Cardiac surgery remains the standard of care for the revascularisation of the most severe coronary artery disease despite improvements in percutaneous coronary intervention. The nature of such surgery confers an ischaemic renal insult and it follows on that AKI is a relatively common complication. However, the reported incidence of AKI post cardiac surgery varies widely depending on the diagnostic criteria used. A recent retrospective analysis of 4572 cardiac surgical patients at the Royal Infirmary of Edinburgh over a 5 year period showed that 12.4% developed AKI by AKIN criteria post operatively. This was associated with an increased risk of death and prolonged inpatient stay.