Cat - Pyothorax

What is pyothorax?

Pyothorax refers to the presence of inflammatory fluid (pus) within the chest cavity surrounding the lungs.

What causes pyothorax?

Pyothorax is usually caused by a bacterial infection in the chest cavity. Usually, pus is present in both sides of the chest although occasionally only one side will be affected.

The source of the infection is rarely found although possible causes include:

1. Penetrating wounds to the chest wall such as a cat bite.
2. Wounds to internal structures such as the oesophagus (food pipe), trachea (wind pipe) for example following ingestion or inhalation of a foreign body.
3. Migrating foreign body such as a grass seed which entered the body elsewhere.
4. Extension of infection from a lung infection (pneumonia).

What are the clinical signs seen with pyothorax?

Rapid shallow breathing which may be painful, depression, lethargy and other signs of ill health such as a reluctance to eat are seen in most cats with pyothorax. The severity of these signs is extremely variable and rarely cats may suddenly die without having had any previous signs of illness.

Cats with pyothorax usually have a high temperature which contributes to some of the clinical signs seen. The breathlessness is caused by the presence of fluid in the chest which prevents the normal expansion of the lungs.

How is pyothorax diagnosed?

Clinical examination by a veterinary surgeon may provide some indication of fluid within the chest particularly on listening to the chest with a stethoscope. In severe cases, it may be necessary to drain the chest immediately. In more mildly affected cases, x-rays may help to demonstrate the presence of fluid which will be found to be pus when drained. Sedation of the cat may be needed to allow drainage of the chest. In most cases the pus can be drained from one side of the chest although it may be necessary to drain both sides in some cats. Sometimes, the fluid is present in 'pockets' and so multiple drainage must be performed. Samples of the fluid may be sent to a laboratory for bacterial culture so that the organism responsible can be found and an appropriate antibiotic given.

In cases of pyothorax where no obvious cause is determined, it may worthwhile checking for causes of immunosuppression such as viral infections.

How is pyothorax treated?

Drainage of the infected fluid plays an important part in the treatment of this condition. Drainage may be needed on multiple occasions over the initial treatment period. In some cases, a permanent chest drain may be inserted surgically allowing drainage of the chest and administration of antibiotics into the chest cavity. Fluids can also be administered via the tube to "lavage" or flush out the chest. This tube may be left in place for several days to allow these procedures to be performed. Treatment with oral antibiotics is also essential and the cat may need to stay on these for several weeks. In very sick cats, supportive treatment with intravenous fluids (a drip) may also be needed in the initial stages.

What is the longterm outlook for a cat with pyothorax?

This depends on the cause of the disease. In those cases where no underlying disease is found, the outlook is frequently very good provided that the cat survives the critical initial stages. Unfortunately, a proportion of cats will die in the early stages of their disease. In those cats that do survive, complications are seen rarely and the longterm outlook is good.