1) Pleural effusion results from perturbations in normal pleural fluid transport and can be caused by abnormalities in Starling's equilibrium, increased capillary and mesothelial permeability, or interference with lymphatic drainage.
2) Evaluation of a patient with a suspected pleural effusion involves a thorough history, physical exam, imaging such as chest x-ray or CT, and thoracentesis to analyze pleural fluid.
3) Analysis of pleural fluid aims to determine if the effusion is a transudate or exudate, which provides clues to potential underlying causes and guides further diagnostic testing and treatment.