight proteinuria, and glycosuria. A high SARS-CoV-2-IgG titre was detected. Kidney biopsy showed acute tubular-interstitial nephritis. Steroid therapy was started with a complete resolution of kidney involvement. Conclusion We can speculate that in both cases SARS-CoV-2 played a major role as inflammatory trigger of the kidney damage. Therefore, we suggest investigating the potential kidney damage by SARS-CoV-2 in children. Moreover, SARS-CoV-2 can be included among infectious agents responsible for pediatric acute tubular interstitial nephritis.

Anti-brush border antibody (ABBA) disease, also called anti–low-density lipoprotein receptor-related protein 2 (anti-LRP2) nephropathy, occurs due to the formation of antibodies against brush border antigens of the renal proximal convoluted tubule. We report a case of ABBA disease in a male farmer in his 30s who presented with 2 years of polyuria, dysuria, nocturia, and urinary urgency. He described a history of long-term occupational exposure to pesticides and silica, evolving into possible pneumoconiosis, and prior pulmonary tuberculosis. At presentation, he had reduced kidney function (serum creatinine 3.6 mg/dL) with hyponatremia, hypokalemia, hypophosphatemia, a normal anion gap, metabolic acidosis, and respiratory acidosis, and 2.2 g/day of urine proteinuria. The kidney biopsy was consistent with ABBA, showing amorphous immune-deposits in the tubular basement membrane and strong positivity on indirect immunofluorescence in the brush border of the proximal tubules. The trigger for production of ABBA is still unknown, but it may be associated with chronic conditions such as pulmonary tuberculosis and occupational exposures such as silica and pesticides, as seen in the patient in this report. Most cases do not respond to immunosuppression, and the prognosis is poor.

Zi-Shan Lin,1,* Xiao-Juan Yu,1,* Xu Zhang,1,2 Su-Xia Wang,1,2 Xi-Nan Cen,3 Fu-De Zhou,1 Ming-Hui Zhao1,4 1Renal Division, Department of Medicine, Peking University First Hospital; Institute of Nephrology, Peking University, Renal Pathology Center, Institute of Nephrology, Peking University, Key Laboratory of Renal Disease, Ministry of Health of China, Key Laboratory of CKD Prevention and Treatment, Ministry of Education of China, Beijing, People’s Republic of China; 2Laboratory of Electron Microscopy, Pathological Centre, Peking University First Hospital, Beijing, People’s Republic of China; 3Department of Hematology, Peking University First Hospital, Beijing, People’s Republic of China; 4Peking-Tsinghua Center for Life Sciences, Beijing, People’s Republic of China*These authors contributed equally to this workCorrespondence: Fu-De ZhouRenal Division, Department of Medicine, Peking University First Hospital, Institute of Nephrology, Peking University; Renal Pathology Center, Institute of Nephrology, Peking University, Key Laboratory of Renal Disease, Ministry of Health of China, Key Laboratory of CKD Prevention and Treatment, Ministry of Education of China, No. 8 Xishiku Street, Xicheng District, Beijing, 100034, People’s Republic of ChinaTel +86-13501162527Fax +86-10-83575694Email zhoufude1801@vip.sina.comBackground: Monoclonal immunoglobulin-associated renal lesions in patients with newly diagnosed myeloma vary. We aimed to determine the pathological spectrum and analyze associated prognostic factors.Methods: Fifty-six patients with newly diagnosed multiple myeloma and biopsy-proven renal lesions were enrolled. Kidney biopsies were reanalyzed, and the baseline clinical characteristics, treatments and outcomes were recorded.Results: Fifty-one patients had monoclonal immunoglobulin-associated renal lesions, with myeloma cast nephropathy (MCN) being the most common pattern. We divided our cohort into pure MCN, MCN+ other pathologies and non-MCN. Patients with MCN had more severe renal injury than those with non-MCN. In our cohort, none of the patients with pure MCN or MCN + other pathologies presented with nephrotic syndrome. Patients with non-MCN had better renal and overall survival than those with pure MCN but similar survivals to those with MCN + other pathologies. Number of myeloma casts (HR 1.08, p = 0.012) was the only independent prognostic factor for renal survival. Male sex (HR: 3.64; p = 0.015) and number of casts (HR: 1.17; p = 0.001) were independent prognostic factors for overall survival.Conclusion: Patients with MCN had more severe renal injury than those with non-MCN. Patients with non-MCN had better renal and overall outcomes than those with pure MCN, but their outcomes were similar to those with MCN + other pathologies. The independent predictors of overall survival were male sex and number of myeloma casts.Keywords: kidney biopsy, multiple myeloma, myeloma cast nephropathy, monoclonal immunoglobulin, prognosis

Zi-Shan Lin,1,* Xiao-Juan Yu,1,* Xu Zhang,1,2 Su-Xia Wang,1,2 Xi-Nan Cen,3 Fu-De Zhou,1 Ming-Hui Zhao1,4 1Renal Division, Department of Medicine, Peking University First Hospital; Institute of Nephrology, Peking University, Renal Pathology Center, Institute of Nephrology, Peking University, Key Laboratory of Renal Disease, Ministry of Health of China, Key Laboratory of CKD Prevention and Treatment, Ministry of Education of China, Beijing, People’s Republic of China; 2Laboratory of Electron Microscopy, Pathological Centre, Peking University First Hospital, Beijing, People’s Republic of China; 3Department of Hematology, Peking University First Hospital, Beijing, People’s Republic of China; 4Peking-Tsinghua Center for Life Sciences, Beijing, People’s Republic of China*These authors contributed equally to this workCorrespondence: Fu-De ZhouRenal Division, Department of Medicine, Peking University First Hospital, Institute of Nephrology, Peking University; Renal Pathology Center, Institute of Nephrology, Peking University, Key Laboratory of Renal Disease, Ministry of Health of China, Key Laboratory of CKD Prevention and Treatment, Ministry of Education of China, No. 8 Xishiku Street, Xicheng District, Beijing, 100034, People’s Republic of ChinaTel +86-13501162527Fax +86-10-83575694Email zhoufude1801@vip.sina.comBackground: Monoclonal immunoglobulin-associated renal lesions in patients with newly diagnosed myeloma vary. We aimed to determine the pathological spectrum and analyze associated prognostic factors.Methods: Fifty-six patients with newly diagnosed multiple myeloma and biopsy-proven renal lesions were enrolled. Kidney biopsies were reanalyzed, and the baseline clinical characteristics, treatments and outcomes were recorded.Results: Fifty-one patients had monoclonal immunoglobulin-associated renal lesions, with myeloma cast nephropathy (MCN) being the most common pattern. We divided our cohort into pure MCN, MCN+ other pathologies and non-MCN. Patients with MCN had more severe renal injury than those with non-MCN. In our cohort, none of the patients with pure MCN or MCN + other pathologies presented with nephrotic syndrome. Patients with non-MCN had better renal and overall survival than those with pure MCN but similar survivals to those with MCN + other pathologies. Number of myeloma casts (HR 1.08, p = 0.012) was the only independent prognostic factor for renal survival. Male sex (HR: 3.64; p = 0.015) and number of casts (HR: 1.17; p = 0.001) were independent prognostic factors for overall survival.Conclusion: Patients with MCN had more severe renal injury than those with non-MCN. Patients with non-MCN had better renal and overall outcomes than those with pure MCN, but their outcomes were similar to those with MCN + other pathologies. The independent predictors of overall survival were male sex and number of myeloma casts.Keywords: kidney biopsy, multiple myeloma, myeloma cast nephropathy, monoclonal immunoglobulin, prognosis

Introduction Foot process effacement and mitochondrial fission associate with kidney disease pathogenesis. Electron microscopy is the gold-standard method for their visualization, but the observable area of electron microscopy is smaller than light microscopy. It is important to develop alternative ways to quantitatively evaluate these microstructural changes because the lesion site of renal diseases can be focal. Methods We analyzed elastica-Masson trichrome (EMT) and periodic acid-Schiff (PAS) stained kidney sections using structured illumination microscopy (SIM). Results EMT staining revealed three-dimensional (3D) structures of foot process, whereas ponceau xylidine acid fuchsin azophloxine solution induced fluorescence. Conversion of foot process images into their constituent frequencies by Fourier transform showed that the concentric square of (1/4)2-(1/16)2 in the power spectra (PS) included information for normal periodic structures of foot processes. Foot process integrity, assessed by PS, negatively correlated with proteinuria. EMT-stained sections revealed fragmented mitochondria in mice with mitochondrial injuries and patients with tubulointerstitial nephritis; Fourier transform quantified associated mitochondrial injury. Quantified mitochondrial damage in patients with immunoglobulin A (IgA) nephropathy predicted a decline in estimated glomerular filtration rate (eGFR) after kidney biopsy but did not correlate with eGFR at biopsy. PAS-stained sections, excited by a 640 nm laser, combined with the coefficient of variation values, quantified subtle changes in the basement membranes of patients with membranous nephropathy stage I. Conclusions Kidney microstructures are quantified from sections prepared in clinical practice using SIM., Graphical abstract

TAFRO (thrombocytopenia, anasarca, fever, reticulin myelofibrosis/renal insufficiency, and organomegaly) syndrome is a systemic inflammatory disease sharing some features with Castleman disease and POEMS (polyneuropathy, organomegaly, endocrinopathy, monoclonal protein, and skin changes) syndrome in relation to abnormal secretions of interleukin 6 and vascular endothelial growth factor. The kidney is a main target organ of TAFRO syndrome but the kidney histopathology associated with TAFRO syndrome is yet to be completely defined. We report 3 TAFRO syndrome cases with different clinical courses in which kidney biopsies were performed. In all 3 cases, kidney biopsies showed similar glomerular lesions of diffuse global swelling of the endothelium and expansion of subendothelial spaces, consistent with severe glomerular endothelial injury. Case 3 showed an additional finding of focal tubulointerstitial injury characterized by marked plasma cell infiltration, which was absent in the other 2 cases. Clinical symptoms in cases 1 and 2, which had lower disease severity scores of TAFRO syndrome, were effectively treated with the administration of corticosteroids or a combination of corticosteroids and cyclosporine A. Case 3, with a higher disease severity score, had an aggressive clinical course that was refractory to corticosteroids and tocilizumab; the patient ultimately died of multiple organ failure. In all 3 cases, kidney biopsy provided indications for the diagnosis process and clinical management of TAFRO syndrome.

Constantina A Bounia,1 Eftichia N Theodoropoulou,1 Stamatic-Nick C Liossis1,2 1Division of Rheumatology, Patras University Hospital, Patras, Greece; 2Department of Internal Medicine, University of Patras Medical School, Patras, GreeceCorrespondence: Stamatic-Nick C LiossisDiv. of Rheumatology, Patras University Hospital, GR 26500, Rion, Patras, GreeceTel +30 2613 603 693Fax +30 2610 993 982Email snliossis@med.upatras.grAbstract: Renal failure or acute/chronic kidney damage may present as a clinical manifestation of rheumatic diseases. In addition treatment with DMARDs or biologic drugs may induce nephrotoxicity. In this case-based review, we present two patients with SpA under anti-TNF-α treatment admitted to our hospital because of renal failure and proteinuria. We review previously published yet isolated cases of TNF-α blocker-induced glomerular disease in patients with SpA. Renal manifestations are occasionally seen in patients with ankylosing spondylitis and psoriatic arthritis with IgA nephropathy being the most common of them. Anti-TNF-α agents although reportedly used for the treatment of glomerular nephropathy as a disease manifestation, they have been considered responsible for provoking renal damage in some cases. A diagnostic approach for patients with SpA treated with anti-TNF-α agents presenting with renal manifestations is proposed herein.Keywords: spondylarthritides, glomerular disease, proteinuria, kidney biopsy, anti-TNF-alpha agents

Introduction d-Serine, present only in trace amounts in humans, is now recognized as a biomarker of chronic kidney disease (CKD). CKD is heterogeneous in its original kidney diseases, whose diagnoses require kidney biopsy. In this study, we examined whether the intra-body dynamics of d-serine, indexed by its blood and urinary levels, reflects the origin of kidney diseases. Methods Patients with six kinds of kidney disease undergoing kidney biopsy were enrolled in a single center. Levels of d- and l-serine were measured using two-dimensional high-performance liquid chromatography. The associations between the origin of kidney diseases and the intra-body dynamics of d-serine were examined using multivariate cluster analyses. Results Unlike the non-CKD profile, patients with CKD showed broadly-distributed profiles of intra-body dynamics of d-serine. The plasma level of d-serine plays a key role in the detection of kidney diseases, whereas a combination of plasma and urinary levels of d-serine distinguished the origin of CKD, especially lupus nephritis. Conclusion Intra-body dynamics of d-serine have the potential to predict the origin of kidney diseases. Monitoring of d-serine may guide specific treatments for the origin of kidney diseases.

Background Soluble tumor necrosis factor receptor (sTNFR)-1, sTNFR-2, YKL-40, monocyte chemoattractant protein (MCP)-1, and soluble urokinase plasminogen activator receptor (suPAR) have emerged as promising biomarkers of inflammation but have not been evaluated across diverse types of kidney diseases. Methods We measured these plasma biomarkers in 523 individuals enrolled into a prospective, observational cohort study of patients undergoing clinically indicated native kidney biopsy at 3 tertiary care hospitals. Two kidney pathologists adjudicated biopsy specimens for semiquantitative scores of histopathology. Proportional hazard models tested associations between biomarkers and risks of kidney disease progression (composite of ≥40% estimated glomerular filtration rate [eGFR] decline or end-stage kidney disease [ESKD]) and death. Results Mean eGFR was 56.4±36 ml/min per 1.73 m2 and the median proteinuria (interquartile range) was 1.6 (0.4, 3.9) g/g creatinine. The most common primary clinicopathologic diagnoses were proliferative glomerulonephritis (29.2%), nonproliferative glomerulopathy (18.1%), advanced glomerulosclerosis (11.3%), and diabetic kidney disease (11.1%). sTNFR-1, sTNFR-2, MCP-1, and suPAR were associated with tubulointerstitial and glomerular lesions. YKL-40 was not associated with any histopathologic lesions after multivariable adjustment. During a median follow-up of 65 months, 182 participants suffered kidney disease progression and 85 participants died. After multivariable adjustment, each doubling of sTNFR-1, sTNFR-2, YKL-40, and MCP-1 was associated with increased risks of kidney disease progression, with hazard ratios ranging from 1.21 to 1.47. Each doubling of sTNFR-2, YKL-40, and MCP-1 was associated with increased risks of death, with hazard ratios ranging from 1.33 to 1.45. suPAR was not significantly associated with kidney disease progression or death. Conclusions sTNFR-1, sTNFR-2, YKL-40, MCP-1, and suPAR are associated with underlying histopathologic lesions and adverse clinical outcomes across a diverse set of kidney diseases., Graphical abstract

Late-onset retroperitoneal hemorrhage from renal intraparenchymal pseudoaneurysm (RIP) following a kidney biopsy is an extremely rare complication but should not be ignored, especially in high-risk populations. Here, we introduce a 32-year-old Caucasian female who presented with sudden-onset left-sided flank pain. She had recently been diagnosed with systemic lupus erythematosus (SLE) and had undergone a computed tomography (CT)-guided core needle biopsy of the left kidney 9 days earlier. The results were consistent with lupus nephritis class III or IV. Initial vitals were within normal limits. She appeared pale and her left flank was tender to palpation without discoloration or abdominal distention. Laboratory investigations showed a hemoglobin level of 7.1 g/dL. The CT scan of the abdomen and pelvis revealed a large hyperdense left perinephric collection consistent with perinephric hematoma with a moderate amount of retroperitoneal stranding most prominent on the left side extending across the midline to the right side. Contrast extravasation was suspected in the lower pole of the left kidney consistent with active bleeding site. Emergent renal angiography revealed a 2 × 1 cm intraparenchymal pseudoaneurysm in the lower pole of the left kidney along with a few small microaneurysms. Coil embolization of the pseudoaneurysm was successfully performed without any complications. In conclusion, SLE or lupus nephritis in this patient may be the predisposing factors for microaneurysm and RIP formations. RIP is an unusual complication after percutaneous kidney biopsy that carries a significant mortality rate if ruptured, causing retroperitoneal hemorrhage. Clinicians should be vigilant when encountering high-risk patients with persistent hematuria, flank pain, or abdominal pain within four weeks after a kidney biopsy.

IgAN se definira kao autoimuna bolest koju karakterizira taloženje imunokompleksa koji sadrže Gd-IgA1 protutijela u mezangiju glomerula s incidencijom 2.5/100000 u godini. Osnovne patomorfološke promjene IgAN, koje se dio Oxford klasifikacije iz 2016. godine, su: mezangijalna, endokapilarna i ekstrakapilarna proliferacija, segmentalna glomeruloskleroza i tubularna atrofija/intersticijska fibroza. U studiju su uključeni pacijenti čija je vrijednost eGFR-a u trenutku biopsije iznosila >15 ml/min/1.73 m2. Isključeni su pacijenti sa sekundarnim oblikom IgAN. Period opservacije iznosio je 3 godine ili manje ukoliko je došlo do razvoja ESRD-a, dijalize ili smrti. Prethodna tri kriterija ujedno su činila završnu točku studije. Ovom studijom utvrđeno je da skupina s razvojem ESRD-a ima manju vrijednost eGFR-a u trenutku biopsije u odnosu na onu bez razvoja istog (p=0.003). Za skupinu s T1+2 kriterijem dokazana je veća učestalost razvoja ESRD-a u odnosu na skupinu s T0 kriterijem (p=0.025). ROC krivuljom, za vrijednosti eGFR-a u trenutku biopsije, dobiven je AUC u iznosu od 0.844 (95% CI 0.657-0.952) (p0.05). Pacijenti imaju veću vjerojatnost razvoja ESRD-a ako je vrijednost eGFR-a u trenutku biopsije 15 ml/min/1.73 m2. Patients with secondary IgAN were excluded. The observation period was 3 years or less if ESRD development, dialysis or death occurred. The previous three criteria also formed the end point of the study. This study found that the group with the development of ESRD had a lower value of eGFR at the time of biopsy compared to those without the development of the same (p=0.003). For the group with T1+2 criteria, a higher frequency of ESRD development was proven compared to the group with T0 criteria (p=0.025). ROC curve analysis, for eGFR values at the time of biopsy, resultated with an AUC of 0.844 (95% CI 0.657-0.952) (p0.05). Patients are more likely to develop ESRD if the eGFR value, at the time of biopsy, is

Background: The simultaneous occurrence of impaired kidney function and paraproteinemia is common in our constantly aging society. Both can be independent entities; however, renal insufficiency can also be caused by the paraprotein. We assessed all kidney biopsies in patients with monoclonal gammopathy in our clinic over the past 20 years and evaluated the histological results. Methods: Biopsies were systematically performed in nearly all patients with paraproteinemia and impaired kidney function (n = 178). The histological findings were systematically evaluated and correlated with the initial clinical diagnosis. Results: We found cast nephropathy (CN) in n = 66 (37.1%) biopsies, AL amyloidosis in n = 31 (17.4%) biopsies, monoclonal immunoglobulin deposition disease (MIDD) in n = 7 (3.9%) biopsies and other renal diseases (ORDs) in n = 74 (41.6%) biopsies. In the latter group, paraprotein-associated changes were found in 37 of 74 (50%) patients, whereas paraprotein-independent changes were found in the other half. Whereas, in the group of patients with MGUS, the findings were heterogenous, most of the patients with known multiple myeloma (MM) or B-NHL showed malignancy-associated changes in the kidney. The biopsy changed the diagnoses in a significant proportion of the patients: The group of patients with MM grew from 71 to 112 patients, whereas, in the MGUS group, only 31 of 44 patients remained. Conclusion: Kidney biopsies in patients with paraproteinemia and renal impairment show a wide range of findings that can lead to a change in diagnosis.

Background: Fabry disease (FD) is a rare lysosomal storage disease causing progressive loss of target organ function. All renal cell types are involved from the early stages, even before clinical signs can be detected. FD-specific therapies can stop/mitigate disease progression. Thus, it is important to validate early markers of renal lesions so that they can be adopted as criteria for timely treatment initiation. Materials and methods: We retrospectively analyzed and extensively evaluated 21 FD case patients; this evaluation included a kidney biopsy. We looked for the influence of pathological findings on the management of FD patients. In addition, we investigated the association between general and FD-specific features and long-term patients’ outcomes. We defined a combined endpoint as being at least one of the following: 50% decrease of estimated glomerular filtration rate (eGFR) from baseline, kidney failure (KF), end-stage kidney disease (ESKD), or death and mortality. Results: Our cohort of 21 FD patients (11 males and 10 females) was stratified according to the presence of the combined endpoint: group 1 (n = 15) included patients without the combined endpoint, while group 2 (n = 6) patients reached the combined endpoint outcome. Patients from group 2 presented lower mean baseline eGFR (72.2 ± 38.7 mL/min/1.73 m2 vs. 82.5 ± 26.4 mL/min/1.73 m2) without statistical significance (p = 0.44), but significantly (p = 0.22) higher median baseline proteinuria (2.7 g/24 h vs. 0.4 g/24 h). Specific lysosomal deposits were identified in all patients. Segmental sclerosis was present in all patients with the combined endpoint and in only 33% of patients without the combined endpoint (p = 0.009). Global sclerosis and interstitial fibrosis were present in both groups, with no significant differences. A total of 15 out of the 16 treatment-naïve patients (7 males and 9 females) started FD-specific therapy after kidney biopsy. Treatment was initiated in all male FD patients and in 8 female patients. In 2 females, pathological findings in kidney biopsy offered important reasons to start FD treatment, although specific criteria of the Romanian protocol for prescription of FD-specific therapy were still not fulfilled. Cox univariate analysis showed that every increase in 24 h proteinuria with 1 g is associated with a 65% risk of developing the combined endpoint (HR = 1.65; 95%CI: 1.05–2.58; p = 0.02), and that the presence of segmental sclerosis increased the risk of developing the combined endpoint by 51.3 times (HR = 51.3; 95% CI: 95% CI: 1.67–103.5; p = 0.01). Kaplan–Meier analysis showed that the cumulative risk of developing the combined endpoint was higher in patients in whom segmental sclerosis (100% vs. 0%, log-rank test, p = 0.03) was present. Conclusions: Histological evaluation is an important tool for the detection of early kidney involvement and provides additional support to the early initiation of FD-specific therapy. Presence of segmental sclerosis can predict the long-term outcomes of kidney disease deterioration and mortality and may be used as an early indicator of disease progression. Additionally, in the absence of other criteria according to current guidelines, specific FD renal lesions as revealed by kidney biopsy might become a distinct criterion to initiate FD therapy.

Kidney biopsy; Renal pathology; Solid organ neoplasm Biòpsia renal; Patologia renal; Neoplàsia d'òrgans sòlids Biopsia renal; Patología renal; Neoplasia de órganos sólidos Background: Currently, following the new advances in cancer treatments and the increasing prevalence of kidney disease in the population, more kidney biopsies are being performed. The aim of our study is to analyze clinical and histological characteristics of patients with active solid organ malignancy who underwent kidney biopsy. This is a multi-center collaborative retrospective study supported by groups GLOSEN/Onconephrology from the Spanish Society of Nephrology. Clinical, demographical and histological data were collected. Results: A total of 148 patients with cancer who underwent a kidney biopsy from 12 hospitals were included. 64.3% men and mean age of 66.9 years old. The indications for biopsy were acute renal injury (67.1%), proteinuria (17.1%), exacerbated chronic kidney disease (8.2%), and chronic kidney disease (7.5%). Most frequent malignances were lung (29.1%) and abdominal (25%), with 49.7% metastatic cancer. As oncospecific treatment, 28% received chemotherapy, 29.3% immunotherapy, 19.3% specific therapies, and 2.1% conservative treatment. At the time of kidney biopsy, median creatinine was of 2.58 mg/dL [1.81–4.1 (IQ 25–75)], median urine protein-to-creatinine ratio of 700 mg/g [256–2463 (IQ 25–75)] and 53.1% presented hematuria. The most frequent renal biopsy diagnoses were: acute interstitial nephritis (39.9%), acute tubular necrosis (8.8%), IgA nephropathy (7.4%) and membranous nephropathy (6.1%). Median follow-up was 15.2 months [5.7–31.4 (IQ 25–75)]. Conclusions: There is a new trend in kidney disease and cancer patients in terms of diagnosis and treatment. Acute interstitial nephritis has established itself as the most common kidney injury in patients with cancer who underwent a kidney biopsy. Renal biopsy is a valuable tool for diagnosis, treatment, and prognosis of solid organ cancer patients with kidney damage. This work was supported by grants from Fondo de Investigación Sanitaria-FEDER, ISCIII, Río Hortega CM20/00111, PI17/00257, PI21/01292, Marató TV3 2020 421/C/2020, Marató TV3 2021 215/C/2021, RD16/0009/0030 (REDINREN), EIN2020-1123381, and RD21/0005/0016 (RICORS 2040).

Introduction Kidney biopsy is an important tool for making diagnoses and for assessing the drug treatment requirements and disease prognosis in the management of kidney diseases. There are variations in the rate of complications associated with kidney biopsies across countries, and this depends on various clinical and technical factors. The aim of this study is to report on complications associated with kidney biopsy performed in low- and middle-income countries. Methods Two reviewers searched studies in MEDLINE, Embase, Cochrane Reviews, and African Journals Online. A random effects meta-analysis method was used to pool estimates of complications. Results We identified 39 studies reporting on 19,500 kidney biopsies with overall complications (major + minor) rate of 14.9% (95% confidence interval = 11.4%–18.7%). Fewer complications were reported in biopsies performed with real-time ultrasound scans compared to those pre-marked using ultrasound or blind procedures (12.4% vs. 14.9% vs. 24.5%; P = 0.037), respectively. Complications, albeit lower for procedures performed with automated needles (13.3%), were not significantly different from those performed with nonautomated needles (17.3%; P = 0.588). Major complications included macroscopic hematuria (1.48%), nephrectomy (0.04%), blood loss requiring red cell transfusion (0.24%), angiographic intervention (0.22%), and death (0.01%). Conclusion Complications associated with kidney biopsy in low- and middle-income countries are low, are comparable to those in other settings, and occur more sparingly when real-time ultrasound techniques or automated kidney biopsy needles are used. This suggests the need to expand the use of this procedure to improve diagnosis of kidney pathologies and choice of therapy when indicated., Graphical abstract

Introduction: Kidney biopsies (KBs) are performed in patients with type 2 diabetes (T2D) to diagnose non-diabetic or hypertensive kidney disease (NDHKD) potentially requiring specific management compared to diabetic and or hypertensive nephropathy (absence of NDHKD). Indications for KB are based on the presence of atypical features compared to the typical course of diabetic nephropathy. In this study, we assessed the association of different patterns of atypical features, or KB indications, with NDHKD. Methods: Native KBs performed in patients with T2D were analyzed. Data were collected from the patients’ records. KB indications were determined according to the presence of different atypical features considered sequentially: (1) presence of any feature suggesting NDHKD which is not among the following ones, (2) recent onset of nephrotic syndrome, (3) low or rapidly declining estimated glomerular filtration rate (eGFR), (4) rapid increase in proteinuria, (5) short duration of diabetes, (6) presence of hematuria, or (7) normal retinal examination. Results: Among the 463 KBs analyzed, NDHKD was diagnosed in 40% of the total population and 54, 40, 24, and 7% of the KBs performed for indications 1–4 respectively. Conversely, no patient who underwent KB for indications 5–7 displayed NDHKD. Logistic regression analyses identified eGFRCKD-EPI >15 mL/min/1.73 m2, urinary protein-to-Cr ratio

BACKGROUND AND OBJECTIVES: ANCA-associated GN is a common cause of rapidly progressive GN, with high relapse rates. The early recognition of an ANCA-associated GN relapse is of importance to prevent loss of kidney function. Urinary soluble CD163 has been identified as a promising marker of active ANCA-associated GN. Previous studies, however, are limited by the lack of histologic data. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: We analyzed urinary soluble CD163 in 95 patients with ANCA-associated vasculitis who underwent a kidney biopsy. In total, 125 kidney tissue sections (first kidney biopsy, n=67; repeated biopsy, n=58) with concurrent 24-hour urine samples were studied. Correlation analyses comparing urinary soluble CD163 levels and morphologic features of ANCA-associated GN were performed using Spearman rank correlation analysis. The diagnostic performance of biomarkers to detect relapsing ANCA-associated GN was evaluated using receiver operating characteristics curve analysis. RESULTS: High levels of urinary soluble CD163 were found in 96 (87%) of 110 biopsies with active ANCA-associated GN compared with one (7%) of 15 biopsies without active ANCA-associated GN and one (6%) of 17 healthy controls. Urinary soluble CD163 correlated with fibrinoid necrosis (Rho=0.48, P

Aim: Kidney biopsy is crucial in management of renal diseases. Biopsies in children have added difficulties. The aim of this study is to investigate our 5-year experience of real-time ultrasound (USG)-guided percutaneous renal biopsy (PRB). Methods: Institutional database of children who underwent PRB in a tertiary hospital between January 2015 and March 2020 were evaluated retrospectively. A single pediatric nephrologist performed all the biopsies using an automated spring-loaded biopsy gun under real-time USG guidance. Results: Thirty-two biopsies were performed in 17 males (53.1%) and 15 females (46.9%), and the median age of the children was 14.5 years. The most common indication for biopsy was nephrotic syndrome in 13 /32 children (40.6%). Median number of glomeruli obtained from biopsy specimens was 18 (min-max=7-54 glomeruli). A diagnosis was achieved in all cases (100%) by a histopathologist. The only complication observed in a 16-year-old boy was a self-limited gross hematuria (3.1%) episode with subcapsular hematoma.Conclusion: Real-time USG-guided PRB with an automated biopsy gun is an effective and safe technique, providing superior yield when performed by a pediatric nephrologist. Performing kidney biopsy is an essential tool in a nephrologist’s workshop., Amaç: Böbrek biyopsisinin böbrek hastalıklarının yönetiminde oldukça önemli bir yeri vardır. Özellikle çocuklarda yapılan biyopsiler ek zorluklar gösterir. Bu çalışmanın amacı, çocuklarda uygulamış olduğumuz beş yıllık ultrasonografi eşliğinde perkutan böbrek biyopsisi (PRB) deneyimimizi değerlendirmektir.Yöntemler: Ocak 2015- Mart 2020 arasında bir üçüncü basamak hastanesinde PRB uygulanan çocukların hastane kayıtları geriye dönük olarak irdelenmiştir. Tüm biyopsiler, eş zamanlı USG altında tek bir çocuk nefroloğu tarafından otomatik biyopsi tabancası kullanılarak uygulanmıştır.Bulgular: Medyan yaşı 14,5 yaş olmak üzere; 17 erkek (%53,1) ve 15 kız çocuğuna (%46,9) 32 böbrek biyopsisi uygulandı. En sık biyopsi endikasyonu, çocukların 13/32’sinde (%40,6) nefrotik sendrom idi. Biyopsi örneklerinden alınan medyan glomerül sayısı 18 (min-max=7-54 glomerül) idi. Histopatolog tarafından tüm olgularda (%100) tanı konulabildi. Gözlenen tek komplikasyon, 16 yaşındaki bir erkek çocuğunda subkapsüler hematomla birlikte kendiliğinden düzelen gross hematüri süreci idi (%3,1).Sonuç: Çocuklarda; PRB Bir çocuk nefroloğu tarafından otomatik biyopsi tabancası kullanılarak, eş-zamanlı USG altında yapıldığında, yeterince fazla örneğin alınmasını sağlayan, etkili ve güvenli bir tekniktir. Böbrek biyopsisi, bir nefroloğun çalışma sorumluluğunda yapması gereken önemli bir uygulamadır.

Background Fatty acid-binding protein 4 (FABP4), but not FABP1 (liver-type FABP), is ectopically induced in injured glomerular endothelial cells, and urinary FABP4 (U-FABP4) level is associated with proteinuria and renal dysfunction in a general population. Methods The clinical significance of U-FABP4 was investigated in 81 patients (male/female: 43/38, age: 57 ± 17 years) who underwent kidney biopsy. Results U-FABP4 was negatively correlated with estimated glomerular filtration rate (eGFR) (r = − 0.56, P r = 0.58, P r = 0.52, P < 0.01). Multivariable regression analysis showed that eGFR, proteinuria and U-FABP1 were independent predictors of U-FABP4. The level of U-FABP4, but not that of proteinuria, eGFR or U-FABP1, in minimal change nephrotic syndrome (MCNS) was significantly lower than the level in membranous nephropathy (MN) and that in diabetic nephropathy. Receiver operating characteristic curve analysis indicated that U-FABP4 level ≤ 0.78 μg/gCr predicted MCNS in patients who had nephrotic-range proteinuria with a high level of accuracy. When divided by the median value of U-FABP4 at baseline in 33 of the 81 patients who could be followed up, the yearly change (post–pre) in eGFR in the low U-FABP4 group was significantly greater than that in the high U-FABP4 group (median: 11.0 vs. -5.0 mL/min/1.73m2/year). Conclusions U-FABP4 level is independently associated with proteinuria and renal dysfunction in patients with glomerular kidney disease. A low U-FABP4 level may predict MCNS in patients with nephrotic syndrome and would be a useful biomarker for differential diagnosis of MCNS and MN, which are common causes of nephrotic syndrome.

Over the past 2 decades, scoring systems for multiple glomerular diseases have emerged, as have consortia of pathologists and nephrologists for the study of glomerular diseases, including correlation of pathologic findings with clinical features and outcomes. However, one important limitation faced by members of these consortia and other renal pathologists and nephrologists in both investigative work and routine practice remains a lack of uniformity and precision in clearly defining the morphologic lesions on which the scoring systems are based. In response to this issue, the Renal Pathology Society organized a working group to identify the most frequently identified glomerular lesions observed by light microscopy and electron microscopy, review the literature to capture the published definitions most often used for each, and determine consensus terms and definitions for each lesion in a series of online and in-person meetings. The defined lesions or abnormal findings are not specific for any individual disease or subset of diseases, but rather can be applied across the full spectrum of glomerular diseases and within the context of the different scoring systems used for evaluating and reporting these diseases. In addition to facilitating glomerular disease research, standardized terms and definitions should help harmonize reporting of medical kidney diseases worldwide and lead to more-precise diagnoses and improved patient care.

Introduction South Africa has the highest prevalence of HIV in the world. The epidemiology of kidney disease among people with HIV infections is well-described in the United States. However, there are limited data coming from South Africa, particularly that involve kidney biopsies. The purpose of this study was to determine what, if any, patient factors are predictive of HIV-associated nephropathy (HIVAN) on kidney biopsy in a South African kidney biopsy cohort. Methods This study prospectively collected data of all patients infected with HIV referred to the Groote Schuur Hospital (GSH) renal unit for a kidney biopsy from 2002 to 2018. Results There were 419 patients included in the study. Mean age was 36.5 years (SD, 9.4); 219 (52.3%) were women; and all were black. Seventy-nine patients (18.9%) were on dialysis at the time of biopsy; the mean estimated glomerular filtration rate among the remainder was 41.4 ml/min per 1.73 m2 (SD, 39.2). Only 163 patients (47.1%) were known to be taking antiretroviral therapy (ART) at the time of biopsy. There were 246 (58.7%) cases of HIVAN detected, and they were comparable on age, sex, kidney function, and kidney size to those with kidney disease of other causes but were less likely to be taking ART (P < 0.001). Biopsy confirmed HIVAN was associated with mortality (adjusted hazard ratio, 1.77; 95% confidence interval [CI]: 1.07–2.91; P = 0.025), and the use of ART at biopsy was protective (adjusted hazard ratio, 0.52; 95% CI, 0.32–0.84, P = 0.008). The proportion of HIVAN on biopsy decreased and the proportion taking ART increased from 2002 to 2018 (P for trend for both < 0.001). Conclusion In summary, HIVAN was the most common etiology of kidney disease in this biopsy cohort from South Africa; however, the proportion with biopsy-proven HIVAN declined over time, perhaps in the setting of greater ART availability., Graphical abstract

Tanapoom Limtrakul,1 Ukrit Rompsaithong,1 Anucha Ahooja,2 Pakorn Kiatsopit,1 Supanut Lumbiganon,1 Kachit Pachirat,1 Wichien Sirithanaphol1 1Department of Surgery, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand; 2Department of Radiology, Faculty of Medicine, Khon Kaen University, Khon Kaen, ThailandCorrespondence: Wichien SirithanapholDepartment of Surgery, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, ThailandTel +66-43-363664Fax +66-43-202491Email wichsir@kku.ac.thBackground: Emergency renal artery embolization (RAE) is a useful method in treating renal trauma and bleeding renal tumors. The aim of this study was to evaluate the clinical efficacy and safety of emergency RAE, and factors associated with RAE failure.Methods: This retrospective study included patients treated with emergency RAE for acute renal hemorrhage between 1 January 2009 and 31 October 2019 in Srinagarind Hospital. The embolization was performed using coils, glues, and/or gel foams. Factors associated with unsuccessful outcomes were analyzed using univariate and multivariate regression analyses.Results: A total of 94 patients were treated at the center during the study period with the clinical success rate of 91.5%. The most common cause of acute renal hemorrhage was iatrogenic injury (76.5%). Factors associated with unsuccessful RAE according to multivariate analyses were hypertension (adjusted odds ratio [AOR] 24.2) and ruptured tumor/aneurysm (AOR 26.8).Conclusion: RAE is an effective procedure for acute renal hemorrhage. Hypertension and ruptured tumor/aneurysm were negative predictors for success.Keywords: renal artery embolization, renal trauma, renal hemorrhage, PCNL, kidney biopsy, renal tumor

Tanapoom Limtrakul,1 Ukrit Rompsaithong,1 Anucha Ahooja,2 Pakorn Kiatsopit,1 Supanut Lumbiganon,1 Kachit Pachirat,1 Wichien Sirithanaphol1 1Department of Surgery, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand; 2Department of Radiology, Faculty of Medicine, Khon Kaen University, Khon Kaen, ThailandCorrespondence: Wichien SirithanapholDepartment of Surgery, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, ThailandTel +66-43-363664Fax +66-43-202491Email wichsir@kku.ac.thBackground: Emergency renal artery embolization (RAE) is a useful method in treating renal trauma and bleeding renal tumors. The aim of this study was to evaluate the clinical efficacy and safety of emergency RAE, and factors associated with RAE failure.Methods: This retrospective study included patients treated with emergency RAE for acute renal hemorrhage between 1 January 2009 and 31 October 2019 in Srinagarind Hospital. The embolization was performed using coils, glues, and/or gel foams. Factors associated with unsuccessful outcomes were analyzed using univariate and multivariate regression analyses.Results: A total of 94 patients were treated at the center during the study period with the clinical success rate of 91.5%. The most common cause of acute renal hemorrhage was iatrogenic injury (76.5%). Factors associated with unsuccessful RAE according to multivariate analyses were hypertension (adjusted odds ratio [AOR] 24.2) and ruptured tumor/aneurysm (AOR 26.8).Conclusion: RAE is an effective procedure for acute renal hemorrhage. Hypertension and ruptured tumor/aneurysm were negative predictors for success.Keywords: renal artery embolization, renal trauma, renal hemorrhage, PCNL, kidney biopsy, renal tumor

Immunoglobulin A nephropathy (IgAN) is the most common chronic glomerulopathy with variable clinical manifestations. IgAN diagnostics became possible in Latvia in 2013. The study aim was to describe IgAN manifestations in the Latvian population by analysing epidemiological, clinical, histological data, and reveal factors that might determine the course of the disease. The retrospective, one-centre study included biopsy-proven IgAN patients over a five-year period in the Nephrology Centre at Pauls Stradiņš Clinical University Hospital. Data from inpatient and outpatient medical records were collected. The study included 69 patients with histologically confirmed IgAN (23% of all renal biopsies): 52% men with mean age of 37. More than a half of them had hypertension, changes in urinalysis and kidney structure, and GFR < ml/min before the biopsy. Pathology data stratified by MEST-C score were: M1 (93%), E1 (5%), S1 (81%), T1 and T2 (24%), C1 (18%). 20% started renal replacement therapy (RRT). Proteinuria, obesity, hyperuricemia, high total MEST-C score, and low serum C3 were associated with a worse prognosis. As a significant part of patients start RRT in the five-year period after the biopsy, the disease course is not benign. IgAN in the study population was diagnosed with clinical and histological signs of advanced disease.

Lymphomatous infiltration of kidney parenchyma is a frequent complication of systemic hematologic malignancies and often shows subtle clinical presentation. Diffuse large B-cell lymphoma represents the most frequent form involving the kidney, with advanced stage at diagnosis, poor outcome, and risk for central nervous system relapse if not adequately treated. Kidney biopsy can provide specific and early detection of these cases, helping in the differential diagnosis with more frequent entities. Finally, further hematologic workup (bone marrow biopsy, complete blood cell count, and positron emission tomography) can distinguish secondary involvement of the kidney from the rarer kidney-limited forms, especially in patients without a previous diagnosis of lymphoma. Making a prompt and correct diagnosis directs the management of these cases and may improve the outcome, as described in the present report.

Acute kidney injury (AKI) is a common presentation which can result from a number of different underlying pathological processes. Haematological malignancies, particularly multiple myeloma (MM), are known to frequently present with AKI. Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a rare condition which can cause crescentic glomerulonephritis (GN), resulting in AKI. We present the case of a 60-year-old man who presented with clinical features suggestive of AAV in the context of blood tests which demonstrated AKI and positive perinuclear ANCA (p-ANCA) and anti-myeloperoxidase (anti-MPO) titres. Further investigations demonstrated an underlying diagnosis of MM. A renal biopsy was ultimately required to determine the cause of AKI, a cast nephropathy. This case is the first to our knowledge which demonstrates a rare situation in which myeloma kidney is associated with positive p-ANCA and anti-MPO titres, without any evidence of a crescentic GN. It highlights the importance of following up on all investigations sent in the context of AKI, even when a potential diagnosis seems evident. Furthermore, it demonstrates the role of renal biopsy in confirming a diagnosis in the context of AKI with multiple differential diagnoses.

The pathogenetic relationship of kidney damage and an aberrant clone of the B-cell line producing nephrotoxic monoclonal immunoglobulin underlies the concept of “monoclonal gammopathy of renal significance” (MGRS). Herein the aberrant clone does not reach the criteria necessary for initiating antitumor therapy according to oncohematological indications. MGRS is a new nosology in modern nephrology and oncohematology. Monoclonal protein’s pathological effects on kidney parenchyma result in irreversible decline of kidney function till the end stage renal disease that in line with the position of International Consensus of hematologists and nephrologists determinates critical necessity for clone specific treatment in patients with MGRS despite the absence of hematological indications for treatment initiation. Main challenge of MGRS in Russian Federation is an inaccessibility of an in-time diagnostic and appropriate treatment for the great majority of patients due to the following reasons: i) limited knowledge about the MGRS among hematologists and nephrologists; ii) lack of necessary diagnostic resources in most health-care facilities; iii) lack of approved clinical recommendations and medical economic standards for treatment of this pathological entity. In order to overcome these limitations, leading oncohematologists and nephrologists of the Russian Federation on behalf of professional communities at the end of 2019 published a conciliation document: “Monoclonal gammopathy of renal significance: Consensus of hematologists and nephrologists of Russia on the establishment of nosology, diagnostic approach and rationale for clone specific treatment”. Consensus document comprises the opinion of experts – leading nephrologists and hematologists of Russian Federation – on the problem of MGRS including the incoherence in nosology classification, diagnostics approach and rationale for clone specific treatment. Consensus document is based on conclusions and agreements reached during the conference of leading nephrologists and hematologists of Russia which was held in the framework of symposia “Plasma cell dyscrasias and lymphoproliferative diseases: modern approaches to therapy”, 15–16 of March 2019, Pavlov First Saint Petersburg State Medical University, Saint Petersburg, Russia. Consensus is intended to define the principal practical steps to resolve the problem of MGRS in Russian Federation that are summarized as final clauses which we present here.

Rationale & Objective Anorexia nervosa is often intractable and induces various physical disorders, including kidney disease and mineral disorders, occasionally progressing to kidney failure. No consensus-based clinical practice guidelines have been established for patients with anorexia nervosa referred to a nephrologist. Study Design Patients with anorexia nervosa–associated kidney disease diagnosed were analyzed retrospectively. Kidney outcomes were defined as doubling of serum creatinine level and/or progression to end-stage kidney disease. Setting & Participants Patients with a history of anorexia nervosa with kidney disease, including electrolyte abnormalities, who were referred to our hospital between 1992 and 2017 were included. Results 14 female patients were included. The time from anorexia nervosa onset to the initial visit with a nephrologist was 17.8 years. At the first visit, median body mass index was 13.4kg/m2, median serum creatinine level was 1.9mg/dL, and median serum potassium level was 2.7mmol/L. All patients showed hypokalemia and addictive vomiting or diuretic/laxative abuse. During the median observation period of 3.1 years, kidney outcomes occurred in 9 patients, and 2 died due to their anorexia nervosa. 4 patients underwent kidney biopsy. The kidney biopsy findings of these patients included hypertrophy of the juxtaglomerular apparatus, advanced glomerular collapse, and interstitial fibrosis, consistent with ischemic kidney injury and hypokalemic nephropathy. Limitations The sample size was small, and kidney function was assessed based on serum creatinine levels in patients with anorexia nervosa with low muscle mass. Conclusions Most patients with anorexia nervosa referred to nephrologists had kidney disease at the time of the first visit. Improving kidney outcomes of patients with anorexia nervosa may require earlier collaboration between psychiatrists and nephrologists.