To validate these findings in an independent cohort of children with differences in AKI etiology, we measured renin concentrations in children with SCD hospitalized with an acute pain crisis. Consistent with findings in children with SM from Cohort #1, renin was elevated in children with SCD-associated AKI compared to children without AKI (median 955 pg/mL (IQR 486, 2185) vs. 420 pg/mL (IQR 197, 723), p<0.0001) (Figure 2A). Here, REN is linked to acute kidney injury.