COVID-19 and Its Effects on the Hepatobiliary System: A Literature Review.

COVID-19 encompasses a wide clinical spectrum, from mild influenza-like illness to severe pneumonia and systemic complications. There is emerging literature on hepatobiliary involvement in COVID-19, especially elevation in liver enzymes as surrogate markers of liver injury. Angiotensin-converting enzyme 2 receptors within the hepatobiliary system are a portal of entry for SARS-CoV-2, after which injury may be perpetuated through hypoxia and cytokine storms. This literature review covers studies published before 2024 from databases such as PubMed, Google Scholar, Springer, and BMC Library. The keywords used were "COVID-19", "liver", "SARS-CoV-2", "chronic liver disease", and other relevant terms to ensure a wide scope of investigation. The most common liver enzymes elevated among COVID-19 patients include aspartate transaminase, alanine transaminase, and alkaline phosphatase, all of which are associated with the severity of the disease. Chronic liver disease (CLD) and hepatocellular carcinoma (HCC) patients have worse outcomes with increased ICU admission rates and increased mortality. COVID-19 vaccination in CLD and liver transplant recipients is very often associated with suboptimal antibody responses, adding to the risks. SARS-CoV-2 causes liver involvement through direct viral cytopathic effects, immune-mediated injury, and systemic hypoxia. Individuals with CLD are particularly vulnerable to severe illness.