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?
Has your cat been recently anesthesetized?
Has your cat been neutered?
What circumstances make the breathing worse?
What is your cat's environment and travel history?
Is there any possibility of trauma?
Is your cat vomiting or gagging?
What medications is your cat currently taking?
What medications has your cat taken in the past, and what was the response to therapy?
Has your cat ever had heartworm disease? Is he on heartworm prevention therapy now?
Has your cat been exposed to any toxins (such as rat poison)?
Does your cat cough? If yes, how often? Is it worse during the day or at night, and does it worsen with exercise?
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 cat with care during the examination so as to reduce stress. If your cat is having a great deal of difficulty breathing, emergency treatment will be necessary.
When your cat 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.
Your veterinarian may recommend additional diagnostic tests to ensure optimal medical care. These are selected on a case-by-case basis if indicated from the examination, prior test results or lack of response. Examples may include:
An angiogram of the cranial vena cava (if not evaluated adequately by chest X-rays or ultrasound)
Blood cultures if signs of sepsis are noted
A coagulation panel (tests ability of blood to clot normally) if there is blood in the chest
Contrast studies (radiographs taken after dye has been administered) of the esophagus, or endoscopy with a fiberoptic scope may be used to evaluate esophageal compression by tumors that arise near it.
Contrast lymphangiography to evaluate the thoracic duct in cases of chylothorax
CT scan to evaluate some tumors
Fine-needle lung aspiration/biopsy
Lymph node aspiration and cytology
Positive contrast peritoneography to rule out diaphragmatic hernia, although ultrasound is probably better
Taurine concentration to exclude taurine deficiency in cats with dilated cardiomyopathy
Evaluation of the urine (urinalysis) in cases of low blood protein (hypoproteinemia)
Consultations with appropriate specialists may be recommended depending on the findings of these tests.
The principles of therapy for pleural effusion are dependent upon the underlying cause. Goals in therapy may include improving heart function, preventing fluid accumulation, preventing further deterioration of the heart muscle and antagonizing chemicals and hormones produced in excessive quantities in pleural effusion. Congenital heart defects should be referred to a specialist for management. The initial therapy should be aimed at the diagnosis and treatment of the underlying cause.
Emergency management of animals with pleural effusion may include:
Placement in an oxygen cage or use of an oxygen mask or nasal tube
Placement of an intravenous catheter (if possible) to allow drugs to be given
Chest tap (thoracentesis)to remove some fluid and allow the lungs to expand more fully
Determination of red cell numbers and protein concentration in the blood (packed cell volume and total protein)
Further therapy will be dependent upon the underlying cause.