Pets are sometimes presented with fluid in the space between their lungs and the chest wall due to some underlying condition. A catheter or needle can be used to collect a sample and remove the fluid using ultrasound guidance. This sterile procedure can often make the pet more comfortable while our veterinarians are evaluating the cause of the fluid. The fluid obtained via this procedure will be laboratory-tested as part of the process of discovering the underlying cause for the condition and arriving at a diagnosis and treatment protocol. This procedure is performed under light sedation.