Porth's Essentials of Pathophysiology, 4e

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Disorders of Blood Flow and Blood Pressure

C h a p t e r 1 8

Iliofemoral vein

Great saphenous vein

Incompetency of great saphenous vein

Intact communicating veins

Incompetency of communicating veins

Small saphenous vein

Incompetency of small saphenous vein

A B FIGURE 18-17. Superficial and deep venous channels of the leg. (A) Normal venous structures and flow patterns. (B) Varicosities in the superficial venous system are the result of incompetent valves in the communicating veins.The arrows in both views indicate the direction of blood flow. (Modified from Abramson DI. Vascular Disorders of the Extremities, 2nd ed. NewYork, NY: Harper & Row; 1974.)

Etiology. Prolonged standing and increased intra- abdominal pressure are important contributing fac- tors in the development of primary varicose veins. 71–75 Because there are no valves in the inferior vena cava or common iliac veins, blood in the abdominal veins must be supported by the valves located in the exter- nal iliac or femoral veins. When intra-abdominal pres- sure increases, as it does during pregnancy, or when

the valves in these two veins are absent or defective, the stress on the saphenofemoral junction is increased. The high incidence of varicose veins in women who have been pregnant also suggests a hormonal effect on venous smooth muscle contributing to venous dila- tion and valvular incompetence. Lifting also increases intra-abdominal pressure and decreases flow of blood through the abdominal veins. Occupations that require repeated heavy lifting predispose to development of varicose veins. Prolonged exposure to increased pressure causes the venous valves to become incompetent so they no longer close properly. When this happens, the reflux of blood causes further venous enlargement, pulling the valve leaflet apart and causing more valvular incompetence in sections of adjacent distal veins. Another consider- ation in the development of varicose veins is the fact that the superficial veins have only subcutaneous fat and superficial fascia for support, whereas the deep venous channels are supported by muscle, bone, and connec- tive tissue. Obesity reduces the support provided by the superficial fascia and tissues, increasing the risk for development of varicose veins. Clinical Manifestations. The signs and symptoms associated with primary varicose veins vary. Most women with superficial varicose veins complain of their unsightly appearance. In many cases, aching in the lower extremities and edema, especially after long periods of standing, may occur. The edema usually sub- sides at night when the legs are elevated. When the com- municating veins are incompetent, symptoms are more common.

To heart

To heart

Vein

Valve open

Valve closed

Contracted skeletal muscles

Relaxed skeletal muscles

FIGURE 18-18. The skeletal muscle pumps and their function in promoting blood flow in the deep and superficial calf vessels of the leg.