What is the best option for a flatter stomach and bigger buttocks if you have underlying medical conditions?

I suspect that weight loss may be the best advice for you prior to considering surgery.  If medical clearance is obtained and it is determined that you are healthy enough to have the procedures, I would start with the lipo/BBL and then do the TT at a later date. Schedule a SKYPE consultation (numerous photos to review) with a board certified plastic surgeon to determine the safest path forward to achieve your goals.

Thank you for your question. To provide a valid medical opinion I will need to see pictures of you body from different angles. I would suggest to be treated by board certified plastic surgeon with experience in this procedure, to get the best desired results.
Respectfully,Dr. Emmanuel Mallol Cotes.-

Dear Magical86975,
generally speaking, BBL is a great option for buttock augmentation. Your medical conditions should be under control prior to surgery. You will probably need to get a clearance from your doctor prior to surgery. If you are considering a surgery, I would suggest you to consult a board-certified plastic surgeon. Only after a thorough examination you will get more information and recommendations.
Daniel Barrett, MD
Certified, American Board of Plastic Surgery
Member, American Society of Plastic Surgery
Member, American Society of Aesthetic Plastic Surgery

Hello dear!!
Thanks for the question and provided information as well. Please talk to your primary doctor to get clearance for plastic surgery and then I suggest you book a consultation with a board certified plastic surgeon to discuss the best options for your goals.
Hope this is helpful. Good luck :)

You should get clearance from your medical physician first. Your next step should be consulting a board certified plastic surgeon. A Skype or FaceTime consultation with a BBL specialist will help you get an accurate recommendation and pricing. 
Respectfully, 
Arian Mowlavi MD, FACS
Realself 100 Hall of Fame Inductee

Moving forward with cosmetic surgery is going to take some serious thought and decision making by both yourself and your physicians.Most likely the best procedure is a Brazilian butt lift.  this is basically liposuction of your torso with grafting fat to your buttocks.The procedure can be done with fairly little impact and can be done as an a week procedure using local anesthesia with mild sedation.There will still be stress on your body including stress on your kidneys.You immuno suppressive drugs put you at increased risk for complications.Lupus is also a very serious medical condition putting you at considerable increased risk.I would venture to say many plastic surgeons may say it’s inappropriate for you to have a BBL procedure.This may also be the opinion of your rheumatologist, nephrologist and internist.Simply having lupus and a transplanted kidney does not necessarily exclude everyone from having cosmetic surgery but more critical decision making needs to happen.Your first step should be talking to your primary care physician as well as your kidney doctor and rheumatologist.It wouldn’t hurt to have some consultations to confirm that you’re a good candidate for the procedure as well.If you indeed are a good candidate and your medical team feels that the risk is relatively small and you feel comfortable taking this risk then it’s possible that you could have this procedure.From the information given I would be on the reluctant side.Best, Mats Hagstrom MD