KLK4 and acute kidney injury: The kallikrein increment in AKI persisted when studied with ICU controls (6.74 ± 1.92 vs. 2.04 ± 0.47 U/gm creatinine; p = 0.028), though kallikrein excretion was modestly elevated in ICU- compared to healthy controls (2.04 ± 0.47 vs. 0.63 ± 0.08 U/gm creatinine; p = 0.005).