Ever wondered if Kim Kardashian has had a butt implant?  She's setting out to prove she has not. 

On tomorrow's episode of Keeping up with the Kardashians, she'll have an x-ray on her bum, then her sisters will compare that x-ray to the one showing her breast implants, and they'll conclude Kim's backside is implant free.

Kim says she is fed up with the rumors that her behind is enhanced with an implant, went ahead and had her butt X-rayed in an attempt to prove her butt is legit.

Kourtney and Khloe reportedly pushed her to do it, and the doctors were all for it.    Khloe says,"The fact that Kim is actually laying on a table and actually getting an X-ray of her [butt] is, like, iconic. Are you serious?!" 

Keeping Up With the Kardashians airs Sunday at 9pm Central on E!.