Acute kidney injury, previously called acute renal failure, indicates a sudden and often reversible reduction in kidney function as measured by glomerular filtration rate, increased serum and plasma creatinine concentration and changes in urine output. This article reviews the pathophysiology and common causes of acute kidney injuries, including pre-renal causes from hypovolaemia, intrinsic renal causes such as glomerular diseases and post-renal obstructive causes. Veterinary nurses should be aware of the common diagnostic tests used and how to deliver support to the hospitalised patient. While an acute kidney injury can be a serious condition for some patients, it is possible for others to recover and maintain a good quality of life with effective nursing care to help maximise the prognosis of these patients.