Acute kidney injury (AKI), formerly called acute renal failure, is a clinical syndrome in which a sudden deterioration in renal function results in the inability of the kidneys to maintain fluid and electrolyte homeostasis. AKI has been conventionally classified into 3 categories: prerenal, intrinsic renal, and postrenal depending on site of injury. The study was done in Upgraded Department of Paediatrics in Patna medical College and Hospital to know the prevalence, etiology and of acute kidney injury.