Acute kidney injury: definition, diagnosis and epidemiology

Acute kidney injury (AKI) is a common complication in hospitalized patients and great efforts by leading experts have been made in order to establish common definitions of AKI. The clinical use of these consensus definitions has led to a substantially improved understanding of AKI. In addition, the consensus definitions allow to compare AKI incidence and outcomes between different patient populations. As a result, it has become evident that AKI in the Western population represents a clinical syndrome with an incidence close to that of myocardial infarction. The aim of this review is to revisit the current concepts and definitions of AKI, to highlight its diagnosis, and to emphasize its epidemiological characteristics. Here, we will focus on the available literature reporting the epidemiology of AKI in critically ill patients. Sepsis, major surgery, and nephrotoxic drugs are the main causes of AKI in these patients, and its occurrence is associated with an increased risk for sustained chronic kidney injury. We also discuss the concept of renal angina as a possible future concept for improved clinical risk stratification to detect AKI. In this regard, we emphasize the importance of the use of novel biomarkers in the diagnosis of AKI, as they hold the potential to improve early diagnosis and prevention in the clinical setting.