 1. Renal ultrasound to measure renal resistive index RRI After visualising the kidney in ultrasound mode, checking for chronic renal damage, an arcuate or interlobar artery will be localized and three successive Doppler measurements at different positions in the kidney high, middle and low will be performed. This will be repeated 3 times in each kidney. So a total number of 9 RRI values will be obtained in each kidney. 