Although early reports suggested a low incidence (3-9%) of AKI among Covid-19 patients, more recent studies have shown higher frequencies of renal abnormalities, including albuminuria and hematuria (1).
A study of 59 patients with Covid-19 reported that 34% had “massive albuminuria” on the first day of admission, and 63% developed proteinuria during their hospitalization (2 [unpublished]). BUN was elevated in 27% of patients and in two-thirds of those who died. In another study involving 710 patients with Covid-19, nearly one-half had proteinuria and hematuria and a quarter had hematuria on admission. Overall, around 15% of patients had an elevated serum creatinine and BUN (3).
Possible explanations for renal manifestations of Covid-19 include sepsis, cytokine storm, secondary infections, and direct cellular injury due to the virus itself (1, 4). Interestingly, SARS-CoV-2 has been reportedly isolated from the urine sample of a Covid-19 patient (1). This should not be surprising given the presence of ACE2 receptors in the proximal tubules and, at lower concentrations, in the glomeruli (5).
An autopsy study of patients with Covid-19 found evidence of diffuse proximal tubule injury with the loss of brush border, vascular degeneration but no vasculitis, interstitial inflammation or hemorrhage. Coronavirus particles were found in the tubular epithelium and podocytes (6).
Bonus Pearl: Did you know that proteinuria (2-3+) and hematuria are independent risk factors for in-hospital mortality (3)?
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1. Naicker S, Yang CW, Hwang SJ. The novel coronavirus 2019 epidemic and kidneys. Kidney International 2020, May. DOI: https://doi.org/10.1016/j.kint.2020.03.001
2. Li Z, Wu M, Guo J, et al. Caution on kidney dysfunctions of 2019-nCoV patients . medRxiv 2020.02.08.20021212
3. Cheng Y, Luo R, Wang K, et al. Kidney disease is associated with in-hospital death of patients with COVID-19. Kidney International 2020;97:829-38.
4. Su H, Yang M, Wan C, et al. Renal histopathological analysis of 26 postmortem findings of patients with COVID-19 in China. Kidney International 2020, April 9. https://www.sciencedirect.com/science/article/pii/S0085253820303690
5. Mizuiri S, Ohashi Y. ACE and ACE2 in kidney disease. World J Nephrol 2015;4:74-82. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4317630/
6. Cheng N, Zhou M, Dong X, et al. Kidney impairment is associated with in-hospital death of COVID-19 patients. medRxive 2020 .0218.20023242. https://doi.org/10.1101/2020.02.18.20023242.
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