Primary Biliary Cirrhosis (cont.)

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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.

  1. Progressive inflammation of the portal tracts and their small bile ducts
  2. The inflammation causes destruction of the small bile ducts and spreads to also involve the nearby liver cells (hepatocytes)
  3. Extensive scars (fibrosis) protrude from the inflamed portal tracts into the region of liver cells
  4. 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.

Medically Reviewed by a Doctor on 1/9/2014

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