4 days post Vaser: one flank is more swollen than other, is this a concern?

Hello,
Thank you for your question. As my colleagues have explained, you are still too early in the healing process to have a sense of your final results. There could be many reasons for the uneven swelling. There may have been a need to remove more tissue on one side, or even because you sleep on one side vs the other. Three months is the minimum amount of time to see your final results and the body can continue to change up to a year after the liposuction. 
Revision liposuction is always an option, however there is nothing about the appearance of your flanks at this time that suggests that will be necessary. Rather than worry, I encourage you to continue with your post-operative care regimen (massage and compression garments), focus on exercise and healthy eating, and relax as your body heals and reveals your new physique. 
Best wishes,
Dr. Moein

Hi and welcome to our forum.
Swelling is the natural response to tissue injury, be it by trauma or by a surgeon's instrument. Swelling is not symmetric. It will be affected by position ( the downward side may swell more), gravity (the swelling may extend to the legs when on your feet),  and even atmospheric pressure (swelling and discomfort may increase with bad weather!). 
Your operative result is presently obscured by asymmetric swelling. It will take 6 weeks or more for the majority of swelling to subside, and 6-12 months to completely subside. Be patient!
If concerned, speak with your surgeon.
Best wishes...

Your body will go through all sorts of healing changes, that will seem odd to you.Uneven swelling, hardness, redness, tenseness, uneven soreness...are all a natural part of the healing.Wearing smooth compression and walking are the top ways to heal optimally.Swelling starts to go down around the second week, and progressively improve over the next 6-8weeks.Best. Dr Brecht