Surgical intervention on an ‘open’ heart during cardio-pulmonary bypass is the method of choice for patients with valvular defects, complicated forms of coronary heart disease and combined pathology. The level of perioperative mortality in these interventions range from 2 % to 10 %. Acute kidney injury associated with cardiac surgery is a common and serious complication which dramatically worsens operative prognoses and results. According to several major studies, the incidence of acute renal injury in cardiac surgery is comparable with the incidence of myocardial infarction, with corresponding unsatisfactory outcomes.The introduction of the term ‘acute kidney injury’ into clinical practise, replacing the concept of acute renal failure, occurred relatively recently. This facilitated a universal definition for this condition, and unified the criteria for diagnosis and stratification of acute renal dysfunction severity. The article defines acute kidney injury using RIFLE, AKIN and KDIGO criteria. Acute kidney injury in cardiac surgery dramatically worsens short-term results and long-term outcomes, and thus increases the economic cost of treating patients. According to some reports, in industrialised countries, the health costs associated with acute kidney injury are estimated at $ 1 billion. Acute kidney injury is associated with approximately 300,000 deaths per annum, as well as approximately 300,000 new cases of chronic kidney disease. Cumulative expenses associated with acute renal injury in cardiac surgery are not directly limited to the hospitalisation period, but are often prolonged and/or deferred. These patients require additional financial expenses after discharge from hospital, which once again exemplifies this problem in cardiac surgery.Manifest acute kidney injury in the postoperative period of cardiac surgery leads to an increased number of extrarenal complications, reduced short-and long-term survival rates, increased economic costs in hospitals and prolonged treatment effects in the long-term. The introduction of a single definition of cardiac acute renal injury according to KDIGO criteria into clinical practise will identify patient groups with a high risk of developing this pathology. Similarly, it will also facilitate timely measures to prevent the development of complications in postoperative periods, which will reduce the risk of complications in cardiac patients.Received 10 July 2020. Revised 2 September 2020. Accepted 9 September 2020.Funding: The study did not have sponsorship.Conflict of interest: Authors declare no conflict of interest.Author contributionsConception and design: N.O. Kamenshchikov, Y.K. Podoksenov, M.L. DiakovaData collection and analysis: N.O. Kamenshchikov, A.M. Boyko, M.L. DiakovaDrafting the article: N.O. Kamenshchikov, M.L. Diakova, A.M. BoykoCritical revision of the article: M.L. Diakova, Y.K. PodoksenovFinal approval of the version to be published: N.O. Kamenshchikov, Y.K. Podoksenov, M.L. Diakova, A.M. Boyko, B.N. Kozlov