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What is Pleural Effusion?

Fluid accumulation in the pleural cavity can occur for a number of reasons, and usually points to an underlying issue. While an injury can result in pleural effusion, conditions involving the lungs, liver, lymphatic system, or heart may not be so obvious. Infections from bacteria or parasites, or even exposure to drugs and toxins can result in the fluid buildup that can lead to chest pain and breathing problems.

Pleural effusion is the condition of an abnormal amount of fluid in the pleural cavity, or the tissue that surrounds the lungs. This fluid can prevent normal lung expansion during inhalation, compromising breathing. Treatment must be sought immediately, as the condition can become life threatening.

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Symptoms of Pleural Effusion in Dogs

Symptoms of fluid accumulation in the pleural cavity can include:

  • Difficulty breathing
  • Rapid, shallow breathing
  • Muffled breathing sounds
  • Dull heart sounds
  • Long intake of air
  • Short, fast exhale of air
  • Chest pain
  • Coughing
  • Bluish color to skin and mucous membranes
  • Lethargy
  • Decreased appetite


Though the symptoms remain the same, there is a distinction made between the types of effusion, or fluid, that is found in the pleural cavity. The makeup of these types of effusions can lead to a diagnosis of the underlying cause of the condition.


This can be further defined into pure or modified, and can be indicative of hypoalbuminemia, heart failure, tumors, or lung conditions.


This can also be further defined. Hemorrhagic, or bloody, is associated with rodenticide exposure, trauma, or bleeding disorders. Chylous is indicative of the presence of lymphatic fluid. Non-septic exudates result from cancer, while septic refers to bacterial infections.

Causes of Pleural Effusion in Dogs

Causes of fluid accumulation in the pleural cavity include:

  • Infections, bacterial, viral or parasitic
  • Injuries, including penetrating chest wounds
  • Heart failures
  • Cirrhosis
  • Pneumonia
  • Pulmonary emboli, or blood clots in the blood vessels of the lungs
  • Tumors and cancers
  • Hypoalbuminemia, or low albumin levels
  • Lung conditions
  • Lung hernia
  • Lymphatic disruption
  • Bleeding or clotting disorders
  • Drug toxicity
  • Rat poison toxicity

Diagnosis of Pleural Effusion in Dogs

To come to a diagnosis of pleural effusion, your veterinarian will look at your dog’s symptoms, listen to his heart and lungs, and may take X-rays, CT scans, or ultrasounds. These imaging tests can help to rule out certain underlying conditions, and show the presence of the fluid accumulation. Besides X-rays, the main diagnostic tool for patients exhibiting compromised breathing is a thoracocentesis, a procedure that uses a needle to penetrate into the pleural cavity to extract air or fluid. This is sometimes aided by an ultrasound. In the case of an effusion, fluid is extracted, and then tested. X-rays are taken after this procedure to further assess the severity of the pleural effusion. The fluid samples are then subjected to cytologic analysis, aerobic and anaerobic cultures.

Further testing may be performed on fluid and blood samples to discern the underlying cause of the effusion, and can include CBC, retroviral screening, infectious disease screening, heartworm testing, triglyceride level testing, and coagulation parameters. An echocardiography may be performed if heart issues are suspected.

Treatment of Pleural Effusion in Dogs

Treatment first aims to provide comfort for the patient, while stabilizing a possible life threatening condition. This involves draining the fluid, either through a thoracocentesis, or with an indwelling drainage tube. Oxygen therapy can be used as needed. Narcotics may be used to sedate your dog while the veterinarian stabilizes him.

Once your dog is stabilized, oxygen therapy may continue, and the underlying condition is treated. Therapies can include antibiotic medications, administration of supplementary fluids, control of bleeding disorders, or surgery for hernias, tumors, other lung problems, or wound management. Oxygen therapy and repeated effusion drainage will continue as needed.

Further testing may be performed to ensure the treatments are working, and your veterinarian will discuss any further therapies that may be necessary depending on the underlying condition.

Recovery of Pleural Effusion in Dogs

In many cases, recovery from pleural effusion is good, as long as the underlying condition can be successfully treated. If the condition is not resolved, the fluid accumulation can recur. Some conditions are harder to treat, and may require further testing and treatments, resulting in a variable prognosis. In any case, prompt treatment for breathing difficulties is necessary for the best chance of survival for your dog. 

Following successful treatment, you should see your dog’s breathing return to normal. Your veterinarian will discuss any further care needed that is specific to your dog’s condition.

Pleural Effusion Questions and Advice from Veterinary Professionals

8 Years
Moderate condition
0 found helpful
Moderate condition

Has Symptoms

pleural effusion

Our family dog has a small mass near his heart that has caused the effusion. The mass is cancerous but we were told will not grow or spread. We drained it once and it's refilling. Can this be controlled with a little time? We don't want to make a rash decision if the prognosis may be good

Dr. Michele King, DVM
Dr. Michele King, DVM
1385 Recommendations
Whether the mass will continue to cause problems or if it will slow down in the amount of fluid that it causes just depend on how Chew's body reacts to the mass. If you are able to keep him comfortable, you may not need to make any decisions for him at this point, but you may have to one day when he isn't comfortable any more.

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