TIMP2 and acute kidney injury: The "renal troponin I" may be found in the novel urinary biomarkers insulin-like growth factor-binding-protein 7 (IGFBP7) and tissue inhibitor of metalloproteinases-2 (TIMP-2).This is an observational study designed to assess the capability of [TIMP-2]•[IGFBP-7] and its variation to predict AKI occurrence with the aim of introducing preventive or therapeutic interventions.