They would need more than a rectum for that. The prostate gland is near the rectum, but it actually encircles the urethra. Technicalities aside, medical illustration might still be a viable use. I suspect they'd want all the innards available though, and not just the anus and rectum.

This is a medical illustration of what's where. I don't think it's against the TOS since it's not erotic at all. However, I'm just going to link to it instead of embedding it. Mods, I'll be glad to remove the link if I'm in error about it fitting within the TOS.

http://images.emedicinehealth.com/images/eMedicineHealth/illustrations/male_torso.jpg

Before they made me they broke the mold!
http://home.roadrunner.com/~kflach/