Diagnostic
Tests for Liver and Gallbladder
Disorders
Laboratories can carry out a variety
of tests that help doctors assess
disorders of the liver, gallbladder, and
biliary tract. Among the most important
are a group of blood tests known as
liver function tests. Depending on a
patient's suspected problem, a doctor
may also order certain imaging tests,
such as an ultrasound scan, computed
tomography, and magnetic resonance
imaging. Also, a doctor may take a
sample of liver tissue for examination
under a microscope, a procedure called a
liver biopsy
Laboratory and Imaging Tests
Breath tests measure
the ability of the liver to metabolize a
variety of drugs. The drug, which is
tagged with a radioactive tracer, may be
given orally or intravenously. The
amount of radioactivity in the person's
breath is a measure of the amount of
drug metabolized by the liver.
Ultrasound scanning
uses sound waves to provide images of
the liver, gallbladder, and biliary
tract. The test is better for detecting
structural abnormalities, such as
tumors, than diffuse abnormalities, such
as cirrhosis. It is the least expensive,
safest, and most sensitive technique for
creating images of the gallbladder and
biliary tract.
Using ultrasound, a doctor can
readily detect gallstones in the
gallbladder. Ultrasound scanning easily
distinguishes jaundice caused by bile
duct obstruction from jaundice caused by
liver cell malfunction. A type of
ultrasound scanning, vascular Doppler
ultrasound, can be used to show the
blood flow in the blood vessels of the
liver. A doctor also may use ultrasound
scanning as a guide when inserting a
needle to obtain a tissue sample for
biopsy.
Radionuclide (radioisotope)
imaging uses a substance
containing a radioactive tracer that is
injected into the body and taken up by a
particular organ. The radioactivity is
detected by a gamma-ray camera attached
to a computer that generates an image. Liver
scanning is a type of
radionuclide imaging that uses
radioactive substances taken up by liver
cells. Cholescintigraphy,
another type of radionuclide imaging,
uses radioactive substances excreted by
the liver into the biliary tract; it is
used to detect acute inflammation of the
gallbladder (cholecystitis).
Computed tomography (CT)
scanning can provide excellent
liver images and is particularly useful
in detecting tumors. It can detect
diffuse disorders, such as fatty liver,
and abnormally dense liver tissue caused
by iron overload (hemochromatosis).
However, because CT uses x-rays and is
expensive, it is not as widely used as
ultrasound.
Magnetic resonance imaging (MRI)
provides excellent images, similar to
those obtained with CT. However, it has
drawbacks: It is more expensive than CT,
takes longer than other imaging methods,
and requires lying in a narrow chamber,
which makes some people claustrophobic.
Endoscopic retrograde
cholangiopancreatography is a
test in which an endoscope (a flexible
viewing tube) is inserted into the
mouth, through the stomach and duodenum,
and into the biliary tract. A radiopaque
substance is then injected into the
ducts of the biliary tract, and x-rays
are taken of the biliary tract. This
test causes inflammation of the pancreas
(pancreatitis) in 3 to 5 percent of the
people.
Percutaneous transhepatic
cholangiography involves
inserting a long needle through the skin
and into the liver, then injecting a
radiopaque substance into one of the
liver's bile ducts. A doctor may use
ultrasound for guidance when inserting
the needle. The x-rays clearly reveal
the biliary tract, particularly a
blockage within the liver.
Operative
cholangiography uses a
radiopaque substance that is visible on
x-rays. During an operation, the
substance is injected directly into the
ducts of the biliary tract. X-rays then
reveal clear images of the biliary
tract.
Simple x-rays can
often reveal a calcified gallstone.
Liver Biopsy
A liver specimen can be obtained
during exploratory surgery but is more
often obtained by inserting a needle
through the skin and into the liver.
Before the procedure, the patient
receives local anesthesia. Ultrasound or
CT scans may be used to locate the
abnormal area from which the specimen is
taken. In most medical centers, a liver
biopsy is performed as an outpatient
procedure.
After the specimen is obtained, the
person stays in the hospital for 3 to 4
hours because there is a small risk of
complications. The liver may be
lacerated, and bleeding into the abdomen
may occur. Bile may leak into the
abdomen, causing inflammation of the
abdominal lining (peritonitis). Because
bleeding can start up to 15 days later,
the person should stay within an hour's
drive of the hospital during that
period. In about 2 percent of people,
these complications cause serious
problems, and 1 in 10,000 die from the
procedure. Mild pain in the upper right
abdomen, sometimes extending to the
right shoulder tip, is common after a
liver biopsy and is usually relieved by
analgesics.
In transvenous liver biopsy, a
catheter is inserted into a neck vein,
threaded through the heart, and placed
into one of the hepatic veins that come
from the liver. The needle of the
catheter is then inserted through the
wall of the vein into the liver. This
technique is less likely to injure the
liver than is a percutaneous liver
biopsy, and it can be used even in
people who bleed easily.
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