text: what is vucg a medical examination.?   a voiding cystourethrogram is an x-ray image of the bladder and urethra during urination.  this test is performed to detect abnormalities of the bladder and the urethra. the test may also detect abnormal bladder emptying or any congenital abnormality. in males, it may detect urethral stricture and the extent of narrowing in the prostatic urethra.  x-rays are a form of electromagnetic radiation like light, but of higher energy, so they penetrate the body to form an image on film. structures that are dense (such as bone) will appear white, air will be black, and other structures will be shades of gray  usually, the urinary bladder does not show up well on conventional x-rays. in this examination, a contrast medium is introduced into the bladder to improve visualization.  x-ray images are taken in various positions with the bladder full of contrast and while the bladder is being emptied.