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Heart Sac Inflammation (Pericarditis) in Dogs

Pericarditis in Dogs

Pericarditis, a condition characterized by inflammation of the pericardium, occurs when the fibrous outer layer and membranous inner layer surrounding the heart become inflamed in dogs. The pericardium comprises these two layers, with the inner layer adhering closely to the heart. Within this sac lies a layer of pericardial fluid composed of serum, a watery substance that helps maintain moisture between the sac and the heart’s surfaces. When inflammation occurs in either layer of the pericardium, the body responds by producing more serum, resulting in an excess of fluid within the pericardium. This accumulation of fluid exerts pressure on the heart, leading to compression and additional inflammation in the surrounding tissues. Pericarditis is a condition that can affect both dogs and cats.

Symptoms and Types

Typically, pericarditis leads to right-sided congestive heart failure in dogs. Additional symptoms may include anorexia, lethargy, abdominal fluid buildup, difficulty breathing, a weak pulse, increased heart rate, and collapse. Dogs often progress to hemorrhagic pericarditis, characterized by blood accumulation in the heart sac. This condition can result in a dangerous buildup of fluid around the heart and tamponade, which involves the compression of the heart by the fluid in the sac. Hemorrhagic pericarditis primarily affects medium to large-breed dogs in their youth to middle age.


Pericarditis may be diagnosed as idiopathic or agnogenic, indicating that its cause is unknown and not related to any specific factor. The primary issue observed is often excess fluid buildup without any apparent underlying cause. However, potential causes can include blunt or penetrating trauma, bacterial infections such as tuberculosis (a mycobacterial disease affecting the lungs), nocardiosis (causing lung lesions that may spread), Pasteurella spp. (a respiratory tract infection), and actinomycosis (invasion leading to lumpy tumors in various body regions). Additionally, fungal infections like coccidioidomycosis, characterized by fever, skin redness, and respiratory symptoms, are also potential contributors, particularly prevalent in hot, dry climates.


Your veterinarian will conduct a comprehensive physical examination of your dog, which may include a blood chemical profile, complete blood count, urinalysis, and electrolyte panel to identify any underlying causes or systemic illnesses. If bacterial pericarditis is suspected, a sample of the pericardial effusion will be taken for aerobic and anaerobic culture to detect bacterial presence in both oxygenated and non-oxygenated tissue.

Essential diagnostic tools include thoracic radiographs (chest X-rays) and echocardiogram images for accurate visual diagnosis. Additionally, cardiac catheterization, involving the insertion of a tube into an artery or vein in the limb and threading it into the heart chambers, and an electrocardiogram to record the heart’s electrical muscle activity, can provide valuable information about heart functionality, including blood pressure and flow, rhythm, and cardiac muscle pumping efficiency.


The treatment approach for pericarditis will vary based on its underlying cause. Hospitalization in an intensive care unit is typically necessary for all affected dogs. Chemotherapy may be administered if cancerous neoplastic conditions are present, while bacterial infections will be addressed with appropriate antibiotic therapy. In some cases, surgical intervention such as pericardectomy, involving the removal of part of the pericardium, may also be required.

Living and Management

Pericarditis may reoccur in some cases. If your dog shows signs of illness again after returning home, contact your veterinarian immediately for guidance and advice. Regular monitoring and prompt action are essential for managing this condition effectively.

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