Prediction of Acute Kidney Injury with Venous Excess Ultrasound (VExUS) Scoring Versus Renal Resistive Index (RRI) in Patients Undergoing On-Pump Coronary Artery Bypass Grafting: A Prospective Observational Study.

BACKGROUND

The diagnosis of acute kidney injury (AKI) using conventional markers such as serum creatinine and urine output is often delayed, prompting interest in bedside ultrasound-based predictors. This study compared renal resistive index (RRI) and venous excess ultrasound (VExUS) scoring for early prediction of AKI after on-pump coronary artery bypass grafting (CABG).

METHODS

In this prospective observational study, 180 adult patients were enrolled. RRI and VExUS assessments were performed preoperatively and within 3 hours of cardiothoracic ICU admission. AKI was diagnosed within 48 hours postoperatively using kidney disease: improving global outcomes (KDIGO) criteria. Receiver operating characteristic (ROC) curves were constructed for RRI and VExUS parameters, and diagnostic accuracy was assessed using area under ROC curve (AUROC), sensitivity, and specificity.

RESULTS

AKI occurred in 48 patients (26.7%). Postoperative RRI showed excellent discrimination for AKI (AUROC 0.854; cut-off ≥0.68: sensitivity 75%, specificity 86%, negative predictive value [NPV] 90.5%), outperforming preoperative RRI (AUROC 0.681). VExUS showed limited predictive performance (preoperative AUROC 0.588; postoperative AUROC 0.623). The baseline estimated glomerular filtration rate (eGFR) in the AKI group was significantly lower than in the patients who did not develop AKI [70.3 ml/min/1.73 m2 vs 79.4 ml/min/1.73 m2]. Diabetes mellitus was more common in the AKI group (62.5% vs 35.6%, P = 0.002). Postoperative urine output remained significantly lower in AKI patients on day 1 and day 2 (P < 0.001).

CONCLUSION

Postoperative RRI ≥ 0.68 demonstrated the best predictive performance for early AKI in our cohort, outperforming preoperative RRI, ΔRRI or change in RRI, and VExUS scores, supporting the predominant role of intrarenal arterial hemodynamic alterations in early postoperative renal injury.