Pleural Effusion in Dogs


Overview of Canine Pleural Effusion

Pleural effusion is an abnormal accumulation of fluid in the pleural space, which is the cavity between the lungs and the thoracic wall. Normally, a small amount of fluid is present in the pleural space which serves to lubricate the surfaces and prevent friction as the lung expands and deflates. A disturbance in the production or removal of this fluid may cause excessive fluid to accumulate. This can interfere with the function of the lungs and lead to the restriction of lung expansion and ventilation. When this occurs the lung lobes may collapse. Severe accumulations are usually life-threatening.

Pleural effusion is a symptom of many diseases, but is rarely a disease itself. Diagnostic tests are needed to determine the underlying cause, and subsequent treatment recommendations are based on these findings. The type of abnormal fluid accumulated can help determine the underlying cause of the fluid. The fluid is usually categorized based on its protein level and the types and numbers of cells present.

Some of the diseases or conditions in which pleural fluid may accumulate include:

  • Heart failure
  • Infection (pyothorax)
  • Chylothorax
  • Cancer (hemangiosarcoma, mammary gland tumors, lymphosarcoma)
  • Liver disease or gastrointestinal disease if the blood protein levels become severely low
  • What to Watch For

    Signs of pleural effusion in dogs may include: 

  • Difficulty breathing (dyspnea)
  • Fast breathing (tachypnea)
  • Weight loss
  • Coughing
  • Lethargy
  • Decreased appetite
  • Exercise intolerance
  • Open-mouthed breathing
  • Diagnosis of Pleural Effusion in Dogs

    Diagnostic tests are needed to exclude other diseases that may cause similar signs and to determine the underlying cause of the effusion. Diagnostic tests that your veterinarian may wish to perform include:

  • A complete medical history and general physical examination, with emphasis on stethoscope examination (auscultation) of the heart and lungs
  • A chest radiograph (X-ray)
  • Measurement of blood pressure
  • An electrocardiogram (EKG)
  • Ultrasound examination of the heart (echocardiogram)
  • Laboratory tests
  • Treatment of Pleural Effusion in Dogs

    The treatment of pleural effusion ultimately will depend upon the underlying cause. Initial treatments may vary depending on the likelihood of the specific diseases based on your pet’s physical examination and history. Treatment may include:

  • Hospitalization with oxygen administration if your pet is having trouble breathing
  • The initial treatment for pleural effusion usually includes thoracentesis or removal of the fluid from the chest cavity to allow the lungs to re-expand. This is done by placing a small needle into the area of fluid accumulation and applying suction with a syringe to remove the fluid. Removing even a portion of the fluid will often improve your pet’s breathing.
  • Minimizing your pet’s stress level may be beneficial.
  • Depending on the cause of the fluid, a diuretic such as furosemide (Lasix®) or spironolactone may be given. If heart failure is suspected, treatment with oxygen and various drugs such as digoxin (Lanoxin®; Cardoxin®) or nitroglycerine ointment may also be initiated in some cases.
  • Home Care and Prevention

    Optimal treatment for a pet with pleural effusion requires a combination of home and professional veterinary care. Follow-up can be critical. Be aware of your pet’s general activity, exercise capacity and interest in the family activities.

    Keep a record of your pet’s appetite, ability to breathe comfortably (or not), and note the presence of any symptoms such as coughing or severe tiring.

    Never withhold water, even if your pet urinates more than normal, unless specifically instructed to do so. Difficult breathing is an emergency. See your veterinarian as soon as possible.

    Administer prescribed medication as directed and be certain to alert your veterinarian if you are experiencing problems treating your pet. Take your medications with you to your recheck examinations to show your veterinarian. Dosing is critical for heart medication.

    Regular examinations that include an interview about your pet’s clinical symptoms and quality of life should be scheduled. Be prepared to answer questions regarding your pet’s activity, appetite, ability to sleep comfortably, breathing rate and effort, presence or frequency of coughing, exercise tolerance and overall quality of life.

    During re-evaluations, a chest X-ray may be performed to evaluate the lungs for fluid. Measurement of arterial blood pressure may also be done periodically. Blood tests to examine kidney function and blood electrolytes are routinely recommended. A blood digoxin test should be done periodically if that drug is being administered and an electrocardiogram is recommended if there is a heart arrhythmia.

    In general, pleural effusion cannot be prevented. Once your pet has been diagnosed with pleural fluid you should prevent excessive physical activity or excitement, avoid high heat/humidity and avoid high salt (sodium) foods or treats.


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