**1.4 KDIGO criteria - AKI severity staging**

KDIGO guidelines [1] split severity into three groups based on specific creatinine levels and urine output (**Table 1**).

Other guidelines such as RIFLE use reduction in GFR as well. Though both serum creatinine and urine output can be used to diagnose, serum creatinine tends to be a stronger predictor of ICU mortality whereas urine output does not independently predict mortality. Some studies suggest that when both criteria were met, elevated


**Table 1.** *KDIGO AKI stages [1].* serum creatinine and reduced urine output, the risk of death or use of RRT was more strongly correlated. Urine output is also dependent on fluid intake, if the patient has limited fluid intake even a healthy individual cannot meet this criterion. Because of this many experts do not agree on diagnosing of an AKI based solely on urine output.
