Etiologies commonly broken into: Pre-renal, intrinsic renal or post-renal causes. Defined by change in GFR, urine output, or both. Wide range in symptoms based on acuity, other co-morbid conditions. Common sx include: fatigue, volume overload--> sob, edema, other. Though can be asymptomatic. May also have pre-existing chronic renal disease, w/AKI superimposed.