An IVU is an X-ray examination of your kidneys and bladder. During the process, a contrast agent is injected, which illuminates the kidneys and bladder and makes them show out considerably more than on a conventional X-ray image. It is possible to examine some of the interior intricacies of the kidneys and determine how each kidney is functioning generally. A micturating/voiding cystourethrogram (MCUG/VCUG) produces X-ray images of the bladder and urinary tract. These help assess the structure and function of the lower urinary tract, in particular the bladder (cysto) and the urethra (a tube which takes urine to the outside of your body). Images are also taken while the patient passes urine. Passing urine can be called micturating or voiding, hence the name. This is done to see whether urine flows away correctly from the bladder.