Bile Duct Cancer in Dogs

Bile serves an important function in your dog’s digestive health, as it breaks down fats into fatty acids, aids in the digestion of lipids, acts as a bactericide, and excretes bilirubin, which is a byproduct of red blood cells. The cancerous mass in the bile duct impairs the ability of the duct to pass bile from the liver to the gallbladder. When the transmission of bile through the bile ducts is impaired, the digestive function is halted, and bile will begin to build up within the liver, fats accumulate, and bilirubin levels rise.

Bile duct cancer is not found to be more common in any specific breed; however, it is more commonly found in female dogs and in dogs over ten years of age. Of liver cancers affecting dogs, bile duct cancer is the second most common, following hepatocellular carcinoma.

Cholangiocarcinoma is aggressive, with a metastasis rate of 67-88%, commonly metastasizing to the abdominal lining, liver’s lymph nodes, diaphragm, intestines, pancreas, spleen, kidneys, bladder, bone and/or lungs. Additionally, due to their location near, or more likely, within the liver, they are difficult to safely remove through surgery, even if they can be diagnosed before metastasizing.

• Lethargy
• Lack of appetite
• Weight loss
• Excessive urination
• Excessive thirst
• Vomiting
• Jaundice, or the yellowing of skin, eyes, and mucous membranes
• Ascites, or fluid accumulation leading to a swollen abdomen

As with any cancer, such as human, the cause of bile duct cancer is largely unknown, although there is suspected to be a connection to environmental exposure to carcinogens.

At the start of the visit, the veterinarian will conduct a thorough physical examination of your dog, palpating for ascites, or fluid accumulation. Reporting of the onset of your dog’s symptoms and health history will aid the veterinarian in diagnosis. Be sure to report any exposure your dog has had to unusual or excessive toxins.

A complete blood count to test for abnormal red or white blood cell and platelet counts will be conducted, and in most cases, the veterinarian or vet technician will complete a chemical blood profile that will measure liver enzymes, albumin, bilirubin, and cholesterol level. A urinalysis will be conducted in order to measure electrolyte levels, elevated liver enzymes, and α-Fetoprotein concentration. Your dog’s blood clotting ability will be tested through a coagulation profile, which consists of a small sample of blood being placed in a vial with diatomaceous earth while the technician measures the time it takes for the clotting factors to activate.

If initial testing points to cancer, x-rays and ultrasounds will be taken in order to locate and identify the mass, as well as surrounding organs in order to detect metastasis. The symptoms of bile duct cancer are similar to those of other liver cancers; therefore, the only way to positively diagnose the origin of the cancer is through these imaging tests. Confirmation of the cancer will depend upon a liver biopsy, which will be conducted by fine needle aspiration or a larger tissue sample through a laparoscope, which requires a small surgical incision in the abdominal cavity. If your dog has ascites, or fluid accumulation, samples of the fluid will be drawn and sent to the lab along with the tissue sample for analysis.

Bile duct cancer is difficult to treat, as chemotherapy has proven to be effective only as a palliative tool. You may consider, along with the veterinarian or veterinary oncologist, chemotherapy treatment in order to slow the spread of the cancer and decrease your dog’s discomfort, but this treatment has not been found to cure the cancer. Due to the high rate of metastasis, the prognosis is poor. Surgical removal of the bile duct tumor requires removal of the affected section of the liver; up to 75% of the liver may be removed if the remaining percent of the liver tissue is healthy. You will need to consult directly with the veterinarian or veterinary oncologist about your dog’s individual prognosis and if she is a capable and possible candidate for surgery; prognosis will depend upon if or how severely the cancer has metastasized, and how much of the liver is affected.

If your dog is determined to be a candidate for surgery, you will need to monitor your dog’s recovery and return to the veterinarian for regular follow-ups, during which your dog’s liver enzyme levels will be tested, and x-ray and ultrasonic imaging will be utilized in order to check for metastasis. Additionally, as with any surgery, you will need to regularly clean and monitor the incision site to ensure proper healing.

In other cases, you will focus on management: keeping your dog as comfortable as possible, whether it is through chemotherapy or simple pain management.