Acute kidney injury (AKI) remains one of the most significant postoperative complications following coronary artery bypass graft (CABG) surgery. A 2026 systematic review and meta-analysis published in Frontiers in Medicine evaluated the major risk factors associated with AKI after CABG by synthesizing data from multiple observational studies involving tens of thousands of patients. The findings provide important clinical insights for cardiothoracic surgeons, intensivists, and perioperative teams aiming to reduce kidney complications and improve surgical outcomes.Â
CABG surgery is one of the most widely performed procedures for patients with advanced coronary artery disease, particularly those with multivessel disease or left main coronary artery involvement. Although the operation significantly improves survival and quality of life by restoring blood flow to the heart, it is also associated with systemic complications due to the physiologic stress of surgery and cardiopulmonary bypass. Among these complications, postoperative acute kidney injury is particularly concerning. AKI can lead to prolonged hospitalization, increased healthcare costs, and a markedly higher risk of mortality. In severe cases, patients may require renal replacement therapy such as dialysis.
According to established KDIGO guidelines, AKI is defined by an increase in serum creatinine of at least 0.3 mg/dL within 48 hours, a 1.5-fold increase within seven days, or reduced urine output below 0.5 mL/kg/h for more than six hours. The incidence of AKI after CABG varies across studies but generally ranges between 5% and 30%. Even mild kidney injury has been shown to increase long-term risks of chronic kidney disease and cardiovascular complications.Â
To better understand the drivers of postoperative AKI, the researchers conducted a systematic review following PRISMA guidelines. They searched major medical databases including PubMed, Embase, Web of Science, and the Cochrane Library through September 2025. After screening 2,738 records and removing duplicates, the investigators included 17 eligible studies comprising 33,809 patients. Among these patients, 3,283 developed AKI following CABG surgery. Most studies were cohort studies, and their methodological quality was considered moderate to high based on the Newcastle-Ottawa Scale.Â
The meta-analysis identified several significant risk factors associated with postoperative AKI. One of the most consistent predictors was advanced age. Older patients demonstrated a higher likelihood of kidney injury following surgery. Age-related physiological changes—including reduced renal reserve, decreased renal perfusion, and the presence of multiple comorbidities—likely contribute to this increased vulnerability. Additionally, elderly patients often have diminished metabolic capacity to handle perioperative medications and physiologic stress, which further elevates the risk.
Another major risk factor identified was prolonged cardiopulmonary bypass time during surgery. Cardiopulmonary bypass is essential for many cardiac procedures because it temporarily takes over heart and lung function while surgeons operate. However, extended bypass duration can compromise renal perfusion, increase inflammatory responses, and expose the kidneys to oxidative stress. The analysis demonstrated that longer bypass times significantly increased the odds of postoperative AKI, emphasizing the importance of optimizing surgical efficiency and perfusion strategies.
Diabetes mellitus also emerged as a significant contributor to postoperative kidney injury. Patients with diabetes frequently develop microvascular disease that impairs kidney perfusion and increases susceptibility to ischemic injury. In addition, hyperglycemia promotes inflammation and oxidative stress, both of which can damage renal tissues. Effective perioperative glucose management is therefore critical to reducing AKI risk among diabetic patients undergoing cardiac surgery.
The study also highlighted the role of intra-aortic balloon pump (IABP) use. IABP is commonly employed in patients with severe cardiac dysfunction to improve coronary perfusion and reduce cardiac workload. However, the meta-analysis found that its use was strongly associated with increased risk of AKI. This association may reflect hemodynamic instability in patients requiring mechanical circulatory support, as well as potential changes in renal blood flow during device operation.
Another significant finding was the relationship between red blood cell transfusions and postoperative AKI. Blood transfusions are often necessary during cardiac surgery due to blood loss or anemia. However, transfusions may trigger inflammatory responses, immune reactions, and microvascular changes that can negatively affect renal function. These findings highlight the importance of careful blood management strategies during CABG procedures.
Despite identifying clear associations, the study acknowledged several limitations. Most included studies were observational, meaning causal relationships cannot be definitively established. In addition, variations in patient populations, surgical techniques, and AKI diagnostic criteria contributed to heterogeneity across studies. Nevertheless, sensitivity analyses confirmed the robustness of the results.
From a clinical perspective, the findings underscore the importance of comprehensive perioperative risk assessment. Patients with advanced age, diabetes, or expected prolonged cardiopulmonary bypass times may benefit from enhanced monitoring and preventive strategies. Optimizing hemodynamic management, minimizing unnecessary blood transfusions, and carefully selecting patients for mechanical circulatory support could help reduce the incidence of AKI.
Future research should focus on prospective studies and randomized trials to confirm these associations and evaluate targeted interventions. Improved predictive models incorporating these risk factors could allow clinicians to identify high-risk patients earlier and tailor individualized treatment plans.
In summary, this systematic review provides strong evidence that several patient and procedural factors contribute to acute kidney injury after CABG surgery. By recognizing these risks and implementing preventive measures, healthcare teams can improve patient outcomes and reduce the burden of postoperative kidney complications.
