Acute kidney injury (AKI) was defined according to the Kidney Disease Improving Global Outcome (KDIGO) classification using both creatinine and urine output criteria.

The KDIGO guidelines define AKI as follows:

• Increase in serum creatinine by ≥0.3 mg/dL (≥26.5 micromol/L) within 48 hours, or
• Increase in serum creatinine to ≥1.5 times baseline, which is known or presumed to have occurred within the prior seven days, or
• Urine volume <0.5 mL/kg/hour for six hours

Patients who will no develop Acute kidney injury (AKI).

The calculation formula for Renal resistive index (RRI) as follows :

(systolic peak flow velocity _ diastolic minimum flow velocity )/systolic peak flow velocity .

will be measured with ultrasound-Doppler using an abdominal curvilinear probe ultrasonography by two independent, trained sonographers (who will not be involved in patient care. After visualizing the kidney in ultrasound mode and checking for renal abnormalities, 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, 3 times in each kidney. So a total number of 9 RRI values will be obtained in each kidney.

The median value of each section will be used and the 3 median values of each kidney will be averaged.

AKI was defined according to the Kidney Disease Improving Global Outcome (KDIGO) classification using both creatinine and urine output criteria.

The KDIGO guidelines define AKI as follows

• Increase in serum creatinine by ≥0.3 mg/dL (≥26.5 micromol/L) within 48 hours, or
• Increase in serum creatinine to ≥1.5 times baseline, which is known or presumed to have occurred within the prior seven days, or
• Urine volume <0.5 mL/kg/hour for six hours

RRI and other hypoperfusion markers after fluid challenge and divided into responder to fluid (Time 1 F) and non responder with noradrenaline administration (Time 1 N) .