What is liver disease?
Liver disease is an acute or chronic damage to the liver, usually caused by infection, injury, exposure to drugs or toxic compounds, an autoimmune process, or by a genetic defect (such as haemochromatosis). The disease can also be categorised by the effect it has on the liver. Hepatitis is an inflammation of the liver, cirrhosis involves scarring and progressive cell death, stones are developed and form blockages, cancer is rare but can be life threatening. Genetic defects cause liver disease by preventing vital functions and by depositing damaging substances in the liver.
There are two major forms of hepatitis: one in which the liver is damaged quickly (called acute hepatitis) and one in which the liver is damaged slowly, over a long 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 that mainly damage the liver, termed hepatitis viruses. These viruses have been named in the order of their discovery as hepatitis A, B, C, D, and E. [See Viral Hepatitis]
- Hepatitis A occurs when the hepatitis A virus is taken in by mouth. An infected person’s hands can become contaminated after using the toilet and the virus is spread by direct contact, or by food, beverages and other objects that were handled by the infected person or is spread through infected water and food and is especially common in children. Most infected people don’t even know they have been exposed to the virus.
- Hepatitis B is fairly common, especially in Asia and Africa; although less common elsewhere. In Australia, carrier rates are likely to be about 0.1 to 0.2 percent amongst Caucasians but can be as high as 10 percent in some aboriginal communities. 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% become chronically infected, able to continue to infect others, and often have chronic damage to the liver. Those with weakened or compromised immune systems are at an increased risk to become carriers (about 10%). Newborns are especially vulnerable, with over 90% becoming carriers.
- Hepatitis C is passed the same way as hepatitis B. Hepatitis C is less common than 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.
- Hepatitis D and E are relatively rare.
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. Drugs (for instance paracetamol), alcohol and even some naturopathic remedies, have the potential to cause life threatening acute liver failure.
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 stabilise 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 gynaecomastia), and a number of other problems. Liver function is monitored with such tests as albumin, prothrombin time, bilirubin, and other liver function tests. In extreme cases, liver transplantation may be needed.
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.
Gallstones, tumours, trauma and inflammation can cause blockage or obstructions in the ducts draining the liver (bile ducts). When an obstruction occurs, bile and its associated wastes accumulate in the blood and the patient’s skin and eyes often turn yellow (jaundice); bilirubin in the urine turns it a dark brown colour, while lack of bilirubin in the intestines causes the stool to become very pale coloured. Blood tests may show elevated levels of bilirubin, alkaline phosphatase (ALP), and other liver enzymes.
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 tumours 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 drugs, others require surgery.
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 NASH (nonalcoholic steatohepatitis), 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.
Hepatitis and cirrhosis may lead to liver cancer in some cases, but cancer from other parts of the body that spreads to the liver is more common. 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.
Haemochromatosis 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. Most of the diseases involve a defective element that results in liver injury (such as biliary atresia, where the bile ducts are absent or too small) or a missing enzyme or protein that leads to damaging deposits in the liver (such as galactosaemia, the absence of a milk sugar enzyme, which leads to milk sugar accumulation; and Wilson’s disease, where copper builds up in the liver).