key: cord-0999346-atv9tr2v authors: Ferlicot, Sophie; Jamme, Matthieu; Gaillard, François; Oniszczuk, Julie; Couturier, Aymeric; May, Olivia; Grünenwald, Anne; Sannier, Aurélie; Moktefi, Anissa; Le Monnier, Ophélie; Petit-Hoang, Camille; Maroun, Nadine; Brodin-Sartorius, Albane; Michon, Arthur; Dobosziewicz, Hélène; Andreelli, Fabrizio; Guillet, Matthieu; Izzedine, Hassane; Richard, Christian; Dekeyser, Manon; Arrestier, Romain; Sthelé, Thomas; Lefèvre, Edouard; Mathian, Alexis; Legendre, Christophe; Mussini, Charlotte; Verpont, Marie-Christine; Pallet, Nicolas; Amoura, Zahir; Essig, Marie; Snanoudj, Renaud; Brocheriou-Spelle, Isabelle; François, Hélène; Belenfant, Xavier; Geri, Guillaume; Daugas, Eric; Audard, Vincent; Buob, David; Massy, Ziad A; Zaidan, Mohamad title: The spectrum of kidney biopsies in hospitalized patients with COVID-19, acute kidney injury, and/or proteinuria date: 2021-02-12 journal: Nephrol Dial Transplant DOI: 10.1093/ndt/gfab042 sha: d950f93aa161be7b0ef86380399186f6d54a3816 doc_id: 999346 cord_uid: atv9tr2v We report a multicentric retrospective case series of patients with COVID-19 who developed acute kidney injury and/or proteinuria and underwent a kidney biopsy in the Paris and its metropolitan area. Forty-seven patients (80.9% men) with COVID-19 who underwent a kidney biopsy between March 08 and May 19, 2020 were included. Median age was 63 years IQR [52–69]. Comorbidities included hypertension (66.0%), diabetes mellitus (27.7%), obesity (27.7%), history of chronic kidney (25.5%), cardiac (38.6%) and respiratory (27.3%) diseases. Initial symptoms were fever (85.1%), cough (63.8%), shortness of breath (55.3%), and diarrhea (23.4%). Almost all patients developed acute kidney injury (97.9%) and 63.8% required renal replacement therapy. Kidney biopsy showed two main histopathological patterns, including acute tubular injury in 20 (42.6%) patients, and glomerular injury consisting of collapsing glomerulopathy and focal segmental glomerulosclerosis in 17 (36.2%) patients. Two (4.3%) patients had acute vascular nephropathy, while eight (17%) had alternative diagnosis most likely unrelated to COVID-19. Acute tubular injury occurred almost invariably in the setting of severe forms of COVID-19, whereas patients with glomerular injury had various profiles of COVID-19 severity and collapsing glomerulopathy was only observed in patients harboring a combination of APOL1 risk variants. At last follow-up, 16 of the 30 patients who initially required dialysis were still on dialysis, and 9 died. The present study describes the spectrum of kidney lesions in patients with COVID-19. While acute tubular injury is correlated with COVID-19 severity, the pattern of glomerular injury is intimately associated with the expression of APOL1 risk variants. In December 2019, a novel coronavirus disease 2019 disease, caused by SARS-CoV-2 virus, occurred in Wuhan, Hubei Province, China, and rapidly spread worldwide [1, 2] . COVID-19 is transmitted via droplets during the incubation period and throughout the course of illness [3] . Up to 20% of infected patients develop moderate-to-severe pneumonia and require hospitalization, and 5-10% are admitted to intensive care unit (ICU) for ventilation support [4] [5] [6] [7] [8] . According to recent studies, SARS-CoV-2 infection is not limited to the respiratory system and other organs can also be affected leading to a broad spectrum of signs. Recent studies have underscored the high frequency of acute kidney injury, proteinuria, and hematuria during COVID-19 [9, 10] . Moreover, kidney involvement is burdened by a dramatic impact on patients' survival [9] [10] [11] . Here, we report a multicentric case series of patients with COVID-19 who developed acute kidney injury and/or proteinuria and underwent a kidney biopsy in the Paris and its metropolitan area. Forty-seven patients from nine Nephrology and ICU departments of Paris and its metropolitan area, including 38 (80.9%) men, were diagnosed with COVID-19 and underwent a kidney biopsy during the recent epidemic from March 8 through May 19, 2020. Of note, during the study period, more than 14000 patients with COVID-19 were admitted to the different hospitals of Assistance Publique-Hôpitaux de Paris, including more than 3000 (21.4%) patients referred to the ICU. The diagnosis of COVID-19 was confirmed by SARS-CoV-2 RT-PCR nasal or pharyngeal swab specimens in 43 (91.5%) patients of cases. In four patients with negative RT-PCR, the diagnosis was established on the results of a chest CT-scan, showing ground glass opacities with or without consolidative abnormalities highly suggestive of COVID- 19 Table 2 ). All patients required hospital admission, including more than 50% of patients who required oxygen therapy on admission (WHO score ≥ 5, Supplementary Table S4 ). Of note, 20 (42.6%) patients did not require oxygen therapy initially (WHO score = [2] [3] [4] ), but were hospitalized because of extra-respiratory features in the setting of COVID-19, including acute kidney injury and proteinuria. Chest CT-scan was performed in 43 patients (91.5%) within the 4 days IQR [1] [2] [3] [4] [5] [6] [7] [8] [9] after initial symptoms and revealed mild, moderate or severe lesions in 3 (7%), 19 (44.2%), and 21 (48.8%) patients, respectively ( [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] after initial symptoms. Seven out of 12 (58.3%) patients with preexisting chronic kidney disease required acute dialysis. All patients displayed a proteinuria > 0.3 g/g with a median urine protein-to-creatinine ratio (uPCR) of 2.52 g/g IQR [1.23-6.80 ]. Eighteen (40%) patients had a uPCR ≥ 3 g/g, while median serum albumin level was 21 g/L IQR [16] [17] [18] [19] [20] [21] [22] [23] . Urine albumin-to-creatinine ratio was not measured in all patients at the time of kidney biopsy. Hematuria was observed in 22 (55%) patients. Other laboratory findings are detailed in Supplementary Table S1 . Kidney biopsies, including two renal graft biopsies, were performed with a median delay of 18 days IQR [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] after initial symptoms. Seventeen patients were biopsied during their ICU stay because of stage III AKI or dialysis requirement, including two anuric patients. Thirteen patients underwent a kidney biopsy after ICU discharge because of persistent AKI and significant proteinuria. Finally, the remaining 17 kidney biopsies were performed in noncritically ill patients because of significant proteinuria (> 1 g/g) in all cases, associated with stage III AKI in all cases. Overall, of the 47 patients, 19 (40.4%) displayed overt nephrotic syndrome with a mean proteinuria level of 12.1 g/g IQR 5.96-11.95] and a mean serum albumin level of 18.2 g/L IQR [16] [17] [18] [19] [20] [21] [22] . All Table S2 ). Histopathological examination revealed two main patterns of kidney damage, i.e. tubulointerstitial injury and glomerular injury in 20 (42.6%) and 17 (36.2%), respectively ( Immunofluorescence study was negative for all cases of acute tubulointerstitial injury. Focal segmental glomerulosclerosis (FSGS) represented the second dominant pattern in 17 patients, including collapsing (Figures 2A-B) , not otherwise specified (Figure 2C) , and tip lesion variants ( Figure 2D ) in 11, 5, and one cases, respectively. Collapsing glomerulopathy was associated with tubular microcystic changes in almost half of cases and PAS-positive protein resorption droplets in proximal tubules in all cases ( Figure 1C ). Almost all patients harbored mild-to-severe acute tubular injury. Immunofluorescence study revealed segmental glomerular deposits of IgM and C3. Predominant vascular lesions were also observed in two patients, including a case with thrombotic microangiopathy characterized by the presence of fibrin thrombi in a glomerulus, and a case with necrotizing arteritis. Both patients also harbored moderate lesions of acute tubular injury. Finally, varying degrees of interstitial fibrosis and tubular atrophy, as well as chronic vascular lesions, were also present in a vast majority of patients regardless the main diagnosis. Ultrastructural examination by electron microscopy was performed in nine cases. No electron dense deposits were observed by electron microscopy in the patients without pre-existing kidney disease. No viral particles were observed. Interestingly, endothelial injury was noted including mild (62.5%) and moderate (32.5%) swelling of endothelial cells in the glomerular in eight cases, and peritubular capillaries in four cases. Tubuloreticular inclusions were observed in seven cases (Figure 3 ). Of note, diffuse effacement of podocytes foot processes was observed in seven cases, all of which corresponded to glomerular predominant lesions except one case with predominant tubular injury. Mild foot process effacement was also observed in a case with dominant tubular injury. Anti-SARS-CoV-2 immunohistochemistry staining was performed on 16 kidney biopsies, including 7 patients with predominant acute tubular injury, 4 with collapsing glomerulopathy, 1 with focal segmental glomerulosclerosis and 4 with alternative diagnosis, and yielded negative results in all cases. Of note, appropriate controls were used, including SARS-CoV-2 positive placenta specimen and SARS-CoV-2 negative kidney biopsy tissues (Figure 4 ). During hospitalization, three profiles of severity could be distinguished based on the worst WHO progression scale. Five patients (10.6%) remained oxygen-free during the whole disease course (WHO score between 2 and 4). Eleven (23.4%) with a WHO score equal to 5 required up to 6 L/min of oxygen therapy, whereas 31 (66%) with a WHO score ≥ 6 required higher amounts (≥ 9/L) of oxygen therapy and were referred to the ICU in 93.5% of cases. with the WHO score < 6. Antibiotherapy based on penicillin, 3G cephalosporin combined with macrolides was given in 40 patients (85.1%) during hospitalization ( Nine patients (19.1%) died either from COVID-19 or related-adverse events ( Table 4 ), but no autopsy was undertaken. We report herein a multicentric case series describing the clinical and histopathological spectrum of kidney damage in patients with COVID-19. Two main histopathological patterns were identified: acute tubular (and interstitial) lesions, and glomerular injury mainly consisting of collapsing glomerulopathy. A minority of patients may display alternative diagnosis, which were likely unrelated to COVID-19, underscoring the value of the kidney biopsy in this setting. Initial histopathological studies dealing with COVID-19 and kidney involvement have been limited to autopsies [12, 13] . More recent series have addressed the renal lesions in patients with COVID-19, reporting cases of collapsing glomerulopathy and acute tubular injury [14] [15] [16] [17] . In the present study, we addressed early renal events in patients with varying degrees of COVID-19 pneumonia, reporting both glomerular and tubular injury. Isolated or combined acute tubular injury represents the predominant pattern, seen mostly in patients with serious forms of COVID-19. Albeit hypoperfusion has been proposed as an underlying mechanism in these patients, almost one-third of patients with acute tubular injury or those admitted to the ICU did not experience prominent hemodynamic instability. These findings suggest that additional factors may likely contribute to tubular damage in the setting of COVID-19 pneumonia, including tissue hypoxia, rhabdomyolysis, and the so-called "cytokine storm", as suggested by the identification by electron microscopy of interferon footprints in glomerular capillaries endothelial cells. Hypercoagulability and microangiopathy with complement cascade activation are also to consider [18] . The swelling of endothelial cells, as assessed by electron microscopy, points to endothelial injury as a potential mechanism to explain severe renal damage, as also reported in other organs, such as lungs and heart [19] [20] [21] [22] . Alternatively, a direct viral cytotoxicity on renal cells has been widely debated in the literature, mainly supported by the expression in the kidneys of proteins that facilitate SARS-CoV-2 infection, including Angiotensin Converting Enzyme 2, and Transmembrane protease serine 2 [18, 23, 24] . Recent reports have shown positive immunohistochemical staining for SARS-CoV-2 nucleocapsid protein in post-mortem kidneys [12, 13, 25] . Nevertheless, the presence of viral particles within tubular epithelial cells and podocytes remains controversial [14, 26, 27] . Similarly to recent reports, we did not observe kidney expression of SARS-CoV-2 nucleoprotein in our study, suggesting the absence of kidney infection by the virus [15, 16, 28] . In addition to tubular damage, COVID-19 may be associated with notable glomerular lesions, particularly in non-critically ill patients, widening the spectrum of COVID-19-associated nephropathy. In line with recent case reports, collapsing glomerulopathy represents the predominant histopathological pattern of glomerular lesions seen in the course of COVID-19 [14, [29] [30] [31] [32] [33] . This peculiar variant of FSGS is characterized by segmental or global glomerular tuft collapse with hypertrophy and hyperplasia of the overlying podocytes [34, 35] . Accompanying acute tubular injury, tubular dilations with microcyst formation and interstitial inflammation, as commonly seen in HIV-associated nephropathy [36] , were less prominent in patients with COVID-19. As in our series, all patients with COVID-19-associated collapsing glomerulopathy previously reported in the literature displayed AKI, heavy proteinuria, and hypoalbuminemia [29] [30] [31] [32] [33] . Noteworthy, collapsing glomerulopathy, and FSGS, coincided with varying degrees of severity COVID-19 pulmonary involvement, suggesting that, unlike to patients with dominant tubulointerstitial lesions, COVID-19-associated glomerular injury is likely multifactorial and somehow unrelated to the severity of respiratory involvement [37] . In this line, some cases of glomerular involvement may also occur after the recovery of respiratory signs [37] . Because collapsing glomerulopathy and FSGS may be primary or secondary to a wide range of causes, including viral infections and inflammatory diseases [35] , many authors suggested a similar causality with SARS-CoV-2 [38, 39] . Nevertheless, and as far as we know, several groups failed to detect SARS-CoV-2 RNA by in situ hybridization or RT-PCR on kidney biopsies [29] [30] [31] 33, 40] . The term of "COVID-19-associated nephropathy" should thus be preferred to that of "SARS-CoV-2 nephropathy" to stress the point that the demonstration of a direct or indirect role of SARS-CoV-2 in kidney injury remains an unsolved issue to date. Importantly, we and other have identified a crucial role of APOL1 high risk variants (i.e. G1/G1, G1/G2 or G2/G2 genotypes) in the risk of COVID-19-associated collapsing glomerulopathy [14] . A plausible model is that COVID-19, irrespectively of a direct or indirect role of SARS-CoV-2, acts as a « second hit » that results in podocyte injury, and various histopathological patterns depending on the genetic background [14] . In conclusion, the spectrum of COVID-19-associated nephropathy includes both tubular and glomerular lesions with likely distinctive pathophysiological mechanisms. Kidney biopsy is very helpful to determine the precise nature of renal lesions during COVID-19 course and guide subsequent management. Tubular damage is predominantly observed in most severe respiratory cases and may be related to hemodynamic changes and other additional factors. Glomerular lesions, including collapsing glomerulopathy and FSGS are predominantly observed in non-critically ill patients without an obvious correlation with the severity of respiratory signs. The carriage of APOL1 high-risk variants is crucial to understand the pattern of glomerular lesions. While a direct or indirect effect of SARS-CoV-2 on kidney lesions is a current "hot topic" in the Nephrology field, further investigations using trustworthy tools are necessary to decipher the pathophysiology of COVID-19-associated kidney damage. Finally, and beyond diagnosis, it will also be interesting to correlate kidney biopsy findings to renal recovery and outcome at distance of COVID-19 episode. We included all patients with COVID-19 who underwent a kidney biopsy in nine different Patients' data were obtained through the retrospective review of the medical electronic records. Three patients have already been reported as single cases [32, 33] . negative renal biopsy and placenta) controls were done and yielded appropriate results. Descriptive statistics were used to summarize the data. Results are reported as medians with interquartile range [IQR] for continuous variables and counts and percentages for categorical variables. Univariate analyses were performed using the Kruskal-Wallis test, and the χ2 or Fisher exact test, as appropriate. A p-value < 0.05 was considered as significant. The authors have no conflicts of interest to declare , x100) . B, Mild interstitial edema and mononuclear inflammation, associated with acute tubular injury, and ischemic glomerulus (Trichrome stain, x200). C, Various tubular changes observed in case of collapsing glomerulopathy with dilatation of tubules filled with hyaline casts (star), and cytoplasmic protein droplets (arrow) (Trichrome stain, x61). D, Marked acute tubular injury with cell fragments within the tubular lumen and flattening of the tubular epithelium (Trichrome stain, x400). Scale bars: 50 µm. 101x307mm (300 x 300 DPI) 324x164mm (300 x 300 DPI) Clinical characteristics of 113 deceased patients with coronavirus disease 2019: retrospective study The Incubation Period of Coronavirus Disease 2019 (COVID-19) From Publicly Reported Confirmed Cases: Estimation and Application Clinical course and outcomes of critically ill patients with SARS-CoV-2 pneumonia in Wuhan, China: a single-centered, retrospective, observational study Clinical Characteristics of 138 Hospitalized Patients With 2019 Novel Coronavirus-Infected Pneumonia in Wuhan, China Novel Coronavirus Outbreak Research Team. Epidemiologic Features and Clinical Course of Patients Infected With SARS-CoV-2 in Characteristics of and Important Lessons From the Coronavirus Disease 2019 (COVID-19) Outbreak in China: Summary of a Report of 72 314 Cases From the Chinese Center for Disease Control and Prevention Coronavirus Disease 2019 (COVID-19) in Italy Renal Involvement and Early Prognosis in Patients with COVID-19 Pneumonia Northwell COVID-19 Research Consortium Acute kidney injury in patients hospitalized with COVID-19 Kidney disease is associated with in-hospital death of patients with COVID-19 Human Kidney is a Target for Novel Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Infection Renal histopathological analysis of 26 postmortem findings of patients with COVID-19 in China AKI and Collapsing Glomerulopathy Associated with COVID-19 and APOL1 High-Risk Genotype Kidney Biopsy Findings in Patients with COVID-19 Northwell Nephrology COVID-19 Research Consortium COVID-19-Associated Kidney Injury: A Case Series of Kidney Biopsy Findings Multicenter Clinicopathologic Correlation of Kidney Biopsies Performed in COVID-19 Patients Presenting With Acute Kidney Injury or Proteinuria COVID-19 and ACE2 in Cardiovascular, Lung, and Kidney Working Group. Acute Kidney Injury in COVID-19: Emerging Evidence of a Distinct Pathophysiology Endothelial cell infection and endotheliitis in COVID-19 COVID-19: the vasculature unleashed Severe COVID-19 infection associated with endothelial activation COVID-19 and Cardiovascular Disease HCA Lung Biological Network. SARS-CoV-2 entry factors are highly expressed in nasal epithelial cells together with innate immune genes Multiorgan and Renal Tropism of SARS-CoV-2 Ultrastructural Evidence for Direct Renal Infection with SARS-CoV-2 Visualization of putative coronavirus in kidney Multivesicular bodies mimicking SARS-CoV-2 in patients without COVID-19 Detection of SARS-CoV-2 in formalinfixed paraffin-embedded tissue sections using commercially available reagents Collapsing Glomerulopathy in a Patient With Coronavirus Disease 2019 (COVID-19) Collapsing glomerulopathy in a COVID-19 patient Acute Kidney Injury Due to Collapsing Glomerulopathy Following COVID-19 Infection Tubuloreticular inclusions in COVID-19-related collapsing glomerulopathy Indirect effects of severe acute respiratory syndrome coronavirus 2 on the kidney in coronavirus disease patients Pathologic classification of focal segmental glomerulosclerosis: a working proposal Focal segmental glomerulosclerosis Associated focal and segmental glomerulosclerosis in the acquired immunodeficiency syndrome COVID-19-Associated Collapsing Glomerulopathy: An Emerging Entity Renal epithelium is a previously unrecognized site of HIV-1 infection Virological synapses allow HIV-1 uptake and gene expression in renal tubular epithelial cells Kidney biopsy findings in a critically ill COVID-19 patient with dialysis-dependent acute kidney injury: a case against "SARS-CoV-2 nephropathy