Non-invasive assessment of kidney allograft fibrosis with shear wave elastography: A radiological-pathological correlation analysis

ObjectivesTo evaluate the use of shear wave elastography in assessment of kidney allograft tubulointerstitial fibrosis. MethodsShear wave elastography assessment was carried out by two independent operators in kidney transplant recipients who underwent allograft biopsy for clinical indications (i.e. rising creatinine >15% or proteinuria >1g/day). Allograft biopsies were interpreted by the same pathologist according to the 2013 Banff Classification. ResultsA total of 40 elastography scans were carried out (median creatinine 172.5mol/L [interquartile range 133.8-281.8mol/L]). Median tissue stiffness at the cortex (22.6kPa [interquartile range 18.8-25.7kPa] vs 22.3kPa [interquartile range 19.0-26.5kPa], P=0.70) and medulla (15.0kPa [interquartile range 13.7-18.0kPa] vs 15.6kPa [interquartile range 14.4-18.2kPa]) showed no significant differences between the two observers. Interobserver agreement was satisfactory (intraclass correlation coefficient of the cortex 0.84, 95% CI 0.70-0.92 and intraclass correlation coefficient of the medulla 0.88, 95% CI 0.78-0.94). The areas under the receiver operating characteristic curves for detection of tubulointerstitial fibrosis were estimated to be 0.75 (95% CI 0.61-0.89), 0.85 (95% CI 0.75-0.95) and 0.65 (95% CI 0.53-0.78) for cortical, medullary tissue stiffness and serum creatinine, respectively. ConclusionsShear wave elastography can be used as a non-invasive tool to evaluate kidney allograft fibrosis with reasonable interobserver agreement and superior test performance to serum creatinine in detecting early tubulointerstitial fibrosis.