The veins carry deoxygenated blood out of the tissue back to the heart and into the lungs, where it is oxygenated. The venous valves play here an important role because they prevent the flow of venous blood back into the legs. In dilated veins, the venous valves are leaking, and it comes
to a reflux of the blood in the wrong direction, namely back into the legs. This results in increased pressure in the leg veins (venous reflux). Over time, this reflux causes a damaging congestion in the leg veins, which leads to the development of varicose veins, and complaints from stagnation.