Chest Imaging

Transudate, pleural

accumulation of excess fluid in the pleural space resulting from increased vascular filtration of low molecular weight proteins and fluid (see pleural effusion). The commonest cause is heart failure, but transudates also occur as a consequence of liver and renal disease. The main differential is from a pleural exudate (see exudative effusion).

Transudates have a low specific gravity (< 1.016), a low protein content (< 3g/dl), a ratio of pleural fluid to serum protein of < 0.5, an absolute LDH of < 200 IU/L or a pleural fluid to serum LDH ratio of < 0.6. Unlike exudates, transudates are usually bilateral. They are anechoic on ultrasound. On CT the pleura is not thickened and there is no enhancement of the pleura or extrapleural fat following intravenous contrast enhancement.

CF - HM