Shear wave elastography tracking evaluation of tubulointerstitial fibrosis: a longitudinal study in a rat model

Renal biopsy is invasive and unsuitable for repeated monitoring of tubulointerstitial fibrosis (TIF). This study evaluated whether renal shear wave elastography (SWE) tracks TIF progression in rats with diabetic nephropathy (DN). The DN group underwent renal ultrasound, urinary microalbumin (MALB) measurement and renal biopsy at weeks 0, 2, 4, and 6. The control group was assessed at baseline. Longitudinal trends and within-subject associations were evaluated using linear mixed-effects models, repeated-measures correlation, and Lin’s concordance correlation coefficient (CCC). Diagnostic performance was assessed using clustered bootstrap analysis, and robustness of rmcorr estimates was evaluated through leave-one-rat-out influence analysis. At baseline, the DN group showed greater renal length and transverse diameter and higher MALB, blood glucose and SWE values than the control group (all P < 0.05). TIF and SWE increased over time (both P < 0.001), whereas MALB and renal morphometric parameters did not show significant time trends. SWE was associated with TIF within subjects ( r = 0.617, P < 0.001) and showed significant concordance (CCC = 0.712, 95% CI 0.501–0.843). For diagnosing fibrosis, SWE achieved the highest diagnostic performance across all tested TIF thresholds (5%-50%). Sensitivity analyses confirmed the robustness of rmcorr estimates. This study supports SWE as a potential noninvasive imaging marker for monitoring renal fibrotic progression.