Dr. Maro: Lymph nodes as a guide to your pet’s health

Your pet's lymph nodes provide vital information about immune health. Attention to their locations and size at home enables pet guardians to raise health concerns with their veterinarian as soon as they arise.

Examination of pets’ lymph nodes is an important part of the both home and in-clinic physical exams. When lymph nodes are enlarged, there may be a variety of conditions, some more serious than others, including localized or widespread infections and one of the most common cancers in dogs and cats: lymphoma.

What are lymph nodes and what do they do?

Lymph nodes are small kidney bean-shaped structures located throughout the body that work to filter lymph fluid. They filter infectious organisms, such as bacteria, viruses and fungal organisms. If infectious organisms become abundant, or if toxins enter the body, the lymph nodes may become enlarged and “reactive.”

Lymph fluid contains protein, white blood cells known as lymphocytes which help combat infection and are an important part of the immune system. Lymph also contains cancer cells (your body fights and filters these cells regularly), damaged cells, minerals, fats and nutrients. This fluid is collected by the lymph nodes and filtered, and then recycled by the lymphatic system.

Lymph nodes contain lymphocytes, B cells, T cells and other cells, including plasma cells, dendritic cells and macrophages, which all work together to eliminate attacks to the immune system and infections.

If there is a local infection, such as an upper respiratory virus, the lymph nodes in the neck may enlarge, but other lymph nodes may stay a normal size. This condition is known as lymphadenopathy of the head and neck, and depending on the underlying cause may be called bacterial or viral lymphadenopathy.

When all of a pet’s peripheral lymph nodes become enlarged, the term generalized lymphadenopathy is used.

Where do I find lymph nodes?

Lymph nodes are named for their location and the areas they collect lymphatic fluid from.

Lymph nodes most easily found by vets and owners are:

• Submandibular – under the lower jaw and upper neck.

• Prescapular – in front of the shoulders.

• Axillary – in the armpits, behind the front legs - these lymph nodes can only be found, in dogs and cats, when they are enlarged.

• Inguinal – on the belly, near the back legs.

• Popliteal – behind the knees at the back of the rear legs.

There are internal lymph nodes within the chest and abdomen, which cannot be felt normally as they are too small. These include mesenteric, thoracic and submandibular lymph nodes.

The peripheral lymph nodes, near the skin surface, can be felt by your veterinarian. Many times pet guardians can feel the lymph nodes when they become enlarged. If the lymph nodes in the area of the lower jaw, upper neck area become very large, they can become visible from a distance and even cause swelling of the head and neck and difficulty swallowing and breathing.

Diagnosis and treatment

Many infections can cause lymph node enlargement, and they are best treated with antibiotics or antiviral agents in pets and people.

When cancer develops in the lymph nodes in the early stages, it can be difficult to determine if there is infection or a cancer of the lymphatic system. A needle or tissue biopsy is necessary to make a diagnosis. In cases of confirmed lymphoma, clinical staging is recommended to determine the type of lymphoma and best course of treatment.

• Testing for clinical staging includes:

• X-rays or CT.

• Abdominal ultrasound.

• PARR testing of the blood to distinguish B vs T cell lymphoma.

• General blood counts and chemistry testing.

Pets with lymphoma may be treated with drug therapy to shrink the lymph nodes. This is known as chemotherapy. Though many pet guardians cringe at the sound of the word chemotherapy, the drugs used for lymphatic cancers in pets do not cause serious side effects for most animals. These drugs can also induce complete remissions, enhancing quality and quantity of life for pets.

My patients who achieve the best remissions are treated with integrative medicine, both chemotherapy to shrink the nodes, and alternative and nutritional therapies to aid the immune system in fighting the cancer.

In cats, lymphoma can be found in a variety of organs or tissues and may be more difficult to pinpoint and diagnose. There are often tumor cells in the intestines and/or abdominal organs, including the kidneys, liver and spleen.

Lymphoma may occur in the spinal cord, brain or even in the oral cavity and look like other oral tumors, such as squamous cell carcinoma (this can occur in dogs, also). Cats can also be treated with chemotherapy alone, integrative medicine with alternative treatments or alternative therapies alone.

As part of your pet’s regular grooming, it is important to feel all over the body for lumps, bumps and tender areas.

Ask your vet to help you feel the peripheral lymph nodes at your pet's next appointment, so you can monitor them at home. If you find any abnormalities, be sure to visit your veterinarian and point out concerns. The sooner a pet is diagnosed and treated for lymph node swellings, the better the potential outcome.

Dr. Cynthia Maro is a veterinarian at the Ellwood Animal Hospital in Ellwood City and the Chippewa Animal Hospital in Chippewa Township. She writes a biweekly column on pet care and health issues. If you have a topic you’d like to have addressed, email ellwoodvet@msn.com.

This article originally appeared on Beaver County Times: Dr. Maro: Lymph nodes as a guide to your pet’s health