If a large volume is present, as it was with Coco, it may need to be drained by thoracentesis, a very delicate procedure in which a large needle is placed very close to the lung. If the kitty cannot be anaesthetized, there can be a very real but unavoidable risk. This is one procedure where absolute confidence is placed in the hands of the person performing it. Percussion and Auscultation. Percussion and auscultation are diagnostic techniques that may be useful in detecting the presence of fluid in the body cavity.
Auscultation is simply the medical term for listening, usually through a stethoscope.
With practice, meaningful information can be obtained by listening with your ear held against your pet's side. The hardest part is often getting the purring to stop. Percussion is a technique in which you listen on one side, and tap on the other. The existence of fluid will effect the resonance of the sound as it passes through the body. Unfortunately, my memory is not fresh enough to accurately describe the limited success I had with these techniques on Coco.