Liver disease is disease that affects the liver and its functions. There are many types of liver disease, including hepatitis, cirrhosis and fatty liver.

The liver is one of the body's largest and most vital organs. It is located on the upper right side of the abdomen just under the rib cage. It is about the size of a football and weighs 3 to 4 pounds.

The liver serves many important functions, including:

• Storing vitamins, glycogen, fats and other nutrients from food
  
  
• Producing and regulating chemicals necessary for digestion, such as bile (digestive fluid that helps break down fats) and enzymes (complex proteins in body cells that regulate chemical reactions)
  
  
• Breaking down toxic substances, such as alcohol and poisonous chemicals
  
  
• Removing waste products from the body
  
  
• Producing immune agents to protect against infection

Healthy livers are cone-shaped with a smooth, rubbery texture and a reddish-brown color (because they hold blood). Blood is supplied to the liver from two sources:

• The portal vein, which carries nutrients and toxins from the digestive system
  
  
• The hepatic artery, which supplies oxygen-rich blood from the heart

All substances that are digested and absorbed, inhaled and absorbed, or absorbed through the skin eventually reach the liver, where they are metabolized (broken down) into byproducts that the body can use or eliminate. Byproducts that carry nutrients are delivered to other parts of the body through the bloodstream. Some waste byproducts are delivered through the bloodstream to the kidney where they are filtered and excreted in urine. Other waste byproducts are transported from the liver in bile to the gallbladder and intestines and later excreted along with solid waste in feces.

The liver has the ability to heal itself by repairing or replacing damaged cells. It can function even after losing a large percentage of its cells to disease. Despite its resiliency, the liver can become damaged in many ways. For example viruses, such as the hepatitis virus, can attack the liver and cause inflammation. Excessive alcohol consumption can result in scarring of the liver. Like other organs, the liver can develop cancer.

Liver disease can result in complications. Some of the most common complications include:

• Portal hypertension. Blood from the intestines, spleen and pancreas enter the liver through a large blood vessel called the portal vein. Scar tissue in the liver alters blood flow, and this often results in increased pressure in the vein, which may cause internal bleeding (see varices).
  
  
• Varices (stretched veins). When blood flow in the portal vein is redirected by the loss of healthy liver cells, this can lead to abnormally increased flow in various vessels. These abnormally enlarged veins or varices are likely to hemorrhage with dire consequences.
  
  
• Fluid retention. Liver disease can cause large amounts of fluid to accumulate in the legs (edema) or abdominal cavity (ascites).
  
  
• Bruising and bleeding. Liver damage interferes with the liver's absorption of vitamin K and the production of proteins that help the blood clot. As a result, patients may bruise easier and bleed more frequently.
  
  
• Jaundice. When the liver is not able to remove bilirubin (substance formed from the breakdown of red blood cells that gives bile its color), jaundice may occur. This causes the skin and whites of the eyes to turn yellow.
  
  
• Itching. Bile salts deposited in the skin can cause itching.
  
  
• Hepatic encephalopathy (abnormal brain function that occurs when toxins from the liver enter the blood). Symptoms include forgetfulness, confusion, mood changes and, in advanced cases, delirium and coma.
  
  
• Infection. The decreased immune system function from liver damage may lead to increased bacterial, viral and other infections.
  
  
• Diabetes. Conditions including fatty liver and hemochromatosis increase the risk of diabetes.
  
  
• Osteoporosis. Chronic liver disease may promote weakening and thinning of the bones.
  
  
• Liver failure. This occurs when damage to the liver becomes so extensive that the liver cannot function. Without a liver transplant, liver failure can be fatal.

More than half a million Americans a year are hospitalized with chronic liver disease, according to the Centers for Disease Control and Prevention (CDC). It was the nation's 12th leading cause of death in 2005, taking 27,530 lives, the CDC reported in 2008.