The purpose of this study is to find out whether a combination of new urine tests and blood tests can show kidney injury in its early stages, before kidney failure sets in. If the investigators find new tests that show kidney injury in early stages, the investigators hope to start treating people with kidney injury earlier, to prevent kidney failure. You/your child are at higher risk for kidney injury and kidney failure than most other people, because of having operations with cardiopulmonary bypass (a machine that pumps your/your child's blood during the operation). This research is being done because there are no tests yet proven to show kidney injury before it leads to kidney failure.