Bile duct cancer starts in the bile ducts, tubes from the liver to the small intestine that carry bile. Bile is made by the liver and its function is to break down the fats and help digestion. Bile is stored in the gallbladder. The many small bile ducts in the liver form left and right ducts that come out of the liver. These are called intrahepatic bile ducts. Then, these two ducts join and form the so-called common bile duct, which passes through the pancreas, connects to the pancreatic duct and empties in the small intestine.
Generally, there are three types of bile duct cancer according to its location:
- Intrahepatic bile duct cancers – inside the liver; sometimes confused with liver cancer because it is also inside the liver
- Perihilar (also called hilar) bile duct cancers – the most common type; the cancer develops where the left and right hepatic ducts join, leaving the liver
- Distal bile duct cancers – close to the small intestine, in the common bile duct
The second and third types are known as extrahepatic bile duct cancers.
By cell type, most of bile duct cancers are adenocarcinomas, which starts in the glandular cells. The other types include sarcomas, lymphomas, and small cell cancers.
This type of cancer, also known as cholangiocarcinoma, is rare, but aggressive.
The symptoms of bile duct cancer occur when a bile duct is blocked. Usually, the symptoms appear at a later stage of the disease, although there are cases when early diagnosis can be made. The symptoms include:
- Jaundice – yellowing of the skin and eyes
- Changed stool, with light color or greasy
- Dark urine
- Abdominal pain, below the ribs; this is more usual in advanced stage
- Weight loss
- Nausea or vomiting
These symptoms or some of them can appear in other conditions, like hepatitis. Therefore, doctor’s consultation is needed.
The cause of bile duct cancer is not known. Latest research have shown how inflammation provokes changes in the DNA of the cells, making them grow abnormally, whose excessive number leads to formation of tumours. The mutation of genes is the most important in cancers. In this type of cancer, one gene, TP53, is found in most cases.
The risks of developing a bile duct cancer are:
- chronic inflammation of the bile ducts which can be caused by many conditions, such as scarred liver tissue, bile duct stones, cysts in the ducts, abnormalities in the structure of the ducts, liver fluke infections from tiny parasite worms, liver cirrhosis, hepatitis B or C virus
- polycystic liver disease
- Caroli syndrome (a dilation of the intrahepatic bile ducts that is present at birth)
- Inflammatory bowel disease, which includes Crohn’s disease and ulcerative colitis
- Age – usually people over 60-70 develop bile duct cancer
- Family history
- Alcohol – due to possible liver damage
- Obesity – these people are more prone to bile duct stones or have hormonal changes
- Radioactive exposure or to asbestos, radon or other chemicals
- HIV infection
The complications of bile duct cancer are liver or metastases in other parts of the body.