[Organ Interactions: Heart and kidney].

The interactions between heart and kidney are various and of clinical relevance. Worsening of one organ often influences the function of the other. With NYHA and KDIGO we have classification systems for heart and kidney failure and those should be used for cardiorenal systems as well. Furthermore there is a useful classification system for cardiorenal syndromes itself. Cardiorenal syndrome is a complex illness which should be treated by interdisciplinary medical teams. A key roll in pathophysiology is the renin-angiotensin-aldosteron-system (RAAS). It's activation is followed by an increased salt and water retention as well as increased systemic an renal vasoconstriction leading to hypervolaemia an left ventricular hyperthrophy. General recommendations for the prevention of cardiovascular disease are good for the prevention of cardiorenal syndromes as well. RAAS-blockers should be used to stop cardial remodelling. A good regulation of hypertension and diabetes is important. Most important is a balanced intravasal volume. With volume overload negative balances can improve renal perfusion and therefor renal function. The furosemide stress test is a good cinical tool to check wether there is appropriate urine excretion and if volume overload can be treated by loop diuretics. Preload reduction can reduce cardiac output ahd renal function can be worsened especially in the beginning of overload-reduction. This may be acceptable.