Cholangiocarcinoma: The Basics

What is bile and what is the biliary system?

Bile is a greenish substance produced by the cells of the liver (hepatocytes) which aids in the digestion of fats. It emulsifies fats, causing the fats to accumulate into droplets which can be easily absorbed in the small intestine. It also aids in the absorption of so call Òfat soluble vitamins, vitamins A, D, E and K. Bile is also the way the body disposes of hemoglobin from old red blood cells which are no longer functional. This is what makes bile green and stool brown. Once hepatocytes have made bile it is transported to the duodenum, the segment of small intestine right after the stomach, where it is secreted through a small hole known as the Ampulla of Vater. It can then form droplets with fat exiting the stomach. The bile also goes to the gallbladder where it can be stored.

The network of ducts which transport the bile is known as the biliary system. This system can be broken down into several sections. The first section is comprised of the ducts which are inside of the liver, also known as the intrahepatic ducts. Small bile ductules in the liver combine with each other to form larger ducts known as intrahepatic bile ducts. The liver can be grossly divided into two lobes, the left and the right. As the intrahepatic ducts combine with each other they form two large ducts known as the right and left hepatic ducts. The left and right hepatic ducts come together to form the common hepatic duct.

The segment of ducts immediately outside of the liver is known as the perihilar ducts. The gallbladder sits on the underside of the liver and the cystic duct delivers bile into and out of the gallbladder. As the common hepatic duct exits the liver it connects with the cystic duct to form the common bile duct. The common bile duct enters the pancreas and combines with the pancreatic duct and secretions from both the pancreas and the common bile duct exit into the duodenum through the ampulla of Vater. These areas of ductal system are known as the distal biliary tree.

What is cholangiocarcinoma?

Cholangiocarcinoma is the name given to cancers of the bile duct. They arise from the epithelial cells which line the bile ducts. Generally, cholangiocarcinomas arise from the intrahepatic (within the liver), perhilar (just outside of the liver) and distal bile ducts. Cholangiocarcinomas excludes cancers which arise from the Ampulla of Vater and the gallbladder. The majority of tumors arise from the perihilar region, which represent 60 to 70% of all cholangiocarcinomas. About 25% arise from the distal ductal system and 5-10% from the intrahepatic ductal system. Cholangiocarcinomas that involve the area where the right and left ducts meet to form the common bile duct have a special name (Klatskin tumors).

Cholangiocarcinomas are rare tumors. They occur in about one to two people per 100,000 and represent approximately 3% of all gastrointestinal cancers. It is estimated that approximately 18,500 primary liver cancers were diagnosed in the US in 2006 and of these; approximately 15% of them were intrahepatic cholangiocarcinomas. There are approximately 2000-3000 cases of extrahepatic cholangiocarcinoma a year. However, there is data that suggests that the incidence of cholangiocarcinomas is slowing rising. Cholangiocarcinoma can be further classified histologically (What type of tumor cells are seen when the tumor is examined microscopically). Adenocarcinomas arise from glandular tissue and are the most common type of cholangiocarcinoma, making up 95% of cholangiocarcinomas.

Am I at Risk for Cholangiocarcinoma?

As with most cancers, increasing age has been linked with cholangiocarcinoma. Additionally, obesity, hepatitis and people with a family history of the disease may be at increased risk. Medical conditions which have been linked to cholangiocarcinoma include primary sclerosing cholangitis, ulcerative colitis, choledochal cysts and biliary infections, such as in typhoid carriers. Chemical exposures to nitrosamines, dioxin, asbestos and polychlorinated biphenyls have also been linked to cholangiocarcinoma.

There are not any guidelines on how to prevent cholangiocarcinomas. However, decreasing exposure to the above mentioned chemicals and getting vaccinated against viruses which cause hepatitis, such as the Hepatitis B virus may help prevent cholangiocarcinoma.

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