[Disturbances in volume and electrolytes with intestinal and kidney diseases]

The intestines and kidney are the most important excretion organs. Both organ systems are key players in keeping the homeostatic balance regarding hydration and electrolytes. Disturbances of function can lead to enormous and sometimes life-threatening complications. Intestinal diseases lead often to diarrhoea, which can be associated with fluid loss of up to 20 l per day. The accompanying electrolyte disturbances can be hypo- or hypernatremia in combination with hypokalemia. The therapy is substitution guided by knowledge of the pathophysiology. Kidney diseases lead to excessive volume and electrolyte balances, depending on the underlying molecular or pathological defect, but deficiencies can also be found. In case of kidney impairment with 30-50% total loss of function, calcium and phosphate metabolism is impaired.