Background: The aim of the study was to evaluate a new diagnostic procedure, ultrasound contrast-enhanced voiding cystography (USVC), for vesicoureteral reflux (VUR) in renal transplant recipients and to compare it with radionuclide voiding cystography (RVC).
Methods: Twenty-three renal transplant recipients with recurrent urinary tract infection were investigated simultaneously by RVC and USVC. After catheterization, the empty bladder was filled with normal saline (mean 250+/-30 ml) and 30-45 mBq of (99m)Tc-labelled colloid. At the end of filling the bladder, 19.5 ml of galactose-based, microbubble-containing echo-enhancing agent, at a concentration of 200 mg/ml, was instilled. During the filling and voiding phases the movement of the radiotracer was recorded by a gamma camera and the presence of microbubbles in the urinary tract by ultrasound. RVC was used to detect and grade the degree of VUR.
Results: Nuclear studies identified VUR in 16 (69.6%) of 23 recipients with recurrent urinary tract infection: VUR grade I in three (13%) recipients, grade II in eight (34.8%) and grade III in five (21.7%) using a simplified grading system. USVC with contrast-enhancement detected VUR in 14 (60.9%) recipients. Overall sensitivity and specificity of contrast-enhanced USVC was 75 and 71%, respectively. Statistical analysis showed that the accuracy of this procedure increased with higher grades of VUR and its sensitivity reached 100% for detection of VUR grade III.
Conclusion: In our preliminary study, contrast-enhanced USVC has proved to be an effective examination, with the same accuracy rate as RVC in detecting grade III VUR episodes with low diagnostic accuracy for low reflux grades.