Evaluating Novel Biomarkers in Acute Kidney Injury

The investigators have a new technique of looking at urine to see whether it contains protein fragments that are released by damaged kidneys. These fragments seem to be more accurate than the current blood tests that the investigators use to diagnose renal failure. This technique needs to be validated with a group of patients that have a relatively high incidence of renal failure, cardiopulmonary bypass. The investigators hypothesise that using novel markers of renal dysfunction will identify patients who go on to develop renal failure earlier, and in a higher number than the standard blood tests. The investigators aim to collect urine from patients before going onto bypass, and then at Day 1 and Day 2 after bypass. This urine will be analysed for protein fragments, as well as other new markers of renal dysfunction. The investigators will also take blood at baseline and for the first two days in Cardiac Intensive Care, and compare the accuracy of the new tests with the 'gold standard' that is creatinine.