Tumors or neoplasms are one of the many pathologies that can affect the liver of dogs. Although primary liver tumors are not frequent in the canine species, the liver is one of the organs where malignant tumors present in other areas of the body most frequently metastasize. Therefore, it is essential to take this type of tumor into account in small animal clinics.
Types of liver cancer in dogs
Before explaining the different types of liver cancer that can affect dogs, it is important to make a brief clarification about the difference between the terms “tumor” and “cancer.
Depending on biological behavior, tumors can be benign or malignant:
- Benign tumors: have a low capacity for local invasion and metastasis.
- Malignant tumors: they have a high capacity for local invasion and variable metastasis.
Usually, the term “cancer” is used to refer to a malignant tumor, so we could conclude that "malignant tumor" and "cancer" are synonymous termsIn dogs, malignant liver tumors, ie liver cancers, are more common. However, in this article we will talk about both benign and malignant tumors.
With this clarification, we can proceed to explain the types of liver tumors that can affect dogs. In general, liver tumors in dogs can be classified into two large groups:
- Primary liver tumors: when they originate in any of the tissues that make up the liver, that is, in the hepatocytes, the ducts bile ducts, connective tissue, or blood vessels.
- Secondary or metastatic liver tumors: when a tumor present in another area of the body metastasizes to the liver.
Depending on the specific type of tumor, they may have a nodular appearance (in the form of well-defined nodules) or diffusely infiltrate the liver, producing an increase in the size of the organ (hepatomegaly).
Next, we talk more in depth about the different types of primary and secondary liver tumors.
Primary tumors
Primary liver tumors are rare in dogs In fact, they both only account for 0.6-1.3% of all canine neoplasms. We can talk about the following primary liver tumors depending on the tissue from which the tumor growth is triggered:
- Origin in hepatocytes: we find hepatocellular adenoma (benign tumor) and hepatocellular carcinoma (malignant).
- Origin in the bile ducts of the liver: cholangiocellular adenoma (benign tumor) and cholangiocellular carcinoma (malignant tumor).
- Origin in connective tissue: fibrosarcomas (malignant tumor).
- Origin in blood vessels: hemangiomas (benign tumor) and hemangiosarcomas (malignant tumor).
As we have already mentioned, malignant liver tumors are more common in dogs. In addition, liver cancer is more common in older dogs Specifically, hepatocellular carcinoma is the most common canine liver cancer, followed by cholangiocellular carcinoma.
Secondary or metastatic tumors
The liver, along with the lung, is one of the organs where malignant tumors present in other areas of the body most frequently metastasize. Among the malignant tumors that can metastasize to the liver are:
- Pancreatic carcinomas.
- Prostate or mammary. You can get more information in these articles on Prostate Cancer in Dogs: Symptoms, Causes and Treatment and Breast Cancer in Dogs: Symptoms and Treatment.
- Melanomas. Check this other post about Melanoma in dogs: symptoms, characteristics and treatment, here.
- Hemangiosarcomas.
- Lymphomas. Do not hesitate to take a look at this other article on our site about Lymphoma in dogs: its treatment and life expectancy.
Symptoms of liver cancer in dogs
As in most liver diseases, the animals initially remain asymptomatic. As the tumor progresses, non-specific signs may appear such as vomiting, diarrhea, polyuria, polydipsia, anorexia, weight loss, apathy and/or depression.
Once the liver's functional reserve capacity is exceeded, clinical signs suggestive of liver disease appear, including:
- Abdominal distension: which occurs for two reasons, which may be an increase in the size of the liver and ascites. Ascites is the presence of free fluid in the abdomen that occurs when the liver is unable to maintain albumin levels in the blood. Read more about Ascites in dogs: causes and treatment, here.
- Jaundice: yellowish discoloration of the mucous membranes caused by an excess of bilirubin (yellow pigment) that is deposited on the tissues. In dogs, it is usually initially detected at the level of the sclera. You can consult more information about Jaundice in dogs: causes, symptoms and treatment in this other article on our site.
- Hepatic encephalopathy: is a neurological condition that is caused by accumulation in the blood of neurotoxic substances not metabolized by the liver, mainly ammonia. Signs that may be seen in these dogs include altered level of consciousness (lethargy, stupor, and eventually coma), weakness or ataxia, pressure of the head against the wall or floor, circling, and seizures. Check out this post about Hepatic Encephalopathy in dogs: symptoms and treatment.
- Bleeding: occurs as a result of decreased synthesis of coagulation factors, platelet function and absorption of vitamin K. Do not hesitate to take a look at this post about Vitamin K for dogs: dosage and uses.
In addition, paraneoplastic syndromes may occur. These are systemic effects of the tumor, which are not a direct consequence of tumor growth. In the case of canine liver cancer, the most frequent syndrome is paraneoplastic hypoglycemia,due to impaired glucose metabolism.
Causes of liver cancer in dogs
Currently, causes of liver tumors in dogs are unknown. However, some experimental studies establish that aflatoxins and nitrosamines may be potential causes of these tumors, so they will be factors to take into account for the prevention of liver tumors in dogs.
Diagnosis of Liver Cancer in Dogs
The diagnostic protocol for liver tumors in dogs must follow the following points:
- History and General Examination: Attention should be paid to the presence of clinical signs consistent with liver disease. On examination of the abdomen, the liver can be palpated when it is enlarged.
- Blood test with liver profile: Values such as total protein, albumin, liver enzymes (ALT, GGT and phosphatase) should be measured alkaline), ammonia, glucose and bile acids.
- Image diagnosis: which can be through an abdominal X-ray or ultrasound. Using the radiography it can be seen whether the liver has increased in size and the displacement of the abdominal viscera towards the caudal. Through the abdominal ultrasound you can see a diffuse increase in echogenicity (whiter color of the organ on the ultrasound) or the presence of hyperechoic nodules (a whitish color in the ultrasound image). However, these images may be compatible with lipidosis and cirrhosis, respectively, so ultrasound does not allow a definitive diagnosis. In addition, it is recommended to perform a magnetic resonance,as it will help to better guide the surgery and detect possible metastases in other organs.
- Biopsy and histopathology: The sample can be taken percutaneously (using biopsy needles) or surgically (via laparotomy or laparoscopy). Histopathological analysis will make it possible to reach a definitive diagnosis and determine the specific type of liver tumor.
Prevention of liver cancer in dogs
As we have explained, currently the causes that give rise to liver cancer in dogs are not known with certainty, which complicates prevention strategies of this disease completely.
In addition to this difficulty in prevention, there is the problem of making an early diagnosis of the disease. Usually, liver tumors begin producing mild and nonspecific symptoms, and it is not until advanced stages that signs compatible with liver disease appear. This makes early diagnosis difficult and that, on many occasions, cancer is diagnosed in advanced stages in which local invasion has already occurred, even a regional or distant metastasis.
Treatment of liver cancer in dogs
Hepatic tumor treatment in dogs varies depending on the type of tumor:
- In single nodular tumors: you should opt for surgical treatment, specifically tumor resection. Because the liver of dogs contains bacteria under normal conditions, a possible complication after surgery is the appearance of an abscess caused by these bacteria. To prevent this complication, it is recommended to administer broad-spectrum antibiotics after tumor resection.
- In multifocal nodular tumors: that is, when there are several nodules in the liver, or diffuse nodules are not operable, so they are you should resort to other treatments such as chemotherapy or radiotherapy For more information on the subject You can consult this article on our site about Chemotherapy in dogs: side effects and medications.
Diet for dogs with liver cancer
Good dietary management is essential in dogs with liver cancer to maintain their body condition. In general, a diet must be provided:
- Very digestible.
- Rich in easily assimilated carbohydrates.
- Low fat.
You may be interested in this other, more specific article on the Diet for dogs with cancer.
Life expectancy for dogs with liver cancer
The prognosis for liver cancer in dogs can depend on the specific type of tumor. Not surprisingly, dogs with benign tumors have a better prognosis and longer life expectancy than dogs with malignant tumors.
However, it is important to point out that there are significant differences in the prognosis of the different types of liver cancer in dogs:
- Colangiocellular carcinoma: is the canine liver cancer that has the worst prognosis, given that it has a high capacity for metastasis (between 80-87% of cases metastasize). Despite surgical resection, survival times are often short due to metastases and recurrence of the tumor in the liver.
- Hepatocellular carcinoma: has a variable prognosis depending on the way it is presented. When it has a nodular appearance, especially when it is a single mass that affects the left lobe of the liver, the prognosis is good. Following surgery, dogs have long survival and a low rate of metastasis. However, when these tumors diffusely affect the liver, the prognosis worsens markedly.
