What is hepatitis?
Hepatitis is the inflammation of the liver, resulting in liver cell damage and destruction. Hepatitis is the Latin word for liver inflammation. It is characterised by the destruction of a number of liver cells and the presence of inflammatory cells in the
liver tissue. Hepatitis can be caused by diseases that primarily attack the liver cells. It can also arise as a result of a disease such as mononucleosis.The liver is the largest organ in the body, occupying the entire upper right quadrant of the abdomen. It performs over 500 vital functions. It processes all of the nutrients the body requires, including proteins, glucose, vitamins, and fats. The liver manufactures bile, the greenish fluid stored in the gall bladder that helps digest fats. One of the liver’s major contributions to life is to render harmless potentially toxic substances, including alcohol, ammonia, nicotine, drugs, and harmful by-products of digestion. Old red blood cells are removed from the blood by the liver and spleen, and the iron contained in them is recycled to the bone marrow to make new red blood cells.
Damage to the liver can impair these and many other processes. Hepatitis varies in severity from a self-limited condition with total recovery to a life-threatening or life-long disease. It can occur from many different causes. In the most common hepatitis cases, specific viruses incite the immune system to fight off infections (called viral hepatitis). Specific immune factors become over-produced that cause injury. Hepatitis can also result from an autoimmune condition, in which abnormal immune factors attack the body’s own liver cells. Inflammation of the liver can also occur from medical problems, drugs, alcoholism, chemicals, and environmental toxins.
Hepatitis may resolve quickly (acute hepatitis), or cause long-term disease (chronic hepatitis). In some instances, progressive liver damage or liver failure may result. Acute hepatitis can begin suddenly or gradually, but it has a limited course and rarely lasts beyond one or two months. Usually there is only spotty liver cell damage and evidence of immune system activity, but on rare occasions, acute hepatitis can cause severe, even life-threatening, liver damage. The chronic forms of hepatitis persist for prolonged periods. Chronic persistent hepatitis is usually mild and nonprogressive or slowly progressive, causing limited damage to the liver. Chronic active hepatitis involves extensive liver damage and cell injury beyond the portal tract.
Most cases of hepatitis are caused by viruses that infect liver cells and begin replicating. They are defined by the letters A through G: Hepatitis A, B, and C are the most common viral forms of hepatitis. Investigators are still looking for additional viruses that may be implicated in hepatitis unexplained by the current known viruses. Other hepatitis viruses include hepatitis E and hepatitis G. Like hepatitis A, hepatitis E is caused by contact with contaminated food or water. It is not serious except in pregnant women, when it can be life threatening. Hepatitis G is always chronic with probably the same modes of transmission as hepatitis C, but to date it does not appear to have serious effects.
Ethanol, mostly in alcoholic beverages, is an important cause of hepatitis. Usually alcoholic hepatitis comes on after a period of increased alcohol consumption. Alcoholic hepatitis is characterized by a variable constellation of symptoms, which may include feeling unwell, enlargement of the liver, development of fluid in the abdomen ascites, and modest elevation of liver blood tests. Alcoholic hepatitis can vary from mild with only liver test elevation to severe liver inflammation with development of jaundice, prolonged prothrombin time, and liver failure. Severe cases are characterized by either obtundation or the combination of elevated bilirubin levels and prolonged prothrombin time; the mortality rate in both categories is 50% within 30 days of onset.
Non-alcoholic steatohepatitis (NASH) is a type of hepatitis which resembles alcoholic hepatitis on liver biopsy (fat droplets, inflammatory cells, but usually no Mallory’s hyalin) but occurs in patients who have no known history of alcohol abuse. NASH is more common in women and the most common cause is obesity or the metabolic syndrome. A related but less serious condition is called “fatty liver” (steatosis hepatis). A liver biopsy for fatty liver shows fat droplets throughout the liver, but no signs of inflammation or Mallory’s hyalin. Anomalous presentation of human leukocyte antigen (HLA) class II on the surface of hepatocytes - possibly due to genetic predisposition or acute liver infection - causes a cell-mediated immune response against the body’s own liver, resulting in autoimmune hepatitis.
Autoimmune chronic hepatitis accounts for about 20% of all chronic hepatitis cases. Like other autoimmune disorders, this condition develops because a genetically defective immune system attacks the body’s own cells and organs (in this case the liver) after being triggered by an environmental agent, probably a virus. Autoimmune hepatitis has a prevalence of 1-2 per 1000. As with most other autoimmune diseases, it affects women much more often than men (8:1). Liver enzymes are elevated, as is bilirubin. Autoimmune Hepatitis can progress to cirrhosis. Treatment is with steroids and disease-modifying antirheumatic drugs (DMARDs).
A large number of drugs can cause hepatitis. Because the liver plays such a major role in metabolizing drugs, hundreds of medications can cause reactions that are similar to those of acute viral hepatitis. Symptoms can appear anywhere from two weeks to six months after starting drug treatment. In most cases, they disappear when the drug is withdrawn; but, in rare circumstances, they may progress to serious liver disease. Among the drugs most prominently cited for liver interactions are halothane, isoniazid, methyldopa, phenytoin, valproic acid, and the sulfonamide drugs. Notably, very high doses of acetaminophen (Tylenol) have been known to cause severe liver damage and even death, particularly when used with alcohol.