Inclusion Criteria for Renal Transplant Recipients group:  Previous renal transplantation Who underwent cardiac surgery with CPB  Inclusion Criteria for Non Renal Transplant Récipients group:  No previous renal transplantation Who underwent cardiac surgery with CPB Apparied with Renal Transplant récipients with the 5 following criteria : age, sex, previous diagnosis of diabete, type of cardiac surgery (isolated coronary artery bypass graft, valvular surgery, aorta surgery, combined surgery), best glomerular filtration rate with CKD-EPI formula at +/- 15 ml/min, in the 3 pre-operative months  Exclusion Criteria:  Patients requiring mechanical circulatory support (Extracorporeal Membrane Oxygenation) Pre-operative permanent dialysis Aorta dissection extended to renal arteries Non-elective surgery for infective endocarditis Previous hepatic, pancreatic or cardiac transplantation Death in the 30 first days after cardiac surgery Patient not meeting the inclusion criteria