Voiding urosonography with ultrasound contrast agents for the diagnosis of vesicoureteric reflux in children. I. Procedure

Abstract

Voiding urosonography (VUS) encompasses examination of the urinary tract with intravesical administration of US contrast agent (UCA) for diagnosis of vesicoureteric reflux (VUR). The real breakthrough for US examination of VUR came with the availability of stabilized UCAs in the mid-1990s. This article presents a comprehensive review of various procedural aspects of VUS. Different US modalities are available for detecting the echogenic microbubbles: fundamental mode, colour Doppler US, harmonic imaging and dedicated contrast imaging with multiple display options. The reflux is graded (1 to 5) in a similar manner to the system used in voiding cystourethrography (VCUG). The most commonly used UCA for VUS, Levovist, is galactose-based and contains air-filled microbubbles. The recommended concentration is 300 mg/ml at a dose of 5-10%, or less than 5%, of the bladder filling volume when using fundamental or harmonic imaging modes, respectively. There are preliminary reports of VUS using a second-generation UCA, SonoVue. Here the UCA volume is less than 1% of the bladder filling volume. There is no specific contraindication to intravesical administration of UCA. The safety profile of intravesical Levovist is very high with no reports of side effects over a decade of use in VUS.

Fig. 1

Scans in fundamental mode before (a, c) and after (b, d) contrast agent administration of a dilated left distal ureter (a, barrow) and pelvicalyceal system (c, d). In the postcontrast scans echogenic microbubbles fill the distal ureter (b) and are also detected in the pelvicalyceal system (d)

Fig. 2

Scans after contrast agent administration in fundamental mode (a, c) and with harmonic imaging (b, d) of the bladder and right dilated ureter (a, bdotted circle) and a duplex kidney (c, d) with a multicystic dysplastic upper moiety. Reflux in the right ureter and in the lower moiety of the duplex kidney (grade II, arrow) are much more conspicuous with harmonic imaging (b, d). Note also the crisper depiction of the cysts in the upper moiety with harmonic imaging

Fig. 3

VUS with the application of dedicated contrast imaging modality using high-MI (agent detection imaging, ADI). Reflux into the right ureter (arrow) and right renal pelvis (grade II). a Using grey-scale display alone the refluxing microbubbles are not easily demonstrated but the renal parenchyma is seen well. b Using “grey scale + contrast” visualization of both the reflux with a colour overlay and the bladder and kidney are noticeably improved. c Using “contrast only” the tissue part has been subtracted and only the microbubbles are seen

Fig. 4

VUS with the use of a dedicated contrast imaging modality using high-MI (agent detection imaging, ADI). Note the time and number of the images (arrow). Once just one image has been documented it is possible as a postprocessing option to switch between the different modalities for display: a “grey-scale + contrast” and b “contrast only” options. In this case of grade III reflux marked intrarenal reflux is present in the upper pole (arrowhead)

Fig. 5

Transperineal voiding urethrosonography (a) as part of VUS in comparison with (b) VCUG. To facilitate the comparison the US image (a) is presented upside down. Note in the transperineal US (a) the microbubbles in the bladder (B) and in the massively dilated posterior urethra (pU). The anterior urethra (aU) is depicted as very thin in the presence of a posterior urethral valve (arrow). The finding was confirmed on VCUG (b) (courtesy of Dr. M. Bosio, Milan, Italy)

Fig. 6

At the end of VUS and bladder emptying there can still be a “layer” of UCA lining the mucosa of the empty bladder. The configuration of the bladder in transverse section in combination with the remaining echogenic UCA resembles the mouth part of a “smile sign”. This sign indicates that there is still sufficient UCA in the bladder and if considered necessary a second filling with normal saline only would suffice to carry out cyclical VUS

Fig. 7

VUS using the second-generation UCA, SonoVue. The scan before contrast agent administration (a) uses the tissue harmonic imaging (THI) modality and the scan after contrast agent administration (b) uses echo contrast imaging (ECI). In the former the MI (arrow) is high (1.1) while in the latter a low-MI (0.2) technique is applied. In THI the kidney and particularly the renal pelvis are very well depicted. The refluxing microbubbles of the second-generation UCA are displayed most conspicuously using the low-MI imaging modality