The lymphatic system is a series of tubular structures (similar to veins) known as lymphatic ducts which pick up excess fluid leaked from the blood capillaries, returning it back to the bloodstream, as this occurs, the fluid (known as lymph) passes through the lymph nodes (bean-shaped organs), where bacteria, viruses, fungi, cancer cells and trapped and destroyed by white blood cells known as lymphocytes.
Lymph node locations:
- Below the jaw – submandibular
- Cervical – neck
- Armpits – axillary
- Chest – tracheobronchial
- Mesentery/intestines – mesenteric
- Pelvis – iliac
- Groin -inguinal
- Rear leg, close to the knee – popliteal
When an infection occurs, the lymph nodes closest to the site of infection become swollen (lymphadenopathy). Swelling occurs as a result of an increase in the number of immune cells.
There are three main causes of swollen lymph nodes:
- Infection (bacterial, viral, fungal, protozoal)
Obviously, swollen lymph nodes are the main symptom, these may be painful to the touch. Other symptoms may be present depending on the underlying cause. For example, if your cat has a dental abscess, the lymph nodes in the throat may become enlarged. Common signs of infection include loss of appetite, fever, lethargy.
Cancer cells can also be found in the lymph nodes, which may have originated in the lymph nodes (primary) or cancer cells which have originated from another location and been transported to the lymph nodes (secondary).
If you notice your cat has swollen lymph nodes, it is important to see a veterinarian to determine the cause. The age of the patient can narrow down probable causes. Infections are more common in young cats and cancer in old cats.
He will perform a complete physical examination and evaluate the swollen gland(s). The number of affected glands, size and location can give a clue as to the underlying cause. A medical history will be necessary, questions may include:
- How long has the gland been swollen?
- Has your cat had a recent infection that you know of?
- What other symptoms (if any) does your cat have?
- Do the symptoms come and go?
- Have there been any changes to your cat’s weight?
Diagnosis will require tests, which can include:
Some veterinarians may recommend a wait and see approach if they suspect an infection. Once it has run its course, the swollen lymph nodes will eventually shrink back to their original size. This can take a few weeks to occur. If however, they remain swollen, it can point to a more serious underlying problem, namely cancer.
- Fine needle aspiration – A small needle is inserted into the lymph node and a sample of material is removed and evaluated by a pathologist.
- Lymph node biopsy – Removal of the lymph node which is evaluated by a pathologist.
- X-ray and/or ultrasound – To evaluate the lymph nodes and look for possible tumours.
The goal of treatment is to find and treat the underlying cause, which may include:
Bacterial infection: Antibiotics.
Fungal infection: Antibiotics or anti-fungals along with supportive care.
Viral infection: Supportive care such as fluid therapy and nutritional support while the cat’s own immune system fights off the virus.
Inflammation: Anti-inflammatory medications such as cortisone.
Cancer: Surgery to remove the tumour where possible along with chemotherapy or radiotherapy as a follow-up, or a stand-alone treatment for cancers where removal is not possible. Affected lymph nodes will also be removed at this time. If the cancer has spread from another location such as the lungs (metastasized), the prognosis is poor.