Feasibility of renal resistive index measurements performed by an intermediate and novice sonographer in a volunteer population

Abstract

Background The Doppler-derived renal resistive index (RRI) is emerging as a promising bedside tool for assessing renal perfusion and risk of developing acute kidney injury in critically ill patients. It is not known what level of ultrasonography competence is needed to obtain reliable RRI values. Objective The aim of this study was to evaluate the feasibility of RRI measurements by an intermediate and novice sonographer in a volunteer population. Methods After a focused teaching session, an intermediate (resident), novice (medical student) and expert sonographer performed RRI measurements in 23 volunteers consecutively and blinded to the results of one another. Intraclass correlation coefficients and Bland–Altman plots were used to evaluate interobserver reliability, bias and precision. Results Both non-experts were able to obtain RRI values in all volunteers. Median RRI in the population measured by the expert was 0.58 (interquartile range 0.52–0.62). The intraclass correlation coefficient was 0.96 (95% confidence interval 0.90–0.98) for the intermediate and expert, and 0.85 (95% confidence interval 0.69–0.94) for the novice and expert. In relation to the measurements of the expert, both non-experts showed negligible bias (mean difference 0.002 [95% confidence interval − 0.005 to 0.009, p = 0.597] between intermediate and expert, mean difference 0.002 [95% confidence interval − 0.011 to 0.015, p = 0.752] between novice and expert) and clinically acceptable precision (95% limits of agreement − 0.031 to 0.035 for the intermediate, 95% limits of agreement − 0.056 to 0.060 for the novice). Conclusions RRI measurements by both an intermediate and novice sonographer in a volunteer population were reliable, accurate and precise after a brief course. RRI is easy to learn and feasible within the scope of point-of-care ultrasound.

Renal resistive index is associated with acute kidney injury in COVID-19 patients treated in the intensive care unit

“…Normal values are around 0.60 [9,10] with 0.70 considered the upper normal threshold in adults [11]. Elevated RRI has shown promise in early detection and prognostication of AKI in mixed ICU populations [12][13][14][15][16], and the method seems feasible within the scope of point-of-care ultrasonography (POCUS) [17].…”

Renal Resistive Index is Associated With Acute Kidney Injury in COVID-19 Patients Treated in the ICU

“…Third, intra-and interobserver variability for the operators were not investigated. Our group has previously shown that RRI measurements by inexperienced sonographers were reliable, accurate and precise compared to an expert after only a brief training session [17], and both operators in our study were experienced with the RRI method. Lastly, our study was affected by some of the well-known pitfalls in AKI-research.…”

“…As a non-invasive and repeatable bedside method, RRI is an interesting tool for the assessment of AKI in critically ill patients with COVID-19. The method has been demonstrated in different settings and centers to be easy and fast to learn even for non-experienced sonographers [17,35], and should be applicable within POCUS-protocols for ICU clinicians even in the present resource scarce times of a pandemic.…”

“…The patients were examined in their ICU bed in supine or prone position depending on their respiratory requirements. Both kidneys were examined, and measurements were made on both or the most accessible side since the difference in RRI values between the right and left kidney has been shown to be negligible both in healthy and critically ill patients [9,12,17]. After obtaining a complete view of the kidney, color-Doppler was applied to visualize the global organization of intrarenal blood vessels.…”

“…ultrasonography (POCUS) [17]. The role of RRI to guide diagnosis and treatment of AKI in patients is unknown.…”