Panniculitis consists of an inflammatory process that affects the adipose tissue. It can be caused by multiple causes, both infectious and non-infectious, although in many cases the specific etiology is unknown. The main clinical sign associated with panniculitis in dogs is the presence of subcutaneous nodules, of variable consistency, which can ulcerate and fistulize. The treatment can be surgical or pharmacological, depending on the specific type of panniculitis and the number of nodules that the animal presents.
Don't miss the following article on our site in which we explain what is panniculitis in dogs, what are its causes, symptoms and treatment.
What is panniculitis in dogs
Panniculitis consists of an inflammatory process located at the level of the adipose panniculus, that is, subcutaneous adipose tissue. In many cases, this inflammation of the adipose tissue is caused by the extension of an inflammation at the level of the dermis (dermatitis), in which case it is called cellulite.
If you want to know more about Dermatitis in dogs, don't hesitate to read this other article that we recommend.
Types of panniculitis in dogs
Panniculitis can be classified according to the type of inflammatory infiltrate, the distribution of the lesion in the adipose tissue and the aetiology.
Types of panniculitis depending on the inflammatory infiltrate:
- Pyogramulomatous panniculitis: Neutrophils and macrophages predominate. It is the most frequent.
- Neutrophilic Panniculitis: Neutrophils predominate.
- Eosinophilic Panniculitis: Eosinophils predominate.
- Lymphocytic panniculitis: Lymphocytes predominate.
Types of panniculitis depending on the distribution of the lesion in the panniculus:
- Lobar panniculitis: the inflammation is located in the lobules of adipose tissue.
- Septal panniculitis: the inflammation is located in the interlobular connective tissue.
- Diffuse Panniculitis: Inflammation affects both compartments (both lobules and septa). It is the most common type in dogs.
Types of panniculitis according to etiology:
- Infectious panniculitis: produced mainly by bacteria and fungi. You can get more information about Fungus in dogs in this other article on our site.
- Non-infectious panniculitis: caused by trauma, burns, vitamin E deficiency, pancreatitis, immune-mediated diseases, reaction to foreign bodies, vaccines or injectable products.
- Sterile panniculitis: they are idiopathic, that is, of unknown origin.
Causes of panniculitis in dogs
The main causes of panniculitis in dogs are the following:
- Infectious agents: mainly bacteria (Staphylococcus pseudointermedius, mycobacteria, Pseudomonas, Proteus) and fungi (Microsporum and Trichophyton)
- Traumatisms and large burns: cause poor blood supply to the subcutaneous tissue, leading to focal ischemia.
- Immune-mediated diseases: In these cases, panniculitis is usually associated with immune-mediated vascular diseases, such as systemic lupus erythematosus.
- Pancreatitis: Occurs as a result of liquefactive necrosis of the subcutaneous tissue. Find out more about Pancreatitis in dogs in this other post.
- Nutritional: due to vitamin E deficiency, although this cause is usually more frequent in cats with diets rich in fish oil. Here you have more information about Vitamin E for dogs.
- Reaction to foreign bodies, vaccines or injectable products: although they can cause panniculitis in dogs, they are more common in cats.
- Idiopathic: of unknown etiology, such as nodular sterile panniculitis or sterile foot panniculitis of the German Shepherd.
Symptoms of panniculitis in dogs
The clinical signs that can be observed in dogs with panniculitis are as follows:
- Presence of one or several subcutaneous nodules: they can be deep and fluctuating and painful or painless. Nodules may be firm and well circumscribed, or soft and poorly defined. Frequently, these nodules ulcerate and fistulize to the exterior, secreting a fatty and bloody fluid. Normally the nodules are usually found on the trunk of the animal, although they can appear in other areas such as the abdomen, chest or head.
- General signs: such as anorexia, lethargy or depression, especially in animals with multiple lesions. If you want to know more information about Anorexia in dogs: its causes, diagnosis and treatment, check out this other article on our site that we recommend.
Diagnosis of panniculitis in dogs
To approach the diagnosis of panniculitis in dogs, it is necessary to take into account other differential diagnoses that can cause similar clinical signs. Among others, subcutaneous neoplasms, abscesses, cysts and granulomas should be considered as differential diagnoses.
The diagnosis of panniculitis should be based on the following points:
- General examination: Deep subcutaneous nodules, often ulcerated or fistulized, may be palpated during examination. Although the entire surface of the animal should be palpated, it is important to pay special attention to the trunk area, since the nodules are usually concentrated in this area.
- Blood analysis (complete blood count and biochemical profile): in case of infection it will be common to find leukocytosis (increase in white blood cells) and in case of of pancreatitis we will find an increase in pancreatic lipase (PLI).
- Fine Needle Aspiration (FNA) for cytology: since pyogranulomatous panniculitis is the most common in dogs, cytology Lipid vacuoles are usually observed together with macrophages that contain droplets of fat inside. In addition, in the case of septic panniculitis, we can observe bacteria or fungi. However, there are studies that suggest that cytologies can lead to the diagnostic error of classifying these nodules as neoplasms, especially when it comes to firm nodules. That is why it is important to perform a biopsy to reach a definitive and precise diagnosis.
- Biopsy: allows tissue to be analyzed by pathology and a definitive diagnosis is reached.
- Culture and antibiogram: In case of infectious panniculitis, it will be important to perform an in vitro culture to identify the causal agent. Subsequently, an antibiogram should be performed in order to determine which antibiotics are effective against the aetiological agent of panniculitis.
We leave you more information about cysts in dogs, specifically, interdigital cysts in dogs and ovarian cysts in bitches.
Treatment of panniculitis in dogs
The treatment will depend on the type of panniculitis and the number of nodules that the animal presents:
- Surgery: Surgical removal of nodules is often the treatment of choice for solitary nodules, as it often offers good results.
- Immunosuppressive treatment: when the animal presents multiple nodules, treatment with glucocorticoids at immunosuppressive doses, such as dexamethasone, is usually chosen or prednisone. Glucocorticoids can be administered orally, topically, or intralesionally. Some dogs may also respond to other immunosuppressive drugs such as cyclosporine.
- Antibiotic treatment: in case of infectious panniculitis, treatment with antibacterial or antimycotic agents will be necessary. In order to avoid antibiotic resistance, antibiotic therapy should be instituted with an antibiotic effective against the causative organism of panniculitis. For this, it is essential to include a culture and an antibiogram as part of the diagnostic protocol.
Most animals achieve prolonged or permanent remission of the inflammatory process. However, in some cases lesions may recur, requiring long-term glucocorticoid therapy.
