Contrast-enhanced voiding urosonography

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Contrast-enhanced voiding urosonography (occasionally abbreviated as ce-VUS) is a relatively novel contrast-enhanced ultrasonographic technique utilizing microbubbles to detect vesicoureteral reflux.

Indications

Suspected or confirmed vesicoureteral reflux is currently the primary indication for contrast-enhanced voiding urosonography.

Technique

During the exam the ultrasound contrast agent is administered intravesically via a urinary catheter (typically in a diluted form). Afterwards both kidneys and the bladder are examined using a low-MI (mechanical index) CEUS preset, frequently alternating between them during the filling and voiding phases. Vesicoureteral reflux can be confirmed by detection of echogenic microbubbles in the upper urinary tract/pelvicalyceal system. The same five-tier VUR grading system which is used in voiding cystourethrography (VCUG) can be applied to contrast-enhanced voiding urosonography as well with minimal modifications :

  • grade I: microbubbles exclusively in the ureter,

  • grade II: microbubbles in the renal pelvis, but no significant renal pelvic dilation

  • grade III: microbubbles in the renal pelvis and significant renal pelvic dilation, plus moderate calyceal dilatation,

  • grade IV: microbubbles in the renal pelvis and significant renal pelvic dilation plus calyceal dilatation,

  • grade V: microbubbles in the renal pelvis and significant renal pelvic and calyceal dilatation plus loss of renal pelvis contour with dilated, tortuous ureters.

Practical points

The main benefit of contrast-enhanced voiding urosonography in comparison with voiding cystourethrography (VCUG) is the absence of ionizing radiation, hence it can be used more frequently for both screening and follow-up in the pediatric patients without the risk of long term detrimental effects of radiation. Recent studies have demonstrated that detection of vesicoureteral reflux with ceVUS is on par with conventional VCUG, while the former has a more favorable safety profile .