A liver transplant is often the only life-saving treatment available to people whose livers have failed -- and thousands die each year waiting for a donor.
Now U.S. researchers are testing an artificial liver, one that could provide a bridge to transplantation or even help seriously ill patients survive long enough for their own livers to regenerate.
"It would be the dream of 40 years of research to have a machine that can replace the liver," says Dr. Andres T. Blei, a liver expert at Northwestern University Medical School in Chicago who is studying the new device.
Normally, the liver removes toxins from the blood. When it stops working, toxins accumulate in the bloodstream, damaging nerves, kidneys and other organs, and increasing pressure on the brain, ultimately culminating in death.
The artificial liver, known as the Molecular Adsorbent Recirculating System, cleanses blood of these poisons.
Developed in the early 1990s by two kidney specialists in Germany, the device works on the same principle as a kidney dialysis machine. Blood is pumped slowly from the body and filtered through a thin membrane coated with albumin, a protein that removes the large, fatty toxins normally filtered out by the liver.
Patients with liver failure are kept on the machine round-the-clock, until they feel better or receive a transplant.
In Germany, the device was first tested on 26 seriously ill patients with chronic liver disease. Of those, nine died, but 17 survived without a transplant.
"Normally, all of them would have died," says Dr. Jan Stange, a co-inventor of the system who is now at UC San Diego in La Jolla. "The machine allowed them to live long enough to recover."
Since it became commercially available in Europe and Asia in 1998, the system has been used on more than 2,500 patients who are waiting for transplants, are in comas induced by toxins in the bloodstream and brain, or have acute liver failure caused by ingestion of a substance toxic to the liver, such as acetaminophen (the active ingredient in Tylenol) or mushrooms.
It was first used in the U.S. in the late 1990s on 20 desperately ill patients.
Two of the patients, who suffered acute liver failure, survived long enough to recover their liver function.
The remaining 18 showed improvement, and six received a liver transplant.
"This encouraged us to study people who were less sick in hopes of getting even better results," says Dr. Robert H. Bartlett, a surgery professor at the University of Michigan in Ann Arbor who did the research.
Since then, a study of 70 patients whose liver failure has put them in a coma has gotten underway at five hospitals across the country, although results won't be available for at least a year.
"The question is whether we can help patients recover their mental status and reverse the coma quickly," says Dr. Robert J. Fontana, medical director of liver transplantation at the University of Michigan Medical Center, who is helping conduct this study.
"Potentially, this device could be a bridge to other interventions, like a life support for patients in liver failure."
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When a liver fails
Liver failure is generally divided into two types: sudden, more commonly known as "acute," and chronic.
Acute liver failure occurs when an otherwise healthy person ingests chemicals toxic to the liver (found in some mushrooms and medications) or as a complication of acute hepatitis. Sometimes the liver can recover by itself but often a liver transplant is required.
Chronic liver failure is much more common, affecting an estimated 4 million to 5 million Americans. It occurs during the end stage of long-term liver problems caused by prolonged alcohol or substance abuse, chronic hepatitis or other infections.
People with chronic liver problems can lead normal lives until an averse reaction to something such as a viral infection or a fatty diet pushes them over the edge into liver failure. Although medication and a restricted diet can help eliminate liver toxins, if the liver is too damaged, a transplant may be the only alternative.