Side Effects of Fluid Around the Chest in a Dog

Lack of energy, fainting and collapse are possible signs of fluid in a dog's chest cavity.
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Side effects generally refer to unintended outcomes of treating a condition. Effects that are caused by the condition itself are referred to as symptoms. While excess fluid in a dog’s chest cavity is itself a symptom of a number of different conditions, some of which can be quite serious, the presence of fluid also has signs and symptoms to watch for. Four different types of this condition exist, and each one presents its own set of symptoms, although there is some overlap.

Pericardial Effusion

Pericardial effusion refers to a buildup of fluid inside the pericardial sac that surrounds the heart. This buildup places pressure on the dog’s heart, restricting its ability to beat and pump blood through the body. This can lead to collapse and possible heart failure. If not treated right away, it can result in death. Signs to watch for include vomiting, loss of appetite and weight loss, lethargy, pale gums or a distended abdomen. This condition also can cause respiratory distress, fast breathing or heart rate, fainting or collapse.

Pleural Effusion

With pleural effusion, fluid accumulates in the chest cavity between the lungs and the thoracic wall. It’s normal to have a small amount of fluid in this space, which lubricates the lungs and chest wall. Excessive fluid, though, can restrict the lungs and make breathing difficult. Severe fluid build-up can collapse the lungs -- a life-threatening circumstance for any dog. Symptoms of pleural effusion include either fast breathing or difficulty drawing breath, open-mouthed breathing, coughing, lethargy, decreased appetite and weight loss. A bluish or purplish tinge to the skin, or your dog trying unusual positions in an attempt to make breathing easier are signs to watch for.


An accumulation of lymphatic fluid in the chest cavity, chylothorax occurs when the digestive fluid chyle leaks out of the thoracic duct on its way from the small intestine to the veins. If enough of this substance accumulates in the chest, it can obstruct the lymphatic vessels, leading to inflammation and buildup of scar tissue, which constricts the lungs and creates breathing problems. This condition is most commonly seen in the Afghan hound and the Shiba Inu. Signs to watch for include coughing, fast breathing, rattling or other sounds in the lungs, a muffled or irregular heartbeat, loss of appetite and weight loss, inability to exercise and depression. A dog with this condition also might have bluish skin or pale gums.


Hemothorax is a very serious condition that refers to internal bleeding within the chest cavity. It’s usually caused by trauma to the chest, but it can be caused by ruptured tumors or blood clotting disorders. Symptoms of hemothorax include trouble breathing, rapid breathing, pale gums, weakness and collapse. You might also be able to observe internal bruising under the skin. This condition shares symptoms with other chest fluid conditions, so it can be difficult to pinpoint, but these symptoms should be treated as an emergency. If your dog shows signs of any of these conditions, he should be taken to an emergency vet and checked out immediately.