no odeama means swelling, ie there is to much fluid in the tissue, thats all it means.
Now there are various reasons for this. One is kidney failure which leads to poor regulation, along a similar line is congestive cadiac failure CCF (which is more common than a compleate blockage of the kidneys, i belive its more common that they tend to lose there ability to STOP water leaving the body rather than keep to much) which DOES lead to odeama of the legs AND acute pulmonry odeama APO during sleep. The reason for this kind of odeama is that more fluid is moving out of the vascular space than the lypatic system can return to the heart, once you lay down however all that flows back in and leaks out into the lungs causing APO
Another cause of odeama is an inability for the lympatic system to move the fluid. This is your lyphodeama you see in women after breast cancer surgury (like my mum) where the lyph nodes are removed.
However the most common form of odeam is a sprained ankle where the releace of inflamitory mediators (for instance Heprin) makes the capilleries more permiable which leads to a build up of fluid (odeama) in the interstitial space. This is why you ice, compress and elivate a sprain, they cause vasoconstriction which means less fluid into the tissues.
This is similar for anaphalaxis and septic shock. The capilleries become more permiable because of those same inflamitory mediators and there for you get more fluid in the tissues which is odeama. Problem is that isnted of it being in the ankle, it tends to be around the layrix and there for can cut off your airway (treatment adrenilin and\or ice packs to the neck to reduce that odeama and concider ventilin to help with the broncospasim)