To investigate the efficacy of the shear wave velocity (SWV) based on acoustic radiation force impulse (ARFI) elastography in the differentiation of normal population with chronic kidney disease (CKD) and acute kidney injury (AKI) in middle aged and elderly patients.

Sixty-four middle aged and elderly patients referred to China-Japan Friendship Hospital and Zhejiang Provincial People′s Hospital with AKI or CKD were enrolled in this study from February 2015 to December 2016 (kidney disease group). Among them, 43 patients were CKD (CKD group), and 21 patients were AKI (AKI group, 15 patients combined with prior CKD, 6 patients without prior CKD). Twenty-nine middle aged and elderly healthy volunteers from China-Japan Friendship Hospital were enrolled at the same time (healthy control group). The SWV values of the renal middle pole cortex were acquired using the ARFI elastography. The differences of the kidney length, cortical thickness and SWV values among healthy control group, AKI and CKD group were compared by variance analysis. The LSD-t analysis was used for the advanced comparison between any two groups. The differences of cortical SWV values among healthy control group, AKI combined with prior CKD group, AKI without prior CKD group and CKD group were compared by variance analysis. The LSD-t analysis was used for the advanced comparison between any two groups. The receiver operating characteristic (ROC) curves of the cortical SWV values for diagnosing kidney disease was drawn.

The mean cortical SWV values of healthy control group, AKI and CKD groups were (2.88±0.63), (2.42±0.83) and (2.06±0.72) m/s, respectively. The SWV values of AKI and CKD groups were significantly lower than that of healthy control group (t=2.158, P=0.033; t=5.234, P<0.001). The SWV values of CKD group were lower than that of AKI group, but there were no significant differences. The SWV values of AKI without previous CKD group and AKI combined with prior CKD group were (2.60±0.84) and (1.80±0.45) m/s, respectively. The SWV values of AKI combined with prior CKD group and CKD group were significant lower than that of healthy control group and AKI without prior CKD group (compared with healthy control group: t=2.916, P=0.004 and t=5.318, P<0.001; compared with AKI without prior CKD group: t=2.054, P=0.043 and t=-2.517, P=0.013). But there were no significant differences between AKI combined with prior CKD group and CKD group, so as to the AKI without prior CKD group and healthy control group. The cutoff value of cortical SWV for diagnosing kidney disease was 2.40 m/s, with an area under ROC curve was 0.767 (95% CI 0.689-0.898, P=0.000). The sensitive and specificity were 57.1% and 81.9%, respectively.

The SWV values of kidneys in middle aged and elderly CKD and AKI patients were significantly lower than those of apparently normal kidneys. The SWV values of AKI patients combined with prior CKD were lower than AKI patients without prior CKD. Determining cut-off SWV values based on ARFI elastography between normal and damaged renal parenchyma can help in the diagnosis of kidney disease in middle aged and elderly patients.