Does the measurement of the difference of resistive indices in spleen and kidney (DI-RISK) allow a selective assessment of chronic kidney injury?

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Purpose:

To assess if calculation of the difference of resistance indices (RI) in spleen and kidney (DI-RISK) would be a more specific ultrasound marker of intra-renal parenchymal damage than measuring intra-renalRI alone.

Materials and Methods:

We defined standard values for renal RI, splenic RI and DI-RISK values in 152 healthy subjects; we assessed carotid intima media-thickness (IMT) as a marker of systemic vascular disease. Next, we measured these ultrasound parameters and collected echocardiographic data in 290 patients suffering from chronic kidney disease stage 2–4, in order to evaluate DI-RISK values across the spectrum of stages of kidney function. Correlation coefficients were calculated by Spearman test, and three multivariate linear regression models analysed independent predictors of renalRI, splenic RI and DI-RISK, respectively.

Results:

In healthy subjects, renal and splenic RI are both associated with IMT (renalRI: r=0.19 [p=0.022]; splenic RI: r=0.23 [p=0.005]); no correlation exists between DI RISK and IMT (r=-0.10 [p=0.215]). Similarly, in chronic kidney disease patients renal and splenic RI correlate with IMT (renalRI: r=0.33 [p<0.001]; splenic RI: r=0.30 [p=0.001]). DI-RISK is specifically associated with estimated glomerular filtration rate (eGFR; r=-0.19 [p=0.001]), but not with IMT (r=0.08 [p=0.174]). In multivariate regression analysis, DI-RISK is independently associated with eGFR, but not with extra-renal factors.

Summary:

In chronic kidney disease patients, renal RI do not selectively indicate organ damage, but also mirror systemic vascular disease. We introduce DI-RISK as new ultrasound marker which more specifically reflects kidney damage.

Ultrasound - CKD