In many cases of acute kidney injury (AKI), it is possible to identify a specific cause. While the previous chapters reviewed the general approach to AKI and its broad causes, this chapter focuses on specific etiologies of AKI. Five cases are presented and each meant to highlight a unique etiology of AKI. The case of contrast induced nephropathy is particularly useful when evaluating AKI in a hospitalized patient given the prevalence of contrast exposure in the hospital. Although hepatorenal syndrome and tumor lysis syndrome are less common causes of AKI, they frequently appear in the differential diagnosis and reviewing the presented cases should assist the reader in diagnosing or excluding these syndromes. In addition to presenting diagnostic criteria, each case discussion includes a brief review of the epidemiology, pathophysiology, prevention/management, and prognosis of the specific AKI etiology.