The pleural cavity is the space within the chest that surrounds the lungs. Disorders in this area impact the lungs from the outside, often making it difficult for a cat to inhale air.
Hemothorax, the accumulation of blood in the pleural cavity, is usually caused by trauma to the chest, blood clotting disorders, or tumors in the chest. Hydrothorax, the accumulation of clear fluid in the pleural cavity, is usually due to interference with blood flow or lymph drainage. Pleural effusion is a type of hydrothorax common in cats that develop congestive heart failure. Chylothorax, the accumulation of a high-triglyceride lymphatic fluid in the pleural cavity, is relatively rare. It may be caused by rupture of the chest duct, but often the cause is unknown. The signs of all 3 conditions include respiratory difficulty, such as rapid shallow breathing with labored inhalation, and weakness. Drainage of the fluid may be necessary to relieve these signs and can be helpful in diagnosing the underlying problem. However, the outlook for many disorders that cause accumulation of fluid in the chest is guarded to poor.
Bacterial and fungal infections can also occur in the pleural cavity. They often spread to the pleural cavity from the lungs or the blood or can be introduced because of an injury. Pleuritis (pleurisy) is inflammation of the pleural cavity, and empyema is the accumulation of pus in the pleural cavity. Affected cats may have a fever, cough, pain, and difficulty breathing.
Air in the pleural cavity, called pneumothorax, may be caused by trauma or occur spontaneously. The lung collapses if a large volume of air enters the pleural cavity, causing difficulty inhaling or rapid, shallow breathing. This condition should be considered an emergency that requires immediate veterinary attention.
Also see professional content regarding respiratory malfunction.