Assessment of kidney tissue stiffness in pediatric patients with hydronephrosis using shear wave elastography: correlation with etiology and grade

Abstract Background Hydronephrosis is the most common pathological condition affecting the kidneys in children. Usually caused by an obstruction to the free flow of urine from the kidney or by vesicoureteric reflux, it entails the dilatation and distension of the renal pelvis and calyces. Interstitial fibrosis gradually develops in both obstructive and non-obstructive hydronephrotic kidneys, resulting in nephron loss and, eventually, a decline in renal function. This study aimed to measure shear wave velocities using ultrasound elastography in hydronephrotic kidneys, to compare these velocities between normal and hydronephrotic kidneys, and to compare velocities across different grades of hydronephrosis. Methods Our study included 40 pediatric patients with hydronephrosis and 20 age- and sex-matched children as a control group. Using a 2–5 MHz convex transducer, we obtained nine valid ARFI measurements for each kidney and simultaneously assessed the degree of hydronephrosis via ultrasonography. Hydronephrosis was classified into grades 0 through 4, with grades 3 and 4 designated as high-grade. Results The mean SWE measurement for all hydronephrotic kidneys (1.8 m/sec, n = 58) was significantly higher than that of normal kidneys (1.6 m/sec, n = 62) with a p -value of < 0.001. Furthermore, mean SWE measurements were significantly higher in high-grade hydronephrosis ( n = 14) compared to low-grade hydronephrosis ( n = 44), with a p -value of 0.005. Of the 40 children who had hydronephrosis, 23 presented with 30 hydronephrotic kidneys diagnosed as obstructive secondary to ureteropelvic junction obstruction (UPJO). The remaining 17 children presented with 28 hydronephrotic kidneys diagnosed as non-obstructive secondary to VUR (grade 3 in seven children, grade 4 in six children, and grade 5 in four children). The mean SWE measurement in non-obstructive hydronephrosis was significantly higher than that in both obstructive hydronephrosis and the normal group, with p -values of 0.0274 and < 0.0001, respectively. Additionally, the mean SWE measurement in obstructive hydronephrosis was significantly higher than that in normal kidneys, with a p -value of 0.0067. Conclusion The average shear wave velocity was significantly higher in patients with hydronephrosis than in the control group. Furthermore, ARFI values were significantly higher in the advanced grades of hydronephrosis.