Advancements in Elastography for Evaluating Fibrosis in Renal Transplants: Current Perspectives

Abstract

Renal fibrosis is a leading cause of chronic allograft nephropathy. While renal biopsy remains the gold standard for diagnosing fibrosis, it is an invasive procedure with potential for severe complications. Elastography, an emerging ultrasound imaging technique, appears to be a valuable tool for quantifying tissue stiffness, which correlates with fibrosis. Indeed, numerous studies have demonstrated a strong correlation between increased tissue stiffness, measured by elastography, and the degree of fibrosis detected in biopsy. Over the past few years, various elastography techniques have been evaluated, including strain elastography, shear wave elastography, and acoustic radiation force impulse. However, challenges such as operator dependence, tissue heterogeneity, and the lack of standardized protocols persist. Despite these limitations, elastography presents itself as a valuable tool for the non-invasive monitoring of renal transplant function and could facilitate the early detection of fibrosis, allowing for timely interventions. Future research should focus on standardizing acquisition protocols, establishing robust reference values, and exploring the clinical utility of elastography in guiding therapeutic decisions. The aim of this review is to explore the current state of elastography in the assessment of fibrosis in renal transplantation.

Keywords: elastography; renal stiffness; renal transplant; renal ultrasound; shear wave velocity; ultrasound.

Figure 1

This figure presents a comparative visualization of a colorimetric elastographic map (right) and a traditional B-mode grayscale ultrasound image (left) of the kidney. The colorimetric map represents the spatial distribution of tissue stiffness, with different colors corresponding to varying degrees of elasticity. The reference scale provides a quantitative interpretation of the color-coded stiffness values. While this dual-modality approach offers a visual representation of tissue heterogeneity, it should be noted that the colorimetric map does not provide specific multiparametric information and therefore this visualization technique, when applied to deep tissue studies, may not yield additional data, thus limiting its diagnostic impact.

Figure 2

This figure illustrates the application of ARFI elastography to assess tissue stiffness in a healthy human kidney. A region of interest (ROI) was placed within the renal cortex to acquire quantitative measurements of tissue elasticity. The obtained values are consistent with the expected range for healthy adult kidney tissue.

Figure 3

This figure presents ARFI elastography data acquired from a transplanted kidney exhibiting signs of chronic dysfunction. The region of interest (ROI) was placed within the renal cortex. Shear wave speed (SWS) measurements within the ROI were significantly elevated, approximately three times higher than the established reference range for normal transplant function. These findings align with clinical expectations for a chronically dysfunctional kidney.