Acute kidney injury (AKI) is a common complication among patients undergoing cardiac surgery. Perioperative ultrasound assessment of renal hemodynamic parameters has emerged as a potential tool for predicting postoperative AKI. This study aimed to investigate whether the renal pulsatility index (RPI) could serve as an early diagnostic marker for the development of AKI (Kidney Disease Improving Global Outcomes, KDIGO-defined) following cardiac surgery.

This prospective observational study enrolled 500 patients meeting the inclusion criteria. The RPI was measured at 4 time points: prior to anesthesia (T0), after anesthesia induction (T1), after the completion of cardiopulmonary bypass (T2), immediately after the surgery (T3). The primary endpoint was the incidence of AKI. Three logistic regression models were constructed to evaluate the association between RPI and AKI. The associations between RPI and moderate to severe AKI were analyzed and served as sensitivity analysis.

A total of 161 patients (32.2%) developed AKI. Among them, 46 classified as moderate to severe AKI. Compared with patients without AKI, patients with AKI had a significantly higher RPI at T3 (1.30 ± 0.28 vs 1.44 ± 0.34, P = 0.004), while no significant differences were observed at the other time points. Multivariable analysis revealed that RPI at T3 was associated with postoperative AKI (OR = 3.72, 95% CI 1.92–7.20; P < 0.001). The restricted cubic splines revealed an RPI cutoff value of 1.305 at T3, above which the risk of AKI increased proportionally.

An elevated RPI immediately after surgery was associated with increased risk of AKI after cardiac surgery.