[Acute renal insufficiency due to vomiting or diarrhea: the Achilles heel of medical support for heart failure].

: Morbidity and mortality of heartfailure are decreasing because of improved medical treatment. The recompensation balance can however be very fragile, which is illustrated by three patients. A woman aged 73 and a man aged 62, both known with heart failure, became seriously ill after diarrhoea; examination revealed uraemia, hyperpotassaemia and raised digitalis levels. A man aged 72, also with heart failure and diarrhoea, developed sensory disorders in both feet. He, also, was found to suffer from renal insufficiency. All patients used an angiotensin converting enzyme inhibitor or an angiotensin-II-antagonist and an aldosterone receptor blocker as well. During the (innocent) intercurrent disease by which their intravascular volume diminished they developed a severe renal insufficiency which needed clinical, intensive treatment. After haemodialysis, all three recovered well. Renal function plays an essential role in the fragile treatment balance that exists in recompensated cardiac patients. The medication that is beneficial for the cardiac functioning may at the same time compromise the renal perfusion. Good monitoring and good instructions about what to do in case of intercurrent diseases are of vital importance in these patients.