Background: Acute kidney injury is a potentially fatal condition with high mortality rate, treatment cost and poor outcome. The most crucial end-point in forecasting AKI is monitoring microcirculation parameters. Renal resistive index has been proposed as a new tool in intensive care unit (ICU) patient's microcirculation monitoring. Objective: The research study aimed to determine if there is a relation between change in renal resistive index (RRI) and acute kidney injury (AKI) in the first week of ICU admission. Patients and Methods: This was an observational prospective study of ICU patients. All participants underwent history taking, clinical examination with calculation of sequential organ failure assessment (SOFA) and acute physiology and chronic health evaluation (APACHE II) score. RRI was calculated using Doppler ultrasound with the following formula: (peak systolic velocity – end diastolic velocity)/ peak systolic velocity. Results: Patients with AKI had significantly higher peak-systolic velocity, end-diastolic velocity and renal resistive index (P< 0.001). Patients with stage III AKI had significant higher RRI in comparison with stage I and stage II (p value < 0.001). RRI had 75% sensitivity, 87% specificity for prediction of stage II and III AKI with over all accuracy was 83%. Conclusions: Assessment of RRI in the first 24 hours of ICU admissions was valuable in predicting the development of AKI especially in the stage II, III and persistent AKI. It is recommended to evaluate it early to prevent AKI development in ICU patients.