Radionuclide Cystography is the study of choice in the evaluation and follow up of children suspected to have vesicoureteral reflux (those experiencing urinary tract infections). It is not only safer than fluoroscopic cystography with iodinated contrast (exposes the gonads to 50 to 150 times less radiation), it is more sensitive (can detect reflux volumes of as little as 1 mL). But, since it is not an anatomic study, it is not used to diagnose causes of reflux (e.g. posterior urethral valves, etc.)

Technetium-labeled sulfur colloid is typically used since Technetium pertechnetate and Technetium-labeled DTPA can be absorbed into the circulation through the bladder wall and appear in the ureters through excretion.

The study is performed by administering approximately 1 mCi of the pharmaceutical directly into the bladder through a urinary catheter. The bladder is then filled with sterile saline. Posterior images are obtained with the patient supine in the filling phase. When the bladder is full, if the patient can void on request, they assume a sitting position on a bedpan and the urinary catheter is removed. Again, posterior images are obtained while the patient voids into the bedpan. In patients who are unable to control their urination, voiding images are obtained while the patient urinates in the original supine position.

An abnormal study demonstrates radiotracer in the ureters and may be seen filling the renal pelvis and calyces. The study is observed real time and if reflux occurs during the filling phase, the volume of fluid infused at the time reflux is seen is noted. The degree of reflux can be described as minimal (confined to the ureter), moderate (involving the pelvicalyceal system), and severe (involving the pelvocalyceal system and accompanied by dilatation of the pelvis or a dilated tortuous ureter).