Causes of Swollen Lymph Nodes in My Dog's Neck

Canine lymphadenitis is a type of lymphadenopathy, meaning it is a disease of the lymph nodes. More specifically, it refers to a swelling of these nodes. Although lymphadenitis is more specific, it is most common to use this term interchangeably with lymphadenopathy. Inflammation causes their size to increase and consistency to change. Although we most often notice swelling in the neck lymph nodes (submandular lymph nodes), they appear on various locations of the dog's body.

Among other functions, the lymph nodes are responsible for filtering the lymph fluid that circulates through the lymphatic system. Since the lymphatic system is in place to help the dog's body fight against disease, especially infection, the lymph fluid needs to be cleaned. For this reason, the lymph nodes are anatomical structures which are highly exposed to infectious agents and microorganisms.

When a pathogenic microorganism passes through the lymph node, it is possible it will trigger an inflammatory response. This is the most common reason for inflammation of the lymph nodes.

Depending on the number of pathogens and distribution of affected lymph nodes, canine lymphadenitis can be:

• Localized: when only the lymph nodes in one region of the body are affected. It indicates that the pathology that has produced the lymphadenitis is circumscribed to the drainage area of the affected lymph node. We most commonly notice them on the lymph nodes of the neck.
• Generalized: when lymph nodes throughout the body are affected. It occurs in systemic pathologies, such as infectious diseases and sepsis.

Since the lymph nodes work to help the dog's immune system, it is common to see systemic symptoms. This can happen even with localized infections, but is more common with generalized diseases.

Within canine lymphadenitis, we find different types depending on its etiology and the type of predominant inflammatory cells. In this section we explain the main types of lymphadenitis in dogs.

Simple nonspecific lymphadenitis in dogs

Simple nonspecific lymphadenitis in dogs can be of two types:

• Acute: neutrophils and eosinophils predominate. Necrosis may occur in the lymph nodes. This type of lymphadenitis is associated with diseases such as salmonellosis, yersiniosis, tularemia, toxoplasmosis and parvovirus. Learn more about the causes and treatment of one such disease with our guide to salmonellosis in dogs.
• Chronic: characterized by the loss of lymph node structure and the appearance of fibrosis. They are usually caused by immunosuppressive viruses, an example of which is pulmonary fibrosis in dogs.

Suppurative lymphadenitis and purulent lymphadenitis in dogs

In suppurative lymphadenitis there is a massive invasion of neutrophils and it exists in the purulent form. In addition to neutrophils, foci of necrosis are observed. It can be seen in canine distemper infections.

Granulomatous lymphadenitis in dogs

In granulomatous lymphadenitis, the inflammation is due to an increase in microphages (a type of white blood cell used in immune response). In addition, areas of caseous necrosis (a specific type of cell death) and/or mineralized granulomas may be seen.

Within this group, we can find certain types lymphadenitis which are of great interest small animal veterinary medicine, including dogs:

• Tuberculous lymphadenitis: produced by mycobacteria that cause tuberculosis. This lymphadenitis is characterized by the presence of epithelioid cells and Langhans cells.
• Pseudotuberculous lymphadenitis: due to tularemia and salmonellosis. Histiocytic cells transforming into epithelioid cells can be seen.
• Lymphadenitis of mycotic etiology: caused by fungal infections such as histoplasmosis, blastomycosis, coccidioidomycosis and sporotrichosis. Microscopic images resemble tuberculosis, but with a tendency to mineralization.
• Lymphadenitis with sarcoid granules: due to protozoan and bacterial diseases such as leishmaniasis, toxoplasmosis and brucellosis. It is characterized by the presence of nodules formed by epithelioid cells and giant cells.

Eosinophilic lymphadenitis in dogs

This type of lymphadenopathy in dogs is characterized by a massive invasion of eosinophils and, to a lesser extent, of plasma cells and mast cells. They are seen in cases of heartworm disease and massive roundworm infestations.

Although in the previous section we have mentioned the different pathologies associated with each specific type of canine lymphadenitis, here we compile the general causes that can lead to lymphadenitis.

As we have explained, lymphadenitis is often the result of the penetration of a pathogenic microorganism into a lymph node, giving rise to an infection within. The different infectious agents that can give rise to canine lymphadenitis are:

• Bacteria: such bacteria include Pasteurella, Salmonella, Bartonella, Bacteroides, Fusobacterium, Yersinia pestis, Francisella tularesis, Mycobacterium and Brucella.
• Viruses: such as parvovirus and morbillivirus (distemper). Canine parvovirus is a very serious disease with a high mortality rate, something you can learn about in our article on life expectancy of dogs with parvovirus.
• Parasites: such as Leishmania, Toxoplasma or Dirofilaria.
• Fungi: such as Histoplasma, Blastomyces, Coccidioides, Cryotococcus, and Sporothrix.

In canine lymphadenitis we can observe both local clinical signs (associated with the affected lymph nodes) and general signs (as a consequence of the infectious process that causes the lymphadenitis). One of the most common signs is swelling of the lymph nodes in a dog's neck.

Local clinical signs include:

• Enlargement of affected lymph nodes: it is also known as lymphadenomegaly. This clinical manifestation often goes unnoticed by guardians, especially when it is not very extensive.
• Greater consistency of the affected lymph nodes: the lymph nodes on the neck or other areas may feel harder than usual.
• Abscesses: occurs in the lymph nodes in purulent types lymphadenitis that create fistulas which drain to the skin.

When lymphadenitis is caused by a systemic infection, we can observe general signs such as:

• Fever: can be mild or high depending on the extent of the underlying pathology.
• Lethargy: it is common to see the dog have less energy than usual.
• Anorexia: a loss of weight and appetite is common, something which can be very serious if prolonged.
• Specific signs (digestive, respiratory, nervous, etc.): these will depend on the causal agent that originates the systemic infection.

The diagnosis of canine lymphadenitis should include the following points:

• Anamnesis: dogs generally present a typical clinical picture of an infection, so looking at their medical history is important.
• General examination: palpation shows an increase in size and consistency of superficial and/or deep lymph nodes in the dog's neck and other areas. In chronic diseases, lymph nodes adhere to adjacent structures. Palpable lymph nodes (submandibular, prescapular and popliteal) can be palpated in both healthy and diseased animals. In diseased animals they will be increased in size/consistency. Deep lymph nodes (parotid, retropharyngeal, axillary or inguinal) are only palpable when they are enlarged due to pathological causes.
• Imaging tests: they will be necessary when the lymphadenitis affects non-palpable lymph nodes, such as the mediastinal or mesenteric ones. Specifically, X-rays will be performed for the thoracic cavity and ultrasound for the abdominal cavity.
• Fine needle aspiration and cytology or biopsy and histopathology: to visualize the predominant inflammatory cells at a microscopic level and be able to diagnose the specific type of canine lymphadenitis.
• Other complementary tests: in order to determine the specific cause of lymphadenitis, other complementary tests can be carried out such as blood tests, urinalysis, microbiological culture, etc.

Swelling on the neck may not be due to the lymph nodes themselves, although this is a common cause. Take a look at our related article on why your dog has a swollen neck to learn more.

The treatment of canine lymphadenitis will be determined by the underlying pathological cause. Depending on the pathogenic microorganism causing the infection, the following types of antimicrobial treatment will be administered:

• Antibacterial: in bacterial infections. It is recommended veterinarians perform a culture and antibiogram in order to detect the antibiotics that are effective against the infection. This will best help to avoid the appearance of antibiotic resistance. Learn about one type of antibiotics for dogs with our article on enrofloxacin use in canines.
• Antiparasitic: in parasitosis caused by infestation of various parasites. This highlights the importance of using preventive medicine such as vaccination and deworming schedules for dogs.
• Antifungals: in mycosis (fungal infections). These treatments can be administered topically or orally, depending on the type of fungi.

Likewise, an appropriate supportive treatment may be established. These depend on the underlying pathology, and may include anti-inflammatories, fluid therapy, etc.

This article is purely informative. AnimalWised does not have the authority to prescribe any veterinary treatment or create a diagnosis. We invite you to take your pet to the veterinarian if they are suffering from any condition or pain.

If you want to read similar articles to Causes of Swollen Lymph Nodes in My Dog's Neck, we recommend you visit our Other health problems category.