# Renal Acoustic Radiation Force Impulse Elastography in Hypertensive Nephroangiosclerosis Patients
## 5 Discussion  
In present, HN represents an important cause of end-stage renal disease [21]. It is the consequence of essential hypertension with a long-term evolution, being characterized by complex histopathological changes, involving intrarenal vessels, glomeruli and tubulointerstitium [9]. The present study is one of the few published related to the HN patients investigated by means of ARFI. By investigating 80 HN patients, it showed that hypertensive kidney damage causes changes in kidney vascularization (evaluated by means of RRI of interlobar arteries) and elasticity (evaluated by means of ARFI, as SWV), but also in biochemical and urinary tests. Glomerular impairment secondary to high blood pressure is evidenced by increased UACR (297.31 \(\pm\) 107.81 mg/g in HN patients versus 18.93 \(\pm\) 4.41 mg/g in controls, \(p\) < 0.0001) and decreased eGFR (45.90 \(\pm\) 11.07 mL/min in HN patients versus 95.86 \(\pm\) 7.38 mL/min in controls, \(p\) < 0.0001). [PERSON] et al. reported that the hypertensive patients presented higher UACR than the normotensive ones (2.17 \(\pm\) 2.67 mg/mmol versus 1.72 \(\pm\) 2.97 mg/mmol, \(p\) = 0.012) [23]. Studying microvascular involvement in hypertensive patients, [PERSON] et al., reported that the decreased of retinal arteries diameter was associated with the reduced eGFR and micro/macroalbuminuria [24]. [PERSON] demonstrated that the albuminuria was associated with hypertensive retinopathy [17]. [PERSON] et al. analyzed the data from the 2011-2012 Korea National Health and Nutrition Examination Survey, including 9519 subjects. The authors reported a positive correlation between the systolic blood pressure, respective diastolic blood pressure and UACR (\(p\) < 0.005) [25]. [PERSON] et al., in their meta-analysis described that albuminuria was associated with small vessel involvement from kidney and brain [26]. In another study, [PERSON] et al. showed that the hypertensive patients presented lower eGFR and higher UACR than the normotensive subjects (\(p\) < 0.001) [27]. In addition to glomerular changes, the hypertensive kidney also has vascular changes (narrowing of the intrarenal arteries and arterioles), as well as interstitial fibrotic ones. Gray-scale ultrasonography reveals renal changes only in advanced stages of HN evolution. But early renal histopathological changes can be identified only by special ultrasonographic techniques, such as Doppler technique (as RRI of interlobar renal arteries), respectively ARFI (as SWV) [11; 12; 13; 14; 15]. RRI is increased in several renal parenchymal diseases, particularly those with pathological changes in tubules, renal interstitium and blood vessels, while patients with isolated glomerular lesions usually have normal RRI [28]. This study identified that the RRI were higher in HN patients than in controls (0.72 \(\pm\) 0.02 in HN patients versus 0.63 \(\pm\) 0.02 in controls, \(p\) < 0.0001). In a group of 211 patients with essential hypertension, higher RRI of interlobar renal arteries was associated with higher prevalence of microalbuminuria (\(p\) = 0.008) [29]. In another study, [PERSON] et al. demonstrated that the increased RRI was associated with low eGFR, this association being related with poor cardiovascular and renal outcomes. [30]. Elevated RRI values were associated with increased UACR and decreased eGFR (\(p\) < 0.01) [20]. ARFI uses short-duration acoustic radiation forces that produce localized displacements in the renal tissue [31; 32]. The renal shear wave velocity (SWV) represents the speed of a transverse wave that propagates perpendicular to the direction of tissue movement, which is a representative factor of renal tissue rigidity [33; 34]. Renal elasticity changes during the HN progression. The speed of shear wave propagation is measured and is proportional to the stiffness of the renal tissue [22; 32; 33]. In the present study the SWV values were between 1.82 and 2.99 m/s.