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Cholangiocarcinoma Imaging

Practice Essentials

Cholangiocarcinoma is a slow-growing malignancy of the bile duct and is the second most common primary hepatic tumor after hepatoma. The cause of bile duct cancer is unclear. Results of some epidemiologic studies have implicated bacteria-induced carcinogens derived from bile salts (eg, lithocholate) as a causative factor in the pathogenesis of cholangiocarcinomas. Biliary ductal calculi occur in 20-50% of patients with cholangiocarcinoma; however, the association of gallstones with cholangiocarcinoma is less marked than it is with carcinoma of the gallbladder. The most common cause of malignant biliary obstruction is pancreatic adenocarcinoma. Gallbladder carcinoma is 9 times more common than bile duct malignancy.

High-risk groups for cholangiocarcinomas include patients with the following
:

Parasitic diseases of the biliary tract with either Clonorchis sinensis or Opisthorchis viverrini infestation (C sinensis infestation is the most common cause worldwide.)

Congenital choledochal cysts

Inflammatory bowel disease (The risk increases 10 times. The incidence of cholangiocarcinomas in patients with ulcerative colitis is 0.4-1.4%, with a latent period of 15 yr.)

Primary sclerosing cholangitis (10% of cases)

History of other malignancy (10% of cases)

Previous surgery for choledochal cyst or biliary atresia

Alpha1-antitrypsin deficiency

Autosomal dominant polycystic kidney disease

Gallstones (20-50% of cases, probably coincidental)

Papillomatosis of the bile ducts

Thorotrast exposure

Chronic typhoid carrier status

Preferred examination

The first-line investigation in a patient with jaundice or right upper quadrant pain is ultrasonography (US). Biliary duct dilatation is easily demonstrated with US, but the tumor mass is seldom localized with it.

CT may demonstrate the tumor if the malignancy is nodular and masslike, but tumors of the diffuse sclerosing variety are difficult to detect.

Compared with the other techniques, endoscopic retrograde cholangiopancreatography (ERCP) is a more definitive investigation that can depict the periampullary tumor. However, with the advent of magnetic resonance cholangiopancreatography (MRCP), easy demonstration of stricture-causing tumors is possible.
The disadvantages of MRCP are its inability to distend the duct and the equivocal findings due to long segments and minimal narrowing in diffuse sclerosing tumors. Celiac axis arteriography is required to assess the vascular supply and the potential for resectability.

MR angiography has shown some promising results, with a sensitivity similar to that of conventional angiography in demonstrating the mesenteric circulation.

The role of endoscopic and intraductal US in the management of these tumors is yet to be defined. Furthermore, determination of the preferred examination is complex in the presence of a predisposing condition such as primary sclerosing cholangitis (PSC). Some study findings have demonstrated the potential role of positron emission tomography (PET), which improves the depiction of cholangiocarcinoma superimposed on PSC.

Plain radiographs usually have no diagnostic value. Calcifications occur in 18% of intrahepatic cholangiocarcinomas. They may appear on plain radiographs when they are large, nodular, and located in the right upper quadrant. Extrahepatic tumors may cause an extrinsic impression, with indentation or infiltration of the stomach or duodenum on an upper gastrointestinal barium series.

Angiographic features of cholangiocarcinoma include arterial encasement, obstruction, and neovascularity and focal encasement of the portal vein. Angiographic findings alone are poor in confirming a diagnosis of cholangiocarcinoma because the features may occur in both hepatocellular and pancreatic malignancies.

Classification

The tumors are classified as extrahepatic tumors (87-92%) or intrahepatic tumors (8-13%).

Extrahepatic tumors are divided into proximal, middle, and distal ductal tumors. Tumors located at the confluence of the right and left hepatic ducts with the proximal common hepatic duct are called Klatskin tumors.

Intrahepatic tumors arise from the small ducts and are often diffuse and multicentric; satellite nodules occur in about 65% of patients.

Solitary well-demarcated tumors are difficult to differentiate from primary hepatocellular carcinomas (HCCs).
The diffuse sclerosing or scirrhous types are densely fibrotic and have annular long strictures. Compared with other tumors, they are less cellular and have relatively few well-differentiated carcinoma cells in a dense connective tissue stroma. They are generally confined to the proximal ducts.

The nodular variety is also called the papillary type. The tumors are nodular on the intraluminal and extraluminal surfaces, and they form irregular strictures. They are most common in the distal duct and in the periampullary region.

The papillary tumors are friable and vascular and tend to bleed easily, causing hemobilia.

Intrahepatic tumors have a special predilection for perineural spread. Hematogenous spread to the liver, peritoneum, or lung is extremely rare.

Lymphatic spread is common and occurs in the cystic and common bile duct (CBD) nodes in about 32% of extrahepatic tumors and 15% of intrahepatic tumors.

Extrahepatic tumors also spread to the celiac nodes in about 16% of cases and to the peripancreatic and superior mesenteric nodes. Infiltration of adjacent liver occurs in 23% of cases, and peritoneal seeding occurs in 9%.

See the image below.

Bismuth classification for perihilar cholangiocarc

Bismuth classification for perihilar cholangiocarcinoma. Shaded areas represent tumor location.

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Criteria for assessing unresectability by imaging

Imaging is an important link in the decision-making process at multidisciplinary meetings while determining resectability. Surgical colleagues depend vastly on imaging in case selection.

The major determinants of resectability are the following:

The extent of tumor within the biliary tree

The amount of hepatic parenchyma involved

Vascular invasion

Hepatic lobar atrophy

Metastatic disease

Determination of resectability is most challenging in patients with Klatskin tumors. About half of patients with Klatskin tumors that are determined to be resectable preoperatively have unresectable disease intraoperatively.

See the image below.

Three-dimensional treatment planning uses CT scan

Three-dimensional treatment planning uses CT scan slices to reconstruct the patient as a volume. Shown here is the display for planning external-beam radiotherapy to the cholangiocarcinoma (green structure). A biliary catheter (red tube) runs through the tumor volume and was used to deliver brachytherapy, which was given in addition to external-beam radiotherapy. Such technology has assisted greatly in the delivery of high doses to the tumor, while sparing vital normal structures, such as the kidney and spinal cord

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The radiologic criteria defining unresectability in patients with hilar tumors is shown below
:

Local tumor invasion

The criteria for local tumor invasion includes the following:

Bilateral hepatic duct involvement up to secondary biliary radicles

Encasement or occlusion of the main portal vein

Unilateral tumor extension to secondary biliary radicles with contralateral portal vein or hepatic artery encasement or occlusion

Hepatic lobar atrophy with contralateral portal vein or hepatic artery encasement or occlusion

Hepatic lobar atrophy with contralateral tumor extension to secondary biliary radicles

Insufficient predicted hepatic reserve following extended hepatectomy

Metastatic disease

The following are characteristic of metastatic diseases:

Lymph node metastases beyond the hepatoduodenal ligament (N2 lymph nodes) (peripancreatic, periduodenal, periportal, celiac, or superior mesenteric lymph nodes)

Distant metastasis (eg, lung, liver, peritoneal)

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