What can be a possible cause of pleural effusion?

Pleural effusion refers to the accumulation of excess fluid in the pleural space between the layers of tissue that line the lungs and the chest cavity. One possible cause of pleural effusion is infection or malignancy. Infections, such as pneumonia, can lead to inflammation and fluid accumulation in the pleural space, known as parapneumonic effusion. Additionally, malignancies, including lung cancer or metastases from other cancers, can also result in pleural effusion by either directly invading the pleura or causing irritation and fluid accumulation as a result of tumor growth. Thus, the connection between infection or malignancy and pleural effusion is well established in medical literature, which makes this option the correct choice.

In contrast, healthy lung function, regular physical activity, and decreased fluid intake do not contribute to the development of pleural effusion. Healthy lungs typically maintain a balance between fluid production and absorption in the pleural space, while regular physical activity and adequate fluid intake are essential for overall health and lung function. Decreased fluid intake could potentially lead to dehydration but is not a direct cause of pleural effusion.