Some dogs can be so lumpy and bumpy! The particular focus today is on lumpy lymph nodes. We will explain what they are, how to feel for them, and why your dog’s lymph nodes could be enlarged.

What Are Lymph Nodes/Glands?

Lymph nodes, or lymph glands, are part of the lymphatic system found in humans, dogs and other animals. The lymphatic system is a collection of vessels and organs that has roles as part of the circulatory system and immune system. 

As part of the circulatory system: when blood moves around the body, some of the fluid ‘leaks’ out into nearby tissue. This is important to move nutrients into the tissue but the excess liquid must be removed afterwards – the fluid drains into vessels of the lymphatic system which carry it back into the heart to re-enter the blood.

More relevant to today, the lymphatic system is also an important part of the immune system. At regular intervals along lymphatic vessels there are lymph nodes. These collections of tissue contain immune cells that filter lymph fluid for bacteria and viruses, damaged body cells and cancerous cells, before it drains back into the blood. This way our body can prevent dangerous infections or diseases from spreading round the body. Each part of the body is served by different lymph glands. For example, excess fluid from our legs is filtered by inguinal lymph nodes at the top of our legs.

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Where are a Dog’s Lymph Nodes?

All over! There are multiple collections of lymph nodes in your dog but there tend to only be a few we can feel from the outside. In a healthy dog, you can often feel the following (on both sides of your dog):

  • Submandibular lymph nodes: found under your dog’s jaw, though can easily be confused with the larger salivary glands that produce saliva. These are the ones we can sometimes feel under our necks when we are sick.
  • Prescapular/superficial cervical lymph nodes: found in front of your dog’s scapula/shoulder blade
  • Axillary lymph nodes: found in your dog’s armpits
  • Inguinal lymph nodes: found in your dog’s groin
  • Popliteal lymph nodes: found at the back of your dog’s knees/stifles

The size of these vary depending on the individual dog, their breed, and which node we’re feeling, but typically range from almost impossible to feel to around the size of a small grape in healthy dogs. They should feel fairly round, uniform in shape and semi-hard. They shouldn’t be hot or painful to touch. 

Causes of Lymph Node Enlargement

Lymph node enlargement is called lymphadenopathy. Lymphadenopathy can cause other lymph nodes that are normally too small to feel, to be felt. There are many reasons why your dog may have lymphadenopathy. 

Reactive Lymphadenopathy/Lymphadenitis:

This is probably the most common cause of lymph node enlargement. As we explained above, our lymph nodes are responsible for removing infection and damaged cells from fluid drained from the blood. When there are a lot of infected or damaged cells present, more immune cells journey to the lymph nodes to help destroy the problem. This results in the lymph nodes growing in size. The general term for this is reactive lymphadenopathy, or lymphadenitis if it is caused by a microbial infection. The lymph nodes usually return to their normal size once their job is done and the problem has been removed. 

Lymph nodes can be enlarged for this reason even if your dog does not appear sick. For example, if your dog has a wound on its leg the inguinal lymph nodes may be enlarged as they destroy any bacteria that have entered the wound. Local respiratory infections or dental disease can cause the submandibular lymph nodes to enlarge. If we find one area of lymph nodes are enlarged it can help us narrow down where the problem lies. 

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Sometimes, infection can be present body-wide which results in many lymph nodes becoming enlarged (generalised reactive lymphadenopathy/lymphadenitis). Usually your dog will be unwell in these cases. Puppies and older dogs often have reactive lymphadenopathy as their immune systems can be less experienced or weaker and so must work harder to fight off infection. 

Depending how unwell your dog is, they may require no treatment, anti-inflammatories, antibiotics or other treatments. 

Lymphoedema:

This difficult-to-spell term basically means a blockage in the lymphatic system has started to cause fluid build-up and swollen lymph nodes. Dogs with lymphedema often have swollen bodies. Again, dependent on where the blockage is, swollen legs are a common finding. This swelling can result in lameness and pain if not treated.

In puppies, lymphoedema can be seen if there is a defect in the lymphatic system at birth. Some of these deformities can be surgically corrected but some cannot. This is primary lymphoedema. Secondary lymphoedema results from damage to the lymphatic system – this can be as a result of trauma, infection, cancer and heart disease. Treatment of secondary lymphoedema depends on the primary (underlying) cause.

Lymphoma and Leukaemia:

The next few causes of lymph node enlargement do not make for the most pleasant of reading, but they are important to know about. 

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The primary immune cells in lymph nodes are lymphocytes. They are normally on your dog’s team, fighting against infection. However, sometimes the cells can become damaged and start to grow uncontrollably. This is cancer of lymphocytes, or lymphoma.

Lymphoma is one of the most common cancers in dogs and unfortunately is usually a nasty one. It can start almost anywhere in the body, including lymph nodes. It forms masses of various sizes and appearances. If lymphoma starts to spread around the body (metastasises), it usually spreads to nearby lymph nodes first. Multiple swollen lymph nodes are a common finding in advanced lymphoma and usually the first time we are aware there is an issue. Some lymphomas can be treated via surgery, chemotherapy or with radiotherapy. However, in many cases the prognosis is poor.

Leukaemia is cancer of immune cells that develops within bone marrow, where immune cells are created. Because immune cells migrate to lymph nodes, leukaemia commonly spreads to lymph nodes and causes swelling. There are many kinds of leukaemia with different treatment and prognoses. 

Metastatic Cancer:

Finally, many other kinds of cancer can also cause lymph node enlargement. Because lymph nodes drain all parts of the body, cancerous cells can break off from tumours, travel to nearby lymph nodes, get stuck and start to grow, causing swelling. If single lymph nodes are enlarged, it may give us a clue where the cancer is. Every cancer is different and requires different treatment options.

How Do I Know Why My Dog’s Lymph Nodes Are Enlarged?

You may be a little worried now and wondering how you can be sure that your dog’s swollen lymph nodes are just reactive lymphadenopathy and not a nasty cancer. Here is how your vet might diagnose the cause of lymphadenopathy.

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To start, your vet will consider your dog’s history and clinical signs. Reactive lymphadenopathy can be seen in any dog but particularly older or younger ones, or those with wounds. Often they have some form of identifiable sickness, and the lymphadenopathy usually develops quickly. Cancer is usually seen in older dogs, progresses slowly and can cause your dog to be very unwell if advanced. Advanced lymphoma is usually quite obvious due to multiple swollen lymph nodes. Lymphoedema causes swelling around the lymph nodes.

However this is usually not enough to confirm the cause, so you vet may want to sample the lymph nodes. This involves taking some cells with a needle and looking at them under a microscope. An increase in immune cells indicates infection, while nasty looking cells can indicate cancer. Sampling lymph nodes is often enough to diagnose the cause. Depending on the cause, your vet may also want to perform ultrasound or x-ray examinations, particularly if cancer is suspected. Enlarged lymph nodes can even be removed if they are causing a problem for your dog.

Final Thoughts

Finding a lump on your dog is always a worry and we recommend you visit your vet if you do find one. Try not to panic though and remember that your dog is more than likely just fighting off an infection. However, feel where your dog’s lymph nodes are and what their normal size is. Feeling for them regularly means you can more easily spot when they are enlarged – this is a good early warning that something is amiss and your dog may have to visit the vets. Ask your vet to show you your dog’s lymph nodes the next time you visit.

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