Pulmonary edema or fluid on the lungs is usually due to a problem with the bodies ability to remove fluid or pump fluid. So the common problems are heart disease and kidney disease. A healthy patient undergoing any surgery is unlikely to get fluid on the lungs. With that said there are cases of flash pulmonary edema that have occurred. However, again these are usually associated with underlying diseases.
It is normal for patients after a tummy tuck to have atelectasis or collapse of the bottom of the lungs due to inadequate, deep breathing. This is temporary and easily resolved by deep breathing and walking. This is not the same as fluid on the lungs.