External deformation of the male urethra by a urinal or other container held against the penis during the voiding phase of a VCUG should not be confused with a true urethral stricture. The urinal artifact can be recognized as an impression on the penile urethra in association with the presence of the urinal or other container at the level of narrowing. Its appearance changes with a change in position of the urinal.
Reference:
AJ Ramos, FB Watts, Jr, and JW Timmons The urinal artifact Radiology 1978 128: 807b-808b.