Primary Sclerosing Cholangitis

Pruned appearance of biliary tree develops over time

• CT/MR

Thickening and hyperenhancement of bile duct wall suggests active inflammation

Visualization of greater than expected number of peripheral ducts on MRCP is clue to presence of peripheral intrahepatic ductal strictures

Chronic involvement results in atrophy of peripheral liver, massive hypertrophy of central liver/caudate (pseudotumor of caudate), and lobulated, rounded liver contour

– Frequent periductal and perivascular fibrosis, as well as confluent fibrosis in central liver: Low density on CT and T2 hyperintense on MR

– Periphery of liver may show patchy T2 hyperintensity on MR due to edema/inflammation

Hepatolithiasis, cholelithiasis, and choledocholithiasis are common and appear as signal voids on MR

Extensive lymphadenopathy common

PATHOLOGY

• Idiopathic inflammatory process with likely autoimmune etiology affecting small, medium, and large-sized bile ducts

• High association with other autoimmune disorders and inflammatory bowel disease (especially ulcerative colitis)

• Increased risk of cholangiocarcinoma and other malignancies (including gallbladder cancer)

CLINICAL ISSUES

• Most commonly seen in young (30-40 years) males, with ↑ incidence in Europe and North America

• Usually worsens progressively with little proven benefit to various medical, endoscopic, or surgical interventions

• Liver transplantation is curative, although primary sclerosing cholangitis (PSC) may recur in liver allograft

(Left) MRCP of a patient with primary sclerosing cholangitis (PSC) shows innumerable intrahepatic strictures. The extrahepatic bile duct is not significantly involved in this case, although the majority of PSC cases involve both the intrahepatic and extrahepatic ducts.

(Right) Catheter cholangiogram shows multifocal strictures and moderate dilatation of the right intrahepatic bile ducts. Note the tight stricture of the main left hepatic duct with partial opacification of a very dilated left intrahepatic bile duct.

(Left) Percutaneous transhepatic cholangiography in a patient with a history of liver transplant for end-stage PSC-induced liver disease shows markedly irregular bile ducts with multifocal strictures and intraductal filling defects, compatible with recurrent PSC.

(Right) Axial CECT in a patient with PSC demonstrates a cirrhotic, lobulated liver and ductal dilatation. The right hepatic duct is dilated, thickened, and hyperenhancing, suggesting active ductal inflammation.

TERMINOLOGY

Abbreviations

• Primary sclerosing cholangitis (PSC)

Definitions

• Chronic, immune-mediated disease causing progressive inflammation, fibrosis, and stricturing of the intrahepatic and extrahepatic ducts

IMAGING

General Features

• Best diagnostic clue

Multifocal biliary strictures, segmental ductal dilation, bile duct wall thickening, and irregular beading of intra- and extrahepatic bile ducts

• Location

Common bile duct (CBD) involved in > 90% of patients

Involvement of both intra- and extrahepatic ducts in 87%

– Isolated involvement of intrahepatic (11%) or extrahepatic (2%) ducts is unusual

Most severely affected segments of biliary tree are usually main right and left bile ducts

Strictures can affect cystic duct and pancreatic duct

• Morphology

In patients with PSC-induced end-stage cirrhosis, liver is markedly deformed (to much greater extent than with other common causes of cirrhosis)

– Contour is grossly lobulated and rounded with peripheral atrophy and central hypertrophy

– Enlargement of central liver and caudate with peripheral atrophy described as “pseudotumoral” enlargement of caudate

– Atrophy/hypertrophy complex may even occur in absence of cirrhosis

MR Findings

• MRCP is best noninvasive imaging technique for evaluating changes in biliary tree

• MRCP demonstrates multifocal “beaded” strictures of intrahepatic and extrahepatic ducts

Alternating sites of irregular strictures, mildly dilated ducts, and normal-caliber ducts

Visualization of greater than expected number of peripheral ducts on MRCP is clue to presence of peripheral intrahepatic ductal strictures

Pruned appearance of biliary tree develops as disease progresses, with obliteration of small peripheral ducts

Hepatolithiasis, cholelithiasis, and choledocholithiasis are common (usually pigmented stones) and appear as signal voids on all pulse sequences

• T1W C+ images (particularly on arterial phase images) demonstrates heterogeneous, patchy hyperenhancement often in periductal distribution

• Thickening and hyperenhancement of bile ducts on T1WI C+ suggests acute inflammation

Irregular wall thickening should raise suspicion for malignancy

• Chronic involvement results in atrophy of peripheral liver, hypertrophy of central liver, and lobulated, rounded liver contour

Liver periphery often shows patchy T2 hyperintensity due to parenchymal edema/inflammation

Periportal and periductal T2 hyperintensity also common

Confluent fibrosis (wedge-shaped site of parenchymal volume loss with capsular retraction) may be seen in chronic setting: Low T1WI signal, high T2WI signal, delayed enhancement

• Extensive lymphadenopathy common, particularly in precaval and aortocaval lymph nodes

CT Findings

• CECT

• Dilation of intrahepatic and extrahepatic ducts

“Beaded” morphology may be difficult to appreciate on CT, but multiplanar reformations often helpful

Irregularity and mild dilatation of peripheral ducts, with sites of dilatation alternating with normal caliber ducts

Abnormal ductal arborization pattern: Cannot follow branching ducts on sequential images

Abnormal thickening and hyperenhancement of bile duct walls suggests active inflammation

Intrahepatic biliary calculi are common

• End-stage PSC: Markedly dysmorphic, cirrhotic liver with progressive hypertrophy of caudate lobe/deep right lobe and atrophy of peripheral liver with abnormally rounded, lobulated liver contour

Markedly hypertrophied central liver/caudate (with atrophy of liver periphery) often described as pseudotumor of caudate

Periphery of liver often appears hypodense due to fibrosis and hepatocellular necrosis resulting from poor biliary drainage of liver periphery

Central liver often relatively higher attenuation compared to peripheral liver due to preserved drainage by patent short bile ducts

– More evident on NECT than CECT

Frequent low-attenuation periductal and perivascular fibrosis, as well as confluent fibrosis in central liver (with wedge-shaped hypodensity and capsular retraction)

• Inclusion of delayed phase images very helpful to evaluate for presence of cholangiocarcinoma

Suggest cholangiocarcinoma in setting of discrete mass with delayed enhancement, progressive segmental/lobar dilation of ducts or nodular bile duct wall thickening

• Lymphadenopathy in right upper quadrant and retroperitoneum common

Radiographic Findings

• Cholangiography (ERCP or PTC)

Multifocal short segment biliary strictures involving both intrahepatic and extrahepatic ducts with intervening sites of normal or mildly dilated ducts

– Alternating segmental dilatation and strictures referred to as “beaded” appearance

– ± diverticula adjacent to strictures

– Mural irregularity of ducts common (50%), ranging from a fine, brush-border appearance to coarse, shaggy, or frankly nodular appearance

↑ nodularity raises concern for cholangiocarcinoma

– “Pruned-tree” appearance can develop over time: Opacification of central ducts with obliteration of small peripheral ducts

Strictures can vary from 1-2 mm to several cm

– Dominant stricture: Marked dilation of duct upstream from tight, long stricture (defined as < 1.5 mm in CBD or < 1 mm in left or right main duct)