The veins have one-way valves to prevent them from backward flow. The correct functioning of the venous system depends on a complex series of valves. Varicose veins develop slowly and become abnormally thick, twisting or dilated over the time when the frail valves of veins are dysfunctional.
It is not clear what exactly causes the venous valves to work less efficiently. Some theories suggest inherited valve problems or abnormalities of the vein wall, causing some patients to have too few valves or have the valves that do not function properly. The result is that when a person with poorly functioning valves stands up, the valves leak and blood flow actually reverses.
The causes of spider veins or telangiectasia can be divided into congenital and acquired factors. The most common acquired cause in the Minneapolis and St. Paul areas is increased venous pressure, or venous hypertension. Spider veins in the legs are often related to the presence of venous hypertension within underlying varicose veins due to valve dysfunction. Acquired telangiectasia, not related to other venous abnormalities, includes Rosacea, sun damage, radiation exposure, trauma, and topical corticosteroids.
Factors that predispose to the development of varicose veins and spider veins include