Voiding cystourethrogram (VCUG). This test uses X-rays of the bladder when it's full and when it's emptying to detect abnormalities. A thin, flexible tube (catheter) is inserted through the urethra and into the bladder while your child lies on his or her back on an X-ray table.
After contrast dye is injected into the bladder through the catheter, your child's bladder is X-rayed in various positions. Then the catheter is removed so that your child can urinate, and more X-rays are taken of the bladder and urethra during urination to see whether the urinary tract is functioning correctly.
Risks associated with this test include discomfort from the catheter or from having a full bladder and the possibility of a new urinary tract infection.