Shear-Wave Elastography Variability Analysis and Relation with Kidney Allograft Dysfunction: A Single-Center Study

Abstract

Shear-wave elastography (SWE) showed the absence or presence of significant differences among stable kidney allograft function and allograft dysfunction. We evaluated the variability of kidney allograft stiffness in relation to allograft dysfunction, respectively, in terms of a correlation of stiffness with patients' characteristics. A single-center prospective study on patients who had undergone renal transplantation was conducted between October 2017 and November 2018. Patients were clinically classified as having a stable allograft function or allograft dysfunction. SWE examinations performed by the same radiologist with a LOGIQ E9 were evaluated. Ten measurements were done for Young's modulus (kPa) at the level of allograft cortex and another ten at the level of medulla. Eighty-three SWE examinations from 63 patients, 69 stable allografts, and 14 allografts with dysfunction were included in the analysis. The intra-examinations stiffness showed high variability, with the quantile covariation coefficient ranging from 2.21% to 45.04%. The inter-examinations stiffness showed heterogeneity (from 28.66% to 42.38%). The kidney allograft cortex stiffness showed significantly higher values in cases with dysfunction (median = 28.70 kPa, interquartile range (IQR) = (25.68-31.98) kPa) as compared to those with stable function (median = 20.99 kPa, interquartile range = (16.08-27.68) kPa; p-value = 0.0142). Allograft tissue stiffness (both cortex and medulla) was significantly negatively correlated with body mass index (−0.44, p-value < 0.0001 for allograft cortex and −0.42, p-value = 0.0001 for allograft medulla), and positively correlated with Proteinuria/Creatinuria ratio (0.33, p-value = 0.0021 for allograft cortex and 0.28, p-value = 0.0105 for allograft medulla) but remained statistically significant only in cases with stable function. The cortical tissue stiffness proved significantly higher values for patients with allograft dysfunction as compared to patients with stable function, but to evolve as an additional tool for the evaluation of patients with a kidney transplant and to change the clinical practice, more extensive studies are needed.

Imaging fibrosis in pediatric kidney transplantation: A pilot study

“…These discrepant findings have led the European Federation for Ultrasound in Medicine and Biology (EFSUMB) to point out that no definitive recommendations for the application of elastography in renal assessment can be made to date 24 . Most of the studies showed a positive correlation between stiffness parameters and fibrosis grades based on the assumption that as renal fibrosis progresses, the renal architecture becomes stiffer leading to faster propagation of the shear waves, which corresponds to higher elastography stiffness values 14,25,26,27,28,29 . Our findings stand in line with this hypothesis.…”

Shear wave elastography and Doppler ultrasound in kidney transplant recipients

“…Although color Doppler is an established method to assess renal allografts, ultrasound elastography seems to show renal impairment earlier. Kidney stiffness has been used as a predictor of renal allograft fibrosis( 30 , 31 , 32 , 33 , 34 ). Renal sampling by SWE has been shown to have a reliability of 97.6% (22) .…”

Color Doppler Ultrasound and Hemodynamics for Evaluating Graft Dysfunction in Recurrent Immunoglobulin A Nephropathy

“…Elec et al [ 15 ] conducted a cross-sectional study of the early post-transplantation period and found that patients with delayed graft function showed lower values for wash-out area under the curve and wash-in and wash-out area under the curve in CEUS, which may be useful to diagnose delayed graft function. Using SWE, Bolboaca et al [ 16 ] identified the differences among stable graft function and graft dysfunction. It has been demonstrated that the cortical tissue stiffness provided significantly higher values for patients with graft dysfunction as compared to patients with stable function.…”