Pleural puncture A procedure that is performed for hydrothorax is an accumulation of fluid in the pleural cavity (between the pleural leaflets). Normally, only a few milliliters of fluid is contained between them, serving the function of lubrication. But in case of hydrothorax, the pleural cavity may contain more than two liters of fluid! The most common causes of this pathology are heart failure, kidney disease and cirrhosis of the liver.