Canine lymphadenitis consists of an inflammation of the lymph nodes, which usually causes an increase in their size and consistency. The filtering function of the lymph that the lymph nodes have means that these organs are continuously exposed to various infectious agents. When any of the pathogenic microorganisms present in the lymph is able to establish itself as it passes through the lymph nodes, an infection is generated that results in this inflammatory response.
Don't miss the following article on our site in which we explain the most relevant aspects of lymphadenitis in dogs, its symptoms, causes and treatment, in addition to your diagnosis.
What is lymphadenitis in dogs?
Canine lymphadenitis consists of an inflammation of the lymph nodes, also known as lymph nodes or lymph nodes, which leads to an increase in size and their consistency.
The lymph nodes are responsible, among other things, for filtering the lymph that circulates through the lymphatic system. The macrophages present in the lymph node are responsible for cleaning the lymph as it passes through. For this reason, the lymph nodes are structures that are highly exposed to infectious agents When a pathogenic microorganism penetrates the lymph node, it can cause an infection in it that triggers an inflammatory response, which we know as lymphadenitis.
Depending on the number and distribution of affected lymph nodes, canine lymphadenitis can be:
- Localized: when only the lymph nodes in one body region are affected. Indicates that the pathology that has produced the lymphadenitis is circumscribed to the drainage area of the affected lymph node.
- Generalized: when lymph nodes throughout the body are affected. It occurs in systemic pathologies, such as infectious diseases and sepsis.
Types of lymphadenitis
Within canine lymphadenitis, we find different types depending on its etiology and the type of predominant inflammatory cells. In this section we collect the main types of lymphadenitis in dogs.
Simple nonspecific lymphadenitis in dogs
In turn, simple nonspecific lymphadenitis in dogs can be of two types:
- Acute form: Neutrophils and eosinophils predominate. Foci of necrosis may occur at the level of the lymph nodes. This type of lymphadenitis is associated with diseases such as salmonellosis, yersiniosis, tularemia, toxoplasmosis and parvovirus. If you want to know more about Salmonellosis in dogs, its symptoms, treatment and prevention, don't hesitate to read this article that we suggest.
- Chronic form: it is characterized by the loss of architecture of the lymph node and the appearance of fibrosis. They are usually caused by immunosuppressive viruses. We leave you this other article on Pulmonary Fibrosis in dogs, its symptoms and treatment, in case you want to know more about the subject.
Suppurative lymphadenitis and purulent lymphadenitis in dogs
In suppurative lymphadenitis there is a massive invasion of neutrophils and, in the purulent form, in addition to neutrophils, foci of necrosis are observed. It can be seen in distemper or canine distemper infections. Check out this post about Distemper in dogs, its symptoms, contagion and treatment in this article on our site.
Granulomatous lymphadenitis in dogs
In granulomatous lymphadenitis, macrophages predominate. In addition, areas of caseous necrosis and/or mineralized granulomas may be seen.
Within this group, there are some of the lymphadenitis of greatest clinical interest in the small animal clinic:
- 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 that transform into epithelioid cells can be seen.
- Lymphadenitis of mycotic aetiology: due to histoplasmosis, blastomycosis, coccidioidomycosis and sporotrichosis. Microscopic images resemble tuberculosis, but with a tendency to mineralization.
- Lymphadenitis with sarcoid granules: due to leishmaniasis, toxoplasmosis and brucellosis. It is characterized by the presence of nodules formed by epithelioid cells and giant cells.
Eosinophilic lymphadenitis in dogs
It 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.
Causes of lymphadenitis in dogs
Although in the previous section we have mentioned the different pathologies associated with each specific type of canine lymphadenitis, in this section we are going to compile all the 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, which gives rise to to an infection in it. The different infectious agents that can give rise to canine lymphadenitis are:
- Bacteria: such as Pasteurella, Salmonella, Bartonella, Bacteroides, Fusobacterium, Yersinia pestis, Francisella tularesis, Mycobacterium, Brucella.
- Virus: such as parvovirus, morbillivirus (distemper). How long does a dog with parvovirus last? Discover the answer in this other article that we recommend.
- Parasites: such as Leishmania, Toxoplasma, Dirofilaria. You can obtain more information about Toxoplasmosis in dogs, its symptoms and contagion, here.
- Fungi: such as Histoplasma, Blastomyces, Coccidioides, Cryotococcus and Sporothrix.
Symptoms of lymphadenitis in dogs
In canine lymphadenitis we can observe both local clinical signs (associated with affected lymph nodes) and general signs (as a consequence of the infectious process that causes lymphadenitis).
Local clinical signs include:
- Increased size of affected lymph nodes: Also known as lymphadenomegaly. However, this clinical manifestation often goes unnoticed by most caregivers, especially when it is not very marked.
- More consistency of affected lymph nodes.
- Adherence to adjacent tissues of lymph nodes in chronic cases.
- Creation of abscesses in the lymph nodes of purulent lymphadenitis that fistulize and drain to the outside.
When lymphadenitis is caused by a systemic infection, we can observe general signs such as:
- Fever: take a look at this article on our site about Fever in dogs, its symptoms, causes and treatment.
- Lethargy.
- Anorexia: don't hesitate to read this article on Anorexia in dogs: causes, diagnosis and treatment to find out more.
- Specific signs (digestive, respiratory, nervous, etc.) depending on the causal agent causing the systemic infection.
Diagnosis of lymphadenitis in dogs
The diagnosis of canine lymphadenitis should include the following points:
- Medical history and anamnesis: Dogs generally present a clinical picture typical of an infection.
- General examination: palpation shows an increase in size and consistency of superficial and/or deep lymph nodes. In chronic cases, lymph nodes adhere to adjacent structures. Palpable lymph nodes (mandibular, prescapular and popliteal) can be palpated in both he althy and diseased animals, although in diseased animals they will be increased in size/consistency. Deep lymph nodes (parotid, retropharyngeal, axillary, inguinal) are only palpable when enlarged due to pathological causes.
- Imaging tests: 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 thus be able to diagnose the type concrete of canine lymphadenitis.
- Other complementary tests: In order to determine the specific cause of the lymphadenitis, other complementary tests can be carried out such as blood tests, urinalysis, microbiological culture, etc.
Treatment of lymphadenitis in dogs
The treatment of canine lymphadenitis will be conditioned by the causal agent that has originated it. Depending on the pathogenic microorganism causing the infection, a antimicrobial treatment will be instituted with:
- Antibacterials: in bacterial infections. It is recommended to perform a culture and antibiogram in order to detect the antibiotics effective against the infection and avoid the appearance of antibiotic resistance.
- Antiparasitics: in parasitic diseases. We leave you more information about internal and external antiparasitic for puppies that you may also be interested in.
- Antifungals: in fungal (fungal) infections. To learn more about Fungi in dogs, their symptoms and treatment, don't hesitate to read this post.
Likewise, an appropriate support treatment will be established depending on the underlying pathology, which may include anti-inflammatories, fluid therapy, etc..
