PSC -- Approach to Diagnosis - PART 3

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Because histologic

findings in PSC tend to be nonspecific, liver biopsy is used primarily for

staging the disease. The staging is based on the

degree of inflammation, ductal proliferation, and ductopenia. In general, early PSC

is marked by inflammation and later, as the disease progresses, fibrosis

predominates. Eventually the bile duct can be replaced

by a solid fibrous cord. However, it is sometimes

difficult to stage PSC histologically because various

manifestations of the disease can occur within the same liver.

Further complicating this issue, the classic description of periductal " onion skin " fibrosis (Figure 3) is

present in less than 40% of biopsy specimens and is not pathognomonic

for PSC.

Figure 3.

(click image to zoom)

Liver biopsy from a patient

with stage II PSC showing concentric periductal

fibrosis ( " onion skin " ) involving interlobular bile duct; hematoxylin-eosin, X40.

The PSC staging system is

similar to that used for primary biliary cirrhosis:

Stage I

(portal stage) -- focal inflammation limited to portal triad, with or without

bile duct abnormalities, without fibrosis;

Stage II (periportal

stage) -- enlargement of portal tracts, periportal

fibrosis with or without periportal inflammation;

Stage III (septal

stage) -- extension of septal or bridging fibrosis

with bridging necrosis; and

Stage

IV -- biliary cirrhosis.

As

previously highlighted by Case 2, one of the diagnostic dilemmas with PSC is

that it can often be challenging to distinguish from secondary causes of sclerosing cholangitis and

malignancy. Causes of secondary sclerosing

cholangitis must be excluded before a diagnosis of

PSC can be established. The most commonly described

secondary causes include stone disease, infection, pancreatitis,

and surgical/procedural trauma.

Another

caveat is the fact that the presence of cirrhosis may interfere with

interpretation of ERCP/MRCP findings. In particular,

subtle intrahepatic ductal changes in PSC can be

difficult to distinguish from biliary tract changes seen with cirrhosis, and

although a liver biopsy can be helpful, history alone may be the only

suggestion of PSC. A high index of suspicion will be

necessary to make an assertive diagnosis in this setting, keeping in mind that

most cases of PSC occur in patients with inflammatory bowel disease.

The best

approach to diagnosing PSC involves a systematic investigation including

historical examination, laboratory studies, and cholangiographic

evaluation. Particular attention should be paid to a

history of IBD, autoimmune disease, or active cholangitis.

Laboratory

testing should be directed at ruling out secondary causes of sclerosing cholangitis as well as

looking for autoimmune markers, which can be more indicative of PSC. Thus, once initial evaluation with a hepatic panel has

suggested cholestasis, further testing with serum autoantibodies and immunoglobulins

is recommended.

The

sensitivity and specificity of MRCP in facilities with radiologists experienced

in biliary tract diseases approaches that of ERCP. Given

the improved safety profile of MRCP compared with ERCP, we anticipate that MRCP

will soon be considered as a first-line imaging investigation in centers with

skilled radiologists. Once signs of obstruction,

dominant strictures, or inconclusive findings are described, the clinician may

proceed with an ERCP for diagnostic and therapeutic maneuvers.

If the patient's presentation is suggestive of cholangitis,

an ERCP should be the procedure of choice.

Finally,

liver biopsy should be reserved for cases in which other studies are

inconclusive or when a diagnosis of small-duct PSC or an overlap disorder is

being considered.

Barb in Texas - Together in the Fight, Whatever it Takes!

Son Ken (33) UC 91 - PSC 99

Listed 7/21 @ Baylor Dallas