Pleural puncture A procedure that is performed for hydrothorax is an accumulation of fluid in the pleural cavity (between the pleural leaflets). Normally there is only a few milliliters of fluid between them, which acts as a lubricant. But with hydrothorax there may be more than two liters of fluid in the pleural cavity! The most common causes of this pathology are heart failure, kidney disease and cirrhosis of the liver.