Acute kidney injury (AKI) is asymptomatic until extremes of loss of function are reached and has no characteristic clinical findings. Diagnosis typically occurs in the context of another acute illness by laboratory tests. Patients with severe cases, however, may be symptomatic and present with listlessness, confusion, fatigue, anorexia, nausea, vomiting, weight gain, or edema. Prerenal, intrinsic renal and postrenal are type of acute kidney injury. The laboratory hallmarks of AKI are increased serum creatinine concentrations or raised plasma urea concentrations, or both. Functional markers, up-regulated proteins, low-molecular weight proteins and enzymes are biomarkers for acute kidney injury. A number of radiologic studies are used to evaluate the patient with kidney disease. These tests are performed alone or in combination for the detection, diagnosis, and/ or evaluation of multiple conditions. Renal biopsy is reserved for patients in whom prerenal and postrenal causes of AKI have been excluded and the cause of intrinsic renal injury is unclear. Renal biopsy is particularly important when clinical assessment and laboratory investigations suggest a diagnosis that requires confirmation before disease specific therapy is instituted.