- alkaline phosphatase (ALP), which also goes up
in biliary obstruction (blockage of the flow of
BILE) - gamma-glutamyltranspeptidase (GGT)
Collectively elevated levels of these enzymes in
the blood indicate damage to the liver that has
caused the death of hepatocytes (hepatocellular
necrosis). Individual elevations may indicate dam-
age to other tissues in the body such as might
occur in theHEARTwith HEART ATTACK. The AST to
ALT ratio is also significant; a ratio greater than
2:1 is common with LIVER DISEASE OF ALCOHOLISM.
Prothrombin time The prothrombin time (PT)
measures the amount of time it takes for the clot-
ting process to take place in the plasma. The nor-
mal range (for a person who is not taking
ANTICOAGULATION THERAPY) is 11 to 13.5 seconds.
Clotting time longer than normal suggests a gen-
eral dysfunction of the body’s clotting mecha-
nisms. Liver function becomes suspect with an
elevated clotting time because the liver synthe-
sizes many of the proteins (CLOTTING FACTORS) nec-
essary for COAGULATION.
Preparation, Procedure, and RecoveryLiver function tests require a blood sample, typi-
cally drawn from a VEINin the arm. No prepara-
tion is necessary and there is no recovery period.
Risks and Complications
Some people experience minor bruising at the site
of the venipuncture, which usually heals in a few
days (though liver disease that affects clotting
mechanisms may extend HEALING).
liver hemodialysis A treatment for acute LIVER
FAILURE that employs extracorporeal (out-of-the-
body) filtration of the BLOODto remove the toxins
the liver otherwise would metabolize. LIVER
hemodialysis is currently of limited availability
and remains largely an investigational treatment.
Two procedures are in use, the extracorporeal
liver assist device (ELAD) and the bioartificial
liver. Each uses a biological approach (cultured
human cells or porcine cells) to emulate the func-
tions of the liver’s hepatocytes (the cells in the
liver that filter the blood). These methods provide
a “bridge” of limited filtration until liver trans-
plantation becomes possible.
See also CARDIAC ENZYMES; VENTRICULAR ASSIST
DEVICES(VADS).liver transplantation An OPERATIONto replace a
diseased LIVERwith a donor liver as a treatment for
end-stage LIVER FAILURE. Following liver transplan-
tation, most people are able to return to full and
active lives though must continue taking medica-
tions to suppress rejection of the donor liver
(IMMUNOSUPPRESSIVE THERAPY).
Surgeons performed the first successful liver
transplantation in the United States in 1967. The
risk of organ rejection curtailed transplantation as
a permanent treatment for liver failure, however,
until the advent of the immunosuppressive med-
ication cyclosporine in 1979. Cyclosporine and its
contemporary counterparts (such as tacrolimus,
which debuted 10 years later) have made trans-
plantation a viable, long-term solution. In 2004
doctors added the monoclonal antibody basilix-
imab to the immunosuppressive arsenal, reducing
rejection to about 10 percent. Surgeons now
perform more than 5,500 such operations each
year, with liver transplantation as a therapeutic
solution limited only by the availability of donor
organs.
Donor livers are either cadaveric (harvested
from donors after death) or living-donor segment
(a living person donates part of his or her healthy
liver). Living-donor segment transplantations are
possible because the liver has the unique ability to
regenerate. After a living donor segment trans-
plantation, the donor’s liver eventually restores
itself to full size and function. Ideally, the segment
implanted in the recipient does the same. This
regenerative capability means, too, that livers
transplanted into children will grow as the child
grows.
There are two basic types of liver transplanta-
tion:- orthotopic liver transplantation (OLT), in which
the surgeon removes the diseased liver and
replaces it with the donor liver - heterotopic liver transplantation (HLT), in
which the surgeon leaves the person’s own dis-
eased liver (the native liver) in place and
attaches the donor liver (or liver segment) in a
“piggyback” fashion
liver transplantation 75