We perform VCUG or voiding cystourethrogram, along with a renal sonogram, which is a test that is commonly done after a child has a urinary tract infection (UTI). A VCUG is a specific x-ray that examines the urinary tract. A catheter (hollow tube) is placed in the urethra (tube that drains urine from the bladder to the outside of the body) and the bladder is filled with a liquid dye. X-ray images will be taken as the bladder fills and empties. The images will show if there is any reverse flow of urine into the ureters and kidneys, which can indicate that the child has vesicoureteral reflux.