Normal pleural space is lined by a thin film of fluid. Visceral and parietal pleura are in opposition and glide over each other during respiration.

When excess fluid accumulates in pleural space, it is called pleural effusion.

Pleural effusion is divided into transudates & exudates according to the biochemical analysis of aspirated pleural fluid. 

Fever and cough with no improvement by an antibiotic, TB infection should be considered as a cause.