ABSTRACT
Patients with pleural effusions may present with symptoms, such as pleuritic chest pain, dyspnea or cough, or the effusion may be suspected on physical examination or observed on chest radiograph. The diagnosis of a pleural effusion signifies that the physiologic balance between normal pleural fluid formation and removal has been disturbed, resulting in pleural fluid accumulation. Since a pleural effusion can be a manifestation of disease in virtually any organ in the body, its presence provides the clinician with the opportunity to support or confirm their clinical diagnosis. Awareness that not only disease in the thorax can cause a pleural effusion, but abnormalities of organs juxtaposed to the diaphragm, such as the liver or spleen, can lead to earlier diagnosis.1 In addition, systemic diseases, such as systemic lupus erythematosus and rheumatoid arthritis, and diseases of the lymphatic system, such as yellow nail syndrome, may also cause pleural effusions. Therefore, the evaluation of a patient with a pleural effusion starts with, and requires, a thorough history and physical examination in conjunction with pertinent laboratory tests to allow the clinician to formulate a pre-thoracentesis diagnosis. Pleural fluid analysis can provide a confident diagnosis when the likelihood of a clinical diagnosis is high.
