# Renal Acoustic Radiation Force Impulse Elastography in Hypertensive Nephroangiosclerosis Patients
## 5 Discussion
The studied HN patients presented low values of SWV than the controls (2.37 \(\pm\) 0.34 m/s in HN patients, versus 2.96 \(\pm\) 0.18 m/s in controls), statistically significant (\(p\) < 0.0001). [PERSON] et al. and [PERSON] et al. reported similar results (\(p\) < 0.001, respective \(p\) < 0.05) [34; 35]. [PERSON] et al., based on the fact that 20% of cardiac output enters the kidneys, and that changes in this flow affect renal function, has shown that renal SWV is dependent on intrarenal vascularization [36]. [PERSON] et al., in their study, demonstrated that renal SWV depends not only on renal fibrosis, but also on intrarenalvascularization [22]. Under HN conditions, reducing the diameter of the intrarenal vessels leads to a reduction in blood flow, and then, SWV [35]. Our study revealed the presence of significant correlations between SWV and eGFR (r = 0.7822, \(p\) < 0.00001), UACR (r = \(-\)0.7633, \(p\) < 0.00001), respectively RRI (r = \(-\)0.7978, \(p\) < 0.00001). Studying by ARFI 46 patients with chronic glomerulonephritis, diabetic nephropathy, hypertensive nephrosclerosis, chronic pyclonephritis, and 58 healthy subjects, [PERSON] et al. demonstrated that the renal SWV values decreased with the reduction of eGFR in renal patients (\(p\) < 0.001) [22]. [PERSON] et al. identified that the SWV decreased with eGFR decline (\(p\) < 0.01) [37]. The same results were obtained by other studies [10; 13; 14; 38]. In HN patients, the reduction of SWV is consistent with the reduction of eGRF and renal histopathological changes. Lesions of intrarenal parenchyma arteries and afferent arterioles generate decreased renal blood flow, which may affect SWV values more than tissue fibrosis affects [37; 39; 40; 41]. [PERSON] et al. studied 163 patients with chronic kidney disease and 32 healthy subjects and investigated the renal parenchyma stiffness in correlation with renal histopathological fibrosis and renal function. SWV showed significantly correlations with pathological parameters (\(p\) < 0.001), serum creatinine (\(p\) < 0.001), and eGFR (\(p\) < 0.001). The authors identified the cutoff values of SWV for the diagnosis of renal dysfunction, as: 2.65 m/s for the mildly impaired kidneys, 2.50 m/s for moderately impaired kidneys, and 2.33 m/s for severely impaired kidneys [42]. [PERSON]'s modulus represents a quantitative and objective parameter for evaluation of tissue elasticity. It is is calculated according to the equation: E = 3 cs2, where E = Young's modulus (kPa), cs = shear wave velocity (m/s) [43]. In the study performed by [PERSON] et al. on the renal patients who underwent renal biopsy, it was demonstrated that the kidney Young's modulus correlated significantly with intrarenal lesions (\(p\) < 0.001) [44]. [PERSON] et al. demonstrated on 227 patients with CKD that these patients presented lower elasticity values than the controls (\(p\) < 0.001). On the other hand, the authors identified significant correlations between renal elasticity and proteinuria (\(p\) < 0.001), eGFR (\(p\) < 0.001). The conclusion of their article was that the renal elasticity was associated with the degree of proteinuria and the risk of renal function deterioration [10]. [PERSON] et al. identified in two studies a statistically significant correlation between the renal stiffness and RRI in hypertensive patients (\(p\) < 0.001, respective \(p\) < 0.05) [45; 46]. The present study showed that the severity of high blood pressure (grade 1 hypertension versus grade 2 hypertension) causes kidney damage dependent on it. The severity of renal impairment is shown by increases of UACR, RRI, respectively reductions of eGFR and SWV in grade 2 hypertension patients, statistically significant (Table 3). [PERSON] et al. reported that the severity of blood pressure elevation often correlates with the degree of renal damage [21]. This study this study had some limitations. First, the number of studied patients with HN was not very large.