Fluid that fills the lungs or the surrounding pleural sac restricts the lungs from expanding fully and prevents the normal intake of oxygen. When breathing is affected, this is a true emergency and requires immediate medical attention. In such cases, excessive fluid is accumulating in or around the lungs while too little of normal outflow is occurring.

The collection of fluid in or around the lungs of cats can refer to either pulmonary effusion or pulmonary edema. Healthy lungs normally have a very small amount of fluid that moves from the lungs to the internal space of the body and also help to prevent the lungs from adhering to the chest wall. However, if this process is disrupted due to added pressure or an underlying condition, fluid can back up into or around the lungs, causing impaired breathing. Both conditions are medical emergencies and should be treated immediately and aggressively since cats are not able to handle diminished lung function well. Cats of all ages, genders, and breeds can experience these conditions, which can affect both the respiratory and cardiovascular systems. If left untreated, permanent damage can occur or cats can pass away, but if addressed properly many cats experience positive results. The conditions have a variety of causes including congestive heart failure, cancer, infections, traumatic injuries or events such as electrocution or a blow to the head.

Symptoms of excessive fluid accumulation include:

There are two main types of fluid collection in the lungs of cats.

This condition refers to fluid accumulating inside the lungs and is associated with conditions such as pneumonia (inflammation) and heart disease. The edema occurs when the blood vessels and tissues involved with the lungs become affected by disease or blunt trauma, which causes fluid to backup into the alveoli. The alveoli are normally used for the uptake of oxygen into the lungs and carbon dioxide elimination, but the air is being replaced with fluid that is leaking into the lungs and is impairing lung function.

This condition occurs when fluid accumulates within the space between the outer surface of the lungs and the inner surface of the chest cavity. Both are lined by a thin wall of tissue called the pleura and fluid becomes trapped. Sometimes the condition involves chylothorax, which is an accumulation of lymphatic fluid in the chest and is very serious. Often times, pleural effusion is a symptom of congestive heart failure, but could be an indicator of other diseases.

There are three different kinds of fluid development in and around the lungs. Treatment will depend on which kind of condition your pet is experiencing.

There are many possible causes for pleural edema and pleural effusion. Some of the more common causes are:

A diagnosis of pulmonary edema or pleural effusion is based on clinical evidence, medical history, and a physical examination such as the use of a stethoscope to detect heart murmurs or changes in heart rate, and to listen for normal movement of air in and out of the lungs. Tests that are typically conducted to determine a diagnosis as well as identify any underlying conditions are:

Underlying conditions that the veterinarian will be checking for are bronchitis, heartworm disease, heart disease (cardiomyopathy), and any upper airway obstructions. 

If you observe your cat having any difficulty breathing at any time, an examination by your veterinarian is extremely urgent and necessary. The earlier the intervention the more positive the outcome. Waiting too long could lead to either permanent damage or death.

When your pet arrives, the vet will first want to stabilize them. Oxygen therapy may be necessary to help your pet breathe if there is inadequate ventilation and perfusion (oxygen coming in and carbon dioxide going out) in the lungs. At this time, the veterinarian may want to hospitalize your pet. Once stable, your cat will be examined.

Once pleural effusion is confirmed during diagnostic testing, the veterinarian will first want to remove the fluid accumulation and relieve the pressure being put on the lungs and heart in order to allow the lungs normal expansion and to improve heart function. This is done through a thoracentesis, which is used for both diagnostic purposes and for treatment. 

A thoracentesis is routinely done to not only remove fluid, but also to determine the cause of the fluid, especially when the origin is not apparent. However, if tests show that pleural effusion is present on both lungs and not just one and there is no chest pain or fever, then a thoracentesis may be avoided and a different course of treatment may be made unless the effusion continues for more than three days while in the veterinarian’s care. It may also not be necessary if the effusion is chronic, has a known cause, and no symptoms are evident.

Periodic x-rays will continue to be taken to monitor treatment progress and medications may be administered to assist with fluid removal and to address any suspected underlying conditions. These medications may include:

Depending on the cause of the fluid accumulation, additional procedures may be necessary over the long term. These include additional thoracentesis or chest drain placement.

A guarded prognosis is always given whenever a cat is experiencing a collection of fluid in the lungs. The long-term outlook will largely depend on the cause for the edema or effusion. If it has occurred due to a chronic condition, fluid accumulation could happen again. If it is due to some kind of trauma, then the prognosis is favorable as long as your cat responds well to treatment and recovers fully from the initial injury.

Once your cat is home, a limited sodium diet and special supplements may be recommended, along with any medications your veterinarian prescribes. Exercise should be restricted until recovery is complete. 

You will need to monitor for returning signs of weakness and tiredness, coughing, decreased appetite, or resistance to exercise. If you observe your cat with these symptoms, call your veterinarian right away.

Pay attention to your cat’s breathing rate if you able. Keeping track, perhaps even keeping a daily log, will allow you to better monitor how your cat is healing. If there are increases in the breathing rate and you notice other previously mentioned symptoms, call your veterinarian.