Thoracic effusion describes a fluid buildup inside the chest that can pressure the lungs and impair breathing.


Urgency level 5


Danger level 5


The predominant symptom of thoracic effusion is labored breathing. This is the result of increased pressure on the lungs caused by fluid buildup inside the chest. Depending on the type of effusion other symptoms may be present, such as weakness, shock (haemothorax), high fever, and depression (pyothorax).


There are different types of effusion, and each type is classified by the type of fluid found inside the chest. Serous fluid: Hydrothorax Hydrothorax occurs when plasma exits the vessels in large amounts. It is then found inside the chest when either the blood density changes or blood flow is impaired. This can occur in cases where the animal is suffering from chronic liver disease or cardiac conditions. Blood: Hemothorax Bleeding inside the chest can occur after accidents, trauma or fights with dogs or other animals. Tumors inside the chest may also rupture and cause heavy bleeding. Pus: Pyothorax Pus consists of protein-rich fluid and cell-debris of dead immune cells. Pus can build-up as result of infections of the pleura (a serous membrane that covers the inside of the chest), pneumonia, or ruptured tumors. Lymph: Chylothorax Most vessels of the lymphatic system drain into a larger duct that passes through the chest. If the duct is ruptured, i.e. after an accident or through a tumor, larger amounts of lymph can enter the thoracic cavity.


Pathologic fluid inside the chest appears on x-rays as shaded regions. Drainage of the thorax will yield some of the fluid that can be examined. By determining the nature of the fluid by examination, veterinarians can gain an idea as to what caused the effusion. Nonetheless, the most important part of treatment is to ensure oxygen supply to the animal. Most patients will have to be hospitalized. If bleeding into the chest is present, surgery might be necessary to ligate (tie up) the ruptured vessel. In case of a pyothorax a suitable antibiotic will be administered over a longer period of time. Draining of the thorax can relieve the harmful pressure on the lungs.

Emergency measures

If you suspect that your dog is suffering from thoracic effusion, consult your veterinarian immediately.

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