SPP1 and acute kidney injury: Recent studies and reviews indicate other novel kidney damage biomarkers investigated in other clinical conditions (e.g. during cardiac surgery or ischemia-reperfusion injury), such as liver-type fatty acid binding protein (L-FABP), interleukin 18 (IL-18), hemojuvelin (HJV) and osteopontin (OPN), while other so-called “pre-injury phase” stress biomarkers (e.g. tissue inhibitor of metalloproteinases-2 (TIMP-2) and insulin-like growth factor-binding protein 7 (IGFBP7)) showed promising results in the beginning stages of moderate AKI [12–14].