Acute kidney injury (AKI) and chronic kidney disease (CKD) are interconnected clinical syndromes, and both manifest kidney injury and a decrease in glomerular filtration rate (GFR). Studies have shown that patients with AKI may still have abnormalities in the renal structure after complete recovery of renal function, thereby increasing the risk of CKD and end-stage renal disease (ESRD). However, some patients with renal dysfunction and structural abnormalities may not reach the current diagnostic criteria of AKI or CKD. Therefore, in 2012, the Kidney Disease: Improving Global Outcomes (KDIGO) clinical practice guidelines for AKI put forward a new concept, acute kidney diseases and disorders, which includes AKI and other newly-identified kidney diseases that do not meet AKI or CKD diagnostic criteria. This new concept was proposed to help increase the identification and exchange of various acute and chronic kidney diseases, and to increase the medical, scientific, and public health levels of the kidney disease field. This article described the concept and staging of acute kidney disease (AKD), as well as the current epidemiological status of AKD and future research directions, aiming to help clinicians correctly identify and assess various acute and chronic kidney diseases.