title: Subacute kidney injury in hospitalized patients.
abstract: OBJECTIVE
  The epidemiology of AKI and CKD has been described. However, the epidemiology of progressively worsening kidney function (subacute kidney injury [s-AKI]) developing over a longer time frame than defined for AKI (7 days), but shorter than defined for CKD (90 days), is completely unknown.
  
  
  METHODS
  This retrospective study used a hospital laboratory and admission database. Adult patients admitted to a teaching hospital in Tokyo, Japan, between April 1, 2008, and October 31, 2011, were included. s-AKI was classified into three grades of severity (mild, moderate, severe) in accordance with the Risk, Injury, and Failure categories of the Risk, Injury, Failure, Risk, Loss, and ESRD classification, but did not use its time frame. Kidney injury (AKI and s-AKI) occurring during each hospital stay was identified, and logistic regression analysis was performed to assess their effect on hospital mortality.
  
  
  RESULTS
  Of 56,567 patients admitted to the hospital during the study period, 49,518 were included. Of these, 87.8% had no evidence of kidney dysfunction, 11.0% had AKI, and 1.1% had s-AKI. Patients with s-AKI had mild renal dysfunction in 82.7% of cases, moderate in 12.1%, and severe in 5.0%. Worsening s-AKI category was linearly correlated with hospital mortality, as previously described for AKI (no injury: 1.2%, mild: 6.5%, moderate: 12.9%, severe: 20.7%). Although mortality (8.0% versus 17.5%) and need for renal replacement therapy (0.2% versus 2.2%) were lower in patients with s-AKI than in those with AKI, multivariable regression analysis confirmed that s-AKI was an independent risk factor for hospital mortality (odds ratio (OR), 5.44; 95% confidence interval [95% CI], 3.89 to 7.44); the OR with AKI was 14.8 (95% CI, 13.2 to 16.7).
  
  
  CONCLUSIONS
  Close to 1% of hospitalized patients develop s-AKI. This condition is independently associated with increased hospital mortality, and the risk for death increases with s-AKI severity. Patients with s-AKI had a better outcome and were less likely to require renal replacement therapy than patients with AKI.
authors: Intensive Care Unit, Department of Anesthesiology, The Jikei University School of Medicine, Tokyo, Japan, †Department of Intensive Care, Austin Hospital, Melbourne, Victoria, Australia.
authors: Tomoko
authors: T
authors: Fujii
authors: Shigehiko
authors: S
authors: Uchino
authors: Masanori
authors: M
authors: Takinami
authors: Rinaldo
authors: R
authors: Bellomo
mesh_terms: D058186:Acute Kidney Injury / Q000175:diagnosis / Q000453:epidemiology / Q000503:physiopathology; D000328:Adult; D000368:Aged; D005260:Female; D017052:Hospital Mortality; D006760:Hospitalization; D006784:Hospitals, Teaching; D006801:Humans; D007564:Japan / Q000453:epidemiology; D007668:Kidney / Q000503:physiopathology*; D007674:Kidney Diseases / Q000175:diagnosis / Q000453:epidemiology* / Q000401:mortality / Q000503:physiopathology / Q000628:therapy; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D016017:Odds Ratio; D011379:Prognosis; D017582:Renal Replacement Therapy; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D012720:Severity of Illness Index; D013997:Time Factors