Abstract： Objective To analyze the underlying diseases,predisposing factors of acute kidney injury (AKI) secondary to chronic kidney disease (CKD) (A/C) and its risk factors affecting the prognosis.Methods Between December 2005 and December 2009,the clinical data of 65 elderly A/C in-patients were retrospectively analyzed for their underlying diseases,predisposing factors and risk factors affecting the prognosis.According to the recovery of kidney function after treatment,the patients were divided into 2 groups,including kidnev function recovered group (combined by kidney function recovered patients and partially recovered patients) and kidnev function unrecovered group (combined by kidney function unrecovered patients and dead patients).Thereafter,the oliguria stage,the level of seralbumin on admission and the highest serum creatinine (Scr) level between the 2 groups were then compared.Results Diabetic nephropathy was the main underlying disease of elderly A/C patients(38.5％,25/65).Furthermore,the drug factor (30.8％,20/65) and severe infection (27.7％,18/65) were the main predisposing factors of elderly A/C patients.Compared with the kidney function recovered group,the kidney function unrecovered group had relatively longer oliguria stage[(11.5±3.4)d vs (4.2±1.8)d,P＜0.05],lower level of seralbumin on admission [(23.6±3.1)g/L vs (26.6±4.5)g/L,P＜0.05] and much higher level of the highest Scr[(601.2± 142.7) μ mol/Lvs (421.3±107.3)μmol/L,P＜0.05].Conclusion The effective treatment for underlying diseases should be performed on the elderly A/C patients so as to eliminate the predisposing factors and the risk factors affecting the prognosis.