Everything You Need to Know
If you’re petting your dog in that favorite spot under their chin and you feel a new lump, it’s not something to ignore. Depending on its position, it could be a swollen lymph node. Swollen lymph nodes in dogs aren’t always life-threatening, but they’re definitely worth bringing up to your vet.
Lymph nodes are a vital part of the immune system, and when they’re enlarged, it can be a sign that the body is responding to something unusual. Causes range from minor infections to more serious diseases like cancer. Knowing what to look for means you can get prompt veterinary attention and potentially an early diagnosis. Catching something early could save your dog’s life.
What Are Lymph Nodes in Dogs?
Lymph nodes are small, bean-shaped glands that are an important interconnected part of the immune system. They contain lymphocytes, a type of white blood cell, that help fight infection and illness.
Kate Vickery, VMD, MS, DACVIM (Oncology), CVA, is an Associate Clinical Professor of Medical Oncology at the Flint Animal Cancer Center at Colorado State University. She describes lymph nodes as being like the body’s waste depot. They filter lymph fluid, which carries proteins, fats, waste products, and immune cells throughout the body.
“If a dog has any inflammation in a specific area of the body, the lymph node will be activated, and that will call in the immune system to help address the inflammation or infection,” she explains.
When the immune system is activated, lymph nodes can enlarge significantly as they fill with immune cells or, in some cases, abnormal cells.
Where Are Lymph Nodes in Dogs Located?
Your dog has hundreds of lymph nodes throughout their body, but only a handful of sets are easy to feel externally. According to Dr. Vickery, the three most common areas are:
- Under the jaw at the base of the ear (mandibular lymph nodes)
- In front of the shoulder region at the base of the neck (superficial cervical lymph nodes)
- On the hindlimbs behind the knee region (popliteal lymph nodes)
It’s also sometimes possible to detect those in the armpits (axillary) and in the groin area (inguinal). There are also lymph nodes inside the chest and abdominal cavities.
How to Tell if Your Dog’s Lymph Nodes in Dogs Are Swollen?
When your dog is healthy, lymph nodes are small and difficult to detect by touch. In small dogs, they’re often around the size of a pea, and in larger breeds, they can be grape-sized.
Even if the lymph nodes are slightly enlarged, it can be hard to distinguish them from the surrounding tissue. However, some swollen lymph nodes can grow to be up to 10 times their normal size, becoming hard to miss very quickly.
“I recommend that owners have an understanding of where on the body to feel for the lymph nodes and to get a sense for what their dog’s ‘normal’ feels like,” Dr. Vickery says. “This way, they will have a better understanding of when things become abnormal.” She describes abnormal lymph nodes as feeling “like a whole walnut in the shell underneath the skin, where it’s firm to the touch.”
Some enlarged nodes can be painful to the touch, especially when caused by infections. Others may not cause your dog any discomfort.
What Causes Swollen Lymph Nodes in Dogs?
There are various causes of swollen lymph nodes in dogs, but the most common include infection, inflammation, and cancer.
Infection
When the body detects invading infections, it produces more white blood cells, which collect in nearby lymph nodes.
According to Dr. Vickery, bacterial or fungal infections may cause swollen lymph nodes across the body, but more commonly, the swelling is localized to the nodes near the infection site. Skin wounds, ear infections, and upper respiratory infections are all common causes of localized swelling.
Vector-borne diseases such as Lyme disease or ehrlichiosis from ticks, leishmaniasis, or tularemia may also lead to widespread lymph node enlargement.
Inflammation
Inflammation can also cause lymph nodes to swell. “[This can include] reactive lymph node enlargement due to focal inflammation,” Dr. Vickery explains. “Dental disease is a good example of this, especially in older dogs.” She also lists cutaneous lupus erythematosus (an autoimmune skin condition) and sterile granulomatous lymphadenitis (often called puppy strangles or juvenile cellulitis) as culprits.
Allergies to environmental triggers or food can also lead to inflammation throughout the body, temporarily enlarging lymph nodes.
Cancer
Lymphoma, a cancer of the lymphatic system, is the most common cancer associated with swollen lymph nodes in dogs. According to Dr. Vickery, you often see the ones at the back of the knees, under the jaw, and in front of the shoulder enlarged.
“Cancer can also spread (metastasize) to a lymph node,” Dr. Vickery says. “For example, a dog with an oral tumor may have cancer spread to one or both of the mandibular lymph nodes, which causes just those lymph nodes to be enlarged.”
Other Signs for Dogs With Swollen Lymph Nodes
In some cases, your dog may not have any other noticeable signs besides swollen lymph nodes. However, Dr. Vickery says swelling and edema (accumulation of fluid) in the tissues around the lymph node are possible, and the swelling may be painful to the touch.
In other cases, dogs may also show symptoms such as:
If you notice any swelling or other concerning changes, don’t delay in contacting your veterinarian. Early evaluation and treatment can lead to a better outcome for your dog.
Diagnosis of Swollen Lymph Nodes in Dogs
Your veterinarian will begin by conducting a thorough physical exam and discussing your dog’s history and symptoms with you.
The most common diagnostic test for enlarged lymph nodes is a fine-needle aspiration. This involves your veterinarian inserting a small needle into the lymph node to collect cells for examination under a microscope. This testing can help determine whether the swelling relates to infection, inflammation, or cancer.
According to Dr. Vickery, additional tests may include:
- Routine lab work (CBC, full chemistry panel, vector-borne disease panel, and urinalysis)
- Fungal serum and urine testing
- Advanced cancer testing, such as flow cytometry and/or biopsy of the lymph node
Treatment of Swollen Lymph Nodes in Dogs
Treatment varies widely depending on the underlying cause and its severity.
When your dog has an infection, your veterinarian may prescribe antibiotics, antifungal medication, or a dental procedure. Anti-inflammatory medications, such as corticosteroids, may help treat inflammatory or allergic conditions. Some dogs with severe infections may require supportive treatment in a veterinary hospital to help them recover.
If your dog receives a lymphoma diagnosis, chemotherapy is the main treatment. Dr. Vickery acknowledges that, while this may sound scary, veterinary chemotherapy is usually tolerated well by dogs. It uses lower doses than the human version, designed to slow the disease’s progression while preserving quality of life. “Some of our canine patients may experience a little bit of a picky appetite or loose stool while they’re going through treatment, but it’s usually very manageable,” Dr. Vickery explains.
While chemo can help to put lymphoma into remission for a period of time, it won’t be the right treatment or accessible in every situation. Veterinarians often prescribe anti-inflammatory steroids as part of a palliative care treatment plan.
Prognosis for Dogs With Swollen Lymph Nodes
Dogs with infections or inflammatory conditions generally make a full recovery once the underlying problem is treated. You can expect your dog’s lymph nodes to return to their normal size within a few weeks.
Lymphoma in dogs isn’t a curable disease. With chemotherapy treatment, the median survival is about one year, although Dr. Vickery notes that she has had some patients live a good quality of life for several years. Without treatment, lymphoma typically progresses quickly. However, with appropriate palliative treatment, many dog owners are still be able to enjoy a comfortable few weeks or months with their dog.