The lymph nodes are involved with the immune system and also help drain fluids from the cells. They are found throughout the inside and outside of the body. Those on the outside that can be palpated are called peripheral lymph nodes.
Lymph node disease is common in dogs and cats, so it is important for their health to understand them and also to know where to find them on your pet.
Lymph nodes can enlarge for several reasons. Sometimes, they’re just doing their job—just because they may be enlarged doesn’t necessarily indicate a disease.
Inflammation in an organ near the lymph node causes enlargement of the lymph node. Sometimes, this inflammation is part of the body’s normal reaction to a toxin, bacteria or a foreign body, and if it’s just a normal reaction, it will resolve on its own. Sometimes, the initiating cause of the lymph node persists, and the lymph node stays enlarged.
Infection in any part of the body near a lymph node will cause it to enlarge as it is doing its job. Sometimes, the body takes care of the infection and the lymph node enlargement resolves on its own. Sometimes, antibiotics are needed.
A dreaded cause of lymph node enlargement is cancer. This tends to be much more common in older pets. The most common one we see in animals is lymphoma, sometimes called lymphosarcoma.
If a persistent enlargement of a lymph node exists and no cause can be found—for example, a foxtail embedded in the skin near the lymph node—then a sample of the lymph node needs to be examined. This can be done with a small needle (called fine-needle aspirate) without any anesthesia because it is only a pinprick.
The small size of the needle means a small sample size for the pathologist to examine microscopically. Sometimes, a piece of the lymph node, or the complete lymph node, needs to be submitted for analysis.
Our lymph node page has much more information. You can also go to our Learning Center and learn how to palpate them at home.
These photos show the sequence of a lymph node examination. The peripheral lymph nodes can be palpated, and a good vet will teach you how if you bring your pet in for an exam. They are small and can take practice to find. If you don’t feel them, that’s good because they may not be enlarged.
The first ones to check are the submandibular (below the lower jaw).
Next are the prescapular (near the shoulder blades).
The third set to palpitate are the axillary (near the armpit).
Finally—the popliteal (the back part of the leg by the knee joint).
All photos courtesy of LBAH.