The bile ducts within the liver come together like the tributaries of a river, to form a right-sided duct (draining all the bile from the right lobe) and a left-sided duct (draining the left lobe). These two then join to form what is called the common bile duct, which emerges from the under surface of the liver, and is roughly the thickness of a drinking straw. The gall bladder (a pear-shaped bag) hangs off the bile duct at this point, just after it has emerged from the liver. The bile duct then runs through the pancreas for a bit, and enters the duodenum (a part of the intestine) where the bile mixes with the food. The pancreatic duct, which drains the digestive juice from the pancreas, also empties into the duodenum at the same place.

Cancerous growths of the biliary system can be divided into:

• Bile duct cancers, which may arise within the liver (i.e. Intrahepatic) or outside the liver (i.e. extrahepatic)
• Cancers of the gall bladder

The term used for bile duct cancer is cholangiocarcinoma. Biliary cancers account for 10-15% of all primary hepato-biliary cancers and 3% of all gastrointestinal cancers worldwide. High-risk areas include Thailand, Japan, Korea, Eastern Europe (European Russia, Czech Republic, Poland), and American Indians. In most areas, biliary tumours (except gall bladder cancers) have a slightly higher incidence in men than women.