Novel modalities for the diagnosis of cardiac surgery associated acute kidney injury: a narrative review of the literature

Abstract

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.