MO937ASSOCIATION OF RENAL ELASTOGRAPHY WITH BANFF MICROVASCULAR INFLAMMATION IN PROTOCOL BIOPSIES FOR SUBCLINICAL RENAL GRAFT REJECTION DIAGNOSIS

Background and Aims The most common cause of renal graft failure is chronic dysfunction in 24.7% and the most common etiology of this is clinical or subclinical rejection. The incidence of subclinical rejection varies from 15 to 50% (25% in protocol biopsies in the first year after transplantation and 35% after two years). Melek E et al have shown that doppler ultrasound is a non-invasive study that, through the resistance index (RI), has traditionally been used for the early diagnosis of acute graft rejection (AR); however, it is influenced by extrarenal systemic factors. Naesens et al published that in 321 kidney transplant recipients, RI wasn´t associated with histological findings of AR in protocol biopsies. Elastography is another ultrasonographic modality for the evaluation of the kidney graft, which measures the stiffness/elasticity of the tissue expressed in Kpa (kilopascals). Stock in 2011 and Kim BJ in 2018 published studies where they showed that increased stiffness was correlated with the diagnosis of kidney graft rejection. The aim of this study was to describe the association between elastography with microvascular inflammation determined by Banff for diagnosis of renal allograft subclinical rejection. Method Observational, analytical and cross-sectional study that included kidney transplant patients who underwent protocol biopsy and renal elastography at the Central Military Hospital in Mexico City between January 2018 and December 2020. The demographic and biochemical characteristics, degree elastography stiffness and Banff 2017 lesions were determined. The sample calculation, determination of correlation degree and ROC curve elaboration were performed. Results We included 146 patients. 56.8% were men; the most common causes of CKD were undetermined and chronic glomerulonephritis with 52.7% and 17.1% respectively. 47.3% were hypertensive at biopsy time and 1.4% had chronic heart failure. The most common immunosuppression schemes were FK/MPA/steroid and FK/mTOR-i/steroid with 60.3% and 13%, respectively. The mean GFR was 65.31 ml/min which shows graft good function. The mean stiffness in the elastography was 15.73 Kpa. The rest of baseline data are shown in Table 1. Had rejection 36.3% of the biopsies, the most frequent chronic AMR C4d- with 15.1% and active AMR C4d- 8.9%. When analyzing the ROC curves, the Banff 2017 lesions AUC values that correlated better with graft stiffness were: v=0.607, i=0.594, g=0.578, C4d deposit=0.519, ptc=0.498. Figure 1. Conclusion Intimal arteritis, inflammation, and glomerulitis are the Banff lesions best associated with elastography graft stiffness in protocol biopsies. Prospective studies are recommended in patients with acute graft dysfunction to find an adequate elastography cut-off value that allows another tool for fast and non-invasive diagnosis of renal graft rejection.