Lymph Node Inflammation (Lymphadenopathy) in Dogs

Lymph nodes are an important part of your dog’s immune response. They belong to the lymphatic system, a circulatory network that produces and transports a white blood cell containing fluid called lymph. Lymph carries infection causing antigens to the lymph nodes, which in turn produce extra antibodies to fight the infection. Lymph nodes play a crucial role in the body’s response to disease, allergic reactions, and auto-immune responses. 

Lymph nodes are found in many different parts of the body, including five external sites as well as inside the abdominal cavity and the chest. A condition or abnormality of the lymph nodes is called lymphadenopathy. Lymph node enlargement is the most common sign associated with lymphadenopathy. In many cases, short-term enlargement is only a minor sign of infection that suggests the immune system is working harder and white blood cells are congregating in the lymph nodes; however chronically or markedly enlarged lymph nodes are an important early sign of cancer. Primary lymph node cancer is called lymphoma, and it is usually marked by swelling of the affected lymph nodes. 

Many types of leukemia also affect the lymphocytes and cause similar symptoms. Other cancers frequently metastasize to the lymph nodes first and may cause inflammation there as the immune system attempts to fight the neoplastic proteins. Veterinarians often evaluate the lymph nodes to determine whether a cancerous condition is in the final or early stages. Not all lymphadenopathies are cancerous. Benign tumors can also make the lymph nodes swollen, and chronic inflammation from an allergic reaction or a persistent infection may cause similar symptoms.

Lymph nodes are small glands that play a crucial role in the immune system in dogs. They are found in many different places in the body, both externally close to the skin and internally in the chest and abdomen. Abnormality or enlargement of the lymph nodes is called lymphadenopathy. This can be caused by many different diseases, including bacterial or fungal infection, and cancer.

Lymphoma is a relatively common cancer in dogs, so it’s a good idea to get your pet checked out if you notice persistent or sudden swelling in this area. These are some of the signs to look for.

Enlarged lymph nodes

• Under the muzzle
• In the shoulder area at the jointure between the front legs and the body
• Either side of the chest or the armpit area
• On the abdomen close to the back legs
• On the back legs, close to the knees

Other symptoms

• Nausea or lack of appetite
• Vomiting
• Difficulty swallowing, eating, or breathing (if the lymph nodes on the jaw are very swollen)
• General malaise
• Fever

Types

Your dog has several different types of lymph nodes.

External – these are lymph located close to the surface where swelling can cause a palpable lump. On dogs, they are found in five specific areas of the body.

Submandibular –on the jaw

Prescapular – shoulder 

Axillary – armpit area

Inguinal - abdomen

Popliteal – knee area on the back legs

Internal – these are lymph nodes located inside the chest and abdominal cavities; enlargement is not detectable with palpation, but it will be visible on an x-ray

These are the main causes of lymphadenopathy

• Many different bacterial, viral, or fungal infections cause the lymph nodes to become enlarged (this can be the lymph nodes’ response to a general infection, or it can be an infection that takes root in the lymph nodes themselves and causes long-term inflammation which is called called lymphadenitis)
• Allergic reaction
• Auto-immune response
• Cancer such as lymphoma or lymphosarcoma, lymphocytic leukemia, metastasis from another type of cancer

The veterinarian will palpate your dog’s lymph nodes during the physical examination. It is much easier for a professional to diagnose enlarged lymph nodes than an untrained dog owner, so many lymphadenopathies are discovered on an examination performed for another reason. If you want to check your dog’s lymph nodes at home on a regular basis, the veterinarian may be able to show you where and what to look for. Lymph nodes that are enlarged because of a neoplastic condition are usually painless and hard, however if lymphadenitis is present, and the lymph nodes are inflamed, they may be tender and warmer than the surrounding area.

Thoracic and abdominal x-rays or ultrasound can diagnose enlargement in the internal lymph nodes. These may be ordered after a physical exam or because your dog is experiencing other symptoms of systemic illness. Depending on the cause of the lymphadenopathy, a blood test may show elevated levels of white blood cells because the body is fighting an infection. This may also be the case with allergic reactions and auto-immune responses. With cancerous conditions like leukemia or lymphoma, abnormal white blood cells may appear on a blood test.

The best way to find the cause of lymphadenopathy is through microscopic examination of a cellular sample. A needle aspirate can be performed on an external lymph node. The veterinarian will insert a very small needle and extract a sample. Since an aspirate only removes a small sample from a specific part of the gland, the veterinarian may also prefer to remove the entire lymph node and examine it. This will determine for certain what kind of condition is causing your dog’s signs.

Treatment will depend on the cause of lymphadenopathy. Bacterial or fungal infections will be treated with an antibiotic or antifungal medication. If an allergic reaction is causing the problem, a specific allergen may be identified and avoided, however this is often difficult. Unknown allergic reactions or autoimmune responses will be treated with medication to reduce inflammation.

For lymphoma, chemotherapy medication is a common treatment. Medication should be started immediately since untreated dogs often die quite quickly. Lymphocytic leukemia is also treated with oral or intravenous chemotherapy medication. Other cancers that are affecting the lymph nodes through metastasis may be removable surgically, followed by chemotherapy or radiation treatment.

Many types of infectious lymphadenopathy are treatable and your dog may make a complete recovery. Cancerous causes often don’t have a good prognosis, but this will depend on the type of cancer and the stage it is in, as well as the treatment that you and your veterinarian decide upon. Your veterinarian will be able to give you a better idea of your dog’s chances upon diagnosis.

The best way to manage the lymphadenopathy is by learning how to check for enlarged lymph nodes, and examining your dog regularly. Lymphoma is a common type of cancer in dogs and early treatment is much more effective. If you take your dog to the veterinarian at the first sign of a problem the chances of recovery will be much higher.

Paying for enlarged lymph nodes out of pocket can be a major financial burden. Fortunately, most pet insurance companies reimburse claims within 3 days, putting 90% of the bill back in your pocket. In the market for pet insurance? Compare leading pet insurance companies to find the right plan for your pet.