Renal Doppler Ultrasound for the Management of Acute Kidney Injury

Abstract

Renal Doppler has been proven to be a valuable tool for assessing large arteries and veins of the kidney. An increasing body of evidences suggests that renal Doppler may help to assess perfusion of kidneys in the critically ill. Two techniques have been proposed: renal resistive index (RI) and contrast-enhanced ultrasound (CEUS). The RI is a Doppler-derived parameter that is calculated as follows: RI = [peak systolic shift − minimum diastolic shift]/peak systolic shift. An increasing body of evidences suggests RI may be of interest for the early diagnosis of acute kidney injury and to evaluate its reversibility. However, numerous physiological and pathological factors have been shown to influence RI and this integrative parameter neither constitutes an alternative to renal biopsy nor provides valuable information on renal blood flow. Although confirmation studies are needed, the potential clinical usefulness, feasibility, reproducibility, and the low cost of the technic probably justify additional investigations in this field. Theoretically, CEUS allows a more precise assessment of renal microcirculation. However, preliminary results in the critically ill are limited and disappointing; reproducibility is limited and the cost of the contrast media is significant. Therefore, although additional studies are expected, CEUS remains mainly a research tool.