Acoustic radiation force impulse (ARFI) in the evaluation of the renal parenchymal stiffness in paediatric patients with vesicoureteral reflux: preliminary results.

To prospectively evaluate acoustic radiation force impulse (ARFI) imaging of the kidneys in children with and without chronic renal disease. METHODS: Twenty-eight children (age range 9-16 years) with primary or secondary vesicoureteral reflux (≥ grade III) underwent scintigraphy and ultrasound with ARFI. Kidneys were divided-according to scintigraphy-into "affected" and "contralateral"; the results were compared with 16 age-matched healthy subjects. An ARFI value, expressed as speed (m/s) of wave propagation through the tissue, was calculated for each kidney through the mean of the values obtained at the upper, middle and lower third. The Wilcoxon test was used; P values <0.05 were considered statistically significant. RESULTS: The mean ARFI values obtained in the "affected" kidneys (5.70 ± 1.71 m/s) were significantly higher than those measured in both "contralateral" (4.09 ± 0.97, P < 0.0001) and "healthy" kidneys (3.13 ± 0.09, P < 0.0001). The difference between values in the "contralateral" kidneys and "healthy" ones was significant (P < 0.0001). The "affected" kidneys with secondary reflux had mean ARFI values (6.59 ± 1.45) significantly higher than those with primary reflux (5.35 ± 1.72). CONCLUSIONS: ARFI values decrease from kidneys with secondary vesicoureteral reflux to kidneys with primary reflux to unaffected kidneys contralateral to reflux to normal kidneys. KEY POINTS: • Acoustic radiation force impulse (ARFI) can quantify tissue elasticity during ultrasound examinations. • Kidneys are highly heterogeneous and difficult to evaluate with ARFI. • Kidneys damaged by vesicoureteral reflux are stiffer than normal. • ARFI can identify initial damage in macroscopically normal kidneys.