 Nowadays, the investigators can measure Renal Resistive Index RRI using renal Doppler ultrasound. The RRI is a sonographic index assessing resistance of the intrarenal arcuate or interlobar arteries and is normally used to assess renal arterial disease. The method has now become available at the bedside in the intensive care unit. RRI is calculated as: peak systolic velocity - end diastolic velocitypeak systolic velocity. Normal values are between 0.60 and 0.70. A mean value of 0.72 has been found in critically ill patients admitted to the intensive care unit personal data. 