COVID-19-Associated Collapsing Glomerulopathy: An Emerging Entity

COVID-19-Associated Acute Kidney Injury and Longitudinal Kidney Outcomes

Importance

COVID-19 infection is associated with a high incidence of acute kidney injury (AKI). Although rapid kidney function decline has been reported in the first few months after COVID-19-associated AKI (COVID-AKI), the longer-term association of COVID-AKI with kidney function remains unknown.

Objective

To assess long-term kidney outcomes of patients who had COVID-19-associated AKI.

Design, Setting, and Participants

This was a retrospective longitudinal multicenter cohort study conducted in a large hospital system using electronic health records data on adult hospitalized patients with AKI and COVID-19 or other illnesses. Included patients were hospitalized during the COVID-19 pandemic (March 2020-June 2022), were screened for SARS-CoV-2, had AKI, and survived to discharge, or had been hospitalized during the 5 years before the pandemic (October 2016-January 2020), had a positive influenza A or B test result, had AKI, and survived to discharge. Patients were followed up for a maximum of 2 years after hospital discharge. Data analyses were performed from December 2022 to November 2023.

Exposure

COVID-19 and influenza.

Main Outcomes and Measures

The primary outcome was major adverse kidney events (MAKE), defined as a composite of mortality and worsened kidney function (estimated glomerular filtration rate [eGFR] decline by ≥25% from discharge eGFR or kidney failure requiring dialysis). Multivariable time-to-event analyses were performed to compare MAKE between individuals with COVID-AKI and those who had AKI associated with other illnesses hospitalized during the same period. For further comparison, this outcome was assessed for a historic cohort of patients with influenza-associated AKI.

Results

The study cohort included 9624 hospitalized patients (mean [SD] age, 69.0 [15.7] years; 4955 [51.5%] females) with AKI, including 987 patients with COVID-AKI, 276 with influenza-associated AKI, and 8361 with AKI associated with other illnesses (other-AKI). Compared with the other 2 groups, patients with COVID-19-associated AKI were slightly younger in age, had a higher baseline eGFR, worse baseline comorbidity scores, higher markers of illness severity, and longer hospital stay. Compared with the other-AKI group, the COVID-AKI group had lower MAKE (adjusted hazard ratio [aHR], 0.67; 95% CI, 0.59-0.75) due to lower all-cause mortality (aHR, 0.31; 95% CI, 0.24-0.39) and lower rates of worsened kidney function (aHR, 0.78; 95% CI, 0.69-0.88).

Conclusions and Relevance

The findings of this multicenter cohort study indicate that survivors of hospitalization with COVID-AKI experience lower rates of MAKE, long-term kidney function decline, and mortality compared with patients with AKI associated with other illnesses.

Implementation and Feasibility of Clinical Genome Sequencing Embedded Into the Outpatient Nephrology Care for Patients With Proteinuric Kidney Disease

Introduction

The diagnosis and management of proteinuric kidney diseases such as focal segmental glomerulosclerosis (FSGS) are challenging. Genetics holds the promise to improve clinical decision making for these diseases; however, it is often performed too late to enable timely clinical action and it is not implemented within routine outpatient nephrology visits.

Methods

We sought to test the implementation and feasibility of clinical rapid genome sequencing (GS) in guiding decision making in patients with proteinuric kidney disease in real-time and embedded in the outpatient nephrology setting.

Results

We enrolled 10 children or young adults with biopsy-proven FSGS (9 cases) or minimal change disease (1 case). The mean age at enrollment was 16.2 years (range 2-30). The workflow did not require referral to external genetics clinics but was conducted entirely during the nephrology standard-of-care appointments. The total turn-around-time from enrollment to return-of-results and clinical decision averaged 21.8 days (12.4 for GS), which is well within a time frame that allows clinically relevant treatment decisions. A monogenic or APOL1-related form of kidney disease was diagnosed in 5 of 10 patients. The genetic findings resulted in a rectified diagnosis in 6 patients. Both positive and negative GS findings determined a change in pharmacological treatment. In 3 patients, the results were instrumental for transplant evaluation, donor selection, and the immunosuppressive treatment. All patients and families received genetic counseling.

Conclusion

Clinical GS is feasible and can be implemented in real-time in the outpatient care to help guiding clinical management. Additional studies are needed to confirm the cost-effectiveness and broader utility of clinical GS across the phenotypic and demographic spectrum of kidney diseases.

COVID-19-Associated Nephropathy: A Devastating Complication

With the rapid emergence and prevalence of SARS-CoV-2 worldwide, cases of COVID-19-associated nephropathy (COVAN) from collapsing focal segmental glomerulosclerosis (cFSGS) have been reported, and the associations between the two are actively being studied. Creating appropriate treatment guidelines for COVAN requires further understanding of the pathophysiology of this type of kidney injury. This case report outlines the case of a 77-year-old patient admitted to the hospital for COVID-19 infection with a subsequent renal biopsy indicating cFSGS, adding to the data exploring the relationship between COVID-19 infections, cFSGS and the associated risk factors. Current guidelines on the treatment of COVAN are similar to those of other causes of cFSGS but continue to have poor outcomes and resistance to treatments. Further research needs to be done on both the clinical assessment and pathophysiology of COVAN to provide timely and life-saving interventions.

Kidney Injury in Critically Ill Patients with COVID-19 - From Pathophysiological Mechanisms to a Personalized Therapeutic Model

Acute kidney injury is a common complication of COVID-19, frequently fuelled by a complex interplay of factors. These include tubular injury and three primary drivers of cardiocirculatory instability: heart-lung interaction abnormalities, myocardial damage, and disturbances in fluid balance. Further complicating this dynamic, renal vulnerability to a "second-hit" injury, like a SARS-CoV-2 infection, is heightened by advanced age, chronic kidney disease, cardiovascular diseases, and diabetes mellitus. Moreover, the influence of chronic treatment protocols, which may constrain the compensatory intrarenal hemodynamic mechanisms, warrants equal consideration. COVID-19-associated acute kidney injury not only escalates mortality rates but also significantly affects long-term kidney function recovery, particularly in severe instances. Thus, the imperative lies in developing and applying therapeutic strategies capable of warding off acute kidney injury and decelerating the transition into chronic kidney disease after an acute event. This narrative review aims to proffer a flexible diagnostic and therapeutic strategy that recognizes the multi-faceted nature of COVID-19-associated acute kidney injury in critically ill patients and underlines the crucial role of a tailored, overarching hemodynamic and respiratory framework in managing this complex clinical condition.

Diagnosis of Chronic Kidney Disease and Assessing Glomerular Filtration Rate

Chronic kidney disease (CKD) is a silent progressive disease. It is diagnosed by assessing filtration and markers of kidney damage such as albuminuria. The diagnosis of CKD should include not only assessing the glomerular filtration rate (GFR) and albuminuria but also the cause. The CKD care plan should include documentation of the trajectory and prognosis. The use of a combination of serum cystatin C and creatinine concentration offers a more accurate estimation of GFR. Social determinants of health are important to address as part of the diagnosis because they contribute to CKD disparities.

Coronavirus disease 2019-associated nephropathy in an African American patient: a case report and review of the literature

BACKGROUND

Acute kidney injury is now recognized as a common complication of coronavirus disease 2019, affecting up to 46% of patients, with acute tubular injury as the most common etiology. Recently, we have seen an increase in cases of collapsing glomerulonephritis in patients with coronavirus disease 2019, also known as coronavirus disease 2019-associated nephropathy. It has been noted to be seen with a higher incidence in African American patients who are carriers of the APOL1 variant allele.

CASE PRESENTATION

A 47-year-old African American male with a past medical history of asthma presented to the emergency department with complaints of intermittent chest pain, shortness of breath, and worsening confusion. On admission, he was found to be hemodynamically stable, but labs were significant for elevated creatinine and blood urea nitrogen, signifying acute kidney injury. He was admitted and taken for emergent dialysis. During his hospitalization, he was found to be positive for coronavirus disease 2019. Renal biopsy was done, which showed collapsing glomerulopathy, and the patient continues to require outpatient dialysis after discharge.

CONCLUSION

Collapsing glomerulonephritis has emerged as a complication in patients with coronavirus disease 2019. This condition should be particularly suspected in African American patients who present with acute kidney injury, nephrotic-range proteinuria, and who are positive for coronavirus disease 2019. Current treatment options are limited to supportive treatment and renal replacement therapy. More clinical cases and trials are needed to better understand and improve therapeutic outcomes in these patients.

Sarcoid-like Uveitis with or without Tubulointerstitial Nephritis during COVID-19

PURPOSE

To report sarcoid-like uveitis with or without tubulointerstitial nephritis (TIN) during coronavirus disease 2019 (COVID-19) and to discuss diagnostic evaluation and treatment.

METHODS

Detailed information on the subject's demographics, medical history, ophthalmic examination findings, and laboratory results were obtained from medical records. Fluorescein angiography (FA) and indocyanine green angiography (ICGA) images were evaluated.

RESULTS

All seven patients aged between 8 and 17 had bilateral granulomatous panuveitis. TIN preceded in four patients. Thorax computed tomography of patient 1 was found to be compatible with COVID-19, patients 2 and 3 were in contact with Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) positive parents, patients 4 and 5 were found to be SARS-CoV-2 PCR positive, and patients 6 and 7 were positive for SARS-CoV-2 IgG antibodies. ICGA revealed hypofluorescent dots in six patients. Intraocular inflammation was controlled with corticosteroid and/or immunomodulatory therapy. Visual acuity was maintained or improved in all.

CONCLUSION

SARS-CoV-2 infection may be related to sarcoid-like uveitis and acute tubulointerstitial nephritis.

A Case of COVID-19-Associated Focal Segmental Glomerulosclerosis

This case report details a 43-year-old female diagnosed with the collapsing variant of focal segmental glomerulosclerosis (FSGS) post-infection with coronavirus disease 2019 (COVID-19). The patient contracted COVID-19 after returning from a trip to Florida and initially presented to the emergency department with gastrointestinal symptoms. Thereafter, the patient was diagnosed with COVID-19 and was admitted for acute kidney injury and worsening COVID-19 infection. FSGS is a glomerulopathy that consists of glomerular scarring that leads to nephrotic syndrome, secondary to podocyte effacement. FSGS has many causes, as well as distinct variants, but is noted to have an association with some viruses, most notably HIV and cytomegalovirus (CMV). Although the association between FSGS and HIV or CMV is well established, the evidence is minimal in regard to other viruses. This case report serves to highlight the potential association of COVID-19 with FSGS.

Targeting TLR-4 Signaling to Treat COVID-19-induced Acute Kidney Injury

The newly discovered severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) has turned into a potentially fatal pandemic illness. Numerous acute kidney injury (AKI) cases have been reported, although diffuse alveolar destruction and acute respiratory failure are the major symptoms of SARS-CoV-2 infection. The AKI, often known as a sudden loss of kidney function, carries a greater risk of mortality and morbidity. AKI was the second most frequent cause of death after acute respiratory distress syndrome (ARDS) in critically ill patients with coronavirus disease 2019 (COVID-19). While most patients with COVID-19 have moderate symptoms, some have severe symptoms, such as septic shock and ARDS. Also, it has been proven that some patients have severe symptoms, such as the failure of several organs. The kidneys are often affected either directly or indirectly. The major signs of kidney involvement are proteinuria and AKI. It is hypothesized that multiple mechanisms contribute to kidney injury in COVID-19. Direct infection of podocytes and proximal tubular cells in the kidneys may lead to acute tubular necrosis and collapsing glomerulopathy. SARS-CoV2 may also trigger a cascade of immunological responses that lead to AKI, including cytokine storm (CS), macrophage activation syndrome, and Toll-like receptor type-4 activation (TLR-4). Other proposed processes of AKI include interactions between organs, endothelial failure, hypercoagulability, rhabdomyolysis, and sepsis.

Furthermore, ischemic damage to the kidney might result from the decreased oxygen supply. This article focuses on kidney injury’s epidemiology, etiology, and pathophysiological processes. Specifically, it focuses on the CS and the role of TLR-4 in this process. To effectively manage and treat acute kidney damage and AKI in COVID-19, it is crucial to understand the underlying molecular pathways and pathophysiology.

Diffuse proliferative glomerulonephritis in a patient with COVID-19 infection

COVID-19 primarily presents with respiratory involvement. Extrapulmonary manifestations as the sole manifestation also occur although rare. The kidney, being one of the organs with the greatest number of ACE receptors, is usually reported as part of multiorgan involvement. We report an early adolescent boy who presented with nephrotic-nephritic syndrome with severe kidney dysfunction from COVID-19 infection. He had low C3 and undetected antineutrophil cytoplasmic antibodies, antinuclear antibody and antistreptolysin O. Kidney biopsy revealed findings consistent with diffuse proliferative glomerulonephritis with a focal glomerular crescent formation and thin basement nephropathy. Due to the rapidly progressive deterioration of kidney function, he was given pulse methylprednisolone therapy followed by oral prednisone. Complete recovery was documented 12 weeks after the onset of post-infectious glomerulonephritis. The possible pathogenesis of glomerulonephritis in a patient with COVID-19, its differential diagnosis and treatment are discussed.

Pathogenesis and histological changes of nephropathy associated with COVID-19

Coronavirus disease 2019 (COVID-19) can cause damage to multiple organ, not only to the lungs, but also to the kidneys. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can cause acute and chronic kidney disease through direct viral infection, indirect injury, and vaccination-related injury. Like lung injury, kidney injury is also an important aspect affecting the severity and prognosis of SARS-CoV-2. This article summarizes the pathogenesis, pathological manifestations, and clinical features of SARS-CoV-2 direct or indirect renal injury. Including direct injury, indirect injury, special comorbidities (receiving kidney transplantation and chronic kidney disease), and vaccine-related renal injury, and exploring the possible therapeutic effect of anti-SARS-CoV-2 therapy on renal injury. The purpose is to provide reference for understanding COVID-19-related renal injury, guiding clinical and pathological diagnosis and treatment, and evaluating prognosis.

Severe COVID-19 in 2 Kidney Transplant Patients in Gabon

BACKGROUND Kidney failure is a public health problem that may require transplantation for patient survival and for those at risk of developing infectious diseases such as COVID-19 due to severe immunosuppression. We report the case of 2 kidney transplant patients who contracted COVID-19. CASE REPORT Patient 1: A 60-year-old Gabonese man presented with 8 days of wet cough, fever, and myalgias associated secondarily with dyspnea, without anosmia or ageusia. His medical history included renal transplant for malignant nephro-angiosclerosis and high blood pressure. The oxygen saturation level subsequently fell to 89-90%. The diagnosis of acute hypoxic respiratory failure secondary to COVID-19 pneumonia with heart and acute renal failure on renal transplant was made based on clinical symptoms, lung imaging results, and a positive SARS-CoV-2 nasal swab PCR test. Patient 2: A 79-year-old Gabonese man presented with 10 days of dry cough associated with intermittent fevers not quantified, anorexia, and fatigue. The patient's medical history was high blood pressure, diabetes mellitus, and renal transplantation. Oxygen saturation level decreased to 85-89% in ambient air. Clinical signs and chest CT scan showed 70% lung lesions with large areas of ground-glass opacity with essentially peripheral distribution of both lungs associated with crazy paving, condensation, bronchiectasis, and arterial dilatation, suggesting severe COVID-19. CONCLUSIONS Those 2 presentations highlight the fact that a severe clinical form of COVID-19 associated with acute renal failure and kidney transplant can be fatal. Kidney transplantation is a risk factor for poor prognosis in patients with severe COVID-19 and greatly worsens the mortality rate of immunocompromised patients.

Is the Use of Dialysis Associated With an Increased Risk of Death in COVID-19-Related Acute Kidney Injury?

INTRODUCTION

Acute kidney injury (AKI) is frequently reported in the setting of severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2) infection. The aim of our work is to evaluate the impact of acute dialysis use on mortality in patients with AKI during the coronavirus disease 2019 (COVID-19) pandemic.

METHODS

This is a retrospective study conducted in the Hassan II University Hospital of Fez, Morocco. From July 2020 to December 2021, we included all patients admitted to a COVID-19 unit with acute kidney injury defined according to Kidney Disease Improvement Global Outcomes 2012 (KDIGO 2012) criteria. Our patients were older than 18 years, and SARS-CoV-2 infection was confirmed by a positive RT-PCR test or thoracic CT scan imaging. Patients with end-stage renal disease (ESRD) and pregnant women were excluded from our study.

RESULTS

The total number of patients hospitalized in the COVID-19 unit during the study period was 2560, including 206 in an intensive care setting. We included 61 patients with AKI, with an incidence in the intensive care unit (ICU) setting of 15.5%. Eighty percent of patients had respiratory distress on admission, which was the main reason for consultation. Stage 1 AKI was found in 1.6% of patients, 25.8% had stage II AKI, and 72.6% had KDIGO stage 3 AKI. The main etiology of AKI was acute tubular necrosis. Lung involvement secondary to infection was severe in 18 patients; 21 had moderate involvement. In our study, twenty-one of our patients (34.4%) were hospitalized in an ICU. Thirteen of our patients were intubated (21.1%). Twenty-one (34.4%) patients were hemodynamically unstable and were put on vasoactive drugs. Twenty-three (37.7%) of our patients received at least one session of conventional acute hemodialysis with an average duration of 2.1 hours ± 0.9 (1-3.5). The indication was overload (27%), severe metabolic acidosis (1.6%), threatening hyperkalemia (1.6%), and symptomatic hyperuremia (62%). The evolution was marked by a return to baseline renal function in two patients, partial improvement in 35 of them at discharge, and no improvement in 24 patients. We recorded a death rate of 34.4% (n=21). In a univariate analysis, we compared the demographic, clinical, paraclinical, and dialytic characteristics of the dialysis and non-dialysis groups. There was a significant difference between unstable, intubated patients and those hospitalized in the ICU in the dialysis group, with respective p-values of p=0.0001, p=0.0001, and p=0.01. We noticed there were more deaths in the dialysis group than in the non-dialysis group; this difference was statistically significant with a p-value of 0.005. In multivariate analysis, a logistic regression model was performed to test the relationship between dialysis and COVID-19 mortality while adjusting for other co-factors. The final model did not show a significant association between dialysis and mortality (p = 0.150, OR: 2.578 [0.710-9.364]). The only factor that remained independently significant was admission to the intensive care unit (p = 0.004, OR: 6.732 [1.847-24.540]).

CONCLUSION

AKI is a frequently encountered complication in patients with COVID-19, especially those hospitalized in the ICU. In the context of the SARS-CoV-2 infection, the use of at least one dialysis session seems to represent an excess risk of mortality related to AKI.

ANCA-associated vasculitis flare might be provoked by COVID-19 infection: a case report and a review of the literature

Mesangial immunoglobulin A (IgA) deposition is the hallmark of IgA nephropathy (IgAN). In some cases, crescentic involvement that might be associated with systemic leucocytoclastic vasculitis is documented. In such cases, the disease is called Henoch-Schönlein purpura (IgA vasculitis). Even more rarely, the coexistence of IgAN and anti-neutrophil cytoplasmic antibody (ANCA) seropositivity has been reported. IgAN might be complicated by acute kidney injury (AKI) due to different causes. Herein we present a patient with mesangial IgA deposition and ANCA seropositivity who developed AKI, haematuria and haemoptysis during the course of coronavirus disease 2019 (COVID-19) disease and was diagnosed with ANCA-associated vasculitis based on clinical, laboratory and radiological findings. The patient was treated successfully with immunosuppressive therapy. We also made a systematic review of the literature to reveal and present the cases with COVID-19 and ANCA-associated vasculitis.

Pathogenic Role of MicroRNA Dysregulation in Podocytopathies

MicroRNAs (miRNAs) participate in the regulation of various important biological processes by regulating the expression of various genes at the post-transcriptional level. Podocytopathies are a series of renal diseases in which direct or indirect damage of podocytes results in proteinuria or nephrotic syndrome. Despite decades of research, the exact pathogenesis of podocytopathies remains incompletely understood and effective therapies are still lacking. An increasing body of evidence has revealed a critical role of miRNAs dysregulation in the onset and progression of podocytopathies. Moreover, several lines of research aimed at improving common podocytopathies diagnostic tools and avoiding invasive kidney biopsies have also identified circulating and urine miRNAs as possible diagnostic and prognostic biomarkers for podocytopathies. The present review mainly aims to provide an updated overview of the recent achievements in research on the potential applicability of miRNAs involved in renal disorders related to podocyte dysfunction by laying particular emphasis on focal segmental glomerulosclerosis (FSGS), minimal change disease (MCD), membranous nephropathy (MN), diabetic kidney disease (DKD) and IgA nephropathy (IgAN). Further investigation into these dysregulated miRNAs will not only generate novel insights into the mechanisms of podocytopathies, but also might yield novel strategies for the diagnosis and therapy of this disease.

A critical role of the podocyte cytoskeleton in the pathogenesis of glomerular proteinuria and autoimmune podocytopathies

Selective glomerular filtration relies on the membrane separating the glomerular arterioles from the Bowman space. As a major component of the glomerular filtration barrier, podocytes form foot processes by the actin cytoskeleton, which dynamically adjusts in response to environmental changes to maintain filtration barrier integrity. The slit diaphragms bridge the filtration slits between neighboring foot processes and act as signaling hubs interacting with the actin cytoskeleton. Focal adhesions relay signals to regulate actin dynamics while allowing podocyte adherence to the basement membrane. Mutations in actin regulatory and signaling proteins may disrupt the actin cytoskeleton, resulting in foot process retraction, effacement, and proteinuria. Large-scale gene expression profiling platforms, transgenic animal models, and other in vivo gene delivery methods now enhance our understanding of the interactions among podocyte focal adhesions, slit diaphragms, and actin dynamics. In addition, our team found that at least 66% of idiopathic nephrotic syndrome (INS) children have podocyte autoantibodies, which was defined as a new disease subgroup-, autoimmune podocytopathies. This review outlines the pathophysiological mechanisms of podocyte cytoskeleton protein interactions in proteinuria and glomerular podocytopathy.

Nephrinuria and podocytopathies

The discovery of nephrin in 1998 has launched a new era in glomerular diseases research, emphasizing its crucial role in the structure and function of the glomerular filtration barrier. In the past 20 years, substantial advances have been made in understanding podocyte structure and function as well as the discovery of several podocyte-related proteins including nephrin. The glomerular filtration barrier is comprised of podocytes, the glomerular basement membrane and endothelial cells. Podocytes, with their specialized slit diaphragm, form the essential backbone of the glomerular filtration barrier. Nephrin is a crucial structural and functional feature of the slit diaphragm that prevents plasma protein, blood cell and macromolecule leakage into the urine. Podocyte damage results in nephrin release. Podocytopathies are kidney diseases in which podocyte damage drives proteinuria, i.e., nephrotic syndrome. Many kidney diseases involve podocytopathy including congenital nephrotic syndrome of Finnish type, diffuse mesangial sclerosis, minimal change disease, focal segmental glomerulosclerosis, collapsing glomerulonephropathy, diabetic nephropathy, lupus nephropathy, hypertensive nephropathy and preeclampsia. Recently, urinary nephrin measurement has become important in the early detection of podocytopathies. In this chapter, we elaborate the main structural and functional features of nephrin as a podocyte-specific protein, pathomechanisms of podocytopathies which result in nephrinuria, highlight the most commonly used methods for detecting urinary nephrin and investigate the diagnostic, prognostic and potential therapeutic relevance of urinary nephrin in primary and secondary proteinuric kidney diseases.

ScoMorphoFISH: A deep learning enabled toolbox for single-cell single-mRNA quantification and correlative (ultra-)morphometry

Increasing the information depth of single kidney biopsies can improve diagnostic precision, personalized medicine and accelerate basic kidney research. Until now, information on mRNA abundance and morphologic analysis has been obtained from different samples, missing out on the spatial context and single‐cell correlation of findings. Herein, we present scoMorphoFISH, a modular toolbox to obtain spatial single‐cell single‐mRNA expression data from routinely generated kidney biopsies. Deep learning was used to virtually dissect tissue sections in tissue compartments and cell types to which single‐cell expression data were assigned. Furthermore, we show correlative and spatial single‐cell expression quantification with super‐resolved podocyte foot process morphometry. In contrast to bulk analysis methods, this approach will help to identify local transcription changes even in less frequent kidney cell types on a spatial single‐cell level with single‐mRNA resolution. Using this method, we demonstrate that ACE2 can be locally upregulated in podocytes upon injury. In a patient suffering from COVID‐19‐associated collapsing FSGS, ACE2 expression levels were correlated with intracellular SARS‐CoV‐2 abundance. As this method performs well with standard formalin‐fixed paraffin‐embedded samples and we provide pretrained deep learning networks embedded in a comprehensive image analysis workflow, this method can be applied immediately in a variety of settings.

Acute Kidney Injury in Critically-Ill COVID-19 Patients

Purpose: Acute kidney injury (AKI) is common in patients with COVID-19, however, its mechanism is still controversial, particularly in ICU settings. Urinary proteinuria profile could be a non-invasive tool of interest to scrutinize the pathophysiological process underlying AKI in COVID-19 patients. Material and Methods: We conducted a retrospective study between March 2020 and April 2020. All patients with laboratory-confirmed COVID-19 and without end-stage kidney disease requiring renal replacement therapy before ICU admission were included. Our objectives were to assess the incidence and risk factors for AKI and to describe its clinical and biological characteristics, particularly its urinary protein profile. Results: Seventy patients were included; 87% needed mechanical ventilation and 61% needed vasopressor during their ICU stay; 64.3% of patients developed AKI and half of them needed dialysis. Total and tubular proteinuria on day 1 were higher in patients with AKI, whereas glomerular proteinuria was similar in both groups. The main risk factor for AKI was shock at admission (OR = 5.47 (1.74−17.2), p < 0.01). Mortality on day 28 was higher in AKI (23/45, 51.1%) than in no-AKI patients (1/25, 4%), p < 0.001. Risk factors for 28-days mortality were AKI with need for renal replacement therapy, non-renal SOFA score and history of congestive heart failure. Conclusions: AKI is common in COVID-19 patients hospitalized in ICU; it seems to be related to tubular lesions rather than glomerular injury and is related to shock at ICU admission.

Post-acute COVID-19 syndrome and kidney diseases: what do we know?

COVID-19, a disease caused by a novel coronavirus (SARS-CoV-2), is a major global threat that has turned into a pandemic. Despite the emergence of multiple vaccination alternatives and developing therapeutic options, dramatic short- and long-term clinical outcomes have been recorded with more than 250 million infected people and over 5 million deaths as of November 2021. COVID-19 presents various respiratory, cardiovascular, neuropsychiatric, musculoskeletal and kidney features during the acute phase; nevertheless, renal involvement in the post-infection period has recently been emphasized. The present review aims to evaluate the growing literature on kidney involvement in the SARS-CoV-2 infection along with clinical features reported both in the acute phase of the infection and in the post-acute COVID-19 period by assessing potential pathophysiological frameworks explaining such conditions. Chronic kidney disease and development of acute kidney injury (AKI) in the course of initial hospitalization are associated with high mortality and morbidity rates. Moreover, growing evidence suggests a decline in renal function in the 6-to-12-month follow-up period even in patients without any signs of AKI during the acute phase. Despite such concerns there are no guidelines regulating the follow-up period or therapeutic alternatives for such patient population. In conclusion, the burden of COVID-19 on the kidney is yet to be determined. Future prospective large scale studies are needed with long follow-up periods assessing kidney involvement via multiple parameters such as biopsy studies, urinalysis, measurement of serum creatinine and cystatin C, directly measured glomerular filtration rate, and assessment of tubular function via urinary β²-microglobulin measurements.

Collapsing Glomerulopathy: A Review by the Collapsing Brazilian Consortium

Collapsing glomerulopathy (CG) is a clinicopathologic entity characterized by segmentar or global collapse of the glomerulus and hypertrophy and hyperplasia of podocytes. The Columbia classification of 2004 classified CG as a histological subtype of focal segmental glomerulosclerosis (FSGS). A growing number of studies have demonstrated a high prevalence of CG in many countries, especially among populations with a higher proportion of people with African descent. The present study is a narrative review of articles extracted from PubMed, Medline, and Scielo databases from September 1, 2020 to December 31, 2021. We have focused on populational studies (specially cross-sectional and cohort articles). CG is defined as a podocytopathy with a distinct pathogenesis characterized by strong podocyte proliferative activity. The most significant risk factors for CG include APOL1 gene mutations and infections with human immunodeficiency virus and severe acute respiratory syndrome coronavirus 2. CG typically presents with more severe symptoms and greater renal damage. The prognosis is notably worse than that of other FSGS subtypes.

COVID-19 in patients with glomerular disease

PURPOSE OF REVIEW

Managing patients with glomerular disease during the COVID-19 pandemic has been challenging, as the infection risk associated with immunosuppression must be balanced against the need to control severe glomerular disease that can lead to kidney failure. This review provides an overview of COVID-19 and the effectiveness of SARS-CoV-2 vaccination in patients with glomerular disease.

RECENT FINDINGS

Registry data, although biased towards outcomes of hospitalized patients, suggest that the mortality from COVID-19 is higher in patients with glomerular disease than in the general population. Glucocorticoid use prior to SARS-CoV-2 infection is associated with adverse outcomes from COVID-19. Rituximab significantly attenuates serological responses to both natural infection and vaccination against SARS-CoV-2, although it is not clear whether this leads to adverse outcomes. Case reports of disease flares occurring after vaccination have been reported, but causality in any of these cases has yet to be proven and the absolute risk remains very small.

SUMMARY

Patients with glomerular disease represent an at-risk group for severe COVID-19 disease and vaccination is key to reducing this risk. As immunosuppressed patients demonstrate an attenuated response to vaccination, the efficacy of a third primary dose followed by a subsequent booster is being investigated.

Spectrum of Kidney Injury Following COVID-19 Disease: Renal Biopsy Findings in a Single Italian Pathology Service

The onset of coronavirus disease (COVID-19) as a pandemic infection, has led to increasing insights on its pathophysiology and clinical features being revealed, such as a noticeable kidney involvement. In this study, we describe the histopathological, immunofluorescence, and ultrastructural features of biopsy-proven kidney injury observed in a series of SARS-CoV-2 positive cases in our institution from April 2020 to November 2021. We retrieved and retrospectively reviewed nine cases (two pediatric and seven adults) that experienced nephrotic syndrome (six cases), acute kidney injury (two cases), and a clinically silent microhematuria and leukocyturia. Kidney biopsies were investigated by means of light microscopy, direct immunofluorescence, and electron microscopy. The primary diagnoses were minimal change disease (four cases), acute tubular necrosis (two cases), collapsing glomerulopathy (two cases), and C3 glomerulopathy (one case). None of the cases showed viral or viral-like particles on ultrastructural analysis. Novel and specific histologic features on kidney biopsy related to SARS-CoV-2 infection have been gradually disclosed and reported, harboring relevant clinical and therapeutic implications. Recognizing and properly diagnosing renal involvement in patients experiencing COVID-19 could be challenging (due to the lack of direct proof of viral infection, e.g., viral particles) and requires a proper integration of clinical and pathological data.

Similarities and Differences between COVID-19-Associated Nephropathy and HIV-Associated Nephropathy

Kidney disease is a major complication of viral infection, which can cause both acute and chronic kidney diseases via different mechanisms such as immune-mediated injury, kidney cell injury from a direct viral infection, systemic effects, and antiviral drug-induced nephrotoxicity. HIV-associated nephropathy (HIVAN), characterized by collapsing focal segmental glomerulosclerosis (cFSGS), has been described 2 decades ago as a major complication of acquired-immunodeficiency syndrome. The pathogenesis of HIVAN has been well studied, including viral entry, host response, and genetic factors. The incidence of this disease has been dramatically dropped with current antiretroviral therapy. In the recent severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) pandemic, acute kidney injury was also found to be a major complication in patients with (coronavirus disease) COVID-19. These patients also developed glomerular disease such as cFSGS in African Americans with apolipoprotein L1 risk alleles, similar to HIVAN. Whether SARS-CoV-2 can infect kidney cells locally remains controversial, but both local infection and systemic effects are likely involved in the pathogenesis of this disease. In this review, we present a comparison of the clinical presentations, pathological findings, disease mechanisms, and potential treatments between HIVAN and COVID-19. Leveraging the knowledge in HIVAN and experimental approaches used to study HIVAN will facilitate the exploration in the pathogenesis of COVID-19-associated kidney disease and improve our management of COVID-19 patients.

GWAS in Mice Maps Susceptibility to HIV-Associated Nephropathy to the Ssbp2 Locus

BACKGROUND

To gain insight into the pathogenesis of collapsing glomerulopathy, a rare form of FSGS that often arises in the setting of viral infections, we performed a genome-wide association study (GWAS) among inbred mouse strains using a murine model of HIV-1 associated nephropathy (HIVAN).

METHODS

We first generated F1 hybrids between HIV-1 transgenic mice on the FVB/NJ background and 20 inbred laboratory strains. Analysis of histology, BUN, and urinary NGAL demonstrated marked phenotypic variation among the transgenic F1 hybrids, providing strong evidence for host genetic factors in the predisposition to nephropathy. A GWAS in 365 transgenic F1 hybrids generated from these 20 inbred strains was performed.

RESULTS

We identified a genome-wide significant locus on chromosome 13-C3 and multiple additional suggestive loci. Crossannotation of the Chr. 13 locus, including single-cell transcriptomic analysis of wildtype and HIV-1 transgenic mouse kidneys, nominated Ssbp2 as the most likely candidate gene. Ssbp2 is highly expressed in podocytes, encodes a transcriptional cofactor that interacts with LDB1 and LMX1B, which are both previously implicated in FSGS. Consistent with these data, older Ssbp2 null mice spontaneously develop glomerulosclerosis, tubular casts, interstitial fibrosis, and inflammation, similar to the HIVAN mouse model.

CONCLUSIONS

These findings demonstrate the utility of GWAS in mice to uncover host genetic factors for rare kidney traits and suggest Ssbp2 as susceptibility gene for HIVAN, potentially acting via the LDB1-LMX1B transcriptional network.

De Novo Minimal Change Disease following Vaccination with the Pfizer/BioNTech SARS-CoV-2 Vaccine in a Living Kidney Donor

Coronavirus disease 2019 has developed as a pandemic. Immunization with the introduction of vaccines against COVID-19 seems be the only way to end this pandemic. We report on a case of a kidney donor, who developed minimal change disease (MCD) within 4 days post-vaccination with the SARS-CoV-2 BNT162b2 mRNA vaccine (Pfizer/BioNTech). She donated her kidney to her husband 4 years ago. After receiving the 1st vaccine dose, she presented with nephrotic syndrome, with complete remission 5 days later. She proceeded with the second dose of the BNT162b2 vaccine at the appointed time. Two days later, she presented with a relapse of full-blown nephrotic syndrome with preserved renal function. We performed an ultrasound-guided percutaneous kidney biopsy and the final diagnosis was consistent with minimal change disease. Oral prednisolone was promptly initiated at a dosage of 1 mg/kg daily and complete remission was achieved 10 days later. More data about this rare appearance of de novo glomerular diseases after SARS-CoV-2 vaccination are emerging and should be interpreted rigorously.

COVID-19 in End-stage Renal Disease (ESRD) Patients Undergoing Hemodialysis: A Close Follow-up of Clinical Findings and Evolutions in Chest CT Imaging: A Retrospective Study

Background: Coronavirus disease 2019 (COVID-19) has infected millions and caused tens of thousands of casualties. Epidemiologic studies show that specific individuals with pre-existing conditions are prone to severe disease caused by the virus. Thus, it is necessary to determine clinical signs and symptoms and disease progression course in various pre-existing conditions, namely end-stage renal disease (ESRD) patients undergoing hemodialysis. Methods: The present retrospective study was conducted on 17 ESRD patients undergoing chronic hemodialysis. Clinical signs and symptoms were extracted, and laboratory test results and imaging findings were retrieved using the health information systems of the institute where the study was performed. Results: Of 17 patients in the study, six patients were females, and 11 were males. The mean age of the patients was 62.29 ± 15.6 years (22 - 82). The most common pre-existing conditions were hypertension and diabetes. The most common imaging signs were ground-glass opacities. The most common pattern of involvement was peripheral, bilateral, and multifocal involvement, and interestingly, uncommon imaging signs such as crazy-paving, peribronchovascular involvement, and reticulonodular pattern of involvement. The most common laboratory findings were lymphopenia, lymphocytosis, increased erythrocyte sedimentation rate, and positive C reactive protein. Conclusions: ESRD patients undergoing COVID-19 seem to have higher mortalities than the general public and show more significant lung involvement on chest CT imaging. Furthermore, uncommon imaging signs are more common in this group of patients.

Mechanisms of Proteinuria in HIV

Proteinuria is common in the setting of HIV infection, and may reflect comorbid kidney disease, treatment-related nephrotoxicity, and HIV-related glomerular diseases. The mechanisms of podocyte and tubulointerstial injury in HIV-associated nephropathy (HIVAN) have been the subject of intense investigation over the past four decades. The pathologic contributions of viral gene expression, dysregulated innate immune signaling, and ancestry-driven genetic risk modifiers have been explored in sophisticated cellular and whole animal models of disease. These studies provide evidence that injury-induced podocyte dedifferentiation, hyperplasia, cytoskeletal dysregulation, and apoptosis may cause the loss of glomerular filtration barrier integrity and slit diaphragm performance that facilitates proteinuria and tuft collapse in HIVAN. Although the incidence of HIVAN has declined with the introduction of antiretroviral therapy, the collapsing FSGS lesion has been observed in the context of other viral infections and chronic autoimmune disorders, and with the use of interferon-based therapies in genetically susceptible populations. This highlights the fact that the lesion is not specific to HIVAN and that the role of the immune system in aggravating podocyte injury warrants further exploration. This review will summarize our progress in characterizing the molecular mechanisms of podocyte dysfunction in HIVAN and other forms of HIV-associated kidney disease.

COVID-19 and APOL-1 High-Risk Genotype-Associated Collapsing Glomerulonephritis

Coronavirus Disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) primarily affects the lungs and can lead to acute respiratory distress syndrome (ARDS). The ongoing global pandemic has created healthcare and economic crisis for almost every nation of the world. Though primarily affecting the lungs, it has also affected the kidney in various ways including acute kidney injury (AKI), proteinuria, and hematuria. It has been increasingly shown that African American (AA) individuals affected with COVID-19 and presenting with AKI and nephrotic-range proteinuria are very susceptible to focal segmental glomerulosclerosis (FSGS). The APOL-1 gene, associated with the African American population, has been increasingly recognized as a risk factor for FSGS affected with COVID-19. Our case highlights a similar case of COVID-19 in a 65-year-old AA descendant with biopsy-proven FSGS and genetically confirmed APOL-1 alleles.

[Epidemiologic and clinical profile, 90 days survival of incident end stage renal patient in haemodialysis during SARS-CoV2 pandemic: Experience of the General Hospital of Douala]

BACKGROUND

The effect of COVID-19 pandemic on end stage renal disease patient who should initiated dialysis are limited in Sub-Saharan Africa is unknown. We sought to describe the epidemiologic and clinical profile of newly admitted patient in chronic haemodialysis during the COVID-19 pandemic in Cameroon and evaluate their survival between 90days of dialysis initiation.

MATERIAL AND METHOD

We conducted a cohort study of 6months from April to October 2020. End stage renal disease patients newly admitted in the haemodialysis facility of the General Hospital of Douala were included. Patients with confirmed or suspected COVID-19 were identified. Socio-demographic, clinical and biological data at dialysis initiation as well as mortality between the 90days of dialysis initiation were registered.

RESULTS

A total of 57 incident patients were recorded from April to October 2020 with a monthly mean of 9.5 patients. The mean age was 46.95±13.12years. Twenty-four COVID-19 were identified with a frequency of 49% among emergency admission. Pulmonary œdema (79.2% vs. 42.4%; P=0.006) and uremic encephalopathy (83.4% vs. 53.6%; P=0.022) were more common in COVID-19. The overall survival at 90days was 48% with a tendency to poor survival among COVID-19 and patients with low socioeconomic level. In Cox regression, low socioeconomic level increase the risk of instant death by 3.08.

CONCLUSION

SARS-CoV2 seem to increase nephrology emergency and poor survival in haemodialysis at 90days.

ANCA-associated vasculitis after COVID-19

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) are systemic autoimmune diseases that may lead to renal failure due to the infiltration of mononuclear cells and the destruction of small- and medium-sized blood vessels. It has been shown that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) may trigger the presentation or exacerbation of autoimmune diseases. Crescentic glomerulonephritis (GN) has rarely been reported in patients with Coronavirus disease-2019 (COVID-19). We present rare two cases with AAV after a recent diagnosis of COVID-19. The first case was 26-year-old male patient, who was presented with acute kidney injury after COVID-19. Serum creatinine increased and active urine sediment was seen. Serological evaluation showed anti-myeloperoxidase antibody was at a level of 80.6 U/mL. Kidney biopsy showed necrotizing GN with cellular crescents. Methylprednisolone, cyclophosphamide and plasma exchange were administered. He was discharged with hemodialysis. Second case was a 36-year-old female who was hospitalized because of fever, cough and dyspnea. After she was diagnosed with COVID-19, she had total hearing loss, with cavitary lesions on bilateral lung parenchyma and an acute kidney injury. Serological evaluation showed an elevated anti-proteinase-3 with a level of 1:32. Kidney biopsy showed necrotizing GN with cellular crescents. Renal function improved after methylprednisolone and cyclophosphamide treatment. With a systematic review of the literature, we found four cases of new-onset AAV due to COVID-19. Herein, we discuss two cases and provide a literature review on cases of new-onset pauci-immune GN after COVID-19 infection.

Pathological diagnosis of Coronavirus-related nephropathy: insight from postmortem studies

A novel coronavirus pneumonia first occurred in Wuhan, China in early December 2019; the causative agent was identified and named as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) by the World Health Organization (WHO), and the resulting disease termed coronavirus disease 2019 (COVID-19), according to the WHO coronavirus disease situation reports. This condition has spread rapidly all over the world and caused more than 125 million cases globally, with more than 2 million related deaths. Two previous outbreaks due to zoonotic coronaviruses have occurred in the last 20 years, namely the severe acute respiratory syndrome coronavirus (SARS-CoV) and the Middle East respiratory syndrome coronavirus (MERS-CoV), causing high morbidity and mortality in human populations upon crossing the species barriers. SARS-CoV-2, SARS-CoV, and MERS-CoV show several similarities in pathogenicity and clinical presentations, the latter ranging from asymptomatic infection to severe acute respiratory distress syndrome (ARDS) and multiorgan impairment. Acute kidney injury (AKI) has been commonly reported in patients with CoV infections; therefore, pathological analysis of renal parenchyma in these patients has been carried out in order to improve knowledge about underlying mechanisms. Viral infection has been demonstrated in the renal tubular epithelial cells by electron microscopy (EM), immunohistochemistry (IHC), and in situ hybridization (ISH), although with conflicting results. Light microscopy (LM) changes have been described in the renal parenchyma primarily in the form of acute renal tubular damage, possibly due to direct viral cytopathic effect and immune-mediated mechanisms such as cytokine storm syndrome. In this review, we describe and discuss the spectrum of histological, ultrastructural, and molecular findings in SARS-CoV, MERS-CoV, and SARS-CoV-2-related renal pathology obtained from postmortem studies, as well as intrinsic limitations and pitfalls of current diagnostic techniques.

Pathophysiology and Clinical Manifestations of COVID-19-Related Acute Kidney Injury-The Current State of Knowledge and Future Perspectives

The continually evolving severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has resulted in a vast number of either acute or chronic medical impairments of a pathophysiology that is not yet fully understood. SARS-CoV-2 tropism for the organs is associated with bilateral organ cross-talks as well as targeted dysfunctions, among which acute kidney injury (AKI) seems to be highly prevalent in infected patients. The need for efficient management of COVID-related AKI patients is an aspect that is still being investigated by nephrologists; however, another reason for concern is a disturbingly high proportion of various types of kidney dysfunctions in patients who have recovered from COVID-19. Even though the clinical picture of AKI and COVID-related AKI seems to be quite similar, it must be considered that regarding the latter, little is known about both the optimal management and long-term consequences. These discrepancies raise an urgent need for further research aimed at evaluating the molecular mechanisms associated with SARS-CoV-2-induced kidney damage as well as standardized management of COVID-related AKI patients. The following review presents a comprehensive and most-recent insight into the pathophysiology, clinical manifestations, recommended patient management, treatment strategies, and post-mortem findings in patients with COVID-related AKI.

Association of Kidney Disease With Outcomes in COVID-19: Results From the American Heart Association COVID-19 Cardiovascular Disease Registry

Background

Emerging evidence links acute kidney injury (AKI) in patients with COVID‐19 with higher mortality and respiratory morbidity, but the relationship of AKI with cardiovascular disease outcomes has not been reported in this population. We sought to evaluate associations between chronic kidney disease (CKD), AKI, and mortality and cardiovascular outcomes in patients hospitalized with COVID‐19.

Methods and Results

In a large multicenter registry including 8574 patients with COVID‐19 from 88 US hospitals, data were collected on baseline characteristics and serial laboratory data during index hospitalization. Primary exposure variables were CKD (categorized as no CKD, CKD, and end‐stage kidney disease) and AKI (classified into no AKI or stages 1, 2, or 3 using a modification of the Kidney Disease Improving Global Outcomes guideline definition). The primary outcome was all‐cause mortality. The key secondary outcome was major adverse cardiac events, defined as cardiovascular death, nonfatal stroke, nonfatal myocardial infarction, new‐onset nonfatal heart failure, and nonfatal cardiogenic shock. CKD and end‐stage kidney disease were not associated with mortality or major adverse cardiac events after multivariate adjustment. In contrast, AKI was significantly associated with mortality (stage 1 hazard ratio [HR], 1.72 [95% CI, 1.46–2.03]; stage 2 HR, 1.83 [95% CI, 1.52–2.20]; stage 3 HR, 1.69 [95% CI, 1.44–1.98]; versus no AKI) and major adverse cardiac events (stage 1 HR, 2.17 [95% CI, 1.74–2.71]; stage 2 HR, 2.70 [95% CI, 2.07–3.51]; stage 3 HR, 3.06 [95% CI, 2.52–3.72]; versus no AKI).

Conclusions

This large study demonstrates a significant association between AKI and all‐cause mortality and, for the first time, major adverse cardiovascular events in patients hospitalized with COVID‐19.

Acute Kidney Injury Due to COVID-19 in Intensive Care Unit: An Analysis From a Latin-American Center

Introduction: The kidney may be affected by coronavirus (COVID-19) in the setting of acute kidney injury (AKI). Data about AKI in intensive care unit (ICU) patients in Latin America are scarce. We aimed to evaluate the risk of AKI, dialysis (HD), and death in ICU COVID-19 patients in a Brazilian center. Methods: Analysis from medical records of COVID-19 patients in a Brazilian center. Results: A total of 95 patients were analyzed. There was male predominance (64.2%), median age: 64.9 years, and previous history of hypertension and diabetes in 51.6 and 27.4%, respectively. AKI was diagnosed in 54 (56.8%) patients, and 32 (59.2%) of them required HD. Mortality rate was 17.9%. AKI patients when compared with no-AKI were more frequently hypertensive/diabetic and more often needed organ support therapies. Workups depicted more anemia, lymphopenia, and higher levels of inflammatory markers and higher mortality. Comparing patients who had undergone death to survivors, they were older, more frequently diabetic, and had worse SAPS3 and SOFA scores and need for organ support therapies, AKI, and HD. Multinomial logistic regression revealed that hypertension (p = 0.018) and mechanical ventilation (p = 0.002) were associated with AKI; hypertension (p = 0.002), mechanical ventilation (p = 0.008), and use of vasopressor (p = 0.027) to HD patients; and age >65 years (p = 0.03) and AKI (p = 0.04) were risk factors for death. Conclusions: AKI was a common complication of ICU COVID-19 patients, and it was more frequent in patients with hypertension and need of organ support therapies. As well as age >65 years, AKI was an independent risk factor for death.

Viral Nephropathies, Adding SARS-CoV-2 to the List

Viral infections in the immunocompetent host can cause both acute and chronic kidney disease either as a direct damage to the infected kidney cells or as a consequence of systemic immune responses that impact kidney function. Since identifying these entities in the 1970s and 80s, major breakthroughs in the understanding of the viral mechanisms have occurred. Viruses have evolved mechanisms to hijack signaling pathways of infected cells to evade antiviral immune responses by the host. Over time, the clinical presentations and management of these diseases have evolved along with our in-depth understanding of the various pathophysiological mechanisms causing these conditions. Similarly, both at the cellular and systemic levels, the host has evolved mechanisms to counter viral subversion strategies for mutual survival. Since the start of the current COVID-19 pandemic, numerous cases of acute kidney injury have been reported in the literature with various possible pathophysiological mechanisms. In this review, we summarize lessons learned from prior viral pandemics related to viral mechanisms utilized in the pathogenesis of numerous renal manifestations to attempt to utilize this knowledge in predicting post-COVID-19 kidney disease.

A review of Covid-19 and acute kidney injury: from pathophysiology to clinical results

Acute kidney injury (AKI) in hospitalized patients with COVID-19 is associated with higher mortality and a worse prognosis. Nevertheless, most patients with COVID-19 have mild symptoms, and about 5% can develop more severe symptoms and involve hypovolemia and multiple organ dysfunction syndrome. In a pathophysiological perspective, severe SARS-CoV-2 infection is characterized by numerous dependent pathways triggered by hypercytokinemia, especially IL-6 and TNF-alpha, leading to systemic inflammation, hypercoagulability, and multiple organ dysfunction. Systemic endotheliitis and direct viral tropism to proximal renal tubular cells and podocytes are important pathophysiological mechanisms leading to kidney injury in patients with more critical infection, with a clinical presentation ranging from proteinuria and/or glomerular hematuria to fulminant AKI requiring renal replacement therapies. Glomerulonephritis, rhabdomyolysis, and nephrotoxic drugs are also associated with kidney damage in patients with COVID-19. Thus, AKI and proteinuria are independent risk factors for mortality in patients with SARS-CoV-2 infection. We provide a comprehensive review of the literature emphasizing the impact of acute kidney involvement in the evolutive prognosis and mortality of patients with COVID-19.

Association between Postmortem Kidney Biopsy Findings and Acute Kidney Injury from Patients with SARS-CoV-2 (COVID-19)

BACKGROUND AND OBJECTIVES

AKI in coronavirus disease 2019 (COVID-19) is associated with higher morbidity and mortality. The objective of this study was to identify the kidney histopathologic characteristics of deceased patients with diagnosis of COVID-19 and evaluate the association between biopsy findings and clinical variables, including AKI severity.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Our multicenter, observational study of deceased patients with COVID-19 in three third-level centers in Mexico City evaluated postmortem kidney biopsy by light and electron microscopy analysis in all cases. Descriptive and association statistics were performed between the clinical and histologic variables.

RESULTS

A total of 85 patients were included. Median age was 57 (49-66) years, 69% were men, body mass index was 29 (26-35) kg/m², 51% had history of diabetes, 46% had history of hypertension, 98% received anticoagulation, 66% were on steroids, and 35% received at least one potential nephrotoxic medication. Severe AKI was present in 54% of patients. Biopsy findings included FSGS in 29%, diabetic nephropathy in 27%, and arteriosclerosis in 81%. Acute tubular injury grades 2-3 were observed in 49%. Histopathologic characteristics were not associated with severe AKI; however, pigment casts on the biopsy were associated with significantly lower probability of kidney function recovery (odds ratio, 0.07; 95% confidence interval, 0.01 to 0.77). The use of aminoglycosides/colistin, levels of C-reactive protein and serum albumin, previous use of angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers, antivirals, nonsteroid anti-inflammatory drugs, and anticoagulants were associated with specific histopathologic findings.

CONCLUSIONS

A high prevalence of chronic comorbidities was found on kidney biopsies. Nonrecovery from severe AKI was associated with the presence of pigmented casts. Inflammatory markers and medications were associated with specific histopathologic findings in patients dying from COVID-19.

SARS-CoV-2 Renal Impairment in Critical Care: An Observational Study of 42 Cases (Kidney COVID)

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection leads to 5% to 16% hospitalization in intensive care units (ICU) and is associated with 23% to 75% of kidney impairments, including acute kidney injury (AKI). The current work aims to precisely characterize the renal impairment associated to SARS-CoV-2 in ICU patients. Forty-two patients consecutively admitted to the ICU of a French university hospital who tested positive for SARS-CoV-2 between 25 March 2020, and 29 April 2020, were included and classified in categories according to their renal function. Complete renal profiles and evolution during ICU stay were fully characterized in 34 patients. Univariate analyses were performed to determine risk factors associated with AKI. In a second step, we conducted a logistic regression model with inverse probability of treatment weighting (IPTW) analyses to assess major comorbidities as predictors of AKI. Thirty-two patients (94.1%) met diagnostic criteria for intrinsic renal injury with a mixed pattern of tubular and glomerular injuries within the first week of ICU admission, which lasted upon discharge. During their ICU stay, 24 patients (57.1%) presented AKI which was associated with increased mortality (p = 0.007), hemodynamic failure (p = 0.022), and more altered clearance at hospital discharge (p = 0.001). AKI occurrence was associated with lower pH (p = 0.024), higher PaCO₂ (CO₂ partial pressure in the arterial blood) (p = 0.027), PEEP (positive end-expiratory pressure) (p = 0.027), procalcitonin (p = 0.015), and CRP (C-reactive protein) (p = 0.045) on ICU admission. AKI was found to be independently associated with chronic kidney disease (adjusted OR (odd ratio) 5.97 (2.1-19.69), p = 0.00149). Critical SARS-CoV-2 infection is associated with persistent intrinsic renal injury and AKI, which is a risk factor of mortality. Mechanical ventilation settings seem to be a critical factor of kidney impairment.

IgA-Dominant Infection-Associated Glomerulonephritis Following SARS-CoV-2 Infection

The renal involvement of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been reported. The etiology of kidney injury appears to be tubular, mainly due to the expression of angiotensin-converting enzyme 2, the key joint receptor for SARS-CoV-2; however, cases with glomerular implication have also been documented. The multifactorial origin of this renal involvement could include virus-mediated injury, cytokine storm, angiotensin II pathway activation, complement dysregulation, hyper-coagulation, and microangiopathy. We present the renal histological findings from a patient who developed acute kidney injury and de novo nephrotic syndrome, highly suggestive of acute IgA-dominant infection-associated glomerulonephritis (IgA-DIAGN) after SARS-CoV-2 infection, as evidenced by the presence of this virus detected in the renal tissue of the patient via immunohistochemistry assay. In summary, we document the first case of IgA-DIAGN associated to SARS-CoV-2. Thus, SARS-CoV-2 S may act as a super antigen driving the development of multisystem inflammatory syndrome as well as cytokine storm in patients affected by COVID-19, reaching the glomerulus and leading to the development of this novel IgA-DIAGN.

Relationship Between Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) and the Etiology of Acute Kidney Injury (AKI)

Coronavirus disease 2019 (COVID-19) is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Since it was first recognized in December 2019, it has resulted in the ongoing worldwide pandemic. Although acute hypoxic respiratory failure (AHRF) and acute respiratory distress syndrome (ARDS) are the main features of the disease, the involvement of other organs needs to be explored. There has been a growing concern regarding the association between acute kidney injury (AKI) and poor outcomes in SARS-CoV-2 patients. Based on current observational data, AKI is the 2nd most common cause of morbidity and mortality behind ARDS in SARS-CoV-2 patients. Angiotensin-converting enzyme 2 (ACE2) receptor has been shown to be the cornerstone of SARS-CoV-2 infection and possibly plays a significant role in the occurrence of renal injury. The pathogenesis of AKI is likely multifactorial that involves not only direct viral invasion but also dysregulated immune response in the form of cytokine storm, ischemia to kidneys, hypercoagulable state, and rhabdomyolysis, among others. We performed a literature search of the Pubmed and Google Scholar database from 1996 to 2020 using the following keywords: severe acute respiratory syndrome coronavirus 2, coronavirus disease 2019, angiotensin-converting enzyme 2 receptor, and acute kidney injury to find the most pertinent and highest-quality of evidence. Any cited references were reviewed to identify relevant literature. The purpose of this review is to discuss, explore, and summarize the relationship between AKI in SARS-CoV-2 patients, with a focus on its epidemiology, association with ACE2 receptors, and pathophysiology of AKI.

Pathology of COVID-19-associated acute kidney injury

Acute kidney injury (AKI) is common among hospitalized patients with coronavirus disease 2019 (COVID-19), with the occurrence of AKI ranging from 0.5% to 80%. An improved knowledge of the pathology of AKI in COVID-19 is crucial to mitigate and manage AKI and to improve the survival of patients who develop AKI during COVID-19. In this review, we summarize the published cases and case series of various kidney pathologies seen with COVID-19. Both live kidney biopsies and autopsy series suggest acute tubular injury as the most commonly encountered pathology. Collapsing glomerulopathy and thrombotic microangiopathy are other encountered pathologies noted in both live and autopsy tissues. Other rare findings such as anti-neutrophil cytoplasmic antibody vasculitis, anti-glomerular basement membrane disease and podocytopathies have been reported. Although direct viral infection of the kidney is possible, it is certainly not a common or even widespread finding reported at the time of this writing (November 2020).

Severe Acute Respiratory Syndrome-Associated Coronavirus 2 Infection and Organ Dysfunction in the ICU: Opportunities for Translational Research

OBJECTIVES

Since the beginning of the coronavirus disease 2019 pandemic, hundreds of thousands of patients have been treated in ICUs across the globe. The severe acute respiratory syndrome-associated coronavirus 2 virus enters cells via the angiotensin-converting enzyme 2 receptor and activates several distinct inflammatory pathways, resulting in hematologic abnormalities and dysfunction in respiratory, cardiac, gastrointestinal renal, endocrine, dermatologic, and neurologic systems. This review summarizes the current state of research in coronavirus disease 2019 pathophysiology within the context of potential organ-based disease mechanisms and opportunities for translational research.

DATA SOURCES

Investigators from the Research Section of the Society of Critical Care Medicine were selected based on expertise in specific organ systems and research focus. Data were obtained from searches conducted in Medline via the PubMed portal, Directory of Open Access Journals, Excerpta Medica database, Latin American and Caribbean Health Sciences Literature, and Web of Science from an initial search from December 2019 to October 15, 2020, with a revised search to February 3, 2021. The medRxiv, Research Square, and clinical trial registries preprint servers also were searched to limit publication bias.

STUDY SELECTION

Content experts selected studies that included mechanism-based relevance to the severe acute respiratory syndrome-associated coronavirus 2 virus or coronavirus disease 2019 disease.

DATA EXTRACTION

Not applicable.

DATA SYNTHESIS

Not applicable.

CONCLUSIONS

Efforts to improve the care of critically ill coronavirus disease 2019 patients should be centered on understanding how severe acute respiratory syndrome-associated coronavirus 2 infection affects organ function. This review articulates specific targets for further research.

Kidney transplantation and COVID-19 renal and patient prognosis

Coronavirus disease 2019 (COVD-19) emerged as a pandemic in December 2019. Infection has spread quickly and renal transplant recipients receiving chronic immunosuppression have been considered a population at high risk of infection, complications and infection-related death. During this year a large amount of information from nationwide registries, multicentre and single-centre studies have been reported. The number of renal transplant patients diagnosed with COVID-19 was higher than in the general population, but the lower threshold for testing may have contributed to its better identification. Major complications such as acute kidney injury and acute respiratory distress syndrome were very frequent in renal transplant patients, with a high comorbidity burden, but further studies are needed to support that organ transplant recipients receiving chronic immunosuppression are more prone to develop these complications than the general population. Kidney transplant recipients experience a high mortality rate compared with the general population, especially during the very early post-transplant period. Despite the fact that some studies report more favourable outcomes in patients with a kidney transplant than in patients on the kidney waiting list, the higher mortality described in the very early post-transplant period would advise against performing a kidney transplant in areas where the spread of infection is high, especially in recipients >60 years of age. Management of transplant recipients has been challenging for clinicians and strategies such as less use of lymphocyte-depleting agents for new transplants or anti-metabolite withdrawal and calcineurin inhibitor reduction for transplant patients with COVID-19 are not based on high-quality evidence.