Late acute kidney allograft rejection: clinical, laboratory and functional imaging predictors

Background. The development of late acute rejection (LAR) remains one of the leading factors of renal allograft dysfunction in the long-term period after surgery. The specificity of this complication, in contrast to early crises, lies in the latent unfolding of the clinical picture. Since the manifestation of LAR often occurs without sharp fluctuations in traditional markers of nitrogen excretory function (in particular, the level of serum creatinine and urea), early verification of the pathological process constitutes a significant diagnostic problem for clinicians.Purpose – to comprehensively investigate the spectrum of clinical, laboratory, and instrumental markers of late acute renal allograft rejection, with determination of the leading diagnostic and prognostic role of quantitative parameters of dynamic radionuclide imaging.Materials and methods. Clinical data, serum creatinine concentration, estimated glomerular filtration rate (eGFR), CRP level, ESR, dynamic renoscintigraphy parameters, and the results of histological examination of kidney biopsies were analyzed in 22 recipients with RT dysfunction that occurred 6 months after transplantation. The comparison group consisted of 28 recipients with satisfactory graft function 6 months after kidney transplantation.Results. In the study group, lower eGFR values (32 vs. 51 ml/min/1.73 m2; p < 0.001) and higher levels of inflammatory markers were detected: ESR (22 vs. 16 mm/h; p = 0.021) and C-reactive protein (8.9 vs. 4.8 mg/l; p = 0.048). According to the data of dynamic renoscintigraphy, a sequential decrease in graft perfusion and function was observed: perfusion index (PI) from 1.02 to 0.82 and 0.65, functional index (FI) from 0.99 to 0.75 and 0.69 (p < 0.001). An inverse relationship was established between the degree of glomerular damage and eGFR. According to the results of multivariate analysis, the independent factors associated with LAR were a decrease in GFR ( = –0.2845; p < 0.0001), deterioration of PI ( = 4.213; p = 0.0379), a decrease in FI ( = 1.092; p = 0.0247), and an increase in ESR ( = 0.3187; p = 0.0096). The relationship with the creatinine level was less pronounced ( = 0.1294; p = 0.035).Conclusions. According to the obtained data, LAR is accompanied by early changes in RT perfusion and function according to dynamic renoscintigraphy data, which may precede changes (increase) in serum creatinine concentration. The use of functional imaging together with standard monitoring of the graft status increases the efficiency of pathology detection and promotes early clinical response. The combination of renoscintigraphy parameters, GFR, CRP, and ESR can be one of the non-invasive markers for diagnosing RT pathology, which improves the risk assessment of late graft rejection.