Skin death sounds nasty, and it is. This is a serious healing problem which is due to poor circulation to the abdominal skin. It occurs because, in order to perform the abdominoplasty operation, your surgeon needs to separate your skin/fat layer from your inner girdle (so that your skin and inner girdle may be tightened). When these layers are separated, some of the circulations are lost. Usually, enough circulation remains to allow healing without skin death (doctors use the term "necrosis"). However, in some cases (especially smokers and obese patients, but possibly in anyone), the remaining circulation is inadequate. The skin above the scar line may then turn black and die. Fortunately, this is uncommon, and if it does occur, it is usually limited to a small area and heals on its own within a few weeks.
Infection may occur following any operation and may require additional surgery, intravenous antibiotics, and hospitalization. The risk is about 1%.
Hematoma is a collection of blood under the skin, which is due to bleeding that occurs after surgery is over. If the hematoma is large, you may require surgery to remove it, and it may predispose to skin death.
Seroma is a fluid collection under the skin and is due to your own body fluids that collect under the skin after surgery. To prevent seromas, many surgeons place drains under the skin at the time of surgery. A seroma may occur, anyway and can be removed using a needle and syringe. Because your abdomen will be numb after this operation, seroma removal is not painful.
Dog ears are puckers of skin on either end of your scar. If you have very very loose skin, you will be more likely to have dog ears. Fortunately, your plastic surgeon can remove your dog ears in the office under local anesthesia as a simple procedure.