 This study will utilize a large, heterogeneous cohort n65,800 of critically ill patients admitted to the ICU over a 12 year period at the University of Pittsburgh Medical Center. The study population will consist of patients who receive intensive monitoring of UO defined as measured at least every 2 hours within the first 48 hours of ICU admission and strict creatinine measurement defined as at least daily. Patients who fail to meet criteria for intensive monitoring will be controls less-intensive monitoring group. AKI will be diagnosed according to the KDIGO stage 1-3 criteria over a 7-day period. Mortality at 30-days from ICU admission will be ascertained using the social security death master file. In order to account for indication bias, a propensity score for intensive monitoring will be built using various risk factors. Risk and severity of illness-adjusted estimates will be generated for susceptibility to AKI and mortality from AKI between intensive and less-intensive monitoring groups. 