Abnormalities in Renal Function after COVID-19

According to Evan A. Farkash, MD, PhD, and colleagues, a significant fraction of patients with coronavirus disease 2019 (COVID-19) display abnormalities in renal function, a marker of poor prognosis. Results of retrospective studies of patients hospitalized with COVID-19 in Wuhan, China, report an incidence of 3% to 7% progression to renal function abnormalities. The cause of renal failure in this patient population is unknown; researchers have hypothesized that the mechanism is direct renal infection by the causative virus, SARS-CoV-2.

Dr. Farkash et al. conducted an autopsy on a patient who died of COVID-19 following open repair of an aortic dissection, complicated by hypoxic respiratory failure and oliguric renal failure. Light and electron microscopy were used to examine renal tissue for evidence of SARS-CoV-2 within renal cells. Results were reported in the Journal of the American Society of Nephrology [doi.org/10.1681/ASN.2020040432].

Geographic isometric vacuolization, corresponding to a focus of tubules with abundant intracellular viral arrays, were seen in light microscopy of proximal tubules. Individual viruses were an average of 76 mm in diameter and had an envelope studded with crown-like, electron-dense spikes. Vacuoles contained double-membrane vesicles suggestive of partially assembled virus.

“The presence of viral particles in the renal tubular epithelium that were morphologically identical to SARS-CoV-2, and with viral arrays and other features of virus assembly, provide evidence of a productive direct infection of the kidney by SARS-CoV-2. This finding offers confirmatory evidence that direct renal infection occurs in the setting of acute kidney injury in COVID-19. However, the frequency and clinical significance of direct infection with COVID-19 is unclear. Tubular isometric vacuolization observed with light microscopy, which correlates with double-membrane vesicles containing vacuoles observed with electronic microscopy, may be a useful histologic marker for active SARS-CoV-2 infection in kidney biopsy or autopsy specimens,” the researchers said.