Acute kidney injury (AKI) is a frequent and severe complication in cardiac surgery. Normal renal function is dependent on adequate renal perfusion, which may be altered in the perioperative period. Renal perfusion can be assessed with Doppler measurement. We aimed to determine the association between Doppler measurements of renal perfusion and the development of AKI. This was a prospective, observational study of 100 patients with ≥ one risk factor for postoperative AKI undergoing open-heart surgery. Doppler ultrasound examinations were performed before surgery and on the first and fourth postoperative day. AKI was defined according to the KDIGO criteria and subdivided into mild (KDIGO stage 1) and severe AKI (KDIGO stage 2 + 3). Thirty-three patients developed AKI, 25 developed mild and eight developed severe AKI. Abnormal renal venous flow pattern on the first postoperative day was significantly associated with the development of severe AKI (OR 8.54 (95% CI 1.01; 72.2), P = 0.046), as were portal pulsatility fraction (OR 1.07 (95% CI 1.02; 1.13), P = 0.005). Point-of-care Doppler ultrasound measurements of renal perfusion are associated with the development of AKI after cardiac surgery. Renal and portal Doppler ultrasonography can be used to identify patients at high risk or very low risk of AKI after cardiac surgery.

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Acute kidney injury (AKI) is a common complication post cardiac surgery and increases mortality during hospitalisation fivefold. If present, it is an independent risk factor for progression to chronic kidney disease. When renal replacement therapy (RRT) is required, it carries a 50% mortality rate for cardiac surgery associated (CSA) AKI. Given the dynamic nature of CSA AKI, it is imperative to implement preventative and management strategies to: prevent or limit ischaemia; reduce systemic inflammation; modify amenable pre- and perioperative risk factors; and address nutritional and fluid status at the pre- intra- and postoperative stages. Conventional modalities in the diagnosis of AKI have proven ineffectual in the timely diagnosis, and rely mostly on nonspecific biometric parameters, namely a rise in serum creatinine, and a decrease in urine output. Novel biomarkers have promoted new ideas in the search for more effective, precise and reproducible tools to aid diagnosis. In addition, ultrasonic tools for renal, hepatic and portal vascular flow patterns using Duplex Doppler for venous flow parameters, together with renal arterial resistive index, have been used as novel predictors of perioperative AKI. Although these parameters require further investigation, Duplex Doppler of the renal, hepatic, portal and cardiac systems appear to have promising results in the early detection of AKI.