Preoperative Renal Function Optimization and Its Impact on Outcomes in Major Surgery: A Systematic Review

Acute kidney injury (AKI) is a frequent complication after major surgery, associated with prolonged hospitalization, increased morbidity, and higher healthcare costs. Preoperative renal optimization has been proposed as a preventive strategy; however, the effectiveness of such interventions remains uncertain. This systematic review evaluated randomized controlled trials (RCTs) assessing preoperative interventions aimed at improving renal outcomes in adult patients undergoing major surgery. A comprehensive search was conducted in MEDLINE, Embase, and LILACS, and risk of bias was assessed using the Cochrane RoB 2 tool. Five RCTs met the inclusion criteria, encompassing pharmacologic strategies, nutritional interventions, and perioperative management approaches. Only one study, evaluating a hypocaloric, protein-restricted diet in living kidney donors, demonstrated a significant improvement in early renal outcomes in transplant recipients. In contrast, most trials did not show significant differences in AKI incidence, need for renal replacement therapy, or mortality. Four of the five studies were judged to present “some concerns” regarding risk of bias, while one was classified as low risk. Overall, the available evidence is limited and heterogeneous, precluding definitive recommendations for routine implementation of preoperative renal optimization strategies. Further large, well-designed clinical trials are needed to clarify the role of targeted preoperative interventions in AKI prevention. Systematic review registration: PROSPERO CRD420251161803