How does the body rid itself of swelling after surgery?

depending on the surgery at time we use drains to manage fluid in empty spaces. Ultimately swelling is transferred back to the lymphatic system and then the deep veins. When you body is ready you will pee out the extra fluid. This can take weeks in some cases and patience in the process is important. 

Welcome to medical school!  A quick lesson on post-surgical fluid dynamics.  In the body there are 3 fluid spaces- 1: intravascular, 2: intracellular, 3: in between the cells and the vessels (so called 3rd space)    This 3rd space is where fluid resides after surgeries like a tummy tuck where we have tissue swelling or edema.  The tissue has been damaged and fluid leaks out of the cells and into the third space.  Eventually through the healing process, the body's lymphatic system absorbs the fluid and shunts it back into the vascular space.  Any excess fluid is managed by the kidneys.  If you suddenly have to much intravascular volume, your kidneys will increase urine production.  Hope this helps.

The swelling/fluid that occurs in the process of healing is sometimes assisted by the use of drains.  Swelling in the tissues is handled by the lymphatic system during healing.  Eventually your body processes it and the waste is eliminated through urination.