Evaluation of renal resistive index in axial spondyloarthritis patients: The association with treatment modalities

ABSTRACT Evaluation of Renal Resistive Index in Axial Spondyloarthritis Patients: The Association with Treatment Modalities Objective: Axial spondyloarthritis (axSpA) is a chronic inflammatory disease which is characterized by neck, back and lower back pain and progressive spinal stiffness, including ankylosing spondylitis (AS) and nonradiographic axial spondyloarthritis (nr-axSpA). In addition to involvement of the spine and sacroiliac joints, extra-articular findings are also present in axSpA. One of the extra-articular manifestations is renal involvement. Renal involvement in patients with axSpA is an important cause of morbidity and mortality. In this study, we aimed to evaluate the association of renal resistive index (RRI) with treatment modalities, its effect on renal involvement and its sensitivity and specificity in predicting early renal involvement. Materials and Methods: A total of 105 patients with a diagnosis of axSpA who were admitted to the Department of Rheumatology and Immunology, Balcalı Hospital, Çukurova University Faculty of Medicine, and 52 healthy controls were included in the study. The patient group diagnosed with axSpA was evaluated as 53 nonsteroidal anti-inflammatory (NSAID) treated and 52 biological agent treated groups according to the treatment modalities they received. Demographic data, clinical characteristics, disease activity scores (BASDAI and ASDAS-CRP), renal ultrasonographic evaluations (renal resistive index, pulsatility index, systole/diastole ratio, renal volume, renal volume/renal resistive index and renal elastography) were noted. Statistical Package for the Social Sciences (SPSS) 25.0 package program was used for statistical analysis of the data. Results: RRI and S/D values were statistically higher in the patient group than in the control group (p<0.001; p=0.011, respectively). The mean corrected RV (cRV) and RV/RRI values were found to be lower in the patient group than in the healthy control group (p=0.022; p<0.001, respectively). According to the analysis, the cut-off value of RV/RRI was calculated as 126.5. This value was found to be statistically significant with an AUC of 70.9%, a sensitivity of 58.1% and a specificity of 80.8% (p<0.001). The RV/RRI value was 126.5 or less in 10 of 52 healthy controls and in 60 of 105 patients with axSpA (p< 0.001). It was statistically significant that the mean RE value of the patients was higher in the NSAID group than in the biologic agent group (p=0.018). Conclusion: In conclusion, our study is the first to investigate RRI and renal ultrasonographic evaluations in patients with axSpA. Renal ultrasonographic evaluations in patients with axSpA showed that renal ultrasonographic evaluations may be useful in predicting renal involvement in the preclinical stage of the disease course and in predicting treatment change in the treatment algorithm. Additionally, these evaluations indicated that inflammation may be an early indicator of disease progression in patients with axSpA. Keywords: Axial Spondyloarthritis, Renal Resistive Index, Renal Elastography, Renal Volume, BASDAI, ASDAS-CRP