Quantification of kidney fibrosis using ultrasonic shear wave elastography: experimental study with a rabbit model.

OBJECTIVES: The purpose of this study was to evaluate the feasibility of ultrasonic shear wave elastography for quantification of renal fibrosis in an experimental rabbit model.

METHODS: Thirty-eight kidneys of 19 rabbits were studied and categorized into 3 groups: group I, ureter obstruction (n = 9); group II, renal vein occlusion (n = 10); and group III, normal control (n = 19). Before surgery, we measured stiffness at the renal cortex using shear wave elastography and evaluated the sonographic findings, including size, echogenicity, and resistive index. We repeated the same sonographic examinations weekly until the fourth week. The degree of histologically quantified fibrosis and the measured stiffness values were statistically compared.

RESULTS: There was no significant difference in the mean stiffness values for the renal cortex in the 3 groups before surgery (8.95 kPa in group I, 9.06 kPa in group II, and 9.74 kPa in group III; P > .05). However, the mean stiffness in each group on the last sonographic examination was significantly different (10.91 kPa in group I, 13.92 kPa in group II, and 9.77 kPa in group III; P = .003). Pathologically, the degree of fibrosis was also significantly different (3.62% in group I, 11.70% in group II, and 0.70% in group III; P< .001). The fibrosis degree and stiffness were positively correlated (ρ = 0.568; P = 0.01).

CONCLUSIONS: Tissue stiffness measured by ultrasonic shear wave elastography was positively correlated with histopathologic renal fibrosis. Ultrasonic shear wave elastography may be used as a noninvasive tool for predicting renal fibrosis.