Elucidation of Renal Scars in Children With Vesicoureteral Reflux Using Contrast-Enhanced Ultrasound: A Pilot Study

Abstract

Introduction: Vesicoureteral reflux is a common disorder in children but can result in kidney scarring following acute pyelonephritis. The gold standard diagnostic to detect renal scars in children is ^99mTc-dimercaptosuccinic acid (DMSA) scintigraphy. DMSA has a number of limitations including radiation exposure, need for sedation, and radiotracer supply shortages. Contrast-enhanced ultrasound (CEUS) is a technique whereby biocompatible microspheres of inert gas are administered i.v. that reflect ultrasonography sound waves and do not involve radiation. Because the contrast agent is rapidly cleared, contrast images must be obtained within minutes of administration. CEUS has been used in a variety of organ systems, but its use in pediatric kidney diseases is limited.

Methods: In this study, we performed CEUS in 7 children with documented renal scars by radiographic imaging consistent with reflux nephropathy.

Results: In all subjects, CEUS detected all previously known radiologic abnormalities as well as detecting new areas of hypoenhancing renal parenchyma. None of the patients experienced any serious adverse events.

Discussion: This study represents the first report of using CEUS to characterize renal scars in children with reflux nephropathy. We conclude that CEUS is a highly sensitive, rapid, and cost-effective diagnostic imaging modality for detecting and monitoring renal scars in children with vesicoureteral reflux.

Keywords: contrast-enhanced ultrasound; reflux nephropathy; vesicoureteral reflux.

Figure 1

(Left) in patient CEUS-008, left kidney has poor corticomedullary differentiation on conventional grayscale ultrasound. (Right) contrast-enhanced ultrasound image taken at same time and in same plane as grayscale image. Arrows highlight large, wedge-shaped, hypoenhancing areas not visualized on grayscale image on left.

Figure 2

(a) ^99mTc-dimercaptosuccinic acid (DMSA) scan of subject (patient CEUS-003) with normal size and shape of left kidney (L). The right kidney has a wedge-shaped filling defect in the upper pole (arrow). Lower pole of right kidney has subtle blunting of renal contour (*). (b) (Left) grayscale conventional ultrasound image with normal corticomedullary differentiation and lower pole contour of right kidney (*). (Right) large area of hypoenhancement of lower pole (*) highlighted by dashed line. Arrow corresponds to wedge-shaped defect demonstrated in a (arrow) DMSA scan.

Figure 3

(Left) in patient CEUS-006, grayscale conventional ultrasound image demonstrating moderate hydronephrosis of the left kidney. (Right) contrast-enhanced ultrasound image taken at the same time and in the same plane as the grayscale image. Arrows highlight areas of parenchymal thinning and demonstrate the collecting system to apparently extend to the renal capsule with no intervening parenchyma between the surrounding soft tissue and collecting system.