The role of retrograde urethrography in the planning of prostate cancer radiotherapy.

This analysis was performed to examine the role of retrograde urethrography in the planning of prostate cancer irradiation. Retrograde urethrograms were performed in 91 patients at the time of simulation. The abrupt narrowing of the contrast column in the urethra was visualized in each case. The distance between the abrupt narrowing of the contrast column and a line connecting the lower poles of the ischial tuberosities was measured in each patient. This distance ranged from 2 to 33 mm with a mean and median of 14 mm. A review of the literature revealed that the abrupt narrowing of the contrast column lies between 5-13 mm inferior to the prostate apex as determined by computed tomography (CT), magnetic resonance imaging (MRI), and ultrasonography. The prostate apex will be adequately covered by placing the inferior edge of the treatment field 15 mm below the abrupt narrowing of the contrast column. This technique will result in at least 20 mm between the prostate apex and the inferior field edge. Performing a retrograde urethrogram at the time of simulation can help prevent geographic misses of the prostate gland when delivering radiation for prostate cancer.