Treatment will depend on the underlying cause, but a pleural tap to remove fluid from the chest cavity and improve breathing will be one of the primary actions.
If the fluid has accumulated rapidly as the result of a trauma, chest tubes will be used to quickly relieve the pressure from the chest organs and prevent dilation of the lymphatic vessels. If accumulation of fluid continues, your veterinarian will need to continue the use of tubes to keep the chest clear, and will probably recommend surgery. The most common and effective surgical treatment is to bind the thoracic duct, and remove a part of the membranous sac that envelopes the heart. Continued use of chest tubes after surgery is likely until your doctor is confident that the chest cavity will remain clear on its own.
Also, depending on the underlying cause, your veterinarian may prescribe medications for treatment, post-treatment, or maintenance.
Ongoing care and maintenance will include periodic pleural taps to remove fluid from the chest cavity. Even if your cat recovers, you will want to have it evaluated from time to time for several years. Asking your veterinarian to do this during routine exams should be sufficient, unless your are advised to do otherwise. You will need to monitor your pet carefully for breathing problems or for the recurrence of attendant symptoms (see description of symptoms above). Chylothorax will sometimes resolve spontaneously, or after surgery, but for some animals there is no effective treatment that will resolve it.
Pertaining to the chest
Anything pertaining to the blood vessel system in the body
The widening of something
To make something wider
Relating to a disease of unknown origin, which may or may not have arisen spontaneously