The surgery disrupted lymphatic return, resulting in functional lymphatic obstruction and lymphedema of the arm. The lymphatic channels are important in scavenging fluid and protein that have leaked into the extravascular tissues from the intravascular compartment. Although the amount of fluid that is drained through the lymphatics is not great, it can build up gradually. Cellulitis is caused by an infection of the skin and subcutaneous tissue, and displays erythema, warmth, and tenderness. Congestive heart failure can lead to peripheral edema, which is most marked in dependent areas such as the lower extremities and over the sacrum (in bedridden patients). Decreased plasma oncotic pressure from hypoalbuminemia, or sodium and water retention with heart or renal failure, leads to more generalized edema. Phlebothrombosis leads to swelling with pain and tenderness, but it is uncommon in the upper extremities.