Official reprint from UpToDate®
www.uptodate.com ©2017 UpToDate, Inc. and/or its affiliates. All Rights Reserved.

Definition and staging criteria of acute kidney injury in adults

Paul M Palevsky, MD
Section Editor
Gary C Curhan, MD, ScD
Deputy Editor
Alice M Sheridan, MD


Acute kidney injury (AKI) refers to an abrupt decrease in kidney function, resulting in the retention of urea and other nitrogenous waste products and in the dysregulation of extracellular volume and electrolytes. The term AKI has largely replaced acute renal failure (ARF), reflecting the recognition that smaller decrements in kidney function that do not result in overt organ failure are of substantial clinical relevance and are associated with increased morbidity and mortality.

Several consensus definitions of AKI have been developed in order to provide a uniform definition of AKI. These definitions are based exclusively on the serum creatinine and urine output and are used primarily to identify patients with AKI in epidemiologic and outcome studies. They are of limited utility in the clinical assessment and management of patients with AKI.

The potential etiologies, diagnosis, and management of AKI are discussed elsewhere. (See "Etiology and diagnosis of prerenal disease and acute tubular necrosis in acute kidney injury in adults" and "Diagnostic approach to adult patients with subacute kidney injury in an outpatient setting" and "Overview of the management of acute kidney injury (acute renal failure)".)


The definition for AKI used in clinical and epidemiologic studies is based on specific criteria that have been sequentially developed. The Kidney Disease: Improving Global Outcomes (KDIGO) definition and staging system is the most recent and preferred definition [1]. Other criteria include the RIFLE criteria [2] and a subsequent modification proposed by the Acute Kidney Injury Network (AKIN) and others [3-5]. These criteria are outlined in the table (table 1).

The KDIGO guidelines define AKI as follows [1]:

To continue reading this article, you must log in with your personal, hospital, or group practice subscription. For more information on subscription options, click below on the option that best describes you:

Subscribers log in here

Literature review current through: Sep 2017. | This topic last updated: Apr 07, 2017.
The content on the UpToDate website is not intended nor recommended as a substitute for medical advice, diagnosis, or treatment. Always seek the advice of your own physician or other qualified health care professional regarding any medical questions or conditions. The use of this website is governed by the UpToDate Terms of Use ©2017 UpToDate, Inc.
  1. KDIGO Clinical Practice Guideline for Acute Kidney Injury. Kidney Int Suppl 2012; 2:8.
  2. Bellomo R, Ronco C, Kellum JA, et al. Acute renal failure - definition, outcome measures, animal models, fluid therapy and information technology needs: the Second International Consensus Conference of the Acute Dialysis Quality Initiative (ADQI) Group. Crit Care 2004; 8:R204.
  3. Mehta RL, Kellum JA, Shah SV, et al. Acute Kidney Injury Network: report of an initiative to improve outcomes in acute kidney injury. Crit Care 2007; 11:R31.
  4. Levin A, Warnock DG, Mehta RL, et al. Improving outcomes from acute kidney injury: report of an initiative. Am J Kidney Dis 2007; 50:1.
  5. Molitoris BA, Levin A, Warnock DG, et al. Improving outcomes from acute kidney injury. J Am Soc Nephrol 2007; 18:1992.
  6. Ad-hoc working group of ERBP, Fliser D, Laville M, et al. A European Renal Best Practice (ERBP) position statement on the Kidney Disease Improving Global Outcomes (KDIGO) clinical practice guidelines on acute kidney injury: part 1: definitions, conservative management and contrast-induced nephropathy. Nephrol Dial Transplant 2012; 27:4263.
  7. Palevsky PM, Liu KD, Brophy PD, et al. KDOQI US commentary on the 2012 KDIGO clinical practice guideline for acute kidney injury. Am J Kidney Dis 2013; 61:649.
  8. James M, Bouchard J, Ho J, et al. Canadian Society of Nephrology commentary on the 2012 KDIGO clinical practice guideline for acute kidney injury. Am J Kidney Dis 2013; 61:673.
  9. Barasch J, Zager R, Bonventre JV. Acute kidney injury: a problem of definition. Lancet 2017; 389:779.
  10. Cruz DN, Bolgan I, Perazella MA, et al. North East Italian Prospective Hospital Renal Outcome Survey on Acute Kidney Injury (NEiPHROS-AKI): targeting the problem with the RIFLE Criteria. Clin J Am Soc Nephrol 2007; 2:418.
  11. Petäjä L, Vaara S, Liuhanen S, et al. Acute Kidney Injury After Cardiac Surgery by Complete KDIGO Criteria Predicts Increased Mortality. J Cardiothorac Vasc Anesth 2016.
  12. Qin JP, Yu XY, Qian CY, et al. Value of Kidney Disease Improving Global Outcomes Urine Output Criteria in Critically Ill Patients: A Secondary Analysis of a Multicenter Prospective Cohort Study. Chin Med J (Engl) 2016; 129:2050.
  13. Claure-Del Granado R, Macedo E, Chertow GM, et al. Toward the optimal dose metric in continuous renal replacement therapy. Int J Artif Organs 2012; 35:413.
  14. Kellum JA, Sileanu FE, Murugan R, et al. Classifying AKI by Urine Output versus Serum Creatinine Level. J Am Soc Nephrol 2015; 26:2231.
  15. Prowle JR, Kolic I, Purdell-Lewis J, et al. Serum creatinine changes associated with critical illness and detection of persistent renal dysfunction after AKI. Clin J Am Soc Nephrol 2014; 9:1015.
  16. Siew ED, Ikizler TA, Matheny ME, et al. Estimating baseline kidney function in hospitalized patients with impaired kidney function. Clin J Am Soc Nephrol 2012; 7:712.
  17. Lin J, Fernandez H, Shashaty MG, et al. False-Positive Rate of AKI Using Consensus Creatinine-Based Criteria. Clin J Am Soc Nephrol 2015; 10:1723.
  18. Levey AS, Levin A, Kellum JA. Definition and classification of kidney diseases. Am J Kidney Dis 2013; 61:686.
  19. Ali T, Khan I, Simpson W, et al. Incidence and outcomes in acute kidney injury: a comprehensive population-based study. J Am Soc Nephrol 2007; 18:1292.
  20. Uchino S, Bellomo R, Goldsmith D, et al. An assessment of the RIFLE criteria for acute renal failure in hospitalized patients. Crit Care Med 2006; 34:1913.
  21. Hoste EA, Clermont G, Kersten A, et al. RIFLE criteria for acute kidney injury are associated with hospital mortality in critically ill patients: a cohort analysis. Crit Care 2006; 10:R73.
  22. Kuitunen A, Vento A, Suojaranta-Ylinen R, Pettilä V. Acute renal failure after cardiac surgery: evaluation of the RIFLE classification. Ann Thorac Surg 2006; 81:542.
  23. Ostermann M, Chang RW. Acute kidney injury in the intensive care unit according to RIFLE. Crit Care Med 2007; 35:1837.
  24. Ricci Z, Cruz D, Ronco C. The RIFLE criteria and mortality in acute kidney injury: A systematic review. Kidney Int 2008; 73:538.
  25. Bagshaw SM, George C, Dinu I, Bellomo R. A multi-centre evaluation of the RIFLE criteria for early acute kidney injury in critically ill patients. Nephrol Dial Transplant 2008; 23:1203.
  26. Thakar CV, Christianson A, Freyberg R, et al. Incidence and outcomes of acute kidney injury in intensive care units: a Veterans Administration study. Crit Care Med 2009; 37:2552.
  27. Joannidis M, Metnitz B, Bauer P, et al. Acute kidney injury in critically ill patients classified by AKIN versus RIFLE using the SAPS 3 database. Intensive Care Med 2009; 35:1692.
  28. Teles F, de Mendonça Uchôa JV, Mirelli Barreto Mendonça D, Falcão Pedrosa Costa A. Acute kidney injury in leptospirosis: the Kidney Disease Improving Global Outcomes (KDIGO) criteria and mortality
. Clin Nephrol 2016; 86 (2016):303.
  29. Bıyık M, Ataseven H, Bıyık Z, et al. KDIGO (Kidney Disease: Improving Global Outcomes) criteria as a predictor of hospital mortality in cirrhotic patients. Turk J Gastroenterol 2016; 27:173.
  30. Hoste EA, Bagshaw SM, Bellomo R, et al. Epidemiology of acute kidney injury in critically ill patients: the multinational AKI-EPI study. Intensive Care Med 2015; 41:1411.
  31. Coca SG, King JT Jr, Rosenthal RA, et al. The duration of postoperative acute kidney injury is an additional parameter predicting long-term survival in diabetic veterans. Kidney Int 2010; 78:926.