Acute kidney injury can occur due to a variety of prerenal, renal, and postrenal causes. Early detection and appropriate treatment are important for optimal outcomes in these often critical patients. This talk will review the causes and risk factors for AKI and review traditional and newer diagnostic options. Urine cystatin B, a novel marker of active renal tubular epithelial cell injury, will be reviewed. Finally, updated recommendations on appropriate fluid therapy and other treatments will be provided.