The liver is the largest organ in the dog’s body, and is a vital organ responsible for a large number of bodily functions and processes. For example, metabolism, storage of glucose (glycogen), decomposition of red blood cells and plasma protein synthesis.
In addition, the liver is one of the main organs responsible for detoxifying many toxic substances circulating in the body.
With so many responsibilities and tasks to do, it is no wonder that the liver is prone to damage and disease, especially in older dogs.
Primary and Secondary Liver Cancer
Two forms of liver cancer can occur in dogs – primary and secondary (metastatic).
Primary liver cancer occurs when there is a tumor that is growing in the liver.
The most common type of primary malignant liver tumor is hepatocellular carcinoma. This tumor usually is locally invasive. It invades into the liver tissue and rarely spreads to other locations of the body.
Primary liver cancer is not common (less than 1.5% of all dog cancers), and it usually occurs in dogs that are 10 years of age or older.
For some reasons, male dogs seem to be slightly more susceptible to primary liver tumors.
The exact cause of primary liver cancer in dogs is not clear, but some vets suspect that exposure to carcinogens (cancer-causing agents) such as certain pesticides may be a possible trigger.
Metastatic liver cancer is cancer that has originated elsewhere in the body (particularly in the spleen, pancreas, and the gastrointestinal tract), and has spread to the liver.
The liver is a common target for metastasis for several reasons:
- It is the largest organ in the body.
- One of its functions is detoxification of toxic substances.
- Two blood vessels, instead of one, supply blood to the liver, so it is more susceptible to cancer cells that are traveling through the blood circulation.
Symptoms of Canine Liver Cancer
Unfortunately, signs and symptoms of canine liver cancer are often non-specific. As the cancer progresses, it can cause some of the following symptoms:
- Loss of appetite
- Weight loss
- Increased thirst
- Excessive urination
- Fluid accumulation in the peritoneal cavity (the space within the abdomen that contains the intestines, the stomach, and the liver)
In addition, as the disease is more advanced, the dog will show symptoms such as:
- Stools with blood (due to internal bleeding)
- Pale gums (due to anemia)
Note that some other diseases involving the liver can cause similar symptoms as described above. For example, liver infections, hepatic abscesses, hepatitis and leptospirosis all cause similar symptoms.
It is therefore extremely important to get your dog to the vet for a proper diagnosis if he shows some of the above signs.
Diagnosis of Canine Liver Cancer
A vet usually uses the following procedures to get a diagnosis:
- Blood Tests: Elevated white blood cell count, low red blood cells, and high platelet counts in the blood are common in dogs with liver cancer.
- Biochemical Profile: The vet uses albumin (a blood protein made by the liver), blood sugar, blood urea nitrogen, etc. to assess the dog’s liver function.
- X-rays, CT scan or MRI: The vet will also use these procedures to check for the presence of masses in the liver.
- Fine-needle Aspiration or Liver Biopsy: The vet may do a biopsy to obtain samples of the tumor for analysis of malignancy.
Conventional Treatment of Canine Liver Cancer
For primary liver cancer caused by a single tumor that has not spread throughout the liver and has not metastasized, surgery to remove part of the liver is possible.
Usually, even if as much as 80% of the liver is removed, it can still function.
Many hepatocellular carcinomas are single masses and operable.
If the vet can successfully remove all the cancerous tumor and cells, the dog can survive at least one year or so after surgery – some even longer (for several years).
Some malignant tumors (e.g. nodular and diffuse hepatocellular carcinoma) cannot be removed surgically because multiple liver lobes are involved.
Also, surgery is not effective if the cancer has metastasized to other parts of the body.
For these cases, the vet may suggest chemotherapy treatment.
Unfortunately, chemotherapy is not so effective in treating primary liver tumors since they are highly resistant to chemotherapy drugs. As a result, prognosis is poor if chemotherapy is the only treatment protocol.
As you can see, there are not too many conventional treatment options for liver cancer in dogs.
In addition, most liver cancer cases are diagnosed rather late due to a lack of distinctive symptoms in the early stage, and the liver can continue to function for a while even with cancer. As a result, canine liver cancer generally carries a very poor prognosis.