Swollen Lymph Nodes in Dogs

Golden retriever looking at veterinarian.
Golden retrievers are considered an at-risk breed for lymphoma, a cause of lymph node enlargement.

Getty Images/skynesher

Lymph nodes are found in various places in the body. These little glands are not typically easy to find or feel but if they become enlarged, you may wonder what it means for your dog. Knowing the potential reasons for swollen lymph nodes and what to watch for can help you better monitor the health of your dog.

What are Lymph Nodes?

Lymph nodes are small glands that are part of the lymphatic system. They are an important part of a dog's immune system and also help to transport fluid and other substances through the body. The numerous bean-sized lymph nodes that a dog has in its body are all connected through the lymphatic system via lymph vessels. A clear fluid called lymph, white blood cells, and other substances that circulate in this system travel to the lymph nodes through the lymph vessels. There they help to destroy toxins and infectious materials. On a dog, there are five locations that lymph nodes can be commonly felt if they are enlarged.

  • Mandibular - Under the chin, on either side of the neck.
  • Popliteal - On the back of the hind legs, behind the knees.
  • Prescapular - On the chest, in front of the shoulders.
  • Axillary - In the armpits.
  • Inguinal - In the groin.

Causes of Swollen Lymph Nodes in Dogs

If a dog has enlarged lymph nodes it may be referred to as having lymphadenopathy or lymphadenomegaly until the reason for the enlargement is determined. One or multiple lymph nodes can become enlarged and this typically occurs due to an underlying disease or infection. If you notice a lump where your dog's lymph nodes are, you should not wait to have it examined by a veterinarian.

Some of the common underlying causes of swollen lymph nodes include:

Lymphoma

The most common reason for enlarged lymph nodes is unfortunately a type of cancer called lymphoma. There are over 30 types of lymphoma in dogs but most of them start in the lymph nodes. This type of cancer involves white blood cells and can affect multiple parts of a dog's body.

Reactive Hyperplasia

This reason for a dog having enlarged lymph nodes is benign. It is an indication of the immune system working hard. It may occur due to an infection elsewhere that the body is fighting off. The lymph nodes become swollen and may be sensitive to touch.

Lymphadenitis

Lymphadenitis means the lymph node is inflamed. It may occur due to an infection that has resulted in chronic inflammation. Systemic fungal infections and some parasites may cause this type of lymph node enlargement.

Hemorrhage

If surrounding tissues are damaged due to trauma or disease, hemorrhage of the lymph node may occur. It may also be seen in dogs with bleeding disorders.

Mineral-Associated Lymphadenopathy

While no one understands completely how this happens, mineral-associated lymphadenopathy occurs when various minerals accumulate in the lymph nodes. These minerals cause the lymph nodes to enlarge.

Other Cancer

If a cancer is spreading through the body, it may cause the lymph nodes to enlarge. Cancerous tissues and fluids enter the lymph nodes and cause this reaction.

Diagnosing the Cause of Enlarged Lymph Nodes in Dogs

If your dog has enlarged lymph nodes your vet will first perform a physical examination. This will help determine how many lymph nodes may be affected and what the reason for the enlargement may be.

Blood tests to check organ function and white blood cell numbers are typically run but a fine needle aspirate (FNA) will also be recommended. This involves inserting a needle into the lymph node in order to collect cells that may indicate the reason for the enlargement. If the FNA is inconclusive, a lymph node biopsy may be performed under anesthesia. This will allow a better look at the lymph node tissue.

Further tests may be needed for various infections depending on what your veterinarian suspects based on symptoms and test results. These may include a urinalysis, fecal test, X-rays, and ultrasounds.

Treatment

Various medications including steroids, anti-inflammatories, antibiotics, anti-parasitics, and even chemotherapy may be recommended depending on the reason for the lymph node enlargement. Surgery or radiation are other treatment possibilities, especially for low-grade, localized lymphomas.

Depending on the cause and stage it is at, the long-term prognosis can vary considerably. Prompt treatment can be very important for conditions that result in enlarged lymph nodes.

How to Prevent Enlarged Lymph Nodes in Dogs

Some dog breeds appear to have a genetic predisposition for developing lymphoma, but no one knows for sure. These breeds may include Golden Retrievers, Boxers, Bullmastiffs, Basset Hounds, Cocker Spaniels, Irish Wolfhounds, Saint Bernards, Scottish Terriers, Airedale Terriers, and Bulldogs. If a dog has a history of lymphoma they should not be bred.

Other reasons for lymph node enlargement are difficult to prevent. Overall, doing what you can to help keep your dog healthy can help decrease the likelihood of infections that may result in lymph node enlargement. Immune supplements, proper nutrition, regular veterinary attention, and practicing good hygiene are all things that may aid in your efforts.