Direct radionuclide cystography, using short half-life radiopharmaceuticals, is considered to be more reliable for detecting vesicoureteral reflux than conventional roentgenographic techniques. In addition to the detection of vesicoureteral reflux, other parameters determined include the bladder volume when reflux occurs, calculation of volume of fluid that has refluxed, accurate calculation of residual urine volume, estimation of reflux drainage time, and the visualization and diagnosis of gross anatomic abnormalities. Currently, a major disadvantage is poor resolution, prohibiting analysis of small bladder defects and urethral abnormalities. The major advantage of nuclear cystography is the small radiation dose delivered with its use. It is estimated that at least 100 radionuclide studies can be performed for the same radiation expense as a single roentgenographic study.