Lymphedema, or lymphatic obstruction, is a long-term condition where excess fluid collects in tissues causing swelling (edema). The main symptom is swelling in arm, or leg that may be accompanied by pain or discomfort. Lymph is a clear, thin fluid that circulates throughout the body to remove wastes, bacteria, and other substances from tissues. Edema is the buildup of excess fluids. So, lymphedema occurs when too much lymph gets collected in an area. The cause of lymphedema is generally cancer treatment where one or two lymph nodes are removed. Normally lymph nodes filter fluids that flow through them, so without normal lymph drainage, fluid can build up in the affected arm or leg and lymphedema develops. Lymphedema can also be present by birth or can develop during puberty.