Comparison of "direct" and "indirect" radionuclide cystography

Thirty children were studied using both direct (catheter) and indirect techniques of radionuclide cystography. Of 54 ureters able to be compared, six showed vesico-ureteric reflux (VUR) on the direct study but were read as negative on the indirect cystogram, and five showed no reflux on the direct cystogram but were read as positive for VUR on the indirect study. (Sensitivity of 68% and specificity of 86%). Regarding ureters read as true positives on indirect study, if that ureter has ever shown reflux at any time, or if it drained a scarred kidney specificity was improved to 97% without changing the sensitivity. Concerns about the validity of indirect cystogram results and the ease of assessment and low radiation dose from the direct cystogram has made direct cystography our preferred technique.