The bile duct is a system of tubes connecting the liver, gallbladder and small intestine. It transports bile from the liver to the gallbladder for storage and the intestines to aid digestion. The portion of the bile duct closest to the intestine is called the distal bile duct. According to the American Society of Clinical Oncology, or ASCO, cancers arising in the bile duct are rare, and cancer arising in the distal portion of the bile duct accounts for about 25 percent of all bile duct cancers.
Causes and Risk Factors
According to the American Cancer Society, or ACS, the exact cause of bile duct cancer is not known, but there are certain associated risk factors. Certain diseases of the liver and gallbladder increase the risk of developing bile duct cancer including liver cirrhosis, primary sclerosing cholangitis, choledochal cysts, bile duct stones, Caroli syndrome and polycystic liver disease. Pancreaticobiliary maljunction, a rare condition that allows pancreatic fluid to flow back into the bile duct, also increases the risk of distal bile duct cancer. Infections with liver flukes, especially Clonorchis sinensis and Opisthorchis viverrini, also increase the risk of developing bile duct cancer. Other disease conditions are also suggested as risk factors in the development of bile duct cancer like Hepatitis B or C infection, ulcerative colitis and pancreatitis.
Additional risk factors mentioned by the ACS include previous bile duct cancer in the family, advancing age, obesity, tobacco use, diabetes, exposure to radioactive compounds like Thorotrast and radon, exposure to asbestos and certain chemicals like polychlorinated biphenyls (PCBs), dioxin and nitrosamines.
Symptoms
According to the ACS, the symptoms of bile duct cancer show up late in the disease process, usually after the bile duct is blocked. Common symptoms include jaundice, or yellowness of skin and eyes, abdominal pains, loss of appetite, unintentional weight loss, itching, fever, light colored stools and dark urine. Nausea and vomiting is not common in distal bile duct cancer, states the ACS, but may be seen in cases with infection developing because of the blocked bile duct.
Diagnosis
A medical history suggestive of bile duct obstruction and a family history of bile duct cancer warrant further physical examination looking for abdominal masses, tenderness, fluid collection in the abdomen and yellowness in the eyes. A suspicion of bile duct cancer leads to further evaluation by blood tests and imaging techniques. Blood tests as noted by the ACS include liver function tests, bilirubin count and tumor markers like carcinoembryonic antigen and CA 19-9. Imaging tests employed in the diagnosis of distal bile duct cancer are ultrasonography, computerized tomography, positron emission tomography scans, magnetic resonance imaging, different forms of cholangiography and angiography. In some cases, direct visualization using laparoscopy or cholangioscopy is employed to examine the tumor and take samples for biopsy, if possible.
Staging
Distal bile duct tumors, explains the ACS, are staged based on the size of the primary tumor and its extent of spread to nearby lymph nodes and structures or distant sites. For treatment purposes, the doctors adopt a simpler staging to determine the choice of treatment. This divides the bile duct cancers into resectable--earlier cancers in patients able to undergo surgery, and non-resectable--later stage cancers that are largely inoperable or tumors in patients too sick for surgery.
Treatment
There are diverse approaches to treatment of bile duct cancer with choices depending on the extent of spread of the cancer and the state of health of the patient. Treatment options in bile duct cancer are mainly surgery and radiation therapy with or without chemotherapy, according to the ACS. Liver transplant may be an option in rare cases.
Outlook
According to the ACS, the outlook for distal bile duct cancers is poor because it is usually discovered late. Five-year survival, a measure of general outlook, does not exceed 30 percent for all cancers of the distal bile duct.
References
- American Society of Clinical Oncology: Bile Duct Cancer Overview
- American Cancer Society: What Are the Risk Factors for Bile Duct Cancer?
- American Cancer Society: How Is Bile Duct Cancer Diagnosed?
- American Cancer Society: How Is Bile Duct Cancer Staged?
- American Cancer Society: How Is Bile Duct Cancer Treated?
