Apparently, it was Kim’s nude Paper Magazine photo shoot that tipped them off. See, Kim Kardashian posed buck naked for Paper Mag – both full-frontal and full-rear – and these plastic surgeons noted how… well, plastic she looked in those images.
For one thing, her waist to butt ratio was practically alien, and for another, her body fat ratio was almost non-existent. Now, discounting photoshop, the only way to achieve that look is through plastic surgery. The surgeons would do a butt lift, but remove the fat from your waist, thighs, and other fatty deposits to inject into your butt.