Sections View Full Chapter Figures Tables Videos Full Chapter Figures Tables Videos Supplementary Content +++ INTRODUCTION ++ Acute kidney injury (AKI) is a clinical syndrome generally defined by an abrupt reduction in kidney function as evidenced by changes in serum creatinine (Scr), blood urea nitrogen (BUN), and urine output. RIFLE (Risk, Injury, Failure, Loss of Kidney Function, and End-Stage Renal Disease), AKIN (Acute Kidney Injury Network), and the Kidney Disease: Improving Global Outcomes (KDIGO) clinical practice guidelines are three criteria-based classification systems developed to define and stage AKI in different patient populations (Table 74-1). All three staging systems have been validated across different patient populations, and their staging correlates closely with hospital mortality, cost, and length of stay. Scr and urine output are the main diagnostic criteria for each staging system. ++Table Graphic Jump LocationTABLE 74-1RIFLE, AKIN, and KDIGO Classification Schemes for AKIaView Table||Download (.pdf) TABLE 74-1 RIFLE, AKIN, and KDIGO Classification Schemes for AKIa RIFLE Category Scr and GFRb Criteria Urine Output Criteria Risk Scr increase to 1.5-fold or GFR decrease >25% from baseline <0.5 mL/kg/hr for ≥6 hr Injury Scr increase to 2-fold or GFR decrease >50% from baseline <0.5 mL/kg/hr for ≥12 hr Failure Scr increase to 3-fold or GFR decrease >75% from baseline, or Scr ≥4 mg/dL (354 μmol/L) with an acute increase of at least 0.5 mg/dL (44 μmol/L) Anuria for ≥12 hr Loss Complete loss of function (RRT) for >4 weeks ESKD RRT >3 months AKIN Criteria Scr Criteria Urine Output Criteria Stage 1 Scr increase ≥0.3 mg/dL (27 μmol/L) or 1.5- to 2-fold from baseline <0.5 mL/kg/hr for ≥6 hr Stage 2 Scr increase >2- to 3-fold from baseline <0.5 mL/kg/hr for ≥12 hr Stage 3 Scr increase >3-fold from baseline, or Scr ≥4 mg/dL (354 μmol/L) with an acute increase of at least 0.5 mg/dL (44 μmol/L), or need for RRT <0.3 mL/kg/hr for ≥24 hr or anuria for ≥12 hr KDIGO Criteria Scr Criteria Urine Output Criteria Stage 1 Scr increase ≥0.3 mg/dL (27 μmol/L) or 1.5–1.9 times from baseline <0.5 mL/kg/hr for 6–12 hr Stage 2 Scr increase 2–2.9 times from baseline <0.5 mL/kg/hr for ≥12 hr Stage 3 Scr increase three times from baseline, or Scr ≥4 mg/dL (354 μmol/L), or need for RRT, or eGFRc <35 mL/min/1.73 m2 (0.34 mL/sec/m2) in patients <18 years Anuria for ≥12 hr aFor all staging systems, the criterion that leads to worst possible diagnosis should be used.bGFR calculated using the Modification of Diet in Renal Disease (MDRD) equation.cGFR calculated using the Schwartz formula.AKI, acute kidney injury; AKIN, Acute Kidney Injury Network; ESKD, end-stage kidney disease; eGFR, estimated glomerular filtration rate; h, hours; KDIGO, Kidney Disease: Improving Global Outcomes; RIFLE, Risk, Injury, Failure, Loss of Kidney Function, and End-Stage Kidney Disease; RRT, renal replacement therapy; Scr, serum creatinine. +++ PATHOPHYSIOLOGY ++ AKI can be categorized as prerenal (resulting from decreased renal perfusion ... Your MyAccess profile is currently affiliated with '[InstitutionA]' and is in the process of switching affiliations to '[InstitutionB]'. Please click ‘Continue’ to continue the affiliation switch, otherwise click ‘Cancel’ to cancel signing in. Get Free Access Through Your Institution Learn how to see if your library subscribes to McGraw Hill Medical products. Subscribe: Institutional or Individual Sign In Username Error: Please enter User Name Password Error: Please enter Password Forgot Username? Forgot Password? Sign in via OpenAthens Sign in via Shibboleth