What causes enlarged lymph nodes in dogs? Expert Advice

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Causes of Swollen Lymph Nodes in Dogs

Lymph nodes enlarge when the immune system is activated, usually by a disease process. If just one or two lymph nodes are enlarged, this often indicates a localized disease. For example, an infected toe could result in enlarged lymph nodes that drain that area.

A systemic infection in which the whole body is affected will often cause many or all of the lymph nodes to be enlarged. Examples include:

  • Demodectic mange
  • Puppy “strangles” (i.e., juvenile cellulitis)
  • Tick-borne diseases (e.g., Lyme disease, ehrlichiosis)
  • Bacterial infection (e.g., Yersinia pestis, which causes canine plague)
  • Reactive hyperplasia (e.g., active immune response)
  • Fungal infection (e.g., Coccidioidomycosis)
  • Immune-mediated diseases (e.g., pemphigus)
  • Cancer (e.g., lymphosarcoma)

    • What Are Swollen Lymph Nodes in Dogs?

    The lymphatic system is part of your dog’s immune system. It includes lymph nodes and a network of lymph vessels called lymphatics that run alongside your dog’s regular blood vessels. The lymph system performs several important functions in your dog’s body, including transporting white blood cells, removing waste products from tissues and cells, and helping to produce disease-fighting antibodies.

    Lymph nodes are small, bean-shaped organs that contain immune cells. When your dog’s body is invaded by viruses or bacteria, or your dog has a disease that triggers an immune response, the lymph nodes become enlarged as they work to fight off the invader. Swollen lymph nodes are called lymphadenopathy or lymphadenomegaly.

    Your vet can tell the difference between swollen lymph nodes and regular lymph nodes by feeling the lymph nodes that are closer to the skin. Lymph nodes that can be felt through the skin are known as “palpable” nodes. These are located in a few areas:

  • Submandibular: Just under the jaw where it meets the neck
  • Pre-scapular: Under the submandibular lymph nodes at the front of the shoulders
  • Axillary: In the “armpit” of the dog, or where the front legs meet the chest
  • Inguinal: On the underside of the dog where the rear legs meet the abdomen (groin)
  • Popliteal: Just behind the stifles (“knees”) of the rear legs

    • During a physical exam when your veterinarian looks like she is petting your dog, she is actually feeling for abnormalities in the lymph nodes, as well as unusual lumps or bumps. Generally, the only palpable lymph nodes are the submandibular and popliteal in a healthy dog.

    Causes of Lymph Node Inflammation (Lymphadenopathy) in Dogs

    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

    • Does your dog have cancer? Lymphoma in the Dog. Vet explains symptoms, diagnosis, and treatment.

    Swollen lymph nodes in dogs can be a sign of many diseases and infections of tissue throughout the body. The lymph nodes are important because they filter blood and store white blood cells. They’re located in many places around the body, such as the neck and shoulder area.

    When tissue in these areas suffers from a disease or infection, white blood cells increase to fight the condition, which is why the lymph nodes in the affected area become swollen. For this reason, swollen lymph nodes often the first indicator that there is something wrong in dogs’ bodies.

    “Lymphadenopathy” is the term for enlarged lymph nodes, which can be caused by many conditions, and “lymphadenitis” is the term for swollen lymph nodes that are caused by infection or inflammation. If your dog’s lymph nodes seem swollen, then you must consult your veterinarian for a diagnosis and treatment.

    Here’s what you should know about the symptoms, causes, and treatments for swollen lymph nodes in dogs.