Primary Biliary Cirrhosis (cont.)
In this Article
What is the role of imaging tests?
Ultrasound imaging of the liver is recommended for patients whose blood tests
show cholestasis. Cholestatic blood tests feature a disproportionately elevated
alkaline phosphatase and ggt, compared to the ALT and AST. The purpose of the
ultrasound exam is to visualize the bile ducts to exclude mechanical blockage
(obstruction) of larger bile ducts as the cause of the cholestasis. Gallstones
or tumors, for example, may cause mechanical obstruction of bile ducts. The
blockage can cause increased pressure in the bile ducts that leads to dilation
(widening) of the upstream bile ducts.
Dilated bile ducts caused by mechanical obstruction can usually be visualized
on the ultrasonogram. The dilated bile ducts can also be seen using other
imaging techniques such as computerized tomographic (CT) scanning, Magnetic
Resonance Imaging (MRI), or an endoscopic procedure called ERCP. On the other
hand, in PBC, the ducts that are being destroyed are so small that any dilation
of upstream ducts cannot be seen with any of the imaging techniques. For the
diagnosis of PBC in patients with cholestatic liver tests, a positive AMA and a
normal ultrasound examination usually is sufficient. In this situation, other
imaging studies of the bile ducts are usually not required.
What is the role of liver biopsy?
The benefits of doing a liver biopsy (taking a tissue sample) include:
- Confirmation of the diagnosis
- Determination of the stage of disease
- Identification of any other concurrent liver disease
Pathologists (physicians who analyze tissue samples) have divided the
evolution of PBC into four stages recognizable by the microscopic appearance of
the liver biopsy.
- Progressive inflammation of the portal tracts and
their small bile ducts
- The inflammation causes destruction of the small bile
ducts and spreads to also involve the nearby liver cells (hepatocytes)
- Extensive scars (fibrosis) protrude from the inflamed
portal tracts into the region of liver cells
- Cirrhosis
From a practical perspective, physicians most often divide the disease into
prefibrotic (before scarring) and fibrotic (scarring or cirrhosis) stages, still
usually using the biopsy findings.
Patients often ask if a liver biopsy is mandatory. The answer usually depends
on the level of confidence in establishing the diagnosis of PBC using the liver
tests, autoantibodies, and ultrasound. In the presence of cholestatic liver
tests, high levels of AMA, and an ultrasound showing no bile duct obstruction in
a middle-aged woman, the diagnosis of PBC can be made rather confidently without
a biopsy. Treatment then can often be started, for example, with ursodeoxycholic
acid (UDCA, a naturally occurring bile acid that is produced in small quantities
by normal liver cells).
Without a biopsy, however, the stage (extent) of the disease would remain
undefined. A biopsy helps the patient know where they are in the natural history
of the disease. Furthermore, knowing the stage of PBC can help physicians decide
about prescribing certain medications (for example corticosteroids) that may be
effective in the early stages and less valuable in later stages.
On the other hand, PBC patients who already have the complications of
cirrhosis (for example, ascites, varices, or hepatic encephalopathy) are
presumed to have advanced liver disease. In these PBC patients the imaging
studies alone are usually sufficient to exclude dilated ducts and a biopsy is
not needed for staging the disease. Otherwise, the presence or absence of other
symptoms (apart from the presence of those clearly due to the complications of
cirrhosis) is not an accurate guide to the stage of PBC on a liver biopsy. For
example, in one large series of patients, approximately 40% of those without
symptoms had cirrhosis on liver biopsy.
Next: What are the criteria for a definitive diagnosis of PBC »
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