Why so important?

Just as you cannot live without your heart or brain, you cannot live without your liver. Your liver performs many functions that are vital to survival. It transforms food into usable body chemicals. It filters waste, bacteria, and poisons from your blood. The liver stores vitamins and sugars that your body uses for energy.

The liver is a wedge-shaped organ located underneath the rib cage. Weighing close to 3 pounds, the liver is the body's largest internal organ. It has four main functions in the body: purification, synthesis, storage, and transformation.

The liver's many roles

• Purification. Your liver changes toxic substances, including alcohol, into harmless substances. Did you know that, even in healthy people, the liver processes alcohol as a poison? While inactivation of substances like alcohol and nicotine is good for the body as a whole, liver cells can be damaged in the process. Detoxification of alcohol, for example, can lead to cirrhosis. Your liver also changes certain medicines into a form your body can use, and inactivates other medicines after they've worked.

• Synthesis. Your liver takes simple chemical building blocks and combines them to manufacture (synthesize) more complex substances. For example, the liver manufactures most of the proteins found in the blood, as well as those needed to clot blood, make new cells, and cause chemical reactions inside of cells.

• Storage. The liver is a warehouse for your body. Besides storing minerals and vitamins, the liver stores sugars that your body uses for energy. Your liver releases these sugars into the bloodstream between meals when other parts of your body, like muscles or the brain, need more energy.

• Transformation. About 90 percent of the food you eat passes through your liver before it can be used. Your liver transforms food into vital body chemicals, including proteins, fats, and cholesterol. It also helps to digest fat and important vitamins carried in fats. When all of this is completed, your liver then sends this nourishment through the blood for cells to use.

When your liver is not well

As mentioned earlier, hepatitis is an inflammation of the liver. As liver disease progresses, other changes occur and damage to the liver increases. For example:

• Fibrosis. After becoming inflamed, the liver tries to repair itself by forming tiny scars. This scarring, called "fibrosis," makes it difficult for the liver to do its job. As damage continues, many scars form and begin to join together, leading to the next stage � cirrhosis.

• Cirrhosis. With cirrhosis, large areas of the liver become permanently scarred from repeated damage. The liver begins to shrink and become hard. Chronic viral hepatitis is a common cause of cirrhosis, as is alcoholism. Scarring prevents blood from flowing freely through the liver, severely impairing liver function.

• Liver failure. As cirrhosis worsens, most liver function is lost. This means the liver is unable to filter wastes, toxins, and drugs from the blood. It can no longer produce the clotting factors necessary to stop bleeding. Fluid builds up in the abdomen and legs, bleeding in the intestines is common, and eventually mental functioning is slowed. At this point, a liver transplant is the only option.

• Liver cancer. Sometimes damage to liver cells includes altering the genes inside cells in a way that causes them to become cancerous. Patients with chronic hepatitis B or C are at higher risk for this form of cancer.