There are two reasons for swelling after tumescent liposcution. First, in the operating room fluid is injected into the fat to help with the fat removal and speed your recovery. Second, any surgery is a form of injury, and injury leads to swelling as part of the healing process.
The tumescent fluid goes away in about a day, and the swelling from the injury of surgery peaks at two to three days. After a few days the swelling will begin to subside. In most areas it goes away from the top down due to gravity pulling the fluid downwards. Less swelling at the top of the abdomen is normal. The other side of this coin is that there will be more prolonged swelling at the bottom of the abdomen.
It takes about three weeks for a significant amount of the swelling to resolve, but even at three weeks there is still swelling. You will usually notice the swelling continuing to decrease for about three months. If you look critically at photographs of liposuction, I can usually notice changes out to a year, but the amount of change becomes more subtle with time.
Properly fitted compression garments can be helpful to decrease swelling and discomfort after surgery. Medications, such as diuretics, are not usually helpful or recommended, but some herbal medications can be helpful with proper guidance.