Blood pools in the veins
The ankles and legs are common sites of swelling because of gravity’s effect on the fluids in the human body. When you stand or sit a lot, the calf muscle pump that transports blood from the legs through the venous system back to the heart is not always at its strongest. Blood pools in the veins as a result. This can cause fluid to leak out into the surrounding tissues and the legs subsequently swell up.
Poor blood return can also occur when the vessels widen during hot, summer temperatures. Legs may swell up in rooms that are too hot, or in rooms with underfloor heating. The swelling mostly begins at the ankles, the lowest point of the large, superficial saphenous vein.
However, in order to best determine why your legs are swelling is be examined by a doctor to see whether a serious venous disease lies behind the symptoms.
Swollen legs: signs of venous disease
The doctor can visualize the blood flow in the veins by taking an ultrasound (Doppler ultrasonography). He can recognize whether the superficial veins or the system of deep veins in the legs is damaged.
For example, when there is a sign of venous disease, the venous valves often do not close properly anymore, so the blood flows backwards in the veins. The blood pools in the veins and widens them. This damages the venous valves further still. If you already have varicose veins in your legs, this is yet another sign of possible venous disease.