Often there is no obvious cause for a cancer to appear in the bile ducts, but there are a number of conditions which have been linked to the development of these tumours.  These include:

• long-standing infection, or inflammation affecting the bile ducts over many months or years can lead to the formation of a cancer.
• gall stones are present in about 1 in 3 people who develop cancer of the bile duct.  But whether there is a real link between gall stones and bile duct cancer is not certain - gallstones are very common and only a very few people who have gallstones will develop a cancer of their bile duct.
• benign (non-cancerous) cysts may develop in the bile ducts (they are called choledochal cysts).  About 1 in 25 of these cysts may develop into a cancer.
• there is a rare condition where people are born with widened, dilated, bile ducts leading out of their livers (dilated hepatic ducts).  This seems to increase the risk of bile duct cancer with between 1 in 10 to 1 in 20 people with this condition getting a bile duct cancer.