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Pleural Effusion in Dogs

What Is Pleural Effusion in Dogs

Pleural effusion, the buildup of fluid around a dog’s lungs, is an uncommon yet serious medical condition that warrants immediate attention, especially if it progresses to the point of causing breathing difficulties.

In dogs, pleural effusion occurs when fluid accumulates in the pleural space, an abnormal condition. The pleural space is a cavity that stretches between the lungs and the chest wall, spanning from the upper chest’s mediastinum to the diaphragm. It is lined with pleura, a thin membrane comprising mesothelial cells, connective tissue, blood vessels, and lymphatics.

The accumulation of fluid in pleural effusion results from either excessive production or influx of fluid into the pleural space, or insufficient reabsorption by the pleura itself. Normally, the pleura generates a small amount of fluid to lubricate the chest wall and prevent it from adhering to the lungs during breathing.

In dogs, respiratory distress always demands immediate veterinary attention. If your dog experiences difficulty breathing, it is crucial to contact a veterinarian without delay.

Symptoms and Types

Symptoms of pleural effusion in dogs can vary from subtle to severe. In instances of minimal effusion, your dog may not display any noticeable symptoms at home. However, as fluid accumulation persists, you may observe the following indicators:

  • Increased respiratory rate: A resting respiratory rate under 30 breaths per minute is normal for dogs. If the rate exceeds 30 breaths per minute or is accompanied by other signs of respiratory distress, it warrants immediate veterinary attention.
  • Difficulty breathing: Signs include panting, extended neck, increased effort to breathe, abdominal movements during respiration, and gasping.
  • Coughing: Frequently occurring coughing may result from pressure exerted by fluid accumulation on the lungs and airways. Any persistent or intense coughing, especially alongside increased respiratory rate or breathing difficulties, requires prompt veterinary assessment.
  • Restlessness: Dogs with moderate to severe pleural effusion may exhibit restlessness or difficulty finding a comfortable position due to fluid buildup. They may prefer positions that allow their necks to stretch and chests to expand, and may experience difficulty sleeping.
  • Exercise intolerance: Sudden fatigue or coughing during physical activity, such as shorter walks or panting after minimal exertion, could indicate underlying lung, heart, or airway issues.
  • Cyanotic gums: Bluish or purplish gum discoloration signifies reduced oxygen levels in the body and demands immediate veterinary attention unless your dog’s breed typically features pigmented gums.
  • Lethargy: General tiredness, though nonspecific, is often associated with pleural effusion.
  • Decreased appetite: Reduced interest in food is a common symptom of pleural effusion, occurring in both early and advanced stages.
  • Vomiting: Although vague, vomiting can occur in the presence of pleural effusion, indicating potential complications in various disease stages.
  • Weight loss: Chronic cases of pleural effusion may lead to noticeable fat and muscle loss over time.


Pleural effusion in dogs stems from various causes. Medical conditions altering body pressures, protein levels, and a compromised lymphatic system can trigger fluid accumulation in the pleural space. This buildup obstructs lung expansion, resulting in breathing difficulties.

It’s important to note the distinction between pleural effusion and pulmonary edema, which involves fluid accumulation within the lungs, not around them. Pulmonary edema, often due to congestive heart failure, pulmonary thromboembolism, choking, drowning, or electric shock, also leads to breathing complications. Treatment approaches for pleural effusion and pulmonary edema significantly differ, underscoring the importance of accurate diagnosis between the two conditions.


To diagnose pleural effusion in dogs, veterinarians begin by gathering a comprehensive history of the dog’s clinical symptoms, past medical conditions, current medications, onset of symptoms, and their progression. Following this, veterinarians conduct a thorough physical examination and may recommend further diagnostic tests based on their findings. In some cases, pleural effusion may be suspected based solely on the physical examination.

Diagnostic testing often includes bloodwork, encompassing a complete blood count, biochemistry profile, heartworm status, and electrolyte panel, to explore potential systemic diseases. Additionally, chest radiographs are commonly performed to visualize fluid accumulation within the chest cavity. These radiographs may reveal varying degrees of fluid presence, ranging from minimal changes to the lungs to severe obstruction of the heart silhouette.


The treatment of pleural effusion in dogs is contingent upon the underlying cause of fluid accumulation. Thoracentesis serves as the primary therapeutic approach for most cases of effusion, serving both diagnostic and therapeutic purposes. This procedure involves the removal of fluid from the pleural space, providing immediate relief and enabling the lungs to expand more effectively. Typically, there is an immediate improvement in breathing once thoracentesis is initiated.

Supplemental oxygen is often considered and administered; however, it does not directly aid lung expansion. Therefore, thoracentesis remains crucial in the therapeutic management of pleural effusion in dogs.

Recovery and Management

Management of pleural effusion in dogs typically involves ongoing care to mitigate the risk of fluid buildup around the lungs. Antibiotics serve as the primary treatment for effusion triggered by bacterial infection, such as Pyothorax. In cases where effusion stems from congestive heart failure, diuretics are commonly prescribed. Additionally, steroids and/or chemotherapy drugs may be necessary if fluid accumulation results from cancer.

It’s crucial to emphasize that regardless of the cause, if the fluid leads to breathing difficulties, prompt drainage is essential to provide relief and facilitate improvement. While medications can aid in reducing fluid re-accumulation around the lungs, they primarily target smaller amounts of fluid.

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