Weeping leg edema is a medical condition in which pressure builds up in small veins in the leg and water from the blood seeps out of the veins and eventually out the skin. Typically the leg will swell up and eventually a clear liquid will start to "weep" out of the area that is swelled.
Veins and capillaries work together to drain the blood out of the body's extremities. Sometimes the veins in the leg can get clogged or blocked, or the lymphatic system is not communicating properly. When this happens, blood does not get drained out the leg properly and it starts to pool in one area. The veins start to fill up with blood and pressure causes the walls of the veins start to break apart. When the walls break apart, the water portion of the blood is able to seep out of the veins and starts to cause the leg to swell up. When the pressure is too high, the water starts to ooze out of the epidermis.
Edema can occur from a number of different issues such as heart failure, lung disease and kidney failure. For this reason, it is important to see a physician if one suspects fluid pooling in their legs, because it could be an indication of a much more serious medical issue.