Impact of acute renal artery stenosis on tissue elasticity of the kidney: an animal study

Abstract

Objective To study the changes of Young′s modulus value of the renal cortex, vertebral body and sinus when there was a different degree of acute renal artery stenosis. Methods 10 Japanese white rabbits were used for this study. The left renal artery was dissected. An ultrasound probe was placed on the left kidney, Young′s modulus of the renal cortex, vertebral body and sinus were recorded using shear wave ultrasound elastic imaging technique during three stages: when the renal artery was intact (0% stenosis), tied with a suture (> 50% stenosis), and ligated (100% stenosis). Renal tissue elasticity with different degrees of renal artery stenosis were compared. Pathological study was carried out in the kidneys, each with either 0%, >50% or 100% renal artery stenosis. Results The mean values of Young′s modulus from the renal cortex, vertebral body and sinus with different degrees of renal artery stenosis were as follows: 0% stenosis, (16.31±1.70) kPa, (13.38±1.63) kPa, and (12.75±2.26) kPa; >50% stenosis, (14.16±2.34) kPa, (11.49±2.70) kPa, and (10.72±2.56) kPa; 100% stenosis, (11.35±1.48) kPa, (8.39±1.29) kPa, and (7.08±1.52) kPa. The mean value of Young′s modulus from the renal cortex was significantly higher than those from the renal vertebral body and sinus (P<0.05). The mean values of Young′s modulus from different parts of the kidney decreased progressively with an increase in renal artery stenosis (P<0.05). The pathological study demonstrated that with the increase in the severity of renal artery stenosis, glomerular volume, renal interstitial capillary diameter and red blood cells decreased. When renal artery stenosis reached 100%, there was patch degeneration and inflammatory cell infiltration within the renal interstitium, and mild degeneration of tubular epithelial cells with obscure cell borders. Conclusions The value of Young′s modulus from the renal cortex was higher than those from the renal pyramid and sinus in rabbits. The values of Young′s modulus from the renal cortex, pyramid and sinus decreased with an increase in the severity of renal artery stenosis, which suggest that, in the study of the elasticity of the kidney, the renal artery blood flow dynamic state can obviously affect the value of the elasticity of the kidney. Key words: Renal artery obstruction; Elasticity imaging techniques; Rabbits