Edema describes a condition where body tissues swell up with fluids other than blood. It is not always a serious condition, but does require medical attention. Edema is common after a traumatic injury and is referred to as "swelling". It is also common with patients who are being given intravenous fluids, and is an indication that their kidneys are not removing fluid as fast as it is being injected.
The only immediately life threatening edema is pulmonary edema, where fluids collect in the lungs and compromise their ability to process oxygen.