How long do I have to keep my feet elevated after the BBL?

Thank you for this most interesting question.  I have been doing liposuction since its inception in the U.S.  It never occurred to me to tell my patients to keep their feet elevated since most of the time I take fat, not only from the lower extremities, but from other areas which might become congested if one's feet are elevated.With reference specifically to a BBL, if one's feet are elevated above the heart, then I am not quite sure how to keep the pressure off the buttocks unless one lays in a relatively contorted position increasing pressure on other portions of the body.  If the recommendation to keep your feet elevated was given to you by your plastic surgeon, then I suggest you query your plastic surgeon as to how long to keep your feet elevated above the heart, and exactly in what position you should put pillows and wedges to comfortably accomplish this mission.

I recommend elevation to lessen swelling of the extremities following surgery.Kenneth Hughes, MD, Board Certified Plastic SurgeonLos Angeles, CA

i do  not routinely have patients keep their feet up after a procedure such as yours.   In fact, after a BBL, I prefer that my patients stay well hydrated and walk around a  bit at home to maintain good blood flow in their legs.

The recovery of BBLs happens in stages and it is very important for patients to understand what to expect during each of those stages. One of the earliest stages during the recover process is swelling. And there can be a lot of swelling. Although keeping your feel elevated can certainly reduce swelling in your lower extremities, I tell most of my patient that it is important to walk early after surgery at least several times a day to prevent a bigger problem - blood clots. Blood clots can be dangerous and can cause very big problems unless they are prevented and early ambulation is something that can help prevent them in many patients. You should always discuss what to do postoperatively with your surgeon and their staff to minimize the risks of complications like blood clots. 
Alternatively, if you sit on your bottom the wrong way after a BBL for a prolonged period of time to keep your feel elevated that can compromise the fat graft and hurt your results. We often have our patients use specialized cushions, lay on their tummies, and turn frequently shortly after a BBL.
So this is a very important question to discuss with your surgeon before the surgery.
I hope this helps.
Good luck and good health!