Sclerosing cholangitis is a chronic disease of the bile ducts which ultimately leads to cirrhosis, portal hypertension, and liver failure. The essential pathology is a progressive obliterative fibrotic inflammation of intra- and extra-hepatic bile ducts, resulting in irregularly distributed multifocal strictures. The common bile duct is involved in nearly all cases, most severely affected at the bifurcation. Intrahepatic and extrahepatic duct involvement is frequent, but less common. The cystic duct is often involved as well.
Clinically, this condition usually manifests with chronic intermittent obstructive jaundice. Abdominal pain, pruritis, fatiguability, and fever are variably present. The diagnosis is made by demonstrating typical cholangiographic abnormalities, and requires exclusion of mimicking conditions, previous biliary tract surgery, biliary tract malignancies, systemic disease (e.g. sarcoid), AIDS-related cholangiopathy, congenital biliary tract abnormalities, exposure to irritant chemicals (intra-arterial floxuridine, formalin), and other types of advanced liver disease (1). The diagnosis is supported by compatible clinical, biochemical and histologic findings. Biochemical findings include cholestatic liver tests (elevated alkaline phosphatase and bilirubin), and low-titer autoantibodies (ANA, SMA, pANCA). The most characteristic histologic feature is periductal concentric obliterative fibrosis of small interlobular bile ducts with or without proliferation of bile ducts in the portal tracts. (2)
Most patients are over 45 years of age, with a 2:1 male predominance. Africans and Afro-Caribbeans may be at increased risk (3). The etiology is unclear, but autoimmunity, portal bacteremia, viral infection, absorption of colonic toxins, toxic bile acids, and ischemic injury has been suggested as possible causes (4). Association with other diseases is common. For example, more than 50% of patients with sclerosing cholangitis also have ulcerative colitis. Other associated conditions include cirrhosis, chronic active hepatitis, pericholangitis, pancreatitis, retroperitoneal or mediastinal fibrosis, Peyronie disease, Riedel thyroiditis, hypothyroidism, or retro-orbital pseudotumor. The most ominous complication is cholangiocarcinoma, which has been reported in 4-20% of cases. Sclerosing cholangitis is also an independent risk factor for developing colorectal dysplasia/cancer in patients with ulcerative colitis. While increased risk for hepatocellular cancer has not been demonstrated in pre-cirrhotic cases, HCC does occur in about 2% of advanced cirrhotic-stage cases (5). As the liver disease progresses to endstage, portal hypertension develops. A unique complication is peristomal varices in patients with portal hypertension who have also undergone colectomy with an ileal stoma for associated ulcerative colitis. Osteopenic bone disease with predisposition to spontaneous fractures is also common.
The case illustrated here shows the classic ultrasound findings of sclerosing cholangitis, namely marked diffuse thickening of the common hepatic and bile ducts. The thickened wall can nearly obliterate the lumen, which on ultrasound may be difficult to distinguish from intraluminal debris. Sonography may demonstrate smooth or irregular wall thickening of the intrahepatic ducts, and brightly echogenic portal triads. Because of the sclerotic nature of PSC, marked dilatation of the intrahepatic ducts may be absent. The intrahepatic ducts are frequently not visualized, and this is the major limitation of sonography. Nevertheless, the typical extrahepatic sonographic findings in the clinical setting of ulcerative colitis or hepatobiliary symptoms are highly suggestive of sclerosing cholangitis. These findings in isolation are non-specific, however, and can also be seen with cholangiocarcinoma, choledocholithiasis, AIDS-related cholangitis, oriental cholangiohepatitis, and pancreatitis.
With CT scan, one sees mural contrast enhancement of the extrahepatic ducts in nearly all cases, along with dilatation, stenosis, wall thickening and nodularity. Dilatation, stenosis, pruning, and beading of intrahepatic bile ducts can be appreciated about 80% of the time. Nodes in the porta hepatitis may be present.
ERCP is a key step in the workup of PSC, and remains the gold standard for the diagnosis. This modality best demonstrates the multifocal strictures with uninvolved “skip” areas, and the “pruned tree” appearance due to diffuse obstruction of peripheral radicles. About 50% of cases will demonstrate coarse nodular mural irregularities (“cobblestone” appearance). Small saccular outpouchings (diverticula/pseudodiverticula), when present, are said to be pathognomonic.
Intrahepatic bile duct dilatation and strictures, extrahepatic duct wall enhancement and stenosis are also well demonstrated with MRI in most cases. Other MRI findings include periportal lymphadenopathy, periportal high T2 signal, and abnormal hyperintensity of the liver parenchyma (6). MR cholangiography holds some advantages over ERCP, since it is less invasive, and allows visualization of portions of the biliary tree which may not be reached by ERCP contrast due to proximal high grade strictures. Such cases would otherwise require transhepatic cholangiography in addition to ERCP for the complete mapping of the biliary tree. On the other hand, cholangiography provides therapeutic opportunities for removal of debris and stones, as well as treatment of strictures as in the presented case.