Abnormal liver enzymes in patients with Covid-19 are common, particularly in those with severe disease.
Elevated levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) have been reported in 14-53% of patients in several case series. More severe cases appear to have a higher prevalence of AST elevation (1). As some cases also have elevated creatine kinase (CK), the relative contribution of muscles to these enzyme abnormalities is unclear (2).
A small study involving ICU patients with Covid-19 reported a prevalence of elevated AST of 62% compared to 25% in non-ICU patients (3). Other studies have confirmed lower incidence of AST abnormality among patients with mild or subclinical disease (4,5).
Although much of the published reports of liver injury in Covid-19 have revolved around AST and ALT abnormalities, gamma-glutamyl transferase (GGT) may also be elevated. GGT was abnormal in 54% of patients with Covid-19 during their hospitalization with alkaline phosphatase elevation reported in ~2.0% (1, unpublished reports). Elevation of total bilirubin has also been reported occasionally (1).
Although the exact mechanism(s) of Covid-19-related is unclear, direct viral infection of liver cells is one possibility as viremia has been documented in some cases (1). Of interest, a related coronavirus, SARS-CoV-1 has been shown to infect liver tissue and cholangiocytes may express ACE2 receptors, a prime target for Covid-19 virus (1,6,7, unpublished reports).
Despite these observations, to date, viral inclusions have not been demonstrated in the liver. Other possible causes of liver injury in Covid-19 include innate immune dysregulation, cytokine storm, hypoxia and drugs (1,2).
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References
1. Zhang C, Shi L, Wang FS. Liver injury in COVID-19:management and challenges. Lancet Gastroenterol Hepatol 2020; March 4. https://doi.org/10.1016/S2468-1253(20)30057-1
2. Bangash MN, Patel J, Parekh D. COVID-19 and the liver: little cause for concern. Lancet Gastroenterol Hepatol 2020;March 20. https://doi.org/10.1016/52468-1253(20)30084-4
3. Huang C, Wang Y, Li X, et al. Clinical features of patients infected with 2019 novel coronavirus in Wuhan, China. Lancet 2020;395:497-506. https://pubmed.ncbi.nlm.nih.gov/31986264/
4. Guan WJ, Ni ZY, Hu Y, et al. Clinical characteristics of 2019 novel coronavirus infection in China. N Engl J Med 2020;published online Feb 28. DOI:10.1056/NEJMoa2003032
5. Shi H, Han X, Jiang N, et al. Radiological findings from 81 patients with COVID-19 pneumonia in Wuhan, China: a descriptive study. Lancet Infect Dis 2020; published onlineFeb 24. DOI:10.1016/S1473-3099(20)30086-4 (lancet 8)
6. Chai X, Hu L, Zhang Y, et al. Specific ACE2 expression in cholangiocytes may cause liver damage after 209-nCoV infection. bioRxiv 2020;published online Feb 4. https://doi.org/10.1101/2020.02.03.931766.
7. Xu Z, Shi L, Wang Y, et al. Pathological findings of COVID-19 associated with acute respiratory distress syndrome. Lancet Respir Med 2020; published online Feb 18. DOI:10.1016/S2213-2600(20)30076-X
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