Last updated: 02/17/2009

The liver is the body's principle chemical factory. It receives all nutrients, drugs, and toxins, which are absorbed from the intestines, and performs the final stages of digestion, converting food into energy and replacement parts for the body. The...

liver also filters the blood of all waste products, removes and detoxifies poisons, and excretes many of these into the bile. It further processes other chemicals for excretion by the kidneys. The liver is also an energy storage organ, converting food energy to a chemical called glycogen that can be rapidly converted to fuel.

When other medical treatment interferes with the functioning of a damaged liver, a transplant is necessary. Since 1963, when the first human liver transplant was performed, thousands more have been performed each year. Cirrhosis, a disease that kills healthy liver cells, replacing them with scar tissue, is the most common reason for liver transplantation in adults. The most frequent reason for transplantation in children is biliary atresia—a disease in which the ducts that carry bile out of the liver, are missing or damaged.

Included among the many causes of liver failure that bring patients to transplant surgery are:

• Progressive hepatitis, mostly due to virus infection, accounts for more than one-third of all liver transplants.
• Alcohol damage accounts for approximately 20% of transplants.
• Scarring, or abnormality of the biliary system, accounts for roughly another 20% of liver transplants.
• The remainder of transplants come from various cancers, uncommon diseases, and a disease known as fulminant liver failure.

Fulminant liver failure most commonly happens during acute viral hepatitis, but is also the result of mushroom poisoning by Amanita phalloides and toxic reactions to overdose of some medicines, such as acetaminophen—a medicine commonly used to relieve pain and reduce fever. The person who is the victim of mushroom poisoning is a special category of candidate for a liver transplant because of the speed of the disease and the immediate need for treatment.

As the liver fails, all of its functions diminish. Nutrition suffers, toxins build, and waste products accumulate. Scar tissue accumulates on the liver as the disease progresses. Blood flow is increasingly restricted in the portal vein, which carries blood from the stomach and abdominal organs to the liver. The resulting high blood pressure (hypertension) causes swelling of and bleeding from the blood vessels of the esophagus. Toxins build-up in the blood (liver encephalopathy), resulting in severe jaundice (yellowing of the skin and eyes), fluid accumulation in the abdomen (ascites), and deterioration of mental function. Eventually, death occurs.

There are three types of liver transplantation methods. They include:

• Orthotopic transplantation, the replacement of a whole diseased liver with a healthy donor liver.
• Heterotrophic transplantation, the addition of a donor liver at another site, while the diseased liver is left intact.
• Reduced-size liver transplantation, the replacement of a whole diseased liver with a portion of a healthy donor liver. Reduced-size liver transplants are most often performed on children.

When an orthotropic transplantation is performed, a segment of the inferior vena cava (the body's main vein to the heart) attached to the liver is taken from the donor, as well. The same parts are removed from the recipient and replaced by connecting the inferior vena cava, the hepatic artery, the portal vein, and the bile ducts.

When there is a possibility that the afflicted liver may recover, a heterotypic transplantation is performed. The donor liver is placed in a different site, but it still has to have the same connections. It is usually attached very close to the patient's original liver; if the original liver recovers, the donor liver will wither away. If the patient's original liver does not recover, that liver will dry up, leaving the donor in place.

Reduced-size liver transplantation puts part of a donor liver into a patient. A liver can actually be divided into eight pieces—each supplied by a different set of blood vessels. In the past, just two of these sections have been enough to save a patient suffering from liver failure, especially if it is a child. It is possible, therefore, to transplant one liver into at least two patients and to transplant part of a liver from a living donor—and for both the donor and recipients to survive. Liver tissue grows to accommodate its job provided that the organ is large enough initially. Patients have survived with only 15–20% of their original liver intact, assuming that that portion was healthy from the beginning.

As of 2003, the availability of organs for transplant was in crisis. In October 1997, a national distribution system was established that gives priority to patients who are most ill and in closest proximity to the donor livers. Livers, however, are available nationally. It is now possible to preserve a liver out of the body for 10 to 20 hours by flushing it with cooled solutions of special chemicals and nutrients, if necessary. This enables transport cross-country.