Acoustic radiation force impulse elastography of the kidneys: is shear wave velocity affected by tissue fibrosis or renal blood flow?
OBJECTIVE
The aim of this study was to identify the main influencing factor of the shear wave velocity (SWV) of the kidneys measured by acoustic radiation force impulse elastography.


METHODS
The SWV was measured in the kidneys of 14 healthy volunteers and 319 patients with chronic kidney disease. The estimated glomerular filtration rate was calculated by the serum creatinine concentration and age. As an indicator of arteriosclerosis of large vessels, the brachial-ankle pulse wave velocity was measured in 183 patients.


RESULTS
Compared to the degree of interobserver and intraobserver deviation, a large variance of SWV values was observed in the kidneys of the patients with chronic kidney disease. Shear wave velocity values in the right and left kidneys of each patient correlated well, with high correlation coefficients (r = 0.580-0.732). The SWV decreased concurrently with a decline in the estimated glomerular filtration rate. A low SWV was obtained in patients with a high brachial-ankle pulse wave velocity. Despite progression of renal fibrosis in the advanced stages of chronic kidney disease, these results were in contrast to findings for chronic liver disease, in which progression of hepatic fibrosis results in an increase in the SWV. Considering that a high brachial-ankle pulse wave velocity represents the progression of arteriosclerosis in the large vessels, the reduction of elasticity succeeding diminution of blood flow was suspected to be the main influencing factor of the SWV in the kidneys.


CONCLUSIONS
This study indicates that diminution of blood flow may affect SWV values in the kidneys more than the progression of tissue fibrosis. Future studies for reducing data variance are needed for effective use of acoustic radiation force impulse elastography in patients with chronic kidney disease.
Department of Nephrology, Kurashiki Central Hospital, 1-1-1 Miwa, Kurashiki 710-8602, Japan. ka11734@kchnet.or.jp.
Kenichiro
K
Asano
Ai
A
Ogata
Keiko
K
Tanaka
Yoko
Y
Ide
Akiko
A
Sankoda
Chieko
C
Kawakita
Mana
M
Nishikawa
Kazuyoshi
K
Ohmori
Masaru
M
Kinomura
Noriaki
N
Shimada
Masaki
M
Fukushima
D000328:Adult; D001783:Blood Flow Velocity; D054459:Elasticity Imaging Techniques / Q000379:methods*; D005260:Female; D005355:Fibrosis; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007668:Kidney / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D012079:Renal Circulation; D051436:Renal Insufficiency, Chronic / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D033081:Shear Strength; D013314:Stress, Mechanical
acoustic radiation force impulse; brachial-ankle pulse wave velocity; chronic kidney disease; genitourinary ultrasound; renal blood flow; shear wave velocity