AKI in the Setting of COVID-19: Histopathologic and Ultrastructural Findings in Postmortem Kidney Biopsy

Introduction: COVID-19 infection is caused by severe acute respiratory syndrome-2 (SARS-CoV-2) SARS-CoV-2, using its Spike protein, interacts with angiotensin converting enzyme-II (ACE2) protein expressed in human kidneys Upon internalization, host cells may go through pyroptosis, a process characterized by membranous pore formation, cytokine storm and cell death We report light microscopy (LM), immunofluorescence microscopy (IF), and electron microscopy (EM) findings in renal biopsies of patients with COVID-19 to further understand the pathological process Case Description: 10 patients were biopsied, age range 25-63 years 7 were confirmed by polymerase chain reaction (PCR) via nasopharyngeal swab 3 patients were suspected, but PCR-negative Common comorbidities include hypertension, hyperlipidemia, and obesity Patients had AKI with elevated creatinine, range 1 2 to 13 48 mg/dL Kidney ultrasound showed enlargement and increased echogenicity Biopsies were performed 9 to 71 days from symptom onset of such as fever, cough, and diarrhea Tissue was fixed in formalin and processed for LM Fresh frozen tissue was utilized for IF Tissue was fixed in paraformaldehyde and processed for EM All had acute tubular injury and viral particles on EM (Figure) Patients received supportive care None required ventilation, but 4 required hemodialysis Survival rate is 100% (8-12 weeks) Discussion: Renal biopsies were evaluated in 7 confirmed and 3 suspected COVID-19 patients Although PCR is the gold standard, it is known to have a 15% false negative rate This may be due to low viral loads and antibody testing may be warranted in suspected PCR-negative patients Coronavirus particles are reported to measure 50-200 nm, and SARS-CoV-2 50-140 nm Viral particles were seen in all 10 patients The particles are contained in vesicles or sacs, and can be found in podocytes, endothelial, and tubular epithelial cells This may contribute to intrinsic injury resulting in AKI seen in patients