Quantitative Ultrasound Renal Parenchymal Area Correlates With Renal Volume and Identifies Reflux Nephropathy

Purpose

Studies show that renal volume on magnetic resonance imaging correlates with differential function and is decreased in children with vesicoureteral reflux diagnosed after urinary tract infection. We examined the correlation between ultrasound renal parenchymal area and magnetic resonance imaging volume to determine whether quantitative ultrasound renal parenchymal area might be a reliable, less costly and less invasive substitute for renal magnetic resonance imaging volume.

Materials and Methods

To determine the correlation of ultrasound renal parenchymal area with magnetic resonance imaging, we identified 82 children with primary vesicoureteral reflux who underwent renal magnetic resonance imaging and ultrasound. Magnetic resonance imaging volume was compared with ultrasound renal parenchymal area, renal length and calculated ellipsoid volume. To determine the correlation of ultrasound renal parenchymal area with reflux grade, ultrasound renal parenchymal area was examined in 96 children with reflux and urinary tract infection, and in 52 with reflux without urinary tract infection. Linear regression and multivariate analysis were performed to find the relationship between ultrasound renal parenchymal area and reflux grade.

Results

The correlation of ultrasound renal parenchymal area with magnetic resonance imaging volume was superior to that of renal length and calculated ellipsoid volume (r² = 0.90 vs 0.83 and 0.84, respectively). Hydronephrosis did not affect the correlation. On multiple regression analysis in children with reflux and urinary tract infection higher reflux grade correlated with decreased ultrasound renal parenchymal area (p = 0.0016). In children with reflux without urinary tract infection reflux grade did not correlate with decreased ultrasound renal parenchymal area (p = 0.47).

Conclusions

Ultrasound renal parenchymal area correlates closely with magnetic resonance imaging derived 3-dimensional renal volume and is capable of detecting progressive renal area loss in patients with reflux and urinary tract infection. More studies are necessary to verify whether data from more invasive tests, such as renal magnetic resonance imaging and dimercapto-succinic acid scan, may be attained from ultrasound renal parenchymal area alone.

Key Words: kidney, vesico-ureteral reflux, ultrasonography, organ size, urinary tract infections

Abbreviations and Acronyms: DMSA, dimercapto-succinic acid, MRI, magnetic resonance imaging, US, ultrasound, US-RPA, US renal parenchymal area, UTI, urinary tract infection, VUR, vesicoureteral reflux