What is liver disease?

Liver disease is categorized both by the cause and the effect it has on the liver. Causes may include infection, injury, exposure to drugs or toxic compounds, an autoimmune process, or a genetic defect (such as hemochromatosis). These causes can lead to hepatitis, cirrhosis, stones that develop and form blockages, fatty liver, and in rare instances liver cancer. Genetic defects can prevent vital liver functions and lead to the deposition and build-up of damaging substances, such as iron or copper.

Hepatitis

There are two major forms of hepatitis: one in which the liver is inflamed quickly (called acute hepatitis) and one in which the liver is inflamed and damaged slowly, over a long period of time (called chronic hepatitis). While hepatitis can be caused by any of the means mentioned above, most commonly it is due to infection by one of several viruses, termed hepatitis viruses. These viruses have been named in the order of their discovery as hepatitis A, B, C, D, and E.

1. Hepatitis A is spread through infected water and food and is especially common in children. Adults may experience symptoms such as jaundice, nausea, diarrhea, and fatigue, but children often do not even know they have been exposed to the virus.
2. Hepatitis B is found throughout the world and is especially common in Southeast Asia and Africa. It is still the most common cause of acute viral hepatitis in North America and Europe and, according to the National Center for Infectious Diseases, about one out of every 20 people in the United States will get infected with the hepatitis B virus at some time during their lives. Hepatitis B can be spread by exposure to blood, through sexual relations, and from mother to baby. Symptoms of hepatitis B may be absent, mild and flu-like, or acute (see Signs and Symptoms). Most people will get better without any intervention, but about 1-3% will become chronically infected, able to continue to infect others, and often experience chronic progressive damage to the liver. Those with weakened or compromised immune systems are at an increased risk to become chronically infected (about 10%). Newborns are especially vulnerable, with over 90% becoming chronically infected.
3. Hepatitis C is spread mainly by exposure to contaminated blood. Some mechanisms of exposure include the sharing of needles or other 'works' used in consuming drugs such as cocaine or heroin; use of contaminated equipment for activities such as body piercing and tattooing; occupational exposure of healthcare workers to used needles or other sharp objects; through sexual activity that results in tissue tears; from mother to baby during childbirth; or from cuts sustained during athletic or other activity. Hepatitis C is less common than hepatitis B as a cause of acute hepatitis, but the majority of the people who contract it become chronically infected, able to spread the infection to others, and usually have chronic damage to the liver.
4. Hepatitis D and E are rare in the U.S.

Since the liver is responsible for the metabolism of alcohol, drugs, and environmental toxins, prolonged exposure to any of these can also cause hepatitis and/or cirrhosis. Combinations of drugs (for instance, acetaminophen) and alcohol have the potential to cause life-threatening acute liver failure.

Fatty Liver

Fatty liver causes liver enlargement, tenderness, and abnormal liver function. The most common cause is excessive alcohol consumption. It is usually a reversible condition, resolving with abstention from alcohol. Another cause of fatty liver is nonalcoholic steatohepatitis (NASH), the most common chronic hepatitis not caused by viruses. While symptoms are usually fairly mild, it may cause cirrhosis. It is seen most commonly in overweight and diabetic individuals.

Cirrhosis

Anything that causes severe ongoing injury to the liver can lead to cirrhosis. It is marked by cell death and scar formation and is a progressive disease that creates irreversible damage. Cirrhosis is treated by trying to limit further damage; if it is caused by a virus or another treatable cause of liver injury, treating the cause can stabilize the disease and prevent deterioration in liver function. Cirrhosis has no signs or symptoms in its early stages, but as it progresses, it can cause fluid build-up in the abdomen (called ascites), muscle wasting, bleeding from the intestines, easy bruising, enlargement of the breasts in men (called gynecomastia), and a number of other problems. Liver function is monitored with such tests as albumin, prothrombin time, bilirubin, and a liver panel. In extreme cases, liver transplantation may be needed.

Obstruction

Gallstones, tumors, trauma, and inflammation can cause blockages or obstructions in the ducts draining the liver (bile ducts). When an obstruction occurs, bile and its associated wastes accumulate in the liver and the patient’s skin and eyes often turn yellow (jaundice); bilirubin in the urine turns it a dark brown color, while lack of bilirubin in the intestines causes the stool to become very pale colored (similar symptoms may develop in acute hepatitis and, occasionally, in cirrhosis). Blood tests may show elevated levels of bilirubin, alkaline phosphatase (ALP), and other liver enzymes.

Cholesterol and bile pigments (bilirubin) in the bile may form stones in the gallbladder, where bile is stored. These stones may or may not cause symptoms and problems, depending on their size and location. If present for a long time, they may damage the gall bladder and prevent it from working properly; this often causes a feeling of bloating and discomfort in the upper abdomen after meals, especially ones high in fat. The gallstones may block the duct that drains bile from the gallbladder, causing sharp pain to develop suddenly in the upper right part of the abdomen, and, in many cases, leading to infection of the gallbladder and fever.

Obstruction of the hepatic vein, the vein from the liver, may also occur, reducing blood flow out of the liver. This obstruction may be due to tumors pushing against the vein or from blood clot formation within the vein. Obstructions may be chronic and cause few symptoms, but they can also be acute and life-threatening. Some can be treated with medications; others require surgery.

Liver Cancer

Hepatitis and cirrhosis may lead to liver cancer in some cases, but more frequently cancer starts in other parts of the body and then metastasizes (spreads) to the liver. When cancer does arise in the liver, it is called primary liver cancer. The most common type is hepatocellular carcinoma, cancer that develops in the liver’s hepatocyte cells. According to the American Cancer Society, this type encompasses about 3 out of 4 cases of primary liver cancer. Another 1 or 2 cases out of 10 are cholangiocarcinomas, cancers that start in the bile ducts. People who have chronic hepatitis or cirrhosis may be checked on a regular basis for cancer, often with an alpha-fetoprotein (AFP) test and/or an ultrasound.

Genetic Disorders

Hemochromatosis is the most common genetic liver disorder. It involves excess iron storage and is usually diagnosed in adults. There are numerous genetic liver diseases that affect children. The most common is alpha 1-antitrypsin deficiency. Most of the genetic liver diseases involve a missing enzyme or protein that leads to damaging deposits in the liver (such as galactosemia, the absence of a milk sugar enzyme, which leads to milk sugar accumulation; and Wilson’s disease, where copper builds up in the liver). Although not genetic, a defective element that results in liver injury (such as biliary atresia, where the bile ducts are absent or too small) may also cause problems with abnormal liver function in newborns.