For those of us treating patients with liver disease throughout the pandemic, we have anticipated evidence-based guidance regarding the contribution of specific liver disease phenotypes and immune suppression/transplantation on COVID-19 susceptibility and outcome. Now, data are emerging to help answer some of the major questions surrounding COVID-19 and the liver.
Does the virus itself cause liver disease?
The answer to this question is still a bit unclear. Multiple early reports1-11 stated that hospitalized patients with SARS-CoV-2 infection frequently had elevated values on liver biochemistry tests. For example, the reported incidence of elevated serum aspartate aminotransferase (AST) or alanine aminotransferase (ALT) levels ranged from 14% to 83%, yet the magnitude of enzyme elevation was generally reported to be mild and normalized as COVID-19 symptoms improved.
Unsurprisingly, patients with severe liver injury (defined as AST and ALT levels more than five times the upper limit of normal) were more likely to have a complicated clinical course, including having elevated inflammatory markers and requiring intensive care unit admission, renal replacement therapy, and/or intubation. Currier and colleagues reported that patients with COVID-19 who had elevated AST and ALT levels had significantly higher odds of these same adverse outcomes and death.
This reflects the multifactorial pathogenesis of enzyme elevation, including a direct injurious effect of the virus on hepatocytes, cytokine or immune-mediated liver damage, drug hepatoxicity, or hypoxia and systemic inflammation.
Pellegrini and colleagues reported that 7% of patients infected with SARS-CoV-2 developed acute liver failure during their hospitalization, with a resulting mortality rate of 74%. Wagner and colleagues suggested that the pattern of peak elevated enzyme elevation was prognostic of severe clinical outcomes in hospitalized patients with COVID-19. Patients with a predominantly mixed pattern (AST/ALT and alkaline phosphatase elevations) had worse outcomes than those with a hepatocellular phenotype (isolated AST and/or ALT elevation).
Severe liver injury associated with SARS-CoV-2 infection is uncommon in children. However, elevated AST and ALT levels may be seen in association with multisystem inflammatory syndrome.12-15
Are patients with preexisting chronic liver disease more susceptible to adverse outcomes?
Early observations suggested that patients with chronic liver disease, such as cirrhosis, who acquire SARS-CoV-2 have high rates of hospitalization and mortality. However, it is unclear whether all such patients are affected or whether certain subgroups are at higher risk.
In results that they hoped would allow for better risk stratification and personalization of care, Kim and colleagues reported that patients with alcohol-related liver disease, decompensated cirrhosis, and hepatocellular carcinoma have the highest risk for all-cause mortality from COVID-19. Separate presentations at Digestive Disease Week 2021 confirmed that patients with preexisting liver disease had a threefold higher rate of mortality, thromboembolism, acute respiratory distress syndrome, and a severe COVID-19 disease course, and that patients with both COVID-19 and cirrhosis had significantly higher rates of mortality (18% vs. 13%), ICU admission (46% vs. 34%), and longer lengths of stay than those without cirrhosis.
Nonalcoholic fatty liver disease (NAFLD) is currently the most common chronic liver disease, and its impact on the course of SARS-CoV-2 infection (and vice versa) is controversial. However, metabolic risk factors, such as obesity, diabetes mellitus, and hypertension, are known to be associated with severe illness from COVID-19. It was also reported that hepatic steatosis was associated with worse outcomes in patients with liver injury and SARS-CoV-2 infection, and that a higher proportion of patients with NAFLD required mechanical ventilation during their hospital course (47% vs. 17%) and had increased mortality (41% vs. 17%).