Purpose or Case Report: Approximately 800 children in the United States undergo renal transplant each year. Allograft failure is driven by interstitial fibrosis often due to chronic antibody mediated rejection. Renal biopsy is the gold standard to detect allograft dysfunction but limited by sampling error and inherent procedural and anesthesia risk. Ultrasound shearwave elastography (US-SWE) is a non-invasive imaging technique that assesses the mechanical stiffness of tissue. The primary aim of this study was to examine the relationship between US-SWE values, pathologic fibrosis/rejections scores and serology in pediatric recipients of renal transplant.
Methods & Materials: Our IRB approved retrospective study includes 83 children (age = 14 ± 4.6 years; 57 males) from October 2017 to August 2019 who had undergone US-SWE and biopsy of renal allografts. Shear wave PQ elastography was performed using EPIQ 7 (Philips Healthcare, Amsterdam, Netherlands) and C5-1 broadband curved-array transducer. Six US-SWE measurements were made in the renal cortex: upper (2), mid (2) and lower (2) poles. Median US-SWE scores were calculated. Renal transplant biopsy results and serological testing including BUN, creatinine, estimated glomerular filtration rate (eGFR) and nuclear medicine derived GFR were reviewed. Data were analyzed to examine associations between renal transplant US-SWE with biopsy and serological results. Since histopathology scores (fibrosis, acute/chronic rejection, C4d) are categorical variables, non-parametric Spearman bivariate correlations between pathology scores and US-SWE were obtained. Pearson correlations between US-SWE, nuclear medicine GFR and serological biomarkers were also examined.
Results: There were no statistically significant or clinically meaningful relationships between US-SWE and allograft fibrosis, rejection scores, nuclear medicine derived GFR or estimated GFR based on the bedside Schwartz equation (all r < 0.15; p >0.5).
Conclusions:
Given the lack of significant relationships between US-SWE and renal pathology scores as well as biomarkers, it is unlikely that US-SWE is meaningfully assesses allograft rejection or pathology. From a healthcare resource utilization perspective, US-SWE does not appear to be an effective test for renal allograft screening in pediatric recipients of renal transplants. These data have implications for allograft screening in this population.