Varicose veins are dilated, thickened, elongated, and twisted vessels with incompetent venous valves, which are inefficient at preventing backflow of blood. This condition can be called valvular insufficiency. Varicose veins can be small spider veins, thread veins, or very large subcutaneous grapelike clusters. The medical term for spider veins is telangiectasias.

Figure 1

There are four main factors that contribute to the development of varicose veins: heredity, female sex hormones, force of gravity, and hydrodynamic muscular forces. It is thought that people with an inherited tendency lose strength of the vein wall and incur damage to the valve in the veins. Varicose veins occur more often in women than men, especially during pregnancy (starting in the first trimester), during the last 14 days of the menstrual cycle, and in standing occupations. The contraceptive pill does not cause varicose veins. The hydrostatic force, or gravitational force of blood, and the hydrodynamic force, or the force of the contracting muscles on adjacent veins, need to work together to stretch skin veins and veins under the skin.

Treatment for varicose veins depends on the cause of venous insufficiency. For example, during early pregnancy a woman's level of progesterone increases to support an expanding uterus. In addition, the veins dilate and become more expandable. This dilation may cause a sudden giving way of a competent valve and a sudden appearance of a telangiectasia (Figure 1).

Figure 1. Perforating veins (connector veins between superficial and deep veins) lose valve function, smaller veins enlarge, and telangiectasias (spider veins) fan out.   (From Gloviczki P, Yao, JST, eds. Handbook of Venous Disorders, 2nd ed. London: Arnold, 2001;29:291: Fig. 29.3.)