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Pleural Effusion

Posted May 13, 2014 in Dog Diseases & Conditions A-Z

Pleural effusion is the presence of abnormal fluid in the thorax. Note, a pleural effusion doesn’t mean there is fluid in the lungs but, rather, in the sterile space surrounding the lungs. As more and more fluid accumulates in the pleural cavity (which is the space surrounding your lungs and heart), it compresses the lungs, making breathing more difficult.

Symptoms of pleural effusion
Unfortunately, clinical signs of pleural effusion can be very subtle, so it’s important to be aware of the symptoms that indicate your dog or cat is having difficulty with breathing.  Such symptoms warrant anTired cat laying down immediate trip to the emergency room – even if it’s in the middle of the night!

Signs of pleural effusion in cats include:

  • Lethargy or not moving much
  • An increased respiratory rate > 40 breaths per minute (bpm)
  • Hiding in unusual places (e.g., under the bed, in the closet, etc.)
  • Hunched over in sternal
  • Open mouth breathing (unless it’s a stressful event like a car ride [note that cats always prefer to breathe through their nostrils])
  • Blue-tinged gums (which indicate severe difficulty and possibly death if not treated immediately)

Signs of pleural effusion in dogs include:

  • Lethargy
  • Seeming out of shape when walking (i.e., exercise intolerance)
  • An increased respiratory rate > 40 bpm
  • Constant panting
  • Anxiety, restlessness, pacing
  • Stretching the neck out to breath
  • Sitting up to breath, with the front legs/elbow spread out (like an English bulldog stance)
  • Using the abdomen to breath better (you’ll notice the sides of the belly heaving in and out more)
  • Blue-tinged gums (which indicates severe difficulty and possibly death if not treated immediately)

This list of signs isn’t all-inclusive, but if you notice any of them, a visit to the veterinarian or emergency veterinarian is a must.

What causes pleural effusion?
There are several causes of pleural effusion in dogs and cats:

  • Congestive heart failure (more common in cats than in dogs)
  • Trauma (resulting in blood in the thorax, called a hemothorax)
  • Cancer (such as lymphosarcoma, adenocarcinoma, etc. [resulting in abnormal fluid leaking into the pleural space secondary to a tumor or mass])
  • A severe infection (resulting in pus accumulating in the thorax, called a pyothorax)
  • Abnormal inflammation or infection
  • Chylothorax (where an abnormal milky, white fluid leaks out of the thoracic duct into the chest cavity, resulting in abnormal fluid accumulation)
  • Metabolic problems (e.g., a very low protein level resulting in fluid accumulation in the

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Justine has more than 18 years of experience in the veterinary industry and is a board-certified emergency critical care veterinary specialist and toxicologist as well as the CEO and founder of Vetgirl. She is also a founding member of IDEXX’s Pet Health Network team.