A method for evaluating a likelihood of the occurrence or nonoccurrence of RIFLE stage I or F acute kidney injury, or of worsening renal function within 48 hours, in a subject, comprising: performing one or more assays configured to detect matrix metalloproteinase-9:tissue inhibitor of metalloproteinase 2 (MMP9:TIMP2) complex and optionally further one or more of Thymic stromal lymphopoietin, Vascular endothelial growth factor receptor 1, C-C motif chemokine 1, C-C motif chemokine 17, C-C motif chemokine 21, C-C motif chemokine 27, FLT-3 Ligand, Immunoglobulin G subclass 3, Interleukin-1 receptor type I, Interleukin-20, Interleukin-29, Interleukin-7, Platelet-derived growth factor A/B dimer, and Platelet-derived growth factor A/A dimer, on a urine sample obtained from the subject to provide an assay result comprising a measured concentration of MMP9:TIMP2 complex; and correlating the assay result(s) to a likelihood of the occurrence or nonoccurrence of RIFLE stage I or F acute kidney injury, or of worsening renal function within 48 hours, by comparing the measured concentration of MMP9:TIMP2 complex to a predetermined threshold selected to be indicative of the occurrence or nonoccurrence of RIFLE stage I or F acute kidney injury, or of the likelihood of worsening renal function within 48 hours, wherein an increased likelihood of the occurrence of RIFLE stage I or F acute kidney injury, or of worsening renal function within 48 hours, is assigned to the subject when the measured concentration is above the threshold relative to a likelihood assigned when the measured concentration is below the threshold, further wherein said worsening renal function is progression to RIFLE stage I or F acute kidney injury. performing one or more assays configured to detect matrix metalloproteinase-9:tissue inhibitor of metalloproteinase 2 (MMP9:TIMP2) complex and optionally further one or more of Thymic stromal lymphopoietin, Vascular endothelial growth factor receptor 1, C-C motif chemokine 1, C-C motif chemokine 17, C-C motif chemokine 21, C-C motif chemokine 27, FLT-3 Ligand, Immunoglobulin G subclass 3, Interleukin-1 receptor type I, Interleukin-20, Interleukin-29, Interleukin-7, Platelet-derived growth factor A/B dimer, and Platelet-derived growth factor A/A dimer, on a urine sample obtained from the subject to provide an assay result comprising a measured concentration of MMP9:TIMP2 complex; and correlating the assay result(s) to a likelihood of the occurrence or nonoccurrence of RIFLE stage I or F acute kidney injury, or of worsening renal function within 48 hours, by comparing the measured concentration of MMP9:TIMP2 complex to a predetermined threshold selected to be indicative of the occurrence or nonoccurrence of RIFLE stage I or F acute kidney injury, or of the likelihood of worsening renal function within 48 hours, wherein an increased likelihood of the occurrence of RIFLE stage I or F acute kidney injury, or of worsening renal function within 48 hours, is assigned to the subject when the measured concentration is above the threshold relative to a likelihood assigned when the measured concentration is below the threshold, further wherein said worsening renal function is progression to RIFLE stage I or F acute kidney injury.