Renal Histopathological Changes in Coronavirus Disease 2019 Patients: A Systematic Review and Meta-analysis of Individual Patient Data

The major targets of coronavirus disease 2019 (COVID-19) are the respiratory and immune systems. However, a significant proportion of hospitalized patients had kidney dysfunction. The histopathological surveys have principally focused on respiratory, hematopoietic, and immune systems, whereas histopathologic data of kidney injury are lacking. Our study aimed to summarize the renal histopathological findings in COVID-19 from the published case report and case series. We conducted a systematic searching of databases such as MEDLINE, EMBASE, and Cochrane Library for published reports of COVID-19 patients with renal histopathological changes from autopsy studies and from "for cause " indication biopsies. Included in our study are case reports and case series with extractable quantitative data on patient demographics such as age, sex, ethnicity, as well as data on renal function tests, their comorbidities, and biopsy to study the histopathological changes. Data were analyzed with Microsoft Excel. To evaluate the methodological quality, we chose the framework for appraisal, synthesis, and application of evidence suggested by Murad et al. Systematic searches of literature found 31 studies that fulfilled the eligibility criteria. These studies included a total of 139 cases, where individual case details including clinical and histopathological findings were available. The median age of the cases was 62 years with a male:female ratio of 2.5:1. Associated comorbidities were noted in 78.4% of cases. The majority of the cases had renal dysfunction with proteinuria which was documented in more than two-thirds of the cases. The histopathological findings observed the frequent tubular involvement manifested by acute tubular injury. Regarding glomerular pathology, collapsing glomerulopathy emerged as a distinct lesion in these patients and was noted among 46.8% of cases with glomerular lesions. A small subset of cases (4.3%) had thrombotic microangiopathy. Collapsing glomerulopathy emerged as a hallmark of glomerular changes among COVID-19 patients. Tubular damage is common and is linked to multiple factors including ischemia, sepsis among others. In the form of thrombotic microangiopathy seen in a subset of patients, vascular damage hints toward the hyper-coagulable state associated with the infection. The demonstration of viral particles in renal tissue remains debatable and requires further study.