Liver Diseases are disorders affecting the liver's cells, blood supply, bile-producing and bile-draining systems or overall architecture. The liver performs numerous functions including nutrient processing, protein synthesis, bile production, hormone and drug metabolism, storage of energy and micronutrients, immune activity and conversion of ammonia into urea. Liver diseases can be acute or chronic, infectious, metabolic, toxic, autoimmune, vascular, genetic or malignant. Important examples include viral hepatitis, metabolic dysfunction-associated steatotic liver disease, alcohol-related liver disease, autoimmune hepatitis, cholestatic diseases, drug-induced liver injury, cirrhosis and hepatocellular carcinoma.
Hepatocytes are the principal functional cells of the liver and perform many metabolic and synthetic activities. The liver receives blood through both the hepatic artery and portal vein, allowing it to process oxygenated blood alongside nutrient-rich blood arriving from the digestive tract. Within hepatic sinusoids, blood comes into close contact with hepatocytes, while bile travels in the opposite general direction through canaliculi into the biliary system. This specialised architecture permits efficient handling of nutrients, hormones, toxins and metabolic waste. Disease can disrupt hepatocyte function, blood flow, bile movement or tissue architecture, and different patterns of injury produce different clinical manifestations.
Hepatitis means inflammation of the liver and can have infectious, autoimmune, toxic or metabolic causes. Hepatitis A and hepatitis E are commonly transmitted through contaminated food or water, while hepatitis B and hepatitis C can be transmitted through blood and other routes and may produce chronic infection. Chronic viral hepatitis can progressively cause fibrosis, cirrhosis and liver cancer in some affected people. Vaccination provides effective prevention against hepatitis A and B, while modern antiviral treatment can cure most cases of chronic hepatitis C. The different hepatitis viruses are biologically distinct, so the prevention, natural history and treatment of each infection must be considered separately.
Metabolic dysfunction-associated steatotic liver disease involves accumulation of excess fat in the liver in association with metabolic risk factors and can range from relatively uncomplicated steatosis to inflammatory disease and progressive fibrosis. Alcohol-related liver disease arises through harmful alcohol exposure and can include steatosis, alcoholic hepatitis and cirrhosis. The amount and pattern of alcohol exposure, individual susceptibility, coexisting metabolic factors and genetics all influence risk. Fat accumulation alone does not necessarily mean that severe liver damage has occurred, and the severity of fibrosis cannot reliably be determined from liver enzymes alone. Assessment may involve imaging, elastography and other clinical investigations.
Fibrosis is a wound-healing response in which chronic injury promotes deposition of extracellular matrix and progressive architectural change. Advanced fibrosis can culminate in cirrhosis, characterised by extensive scar formation and regenerative nodules that distort normal hepatic architecture. Cirrhosis can cause portal hypertension, ascites, variceal bleeding, hepatic encephalopathy, jaundice and impaired synthesis of proteins and coagulation factors. It also increases susceptibility to hepatocellular carcinoma. Fibrosis is not always irreversible in its earlier stages because successful removal or control of the underlying cause can allow substantial improvement, whereas advanced cirrhosis may produce permanent structural changes and complications.
Liver tests provide different types of information rather than one universal measure of liver function. Alanine aminotransferase and aspartate aminotransferase can indicate hepatocellular injury, while alkaline phosphatase and gamma-glutamyl transferase can increase in cholestatic or other conditions. Bilirubin reflects processing and excretion of haemoglobin-derived pigment, while albumin and coagulation measurements provide information related to synthetic capacity. Imaging can assess liver structure and biliary anatomy, and elastography can estimate tissue stiffness associated with fibrosis. Abnormal liver tests can have many causes, so interpretation requires consideration of medications, alcohol, metabolic factors, infections, muscle injury and other relevant conditions.
Autoimmune and inherited Liver Diseases demonstrate the diversity of hepatic pathology. Autoimmune hepatitis involves immune-mediated hepatocellular inflammation, while primary biliary cholangitis and primary sclerosing cholangitis primarily involve bile ducts through different pathological mechanisms. Hereditary haemochromatosis can lead to excessive iron accumulation, while Wilson disease causes abnormal copper accumulation and can affect the liver and nervous system. Alpha-1 antitrypsin deficiency can also cause liver disease through abnormal protein processing. Drug-induced liver injury can be caused by prescribed medicines, over-the-counter products or supplements, and its presentation can range from mild enzyme elevation to severe hepatic failure.
Common misconceptions include the belief that liver disease always causes pain or jaundice, that abnormal liver enzymes necessarily indicate irreversible damage, or that commercial detoxification products cleanse the liver. Many significant liver diseases are asymptomatic until substantial injury has occurred, while liver enzyme concentrations do not directly measure the amount of fibrosis. The liver already performs its own physiological processing and does not require routine detox diets. Some supplements and herbal products can themselves cause liver injury. Persistent jaundice, abdominal swelling, gastrointestinal bleeding, confusion, unexplained weight loss or markedly abnormal liver tests require medical evaluation because the underlying causes and potential complications vary substantially among Liver Diseases.
