Swollen Lymph Nodes (Lymphadenopathy) in Dogs

Key Takeaways

Lymphadenopathy is enlargement of the lymph nodes, and is a common finding in many diseases, illnesses, and conditions. 

• During times of illness, the body produces more white blood cells, causing the lymph nodes to swell

• Lymphadenopathy is most often a response to an infection or cancer of the lymphatic system

• Swollen nodes are not an emergency, but they should always be treated as a medical concern

• Diagnostics for lymphadenopathy include physical examination, blood work, fine-needle aspiration, and/or node biopsy

• Treatment and prognosis depend on the underlying cause

A Closer Look: What is Lymphadenopathy in Dogs?

Lymph nodes are small, nodular components of the immune system which store white blood cells and respond to immune stimuli. They can also become enlarged when inflammatory cells pass through them, or if cancerous cells enter the node. Typically, lymph nodes are difficult to find in dogs, unless the nodes are enlarged.

There are 5 different kinds of lymph node on a dog:

• Below the jaw where the mandible meets the neck (submandibular) • In the groin region (inguinal)

• Where neck meets the chest, in front of the shoulder blades (prescapular)

• Behind each of the front legs where it meets the torso (axillary) • Behind each of each rear leg’s knee (popliteal)

The causes of lymphadenopathy are widely varied. Some potential causes, such as cancer, are life-threatening, while others are more benign. Lymphadenopathy itself is not an emergency, but it is always a matter of medical concern until the root cause is determined.

Possible Causes

The specific causes of lymphadenopathy vary widely, but fall under one of the following categories: 

• Reactive hyperplasia: an indication that the nodes are working more actively, in response to an immune stimulus.

• Lymphadenitis: when inflammatory cells from elsewhere move into a lymph node to fight an infection, and the node becomes inflamed.

• Neoplastic infiltration: when lymph nodes swell as a result of cancer cells within the node.

Risk Factors

Normal lymph nodes feel firm and are slightly mobile under the skin. The normal size of a lymph node depends on the size of the dog, and the location of the lymph node. Inguinal, prescapular, and axillary lymph nodes are very difficult to identify unless they are enlarged. 

A swollen lymph node can grow up to ten times its normal size. Swollen lymph nodes are typically hard to the touch, while inflamed lymph nodes are soft, warm, and tender.

Swollen lymph nodes in a particular area on a dog are most likely caused by a condition in the local tissue. In some conditions, certain lymph nodes swell for unknown reasons. If multiple nodes are swollen across the body, that is indicative of a more systemic condition, such as lymphoma.

Testing and Diagnosis

Diagnostics to determine the cause of lymphadenopathy include:

• Physical exam • Urinalysis • Blood tests • Testing for specific infectious diseases

• Diagnostic imaging • Fine-needle aspiration • Biopsy of the lymph node(s)

Treatment depends on the underlying condition.

Similar symptoms

Lymph nodes can be difficult to find unless engorged, and may be mistaken for a cyst.

Associated Symptoms

As lymph node enlargement is a common response to any number of illnesses, other symptoms vary widely. Common associated symptoms include fever, reduced appetite, or general discomfort, but there may be other, more specific symptoms depending on the cause.