REN and acute kidney injury: Models pretreated with dehydration to activate the renin-angiotensin system that causes renal vasoconstriction in CI-AKI, including water deprivation and the use of furosemide, showed a mild degree of pathological injury, with changes in serum creatinine that hardly meet the definition of a 26.5 μmol/L increase within 48 h [21,22].