Renal Doppler Indices for Predicting Acute Kidney Injury After Isolated CABG

Acute kidney injury can occur after coronary artery bypass grafting (CABG). This prospective, single-center observational study will evaluate whether two measurements obtained from renal Doppler ultrasound-the renal augmented velocity index (AVI) and renal resistive index (RRI)-can help predict postoperative acute kidney injury. About 200 adults undergoing elective isolated CABG with cardiopulmonary bypass will have bilateral renal Doppler examinations one day before surgery, within 60 minutes after admission to the intensive care unit, and 6 hours after intensive care unit admission. The primary outcome is acute kidney injury within the first 7 days after surgery, defined according to Kidney Disease: Improving Global Outcomes (KDIGO) criteria. Ultrasound measurements will be analyzed offline and will not influence clinical care.

Inclusion Criteria: * Age 18 years or older. * Scheduled for elective isolated coronary artery bypass grafting with cardiopulmonary bypass (on-pump). * Able and willing to provide written informed consent. * Both kidneys present. * Adequate bilateral preoperative renal Doppler signal for study measurements. Exclusion Criteria: * Preoperative chronic dialysis or renal replacement therapy. * Urgent or emergency surgery. * Combined cardiac surgery, including valve, aortic, or another major additional procedure. * Off-pump coronary artery bypass grafting or conversion of the planned surgical technique. * Clinically significant rhythm disturbance preventing acquisition of three interpretable cardiac cycles. * Renal transplant, solitary kidney, significant renal artery stenosis, previous renal artery intervention, hydronephrosis, or other relevant renal vascular or structural disease. * Inadequate bilateral preoperative renal Doppler examination. * Withdrawal of consent.