Shear wave elastography: usefulness in chronic kidney disease

Abstract

Purpose: Chronic kidney disease (CKD) is recognized as a major worldwide health problem. For all CKD, intra-renal fibrosis is a final common pathway that can be correlated with disease severity. Tissue stiffness can be measured non-invasively using shear wave elastography. This study evaluates the use of Young's modulus derived by SWE as a biomarker that can distinguish normal from diseased kidneys. Also, Young's modulus was correlated with Doppler findings and estimated glomerular filtration rate (eGFR).

Material and methods: This prospective study was performed in 2 phases, in which initially 50 CKD patients and 50 controls were studied to arrive at a median Young's modulus value in both the groups. In the later phase, a cross-sectional comparative study was conducted on 58 diabetic and 56 non-diabetic patients with SWE and renal Doppler, and the findings were correlated in various stages of CKD.

Results: Using Young's modulus, the renal cortex elasticity of CKD patients was shown to be considerably reduced as compared to normal kidneys. There was significant correlation between Young's modulus, eGFR, and renal resistive index. Young's modulus values did not show significant differences between diabetic and non-diabetic groups, revealing its inability to arrive at the aetiopathogenesis of CKD.

Conclusions: Correlation of renal tissue Young's modulus with eGFR suggests that SWE may be used as an indicator of renal tissue injuries in CKD patients. SWE can never replace the gold standard biopsy, but it can be used for staging of CKD. Even though SWE cannot predict the aetiopathogenesis of CKD, it may be a low-cost way to provide additional diagnostic information in CKD.

Keywords: Young’s modulus; chronic kidney disease; eGFR; renal resistive index; shear wave elastography.

Figure 1

Median Young’s modulus in cases and controls

Figure 2

Intrasubject variability of Young’s modulus in sample case A and control B

Figure 3

ROC curve for detecting presence of chronic kidney disease by shear wave elastography

Figure 4

Scatter diagram illustrating correlation of Young’s modulus and estimated glomerular filtration rate (eGFR)

Figure 5

Scatter diagram illustrating correlation of Young’s modulation and renal resistive index (RRI)

Figure 6

ROC curve to determine cut-off of Young’s modulus to distinguish ≥ IV stages of chronic kidney disease from lower stages

Figure 7

52-year-old diabetic male with stage IV chronic kidney disease – average Young’s modulus = 8.32 kPa

Figure 8

34-year-old non-diabetic female with stage IV chronic kidney disease – average Young’s modulus = 6.67 kPa

Figure 9

32-year-old diabetic female with stage V chronic kidney disease – average Young’s modulus = 10.9 kPa

Figure 10

51-year-old non-diabetic male with stage V chronic kidney disease – average Young’s modulus = 9.81 kPa