Etiology of Liver Injury
Inflammatory and degenerative processes in the hepatic tissue are polyetiological. The causes are divided into two broad categories: infectious agents and non-infectious factors.
Infectious Causes:
- Hepatotropic viruses: The primary cause of viral hepatitis. Clinical practice recognizes eight types designated by letters from A to G, along with the specific TTV virus.
- Bacteria: Injury occurs via direct invasion or through the systemic effects of microbial exo- and endotoxins.
- Parasites: Notably, Plasmodium species, which are the causative agents of malaria.
Non-Infectious Triggers:
- Intoxications: Hepatotoxic chemicals and drugs play a massive role. Potent poisons include ethanol and carbon tetrachloride. Notable pharmacological threats include paracetamol, the antibiotic chloramphenicol, and radiocontrast agents used in cholecystography.
- Immune-mediated disorders: Pathology can develop due to attacks by autoreactive lymphocytes and macrophages, as well as cytotoxic immunoglobulins (Igs).
- Malignancies: Primary liver tumors or metastasis from other organs inevitably destroy the parenchyma.
Key Pathogenetic Mechanisms
Regardless of the primary injurious factor (virus, toxin, or autoimmune reaction), hepatocyte death follows universal pathophysiological pathways. These mechanisms mutually reinforce one another, driving progressive and widespread tissue damage.
- Oxidative stress and enzyme activation: Excessive activation of free radical reactions and the release of cellular hydrolases lead to direct chemical damage of vital macromolecules: proteins, phospholipids, and nucleic acids.
- Destruction of membrane structures: Both the plasma membrane of hepatocytes and the membranes of intracellular organelles are damaged, disrupting the cytoskeleton.
- Inflammation: A local inflammatory response is triggered in response to massive necrosis and tissue alteration.
- Immunopathology: Hypersensitivity reactions and autoimmune aggression develop, causing the immune system to destroy native hepatic cells.
Viral Hepatitis: Clinical Presentation
Viral hepatitis is characterized by a diffuse inflammatory process. It is a systemic disease affecting not only the biliary tract, but the entire body.
Main Clinical Syndromes:
- Asthenovegetative syndrome (marked fatigue, weakness, autonomic dysfunction).
- General toxic syndrome (systemic reaction to accumulated metabolic waste and viral toxins).
- Jaundice (impaired bilirubin metabolism).
- Hepatosplenomegaly (concomitant enlargement of the liver and spleen).
Additionally, a robust immune response leads to extrahepatic manifestations. Patients may develop autoimmune arthritis, glomerulonephritis (kidney damage), and polyarteritis nodosa (vascular inflammation).
Progression to Liver Cirrhosis
Liver cirrhosis is the chronic, end-stage consequence of various progressive hepatic injuries, driven by ongoing parenchymal damage and massive hepatocyte loss.
The hallmark pathomorphological feature of cirrhosis is fibrosis. Dead functional parenchyma is replaced by dense connective tissue, disrupting the normal architecture of the organ. This leads to two fatal consequences:
- Critical impairment of intrahepatic blood flow.
- Severe impairment of all liver functions, as the remaining healthy cells are insufficient to maintain homeostasis.