COVID-19 and liver diseases

In patients with coronavirus disease 2019 (COVID-19), hepatic involvement occurs in up to 53% of all cases. Via the primary target for severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2), the angiotensin-converting enzyme 2 (ACE2) receptor, expressed on cholangiocytes, sinusoidal endothelial cells, and hepatocytes, direct damage to the liver may occur. Furthermore, indirect (= not receptor-mediated) damage to the liver plays a crucial role in the context of COVID-19 due to severe systemic inflammation with cytokine storm, hepatic thrombosis, and systemic hypoxia. In COVID-19, liver enzymes are considered significant predictors of outcome. Thus, it is essential to rule out other causes of liver enzyme elevation, such as other viral infections, drug-induced liver injury, and metabolic, autoimmune and other liver diseases. Secondary sclerosing cholangitis in critically ill patients (SSC-CIP) is highly relevant in treating critically ill patients in the intensive care unit (ICU). Risk factors for SSC-CIP include high doses of catecholamines, high positive end-expiratory pressure (PEEP), and extracorporeal membrane oxygenation (ECMO) therapy. Early recognition of this disease and treatment by endoscopic retrograde cholangiography (ERC) is crucial. Furthermore, liver transplantation should be evaluated. Some patients with COVID-19 are diagnosed with SSC, which is termed COVID-19-associated SSC. COVID-19-associated SSC and SSC-CIP are comparable with regard to clinical phenotype, risk factors, prognosis, and graft-free survival. Patients with pre-existing liver disease are not at increased risk for infection with SARS-CoV-2 but show more severe clinical courses of COVID-19 than patients without pre-existing liver disease. Patients with pre-existing liver cirrhosis may develop acute-on-chronic liver failure (ACLF) upon infection with SARS-CoV-2. ACLF has a high mortality rate, which must be treated in the ICU.