Pleural Effusion in Dogs

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In-depth Information on Canine Pleural Effusions

There are dozens of reasons for coughing, difficulty or labored breathing and fatigue. The conditions that are most likely to cause these signs are diseases of the airways and lung, abnormalities of the heart and blood vessels, and accumulation of air in the chest cavity (pleural space). Examples of such diseases include:

  • Heart failure
  • Lung cancer
  • Lung infection (fungal, bacterial, parasites)
  • Tumors in the airways
  • Obstruction of the airways (foreign bodies, tumors)
  • Deficiency of protein in the blood stream (hypoproteinemia)
  • Overhydration (such as when an excessive volume of fluid is given intravenously)
  • Trauma causing a diaphragmatic hernia
  • Trauma to the chest wall, lungs or heart
  • Diseases of the pancreas, such as pancreatitis (uncommon)
  • Liver disease
  • Blood clots in the large vessels
  • Abdominal surgery
  • Idiopathic (unknown cause)

    When severe, the accumulation of fluid around the lungs (pleural effusion) will cause your pet to have difficulty breathing. The condition can become life threatening. Though dramatic, the symptoms of difficulty breathing (dyspnea) are not specific for only one condition. There are numerous causes of pleural effusion and it is imperative that your veterinarian determine the cause in order to institute appropriate and specific therapy.

    However, initial treatment of pleural effusion in all cases where the animal is having difficulty breathing, is directed at removing the fluid in order to allow the lungs to re-expand and to improve ventilation (air intake).

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    In-depth Information on Diagnosis

    Diagnostic tests are needed to recognize pleural effusion and exclude other diseases that may cause similar symptoms. A complete medical history will be taken which will likely include the following questions:

  • Is there a history of illness?
  • What medications is your pet currently taking?
  • What medications has your pet taken in the past, and what was the response to therapy?
  • Has your pet been recently anesthesetized?
  • Has your pet been neutered?
  • Does your pet cough? If yes, how often? Is it worse during the day or at night, and does it worsen with exercise?
  • What circumstances make the breathing worse?
  • Has your pet ever had heartworm disease? Is he on heartworm prevention therapy now?
  • What is your pet’s environment and travel history?
  • Has your pet been exposed to any toxins (such as rat poison)?
  • Is there any possibility of trauma?
  • Is your pet vomiting or gagging?

    Your veterinarian will perform a thorough physical examination. The number of diagnostic tests that are necessary depends on the duration of signs, the extent of the illness, and what your veterinarian finds on the physical examination. The physical examination should include observation of respiration, auscultation of the heart and lungs, and determination of the color of mucous membranes. Your veterinarian will handle your pet with care during the examination so as to reduce stress. If your pet is having a great deal of difficulty breathing, emergency treatment will be necessary.

  • When your pet is stable, additional tests that may be performed include a complete blood count and other blood tests. These tests will help determine if anemia is a complicating factor and will allow your veterinarian to evaluate organ function (such as the kidney). A blood test to detect heartworm infection may be recommended in some patients.
  • X-rays (radiographs) are usually taken as soon as the patient is stable. The radiographs will be evaluated for heart enlargement, fluid, fractures, tumors and lung abnormalities. X-rays are often repeated after removing fluid for better visualization of structures.
  • Determination of the type of fluid that was in the chest involves evaluating the fluid for color, clarity, cell counts and protein levels. Fluids that are suspected of being chyle will have triglyceride concentrations done in serum (blood sample) and fluid for comparison.
  • Blood pressure will usually be measured. This is done with a special device that measures blood flow noninvasively through the vessels in the legs or tail. Both high and low blood pressure values need to be identified because either can occur in patients with pleural effusion.
  • An electrocardiogram (EKG) is often obtained to identify heart enlargement and determine the electrical activity of the heart. The electrocardiogram is a noninvasive test done by attaching small contact electrodes to the limbs and body.
  • Ultrasound examination of the heart (echocardiogram) may be needed for a definitive diagnosis. This noninvasive test requires sophisticated equipment that creates high frequency sound waves, much like the sonar of a submarine. An image of the heart is created. The echocardiogram is usually the test of choice to establish the cause of pleural effusion, but this examination may require referral to a specialist.

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