Dog cancer spread to the liver is not an uncommon happening unfortunately. There are many malignant cancers in dogs that spread to the dog's liver. The process of a cancer spreading from a localized area to other organs is medically known as metastasis. Anytime a dog has an aggressive type of cancer it is therefore important that it is monitored and checked for signs of spreading. This is often done through ultrasounds, CT scans and MRI. When there is dog cancer spread to the liver it is important to monitor the situation with the help of your vet.
Dog Cancer Spread to the Liver
A primary cancer of the liver, that is, a cancer that primarily originates from the liver is quite a rare occurrence in dogs. According to the handbook "Clinical Veterinary Oncology" by Stephen J. Withrow and Gregory MacEwen, primary liver cancer accounts only for 0.6 to 1.3 percent of all canine cancers.
Most dog cancer spread to the liver occurs secondarily as a result of metastasis, the development of secondary malignant growths at a distance from the primary site of cancer.
Cancer cells basically start floating in the bloodstream and replicating themselves in new areas. For example, haemangiosarcoma of the spleen is a very aggressive type of cancer which spreads very readily to the dog's liver.
The liver is an organ that is often overrepresented as a site of metastasis for the simple fact that this organ has a proficient blood supply through the hepatic artery and portal vein. This characteristic provides a fertile ground for invading cancer cells. When it comes to the amount of blood flow per minute, the liver's rich blood supply is second only to the lung which is another preferred site for metastasis.
When cancer cells spread to the liver from a primary cancer found elsewhere in the dog's body, it is often referred to as secondary cancer in the liver, liver metastasis or metastatic liver disease. This new form of cancer therefore is not to be confused with a primary cancer of the liver such as hepatocellular carcinoma. In the hemangiosarcoma of the spleen example explained above, the dog is therefore suffering from spleen cancer that has spread to the liver (secondary cancer of the liver).
Diagnosis of Dog Cancer Spread to the Liver
Liver metastasis may be found when the original (primary) cancer is diagnosed, or it can take place days, weeks or months after the primary tumor is discovered (or even removed). Diagnosis of dog cancer spread to the liver may be found in several ways but definite diagnosis is mostly obtained by biopsy.
Upon physical examination, a skilled veterinarian may palpate the presence of an abdominal mass in the location of the liver (due to liver enlargement) or may detect distention of the dog's abdomen as a result of leaking fluids (ascites)which may take place when the liver is compromised.
Bloodwork may reveal abnormalities in the dog's biochemistry profile such as increased alkaline phosphatase (ALP), increased serum alanine aminotranferase (ALT) and serum aspartate aminotransferase (AST). Other blood tests that may be abnormal include a dog's complete blood count (CBC), blood clotting tests and liver function tests.
An ultrasound is a non-invasive imaging technique that utilizes high-frequency sound waves to generate images. It can reveal liver enlargement and changes in the liver's shape or texture. An ultrasound may also be used to guide a biopsy needle to collect cells from an abnormal looking liver.
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A computed tomography (CT) scan which is an imaging method using x-rays to form pictures of cross-sections of the dog's body may also reveal masses on the liver. A CT scan may also reveal metastases in organs and tissues found around the dog's liver. This procedure though requires the dog to stay still for several minutes at a time and therefore requires sedation.
Magnetic resonance imaging (MRI) can help detect small metastatic masses in the liver. An MRI is usually used when vets have attained dubious results from other imaging tests such as CT scan or ultrasound.
As much as these mostly non-invasive techniques can be used to detect dog cancer spread to the liver, as mentioned the only definite way is through biopsy of tissue. This can help differentiate malignant masses from possible benign nodules found on the liver of older dogs.
Signs of Dog Cancer Spread to the Liver
Liver metastasis may not cause any particular symptoms in the affected dog at first because the liver is a large organ which is capable of functioning normally despite being affected by cancer. Initially, the symptoms of dog cancer spread to the liver may therefore be vague. Dogs may develop loss of appetite, weight loss, anorexia, vomiting and diarrhea and lethargy.
As the secondary cancer progresses, dogs may develop an aching sensation or pain in the area of the liver nearby the right shoulder (the liver is located below the right lung), an elevated temperature, a swollen abdomen, which may be indicative of fluid build-up (called ascites), and sometimes jaundice, a yellow tinge to the skin and whites of the eyes.
In the case the enlarged liver is putting pressure on the lungs, dogs may as well develop respiratory signs. Fluid build-up in the dog's abdomen, which is common with liver cancer, can also have a similar effect.
On top of these signs of cancer spread to the liver, dogs may manifest clinical signs associated with their primary cancer. Primary cancers in dogs that tend to spread to the liver in dogs include metastatic carcinoma, melanoma, lymphoma, hemangiosarcoma, and histiocytic sarcoma.
Options for Dog Cancer Spread to the Liver
By the time there is dog cancer spread to the liver, the primary cancer is quite advanced. Treatments mostly aim to control further growth of cancer and treat symptoms and pain. Chemotherapy and surgery may be options for dog cancer spread to the liver, but reoccurance is a matter of when rather than if.
While surgery on the liver is possible, it's overall a difficult organ to operate on and in many cases the cancer cannot be entirely removed especially when both lobes are involved. An ultrasound may show whether the tumor can be potentially resected or not.
Consulting with an oncologist is important in the case of dog cancer spread to the liver. Chemo may be an option in some cases; however, there are different forms of cancer and not all of them necessarily are responsive to chemo. Although chemotherapy does not provide a cure, temporary remissions may still be possible.
Advanced cases may only benefit from palliative care. Palliative care treats symptoms and pain so to improve quality of life in stabilized dogs. Appetite stimulants, nausea meds and pain meds are some options. Unfortunately, in the cases of advanced cancer where the dog is in pain, humane euthanasia may be the kindest option.