Commentary on COVID-19-induced liver injury in various age and risk groups

Table 1 Events in the liver from a broad perspective of severe acute respiratory syndrome coronavirus 2 infection

Effect	Mechanism	Result	Outcomes and morphological changes
SARS-CoV-2 virus	Genomic translations and replication	More viruses in circulation	Inflammation features. Usually, the biliary intrahepatic tree and bile duct did not show any significant histological alteration. Actin smooth muscle antibodies existed in pericytes which were in portal vein walls and adventitial areas
Viral proteins of SARS-CoV-2	SIRS -> stimulate cytokine storm	Increased TNF-α, IL-6, IL-1β, IL-2, IL-8, CCL2, CCL3, CCL5, CXCL10 levels. Decreased (CD4+) T cell and NK cell counts	Increase in the number of portal vein branches associated with lumen massive dilatation and focal periportal abnormal vessels. Portal vein endotheliitis (fragmented smooth muscle layer). Scattered portal and lobular lymphocytes. Extremely activated Kupffer cells with large cytoplasm containing necrotic debris
Hypoxia	Hypoxic ischemic injury of all organs and also liver	Decreased SpO2 levels, mitochondrial dysfunction, and hypoxic hepatocytes express higher ACE-2 levels	Partial or complete luminal thrombosis of the portal and sinusoidal vessels, focal portal vein parietal fibrosis, enlarged and fibrotic vessels. A diffuse network of sinusoids decorated by CD34 suggests a disturbed circulation of blood within the liver
Drugs (antivirals, immune stimulants)	Liver damage	Increase in ALT, AST, LDH, CRP, D-dimer, ferritin, and bilirubin levels and a decrease in albumin levels	Portal fibrosis, lobular and mild portal inflammation
Drugs and viral proteins	The cytopathic effect, oxidative imbalance	Apoptosis and steatosis	Small and/or large droplets of steatosis in hepatocytes

ACE-2: Angiotensin-converting enzyme 2; ALT: Alanine aminotransferase; AST: Aspartate aminotransferase; LDH: Lactate dehydrogenase; CRP: C-reactive protein; SARS-CoV-2: Severe acute respiratory syndrome coronavirus 2; SIRS: Systemic inflammatory response syndrome; TNF-α: Tumour necrosis factor-alpha; IL: Interleukin.