500 patients with normal renal function will be prospectively studied and incidence, spectrum and natural history of AKI (Acute Kidney Injury) will be observed in them and in 200 patients with abnormal renal function fulfilling AKI (Acute Kidney Injury) criteria will be prospectively studied for 1 year. Also biomarkers will be studied and validated as early predictors of AKI (Acute Kidney Injury).