Radiologic Studies
ERCP traditionally had been the gold standard for the diagnosis of PSC. With its significant safety advantages and advances in quality, magnetic resonance cholangiopancreatography (MRCP) has challenged this concept. Early cholangiographic changes can include fine or deep ulcerations of the common bile duct.[2] In a small subgroup of patients, these changes can affect the cystic duct or gallbladder.[30] As PSC progresses, segmental fibrosis develops within the bile ducts, with saccular dilatation of the normal areas between them, leading to the typical "beads-on-a-string" appearance seen on cholangiography (Figure 1).[31,32] Although these strictures can be found anywhere on the biliary tree, the intrahepatic and extrahepatic bile ducts are simultaneously involved in the vast majority of cases.[2]
Figure 1.
ERCP from a patient with elevated serum ALP and a history of ulcerative colitis. The right and left intrahepatic branches show multiple diffuse areas of attenuation, stenosis, and dilatation consistent with PSC.
A subgroup representing 5% to 10% of all PSC patients will have "small-duct PSC," with histologic features and cholestatic liver test findings typical of PSC, yet no cholangiographic changes.[24,28] Small-duct PSC may progress into large-duct disease, although the actual proportion of patients who experience progression is unknown.
The emergence of MRCP is a noninvasive method of diagnosing PSC. The typical finding on MRCP is high T2 signal intensity in wedge-shaped areas with bile duct dilatation (Figure 2 and Video). Multiple studies have compared the diagnostic accuracy of MRCP to that of ERCP ( Table 1 ). Most of these studies have shown that the effectiveness of MRCP, read by experienced radiologists, may approach that of invasive cholangiography. Although MRCP will never replace ERCP completely, it may eventually become a better diagnostic option given its obvious safety advantages. Recent studies have also shown that MRCP may be more cost effective in certain clinical situations.[33]
Figure 2.
MRCP from the same patient as in Figure 1, showing areas of narrowing within the intrahepatic branches.
Video. MRCP "movie" showing multiple areas of stenosis and dilatations within the intrahepatic ducts and mild narrowing of the common bile duct.
Occasionally, ultrasound changes can be seen in PSC. Radiologists experienced in biliary tract imaging may pick up subtle findings such as gallbladder wall thickening, increased gallbladder volume, thickening of the bile duct, or biliary tract dilation.[34] While these changes may not be specific, they are suggestive of PSC and often lead to its eventual diagnosis.
Cholangiography performed by interventional radiologists is useful in cases where ERCP or MRCP is not available or not able to provide adequate imaging. Cholangiography is also helpful in the biopsy, drainage, and stenting of intrahepatic and extrahepatic strictures that are not reachable with ERCP.
© 2007
Medscape
Cite this: Primary Sclerosing Cholangitis -- Approach to Diagnosis - Medscape - Apr 25, 2007.
Comments