Thoracocentesis in Dogs

Thoracocentesis is the procedure in which air or fluid is removed from the chest using a needle. It can be done either to obtain fluid for evaluation or to remove large amounts of fluid if the accumulation of fluid is interfering with the pet's ability to breath. Thoracocentesis is also performed if excess air, pneumothorax, is affecting the pet's ability to breath.

Any fluid or air accumulation within the thoracic (chest) cavity is considered abnormal. Determining if excess air or fluid is present and what type of fluid – clear, cloudy or blood tinged – is an important part of determining any underlying illness.

Thoracic fluid may develop in association with heart failure, cancer, traumatic injury, infection or viral diseases. Excess air within the chest is most often associated with traumatic injury.

There are no real contraindications to performing this test in an animal with suspected thoracic air or fluid.

What Does a Thoracocentesis Reveal?

A thoracocentesis reveals whether fluid is present within the chest. In order to detect fluid, a certain amount needs to be present in order to draw the fluid into a syringe, so in some cases, small amounts of fluid present in the chest may not be detected. Any fluid removed from the chest is abnormal and may need to be microscopically evaluated. Air removed from the chest may indicate penetration into a lung and is not always abnormal. Excess air can be detected on a radiograph (X-ray). Based on the results of fluid evaluation, the underlying cause of the fluid accumulation may be determined.

How Is a Thoracocentesis Done?

In order to perform a thoracocentesis, your veterinarian will likely shave a small area of hair from the chest. The skin is disinfected and a needle is inserted into the thoracic cavity. Fluid is collected with special tubing or syringe. After the fluid is collected, analysis helps determine the potential underlying cause of the fluid accumulation. Analysis of the fluid may be done by your veterinarian or submitted to an outside laboratory. Test results may not be available for up to 3 to 5 days but sometimes, results may be available within a couple of hours. The length of time will depend on which tests are necessary. Collected air is not evaluated but is most often measured to determine the amount of air removed.

Is a Thoracocentesis Painful?

Any pain involved is associated with the collection of a fluid or air sample. A needle is used to pierce the skin and enter the thoracic cavity. As with people, the pain experienced from a needle will vary from individual to individual.

Is Sedation or Anesthesia Needed for a Thoracocentesis?

Neither sedation nor anesthesia is needed in most patients; however, some pets resent needle sticks and may need tranquilization or ultrashort anesthesia.