Advanced ultrasound methods to improve chronic kidney disease diagnosis.

Chronic kidney disease (CKD) affects 850 million people worldwide and is associated with significant cardiovascular morbidity and mortality. Routine laboratory tests do not reflect early stages of microcirculatory changes and vascular rarefaction that characterise kidney fibrosis, the common endpoint of CKD. Imaging techniques that detect CKD in early stages could promote timely treatment with new drugs like SGLT2 inhibitors, thus, decreasing CKD progression and the cardiovascular disease burden. Ultrasound is the most used imaging modality in CKD, as it is non-invasive and radiation free. Initially, ultrasound imaging was applied to assess kidney macro-morphology and to rule out ureteral obstruction. The development of higher frequency probes allowed for more detailed imaging of kidney parenchyma, and advances in Doppler ultrasound provided insights into segmental arterial flow patterns including resistive indices as an indirect measure of microcirculatory impedance, elevated values of which correlated with progressive organ failure and fibrosis. Today, low-flow detection methods and matrix probes better resolve organ parenchyma and smaller vascular beds, and contrast-enhanced ultrasound allows perfusion measurement. Particularly, super-resolution ultrasound imaging, a technology currently being in clinical translation, can characterise the microcirculation morphologically and functionally in unrivalled detail. This is accompanied by rapid developments in radiomics and machine learning supporting ultrasound image acquisition and processing, as well as lesion detection and characterisation. This perspective article introduces emerging ultrasound methods for the diagnosis of CKD and discusses how the promising technical and analytical advancements can improve disease management after successful translation to clinical application.