Liver cancer in dogs, especially metastatic liver cancer, is quite common and unfortunately hard to detect because many dogs do not show any symptoms until at a very late stage. Moreover, many symptoms are rather indistinct.
Liver cancer is a silent killer. It happens rather frequently in canines and since many dogs do not show any distinct symptoms until it is too late, it feels as if the cancer can raise its head and kill overnight.
As dog parents, we need to be mindful of this killer cancer and educate ourselves as much as we can.
Dogs can develop primary liver cancer, or metastatic (secondary) liver cancer.
Primary liver cancer is the result of a primary liver tumor (i.e. one that originates in the liver). The most common primary liver tumor is the hepatocellular carcinoma which usually does not spread to other parts of the body. Instead, the tumor invades into the liver tissue.
Primary liver cancer is less common than metastatic liver cancer in dogs. Primary liver cancer occurs more frequently in older dogs (10 years of age or older).
There is a slightly increased risk of primary liver tumors in male dogs. Although rather rare, primary liver cancer in dogs can also metastasize to other parts of the body.
Metastatic, or secondary, liver cancer is one that has spread to the liver from other organs. Metastatic liver tumors are generally multiple nodules.
Why is metastatic liver cancer so common in dogs?
The liver is the largest organ in the dog's body, and it is involved in a large number of bodily functions and processes.
In particular, the liver is one of the main organs responsible for detoxifying many toxic substances circulating in the body. A lot of medications are metabolized in the liver, putting a lot of stress on the organ.
It is understandable, therefore, that the liver is one of the primary targets of almost all metastatic cancers.
Cancer that metastasizes tends to travel to the liver through the blood stream or the lymphatic system, and the fact that the liver is supplied blood through two blood vessels instead of one makes it all the more vulnerable.
In the early stage of canine liver cancer, clinical signs are vague and not distinctive. As the disease progresses, some symptoms of canine liver cancer include:
As you can see, quite a few other diseases, especially diseases that involve the liver, may cause the same signs as listed above.
Other common liver diseases that may cause similar symptoms include hepatitis, leptospirosis (an infectious liver disease in dogs caused by a kind of bacteria called a spirochete), viral and fungal infections of the liver, etc.
Due to a lack of distinctive symptoms in the early stage and the fact that the liver can continue to function for a while even having been afflicted by cancer, most liver cancer cases are diagnosed rather late, resulting in a poor prognosis.
The cause of primary liver cancer may be related to environmental factors, such as exposure to cancer-causing chemicals (carcinogens).
You may be surprised by the fact that dogs are exposed to toxins and carcinogens more often than expected. Dogs are exposed on a daily basis to such chemicals and toxins as may be contained in some household cleaners and pesticides.
If a dog is being fed a low-quality commercial pet food, he is also constantly being exposed to harmful chemicals contained in the food, such as food additives, artificial coloring and flavors.
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If canine liver cancer is suspected, usually the following tests will be done:
For primary cancer cases that show no evidence of metastatic disease, surgical removal of the liver tumor may be possible.
If complete removal of the cancerous cells can be achieved, the dog patient can live for about a year after surgery. Some may even survive for several years.
Chemotherapy is usually not effective and therefore not used for primary malignant liver tumors, which are highly resistant to chemotherapy drugs.
Malignant tumors that cannot be surgically removed due to severe involvement of the liver and/or metastatic spread to other parts of the body carry a very poor prognosis.
In cases of secondary liver cancer, chemotherapy is sometimes recommended.