Radiographic appearance of the pars nuda urethrae in the voiding urethrogram.

The pars nuda is the most anterior segment of the male membranous urethra, extending from the urogenital diaphragm to the urethral bulb. It differs from adjacent urethral segments in being incompletely supported by corpus cavernosum and musculature. Usually, this part of the urethra is difficult to distinguish in a voiding urethrogram. Occasionally, however, it may stand out clearly in certain phases of urethral muscular activity, resulting in a roentgen picture which may mimic an abnormality.