Diagnostic approach to pleural effusion based on pathogenesis and radiological findings: A narrative review

Pleural effusion (PE) is a common feature of various diseases. The most common causes of PEs are infection, pulmonary embolism, and heart failure. Other diseases include rheumatological diseases, ovarian hyperstimulation syndrome, liver cirrhosis, hypoalbuminemia, and nephrotic syndrome. The principle of PE pathogenesis is either increased fluid production or decreased fluid removal from the pleural cavity, mainly by the parietal pleural layer. According to the underlying cause, the pathogenesis could be due to increased permeability, decreased oncotic pressure or increased hydrostatic pressure of parietal pleural capillaries, increased fluid oncotic pressure, tumor invasion to the pleura, increased lymphatic vessel hydrostatic pressure, lung inflammation, and increased lung interstitial fluid content. Exploring the underlying cause and pathogenic mechanism is the best approach and is immensely helpful in planning the treatment of PE. Treating the underlying cause is the primary approach in treating PEs; thoracocentesis, pleurodesis, pleurectomy, and other possible modalities are applied when indicated, mainly to relieve symptoms. Hence, this review article will discuss the conceivable pathophysiological mechanisms of PEs, common etiologies, radiological diagnostic modalities, and the available therapeutic options.