This lecture will review the aetiology and pathophysiology of acute kidney injury applicable to all species. It will discuss the most common causes of AKI in cats and how to distinguish between hospital versus community acquired AKI. The optimal diagnostics to identify AKI will be discussed particularly in relation to differentiating from chronic kidney disease and acute on chronic disease. An overview of optimal monitoring of AKI cats and supportive care will be provided. This lecture will aim to consolidate knowledge on the diagnostic approach to cats presenting with AKI.