Etiology of Liver Damage
The development of inflammatory and degenerative processes in liver tissue is polyetiological in nature. All causes can be divided into two broad categories: infectious agents and non-infectious factors.
Infectious causes:
- Hepatotropic viruses. This is the main cause of viral hepatitis. Today, clinical practice distinguishes 8 types of pathogens, designated by Latin letters from A to G, as well as the specific TTV virus.
- Bacteria. Damage occurs both through direct invasion and via the effects of exo- and endotoxins of microorganisms.
- Parasites. In particular, plasmodia, which are the causative agents of malaria.
Non-infectious triggers:
- Intoxications. Hepatotoxic substances and medications play a huge role. Strong poisons include ethanol and carbon tetrachloride. Among medications, threats include paracetamol, the antibiotic chloramphenicol, and radiopaque agents used for cholecystography.
- Immune disorders. Pathology can develop due to attacks by the body's own lymphocytes and macrophages, as well as under the influence of cytotoxic immunoglobulins (Ig).
- Oncology. Various neoplasms of the liver itself or metastases from other organs inevitably destroy the parenchyma.
Key links in pathogenesis
Regardless of the primary damaging factor (virus, poison, or autoimmune reaction), hepatocyte cell death proceeds via universal pathophysiological mechanisms. These factors mutually reinforce each other, making tissue damage total and progressive.
- Activation of oxidative stress and enzymes. An excessive trigger of free radical reactions and the release of cellular hydrolases occurs. This leads to direct chemical damage to critical molecules: proteins, phospholipids, and nucleic acids.
- Destruction of membrane structures. Both the plasma membrane of hepatocytes and the membranes of intracellular organelles are damaged. The integrity of the cytoskeleton is disrupted.
- Development of inflammation. In response to massive necrosis and tissue alteration, a local inflammatory reaction forms.
- Immunopathology. Allergic reactions and processes of immune autoaggression are triggered, when the body begins to destroy its own liver cells.
Viral hepatitis: clinical picture
Viral hepatitis is characterized by the development of a diffuse inflammatory process. It is a systemic disease that affects not only the biliary tract, but the entire body.
Main clinical syndromes:
- Asthenovegetative (pronounced weakness, fatigue, autonomic disorders).
- General toxic (the body's reaction to the accumulation of metabolites and viral toxins).
- Jaundice (disruption of bilirubin metabolism).
- Hepatosplenomegaly (combined enlargement of the liver and spleen).
In addition, a powerful immune response leads to extrahepatic lesions. Patients may develop autoimmune arthritis, glomerulonephritis (kidney damage), and polyarteritis nodosa (inflammation of blood vessels).
Progression to liver cirrhosis
Liver cirrhosis is a chronic, end-stage condition of many liver diseases. It is based on progressive damage and massive death of hepatocytes.
The main pathomorphological feature of cirrhosis is fibrosis. The dead working parenchyma is replaced by coarse connective tissue. Because of this, the organ loses its normal architecture. This leads to two fatal consequences:
- Critical disturbance of blood flow within the liver.
- Severe deficiency of all hepatic functions, since the remaining healthy cells are insufficient to maintain homeostasis.
Briefly: answers to topical questions
Which hepatotropic viruses are transmitted mainly through the enteral route?
Hepatitis A and E viruses are transmitted mainly via the enteral (fecal-oral) route. The rationale for dividing viruses is based on their mechanism of entry into the body.
- Hepatitis A virus is the most important in the group of acute hepatitis.
- Hepatitis E virus is also characterized by a fecal-oral transmission mechanism.
What is the pathogenesis of hepatic encephalopathy in cirrhosis?
The pathogenesis of hepatic encephalopathy in cirrhosis is associated with impaired detoxification in the liver: substances that are normally detoxified into urea and other neutral substances enter the general bloodstream and central nervous system, causing brain dysfunction.
- Ammonia is formed in the intestine and is not fully detoxified in cirrhosis; it enhances the synthesis of false neurotransmitters and serotonin.
- Aromatic amino acids — phenylalanine, tyrosine, tryptophan; their elevation inhibits dopamine synthesis, forming octopamine and phenylethanolamine, which act as false neurotransmitters and disrupt nerve-synaptic transmission.
- Gamma-aminobutyric acid (GABA) is formed in the intestine, is not detoxified, enters the brain, and causes inhibition of its functions.
What types of portal hypertension are distinguished depending on the location of the blood flow block?
Depending on the anatomical location of the obstruction to blood flow, three types of portal hypertension are classified.
- Posthepatic — characterized by involvement of the splenic, mesenteric, or portal vein.
- Intrahepatic — occurs in various diseases of the liver itself.
- Suprahepatic — caused by diseases leading to impaired venous outflow from the liver.
To easily recall the key syndromes of hepatitis, use the abbreviation: Hepatosplenomegaly, Asthenovegetative, Jaundice, General toxic.
Class and exam questions
What is the main difference between hepatitis and cirrhosis?
Hepatitis is an inflammatory process that can be acute or chronic, whereas cirrhosis is a progressive stage of injury in which dead cells are irreversibly replaced by connective tissue (fibrosis develops).
What extrahepatic manifestations are characteristic of viral hepatitis?
Due to immune system malfunctions, viral hepatitis can be accompanied by damage to other systems: arthritis, glomerulonephritis, and polyarteritis nodosa develop.
Which chemical substances are most toxic to hepatocytes?
Typical hepatotoxic poisons include ethanol and carbon tetrachloride. Among medications, the greatest danger is posed by paracetamol, chloramphenicol, and cholecystography agents.
What else to study on this topic
- Mechanisms of immune autoaggression formation in chronic inflammation
- Free radical oxidation of hepatocyte membrane phospholipids
- Pathogenesis of hepatic failure in massive fibrosis
- Hemodynamic disorders in the liver during connective tissue proliferation
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