Primary Sclerosing Cholangitis
Approximately 71% of patients with primary sclerosing cholangitis (PSC) also have inflammatory bowel disease. Approximately 87% of these patients have ulcerative colitis and 13% have Crohn’s disease. PSC results in cholestasis with progression to secondary biliary cirrhosis and hepatic failure.
The imaging appearance of PSC is characterized by multifocal, irregular strictures and dilatations of segments of the intra- and extrahepatic biliary tree. MRCP has shown to be an adequate method for the diagnosis and follow-up of PSC.
Factors that can lead to difficulties in interpreting the MR images and to false-positive and false-negative diagnoses are:
- the presence of liver cirrhosis and
- PSC limited to the peripheral intrahepatic ducts.
Cirrhosis may lead to distortion of the biliary tree, which may mimic PSC even on ERCP images.
The MRI findings of PSC include: peripheral, wedgeshaped zones of hyperintense signal on T2-weighted images measuring 1–5 cm in diameter, periportal edema, or inflammation, seen as high signal intensity along the porta hepatis on T2-weighted images.
On pre-gadolinium T1-weighted images, areas of increased signal intensity are observed without fatty infiltration. On immediate post-gadolinium images, increased parenchymal enhancement is present with patchy, peripheral, segmental, or a combination of these patterns.
On delayed phase post-gadolinium images, thickening of bile duct walls and wall enhancement may be seen. Other findings occasionally associated with PSC are atrophy of liver segments, periportal lymphadenopathy, and findings attributable to liver cirrhosis and portal hypertension, such as hypertrophy of the caudate lobe, regenerative nodules, and abdominal varices.
PSC is associated with an increased malignant potential, and the most important and common malignant entity that may occur in these patients is cholangiocarcinoma (Bader et al. 2003).