Voiding Urosonography (VUS) for Vesicoureteral Reflux
During the last 15 years ultrasound cystography with contrast agent which is called contrast-enhanced voiding urosonography (VUS) has emerged as a reliable alternative radiation free method for detection of vesicoureteral reflux (VUR) and in many cases it has substituted the classical methods which use ionizing radiation, namely radionuclide cystography (RNC) and fluoroscopic voiding cystourethrography (VCUG).
The production of stable ultrasound contrast agents by drug industry after years of research gave great impetus to the ultrasound diagnosis of VUR. Levovist (Bayer-Schering, Berlin, Germany) was for many years the most common ultrasound contrast agent used for this purpose. The last decade Bracco released SonoVue a second generation contrast agent, which contains sulphur hexafluoride microbubbles stabilized with phospholipid shell.
In clinical studies these two contrast agents proved to be absolutely safe and no major side effects have been reported during their intravesical administration. The symptoms of dysuria (tingling), observed at a rate less of 3%, are similar to those after simple bladder catheterization and rather attributed to the catheter itself than the contrast agent.
The contrast-enhanced VUS requires catheterization and filling of the urinary bladder with ultrasound contrast agent and normal saline. The examination begins with the preliminary typical ultrasound scanning of the kidneys, ureters and bladder which is repeated during filling of the bladder and voiding. The bladder and the ureters are examined in supine position and the kidneys in prone or supine during both filling and voiding. During voiding the urethra is also examined in supine position. The diagnosis of reflux is based on visualization of contrast microbubbles in the ureters or in the pelvicalyceal system. The classification of reflux is performed in a manner similar to that of the international system of classification of reflux in the classical fluoroscopic cystography. The biggest advantage of the contrast-enhanced VUS over the other two methods is that VUS lacks ionizing radiation while both the radionuclide cystography and fluoroscopic voiding cystourethrography enable the risks from irradiation of ovaries and testes which are adjacent to the bladder.
The modern trend worldwide is to apply the highest radiation protection, especially in childhood. The most effective and complete way of radiation protection is the avoidance of radiation, selecting methods which lack radiation and such is ultrasound. Furthermore the ultrasound cystography has greater sensitivity in the detection of reflux in comparison with the counterparts RNC and VCUG. Moreover, after the recent improvement of ultrasound techniques with specific software dedicated to second generation contrast agents the reliability of the method has been further increased and the detection of reflux became easier technically.
A recent electronic survey in the form of a questionnaire in pediatric radiologists from European countries showed that about 5,000 children underwent contrast-enhanced VUS with second generation contrast-agent and no adverse events from the contrast agent were reported. Furthermore, by the same research team, another, under publication, meta-analysis of the existing literature on the diagnostic accuracy of the method showed that VUS is a reliable and safe method for imaging reflux and urethra and it can be performed as a substitute of the classical methods with the grate benefit of avoiding the radiation risks.