Contrast cystography uses X-rays and contrast agents (dyes) to assess the bladder for rupture, vesicoureteral reflux, or demonstrate a vesical fistula. Vesicoureteral reflux, is defined as urine backflow caused by an obstruction or congenital defect. During past decades, urologists have added a nuclear version of this test, called a radionuclide cystogram, to their arsenal, particularly to study reflux (see radionuclide cystogram). Many physicians believe this technology is a better surveillance tool for tracing the migration of urine through the urinary tract because it uses less radiation exposure (some estimates suggest up to 200 times) than the conventional cystogram. It also does not rely on fluoroscopy, a radiological technique for visually examining the bladder, which contributes to the higher radiation exposures.
The doctor will insert a catheter through the patient's urethra and into the bladder. The dye or radioactive agent is then injected through the catheter into the bladder. Images are taken at various stages of filling, from various angles, to visualize the bladder. Additional images are taken after drainage of the dye (see voiding cystourethrography). In surveying for vesicoureteral reflux, the urologist employs the same steps, using the radio-pharmaceutical, to collect continuous images every 10 to 15 seconds. While conventional voiding cystograms are still necessary to evaluate the male urethra for posterior valves and bladder trauma, the majority of reflux studies today are done effectively with radionuclide cystography.
While the risks are low, patients may experience urinary tract infections from the catheter. The incidence of reaction to the contrast dye or radioactive agent is rare, since the agents are administered directly into the urinary system and not into the blood stream.