Association between the C-reactive protein–triglyceride glucose index and postoperative acute kidney injury after elective abdominal surgery: a retrospective cohort study

Background Postoperative acute kidney injury (PO-AKI) is a common and serious complication following abdominal surgery and is strongly associated with poor prognosis. Traditional diagnostic markers lack sensitivity. The novel C-reactive protein–triglyceride glucose index (CTI) has emerged as an innovative composite marker for evaluating metabolic-inflammatory dysregulation, comprehensively integrating markers of insulin resistance and systemic inflammation. However, its relationship with PO-AKI risk remains unclear. Methods This single-center retrospective study included adult patients who underwent elective major abdominal surgery between April 2020 and April 2025. The preoperative CTI was the primary exposure variable. The primary outcome was the incidence of AKI within 7 days post-surgery, defined according to the KDIGO creatinine criteria. Multivariable logistic regression was used to assess the association between CTI and PO-AKI, and restricted cubic splines (RCS) were applied to examine dose–response relationships. Receiver operating characteristic (ROC) curve analysis was performed to compare the predictive performance of CTI and the TyG index for PO-AKI. Subgroup analyses and sensitivity analyses were conducted to evaluate the robustness of the findings. Results A total of 4,658 patients were included, of whom 222 (4.77%) developed PO-AKI. After full adjustment for confounders, higher CTI was significantly associated with increased PO-AKI risk (OR = 1.28, 95% CI: 1.09–1.52). Compared with patients in the lowest CTI quartile, those in the highest quartile had a significantly higher risk (OR = 1.86, 95% CI: 1.12–3.11). RCS analysis revealed a linear positive association between CTI and PO-AKI. The area under the ROC curve (AUC) for CTI was significantly greater than that for the TyG index alone (0.643 vs. 0.587; P = 0.0003). Moreover, CTI values above approximately 9.5 were associated with prolonged postoperative hospital stay. Conclusions The preoperative CTI, a surrogate marker for the systemic immuno-metabolic phenotype, is an independent risk factor for PO-AKI after abdominal surgery. Notably, a CTI threshold of 9.5 serves as a cclinical decision node, offering superior predictive value for prolonged care trajectories and informing targeted perioperative prehabilitation strategies.