An accumulation of serous fluid in the cavity of the chest.
accumulation of fluid in the pleural cavity (the space between the lungs and the walls of the chest) often resulting from disease of the heart or kidneys
Excessive collection of serous fluid in the thoracic cavity.
a non-inflammatory accumulation of serous fluids in one or both of the lung cavities in the pleural space.
A hydrothorax is a condition that results from fluid accumulating in the pleural cavity. In hemothorax this fluid is blood (as in major chest injuries), in pyothorax the fluid is pus (resulting from chest infections), in chylothorax it is chylus (resulting from rupture of the thoracic duct).