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.
Highlights
The kidney is one of the most frequently transplanted organs with 58.9% kidney transplants in the United States of America (USA) from 1988 to 2019 [1]
All patients with kidney transplantation evaluated at the Clinical Institute of Urology and Renal Transplantation (CIURT), Cluj-Napoca were eligible to participate in the study
Eighty-three patients with a kidney transplant were evaluated during the period of the study, and all agreed to participate in the study, cumulating 160 examinations
Summary
The kidney is one of the most frequently transplanted organs with 58.9% kidney transplants in the United States of America (USA) from 1988 to 2019 [1]. An increase in kidney transplantation has been observed in most European Union member states, from 36.8 pmp (performed kidney transplantations per million people) in 2011 to 38.1 pmp 2016 [2]. A slight increase in the kidney transplantation rate is observed in all non-EU member states, from 11.3 pmp in 2011 to. Ultrasonography (US) is one imaging method used for the evaluation and follow-up monitoring of kidney allografts [3]. The grey scale US examination is mainly used to evaluate the kidney allograft (position, dimensions, and presence of masses) [4,5]. The kidney transplant vascularity is evaluated by Doppler examination, aimed to identify artery stenosis, thrombosis, dissection, or post-biopsy arterio-venous fistulae [6]. The resistivity index (RI) is influenced by extra-renal factors and has low sensitivity and low specificity in the identification of acute renal allograft rejection [7]
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