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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

Bichon Frise
14 Years
Critical condition
0 found helpful
Critical condition

Has Symptoms

Increased thirst
Increased Urination
Breathing Difficulty
Heart Murmur
Blood In Stool
liquid in chest cavity

Medication Used


Our Bichon had a history of heart murmur ever since we rescued him at age 9. He is almost 14 this year. 3 months ago he started drinking and peeing excessively, vet didn't identify any kidney issues or infection through urine test and x-ray. 1 month ago he started not eating well and became lethargic. 2 weeks ago he started having some breathing issues at night and eating even less. We took him to the vet after he started having blood in his diarrhea about 1 week ago. He had fluid accumulation in chest cavity, they tapped almost 1L of light yellow fluid in his first visit after seeing it in the x-ray, despite him being a small dog (19 lbs before the chest tap). We didn't opt for further diagnostics since the vet said the prognosis is not good. Thursday they did ultrasound and said there's not that much fluid in his chest so they didn't tap it again and said they didn't see any issues in his chest cavity otherwise. His condition deteriorated quickly after Thursday and on Saturday night he was again having difficulty breathing and couldn't sleep. We didn't take him to a vet right away and he died Sunday morning. Given the description, what's the most likely cause of his ailment and his ultimate death? Is it likely that his condition could have been controlled and he could have lived longer if we saved him?

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Doberman Pinscher
8 Years
Critical condition
1 found helpful
Critical condition

Has Symptoms

Panting, rapid heart beat,thirsty

We went to emergency vet and he said to take pills for sore throat and stomach pills for gas. Did not do blood work. We went to family vet couple days later and he said stop taking pills but go to other clinic to get ultrasound. No blood work. We called to make appointment for ultrasound but it would have taken four day for someone qualified to be there to do it. Her heart was racing and breathing more difficult so we called around and a london vet clinic told us they do ultrasound so we raced there. When we got there they told us they don't do ultrasound until Monday which is six days for qualified person but sometimes they can call them in. We couldn't believe it. Vet said going to get blood work and get xrays then tap chest to release fluids after seeing results of tests. They take our lucy and said going for xrays. More than expected time lapsed then the lady who took her for xrays came and said you guys need to come now she turned for worst. Us in shock ran out and she was on bed having CPR done to her. She came back for 30 seconds I think cause she heard us and tried to get up. They laid her back down and she flat lined again. I said to the vet wtf is happening she was suppose to be going for xrays and now our dog is dying wtf. Well she passed away horrifically and only then did the vet show us blood work which was bad results.she should have called to get ultrasound person in with those results. I feel they killed my angel lucy. I called my family vet and asked why he didn't do blood work. He didn't answer why but put in my head maybe foxtails but uncommon in dogs. I had no idea about them until he told me and I know she ate grass cause I let her cause I read article grass is good with no mention of foxtails. So after reading up on foxtails I started thinking with that minor cough she had couple months ago that went away I wonder if i killed my dog by not bringing her to the vet. I'm sad and angry and disappointed in myself for not bring her to vet for minor cough and i really want to make sure i didn't miss the foxtails. Regardless i know know that i should have brought her and I will have to live with that. Never did get reason for her illness. They just put down cardiac arrest. So much wrong happened here

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8 Years
Moderate condition
1 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
1611 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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