Cardiorenal syndrome refers to the interaction between the heart and the kidneys, in which the disease state of one organ alters and impairs functioning of the other. A more precise definition has not been presented before, but a new classification has now been published. Examples of clinical manifestations of the syndrome include profuse and serious cardiac events in dialysis patients, often simultaneously occurring renal insufficiency in a cardiac patient as well as rapid impairment of renal function and diuretic resistance in connection with acute cardiac insufficiency.