Figure 5. Bulbocavernosus muscle. CT scan shows the posterior margin of the bulbocavernosus muscle (arrows). The bulb of the penis (b) is surrounded by this muscle (arrowheads). Note the small fat planes (areas of low attenuation) along the posterior margin of the bulbocavernosus muscle. The right UGD fat plane at the level of the ischiocavernosus muscle is outlined with white.