PROJECT SUMMARY Community-acquired acute kidney injury (CA-AKI) is the development of AKI outside of the hospital setting and is the most common form of AKI. Much of the research to date on CA-AKI has been limited to episodes during an acute hospitalization (i.e. patients found to have AKI upon admission), which represents only a fraction of the overall CA-AKI burden. Notably, these CA-AKI estimates are largely assessed in studies conducted in integrated health systems outside of the United States (US); such national estimates are lacking in US populations. Despite this scant evidence base, estimates indicate that a majority of CA-AKI events do not result in acute hospitalization, yet outpatient CA-AKI events remain poorly characterized. Regardless of setting, CA-AKI portends a significantly high risk of poor long-term outcomes, including increased risk of hospitalization, poor renal outcomes and death. Moreover, there is a limited evidence that informs the few guidelines directing CA-AKI management, and none delineate the role of the provider in CA-AKI aftercare or outcomes. Through a systematic program of research, the goal of this study is to assess the continuum of CA- AKI through rigorous evaluation of 1) measurement approaches for identifying CA-AKI, 2) CA-AKI clinical outcomes, and 3) risk factors and etiologies for CA-AKI development. This will be accomplished by merging several years of national Veterans Healthcare Administration's laboratory and administrative data with Medicare administrative data to facilitate a national evaluation of CA-AKI development and subsequent clinical consequences. This project has three specific aims: Aim 1 of this study will describe the epidemiology of CA- AKI, by applying various clinical measurement approaches to define CA-AKI development and describe CA- AKI incidence in the Veterans Health administration, and Aim 2 will assess the risk of adverse clinical outcomes including hospitalization or death associated with CA-AKI development. Building from this work, Aim 3 will classify the most common clinical types of CA-AKI among veterans with identified CA-AKI. Our approach is innovative because it will be the first study to: (1) use national datasets to comprehensively examine outpatient-based CA-AKI outcomes in a US population cohort and (2) identify the most common types of CA- AKI which will inform tailored CA-AKI risk stratification. This project will identify areas for improving care standards for prevention and clinical management of CA-AKI, provide a critically needed empirical basis to refine clinical guidelines, and inform the development of future, targeted interventions designed to improve the clinical management of CA-AKI and related morbidity and mortality.