Final answer:
A pleural effusion is a buildup of fluid between the layers of the pleura. It can be detected on physical exam by decreased breath sounds and dullness to percussion. Thoracentesis and cytology can be done to evaluate the pleural effusion.
Step-by-step explanation:
A pleural effusion is a buildup of fluid in the space between the layers of the pleura, which are the membranes that line the lungs and chest cavity. On physical exam, a pleural effusion may reveal decreased breath sounds and dullness to percussion, indicating reduced air entry and increased fluid in the affected area. Evaluation of a pleural effusion typically involves thoracentesis, a procedure in which a needle is inserted into the chest to drain the fluid. The collected fluid can then be analyzed for cytology to detect any abnormal cells, which can help diagnose the underlying cause of the effusion.